UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Some postmortem aspects of broiler breast muscle Wood, Darrell Fenwick 1973

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1973_A1 W65.pdf [ 5.76MB ]
Metadata
JSON: 831-1.0101137.json
JSON-LD: 831-1.0101137-ld.json
RDF/XML (Pretty): 831-1.0101137-rdf.xml
RDF/JSON: 831-1.0101137-rdf.json
Turtle: 831-1.0101137-turtle.txt
N-Triples: 831-1.0101137-rdf-ntriples.txt
Original Record: 831-1.0101137-source.json
Full Text
831-1.0101137-fulltext.txt
Citation
831-1.0101137.ris

Full Text

SOME POSTMORTEM ASPECTS OF BROILER BREAST MUSCLE \Gl  by  DARRELL FENWICK WOOD B.Sc.(Agr.), McGill University, 1963 M.Sc.,  McGill University, 1965  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY  i n the Department of Food Science  We accept t h i s thesis as conforming to the required standard.  THE UNIVERSITY OF BRITISH COLUMBIA February, 1973  In presenting this thesis i n p a r t i a l fulfilment of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t freely available for reference and study. I further agree that permission for extensive copying of this thesis for  scholarly purposes may be granted by the Head of my Department or  by h i s representatives. of  It i s understood that copying or publication  this thesis for f i n a n c i a l gain s h a l l not be allowed without my  written permission.  Department of  Food  Science  The University of B r i t i s h Columbia Vancouver 8, Canada  Date  M a r c h 30, 1973.  - iii -  ABSTRACT The a b i l i t y of b r o i l e r Pj^ major muscle to develop postmortem isometric tension was studied under a v a r i e t y of conditions.  Muscle s t r i p s developed and released tension while  suspended i n phosphate buffer pH 7.2. .The addition of calcium or magnesium to the buffer enhanced tension release, as d i d the presence of either of these two ions and EDTA. D i f f e r e n t rates of tension release v/ere evident from b i r d to b i r d and the rate of release was f a s t e s t i n birds which required the shortest time to reach maximum tension.  The "  proportion of tension released within one hour of reaching maximum tension correlated s i g n i f i c a n t l y with subsequent proportions from 2 through 12 hours a f t e r maximum tension, making i t possible to p r e d i c t , with reasonable accuracy, tension release from 1 hour values.  The one hour release values had a s i g n i f i c a n t r e l a t i o n -  ship with time to maximum tension but no r e l a t i o n s h i p with tenderness suggesting  that tension release, from b i r d to b i r d ,  i s not i n d i c a t i v e of tenderness. Free struggle at slaughter, hot water scalding and mechanical plucking were shown to have an additive e f f e c t on tension parameters and tenderness of b r o i l e r P.major. Pre-slaughter  epinephrine  i n j e c t i o n was shown to  deplete muscle glycogen l e v e l s within 8 - 1 2 hours postinjection.  ATP l e v e l s remained high r e s u l t i n g i n considerable  tension development.  I t appears that such tension development  i s s u f f i c i e n t to account f o r the subsequent toughening observed  -  in  iv -  the muscle. B r o i l e r s were s u b j e c t e d t o t h r e e d i f f e r e n t  situations cant  (commercial  changes i n postmortem muscle  result  o f these treatments.  differently shortening and  handling, cold  cold  under  Broilers  the d i f f e r e n t  A cold  c o n d i t i o n s with heat  o f temperature  5°C t o 0°C.  s h o r t e n i n g o c c u r r e d and no f u r t h e r  of  strips  resulted  even  after  from  tension  and  s h o r t e n i n g e f f e c t v;as o b s e r v e d  from  36 h o u r s  tension.  during the  as  The  temperacold  t e n s i o n development  was  at this  temperature. after  t e n s i o n development  The c o l d  commercial  A t 2°C, t h e i n i t i a l  no t e n s i o n was o b s e r v e d when 36 h o u r room t e m p e r a t u r e .  as a  stress  on t e n s i o n p a t t e r n .  2°C t o room t e m p e r a t u r e  i n some f u r t h e r  signifi-  t o respond  s h o r t e n i n g o b s e r v e d was i n c r e a s e d  t u r e was l o w e r e d  observed  appeared  l e n g t h e n i n g t h e t i m e t o maximum  study o f the e f f e c t amount o f c o l d  No  q u a l i t y were o b s e r v e d  t h e t i m e t o r e a c h maximum  stresses  and h e a t ) .  stress  Removal  12 and 24  hours  but essentially  s t r i p s were b r o u g h t t o  shortening d i d not significantly  lower muscle  ATP and c r e a t i n e  d e c r e a s e was  observed.  phosphate  levels  although a  -  V  -  TABLE OF CONTENTS Page iii  Abstract L i s t of Tables L i s t of Figures Acknov.'ledgements  viii x xi  INTRODUCTION LITERATURE REVIEW  3  General Muscle Tenderness  3  Antemortem Tenderness Related Factors  4  Breed and Strain  4  Sex and Age  5  Ration  6  Muscle Type  6  Slaughter and Processing Tenderness Related Factors  7  Humane Slaughter  7  Scalding  8  Beating-Picking  9  Hot Cutting Pre-Rigor Tenderness Related Factors  10 10  Chemical Changes  11  Physical Changes  13  Post-Rigor Tenderness Related Factors  15  Resolution of Rigor  15  Aging and Frozen Storage  16  - viPage  Methods of Measuring Muscle Tenderness  17  Isometric Tension Measurement  18  Antemortem Stress and Postmortem Muscle Quality  20  MATERIALS AND METHODS Isometric Tension Experiments  22 22  Muscle Source  22  Isometric Tension Measurement  22  The E f f e c t of Environment on Tension Pattern  25  The E f f e c t of pH on Tension Pattern  25  The E f f e c t of Calcium, Magnesium and EDTA on Tension Pattern The E f f e c t of Temperature on Tension Pattern  25 26  E f f e c t of Processing Techniques on Tension Pattern and Tenderness Epinephrine Experiments  26 28  Preliminary Experiment  28  Experiment 1  28  Experiment 2  29  Sample Preparation f o r Metabolite Assay  29  pH  29  Metabolite /analyses  30  Stress Experiments  30  Commercial Stress  30  Heat Stress  31  - vii Page Cold Stress  -  31  Cold Shortening Experiments  32  Experiment  1  32  Experiment  2  33  RESULTS AND DISCUSSION  34  Isometric Tension Experiments  34  The E f f e c t of Environment on Tension Pattern  34  The E f f e c t of pH on Tension Pattern  36  The E f f e c t of Temperature on Tension Pattern  40  The E f f e c t of Calcium, Magnesium and EDTA on Tension Pattern  44  The E f f e c t of Processing Techniques on Tension Pattern and Tenderness  55  Segregation of B r o i l e r Controls on the Basis of Time to Reach Maximum Tension  58  The Relation Between One Hour Tension Release, Time to Maximum Tension and Shear Value Epinephrine Experiments  64 66  Preliminary Experiment  '  66  Epinephrine Experiment  1  68  Epinephrine Experiment  2  71  Stress Experiments  81  Cold Shortening Studies  88  SUMMARY AND CONCLUSIONS  95  LITERATURE CITED  99  - viii LIST OF TABLES Table I  II  III  IV  Page Means and Standard Errors of Time and Tension Development f o r Strips of B r o i l e r major Muscle Run i n Phosphate Buffer at Four Different pH Levels.  38  Means and Standard Errors of Time and Tension Development f o r Strips of B r o i l e r Pj. major Muscle Run i n Buffers at Various Temperatures.  41  Means and Standard Errors of Time and Tension Development f o r S t r i p s of B r o i l e r and Fowl P^ major Muscle Run i n Phosphate Buffer and Buffer Containing Three Levels of Calcium,  45  Means and Standard Errors of Time and Tension Development f o r Strips of B r o i l e r P_a. major Muscle i n Phosphate Buffer and Buffer Containing Mg++, EDTA, C a + EDTA and Mg + EDTA,  53  Means and Standard Errors of Tension Parameters f o r Inner and Outer Strips of B r o i l e r major Muscle Subjected to Various Post-Slaughter Treatment.  56  + +  V  VI  VII  VIII  IX  X  ++  Means and Standard Errors of Pooled Tension Parameters and Shear Value Data f o r Inner and Outer Strips of B r o i l e r Pj_ major Subjected to Various Post-Slaughter Treatments, 57 Time and Tension Means and Standard Deviations f o r Three E r o i l e r Groups Segregated on the Basis of Time to Reach Maximum Tension,  59  Regression Line Parameters f o r Tension Release (Independent Variable) Versus Time (Dependent V a r i able) from Three Groups of B r o i l e r Controls and f o r the Pooled Groups,  61  Simple Correlations of One Hour Tension Release Values with Subsequent Hourly Values from Three Groups of Control B r o i l e r s and f o r the Pooled Data from the Three Groups, 62 Simple Correlations of Two Hour Tension Release Values with Subsequent Hourly Values from Three Groups of Control B r o i l e r s and f o r the Pooled Data from the Three Groups,  63  - ix Table XI Tension Parameters and Shear Values f o r Pj_ major Muscle from B r o i l e r s Injected with Epinephrine at Various Times Pre-Slaughter.  Page  67  XII Analysis of Variance f o r Parameters Studied i n Epinephrine Experiment 1.  68  XIII Duncan's New Multiple Range Test on S i g n i f i c a n t Treatment Means from Epinephrine Experiment 1.  69  XIV Correlation Matrix f o r Parameters Studied i n Epinephrine Experiment 1.  70  XV Analysis of Variance of Parameters Studied i n Epinephrine Experiment 2,  72  XVI Duncan's New Multiple Range Test on S i g n i f i c a n t Treatment Means from Epinephrine Experiment 2.  73  XVII Correlation Matrix f o r Parameters Studied i n Epinephrine Experiment 2.  78  XVIII Means and Standard Errors of Parameters of major Muscle from B r o i l e r s i n the Commercial Stress Experiment.  82  XIX Means and Standard Errors of Parameters of P_j_ major Muscle from B r o i l e r s i n the Heat Stress Experiment.  84  XX Means and Standard E r r o r s of Parameters of Pj, major Muscle from B r o i l e r s i n the Cold Stress Experiment.  85  XXI Means and Standard Errors of Tension Parameters of B r o i l e r Pj. major Muscle Subjected to Various PostSlaughter Temperature Treatments. XXII Means and Standard Errors of ATP, HMP and CP Content of B r o i l e r P_j_ major Muscle Subjected to Various Temperature Treatments.  89  92  - x  -  LIST OF FIGURES Figure 1  Page E f f e c t of d i f f e r e n t e x t r a c e l l u l a r i n c u b a t i o n media on i s o m e t r i c t e n s i o n p a t t e r n of b r o i l e r P_^ major muscle.  35  2  E f f e c t of e x t r a c e l l u l a r pK on i s o m e t r i c p a t t e r n of b r o i l e r Pj^ ma j or muscle.  37  3  E f f e c t of 1Q~3 i-l c a l c i u m on t e n s i o n d e l c i n e i n b r o i l e r P^ major muscle,  47  4  E f f e c t of 10"*"* M c a l c i u m on t e n s i o n d e c l i n e i n fowl p ^ major muscle,  48  E f f e c t of 10" M magnesium, EDTA and calcium-EDTA on t e n s i o n d e c l i n e i n b r o i l e r P_j_ major muscle.  52  5  tension  3  6  I s o m e t r i c t e n s i o n d e c l i n e i n t h r e e groups of b r o i l e r s s e p a r a t e d on the b a s i s of time r e q u i r e d to reach maximum t e n s i o n , 60  7  R e l a t i o n between t e n s i o n , time t o maximum t e n s i o n and shear v a l u e i n P_j_ major muscle from e p i n e p h r i n e treated b r o i l e r s .  75  R e l a t i o n between muscle glycogen and ATP l e v e l s shear v a l u e i n Pj^ major from e p i n e p h r i n e t r e a t e d broilers,  76  8  9  and  R e l a t i o n between pH, muscle l a c t a t e and shear v a l u e i n P^ major from e p i n e p h r i n e t r e a t e d b r o i l e r s ,  77  - xi-  ACKNOWLEDGE MENTS  The a u t h o r w i s h e s  to express h i s sincere  appreciation  to h i s a d v i s o r , Dr. J . F . R i c h a r d s , A s s o c i a t e P r o f e s s o r , Department o f F o o d S c i e n c e f o r h i s g u i d a n c e the c o u r s e o f t h i s  and encouragement d u r i n g  study.  He i s a l s o  t h a n k f u l t o t h e members o f h i s g r a d u a t e  committee: Dr. S. N a k a i , D e p a r t m e n t o f F o o d S c i e n c e Dr, W.D. P o w r i e , D e p a r t m e n t o f F o o d S c i e n c e D r . C.W. R o b e r t s , D e p a r t m e n t o f P o u l t r y S c i e n c e P r o f e s s o r L.M. S t a l e y , D e p a r t m e n t o f A g r i c u l t u r a l Engineering D r . M.A. T u n g , D e p a r t m e n t o f F o o d S c i e n c e . for  their  encouragement  and  f o r the review  t o Dr. Tung  of this  f o r computer  The Science  and c o n t i n u e d i n t e r e s t  author  thesis  and a s p e c i a l  i s grateful  f o r the use o f p o u l t r y  t o t h e Department o f P o u l t r y  farm  used  t o Mr. G a r t h S u n d e e n  f o r technical  and  f o r computer  to the l a t e  used  Financial Columbia  through  i n this  assistance  Mr, W. G l e a v e  i n the isometric  note o f thanks  assistance.  some o f t h e b r o i l e r s  Robinson  i n the research  facilities  study.  and f o r s u p p l y i n g  He i s a l s o  grateful  a s s i s t a n c e ) to- M i s s  Lynne  and p r e p a r a t i o n o f t h e f i g u r e s  f o r c o n s t r u c t i o n o f t h e chambers  tension studies.  support of the U n i v e r s i t y  of B r i t i s h  a post-graduate Fellowship i s g r a t e f u l l y  acknowledged, A special wife, the  Carol,  note  of gratitude  f o r h e r encouragement  course o f t h i s  study  i s also  expressed  t o my  and u n d e r s t a n d i n g d u r i n g  and f o r t h e t y p i n g  of this  manuscript.  INTRODUCTION  Until the  study  nature  r e c e n t l y , muscle b i o l o g y  of muscle  of these  by D r . B.B.  two  Marsh  areas  o f meat.  of study  The  complementary  i s o b v i o u s and was  i n the i n t r o d u c t i o n t o the Second  on t h e P h y s i o l o g y i n w h i c h he  and t h e s t u d y  has been d i v i d e d i n t o  and B i o c h e m i s t r y  stressed  Symposium  o f M u s c l e as a F o o d  (1970),  stated:  " I n o u r s t u d y o f p o s t m o r t e m m u s c l e we must c o n s i d e r more and more t h e f a c t o r s w h i c h d e t e r m i n e e n e r g y p r o d u c t i o n and u t i l i z a t i o n i n the l i v i n g t i s s u e s the purpose which the m u s c l e s e r v e s , t h e s p e e d a t w h i c h i t moves, the d u r a t i o n o f i t s p e r i o d s of continuous u s e , t h e age, s p e c i e s , a n d d e g r e e o f domest i c a t i o n o f the a n i m a l , t h e s t r e s s e s (both l o n g - and s h o r t - t e r m ) t o w h i c h i t h a s b e e n exposed. O n l y when t h e f a c t s o f l i f e i n m u s c l e a r e known can, we e x p e c t t o i n f l u e n c e i t s q u a l i t i e s i n death," Two rigor, tion the  closely  postmortem  muscle.  animal carcass,  repeatedly  are a shortening  information  muscle  shortening  i n the s o - c a l l e d r i g o r  associated  as f o o d .  on t h e s e  or  chemical  changes  i n precontrac-  phase,  tension  stiffening. have  been  acceptability  However, o n l y  on  of  a meagre amount  relationships i s available for poultry  systems. A study  i t s relation  muscle  The  shown t o i n f l u e n c e t h e u l t i m a t e  many m u s c l e s y s t e m s  occur  i s c h a r a c t e r i z e d by an i s o m e t r i c  results  T h i s phenomenon and  and  These  and a l o s s o f e x t e n s i b i l i t y .  development which  of  r e l a t e d p h y s i c a l changes  of simulated to tenderness  i s reported  in this  isometric tension in broiler  thesis.  development  P e c t o r a l i s major  B r o i l e r s were  subjected  to some s t r e s s o r s v.'hich may  be encountered p r i o r t o s l a u g h t e r  under commercial c o n d i t i o n s and the e f f e c t of these s t r e s s o r s on postmortem muscle q u a l i t y i s a l s o  reported.  - 3 -  LITERATURE REVIEW  General Muscle Tenderness Tenderness,  from the consumer viewpoint, i s high on  the l i s t of factors determining the a c c e p t a b i l i t y of muscle as a food.  In view of t h i s f a c t , food s c i e n t i s t s have devoted  considerable time and e f f o r t to the study of meat tenderness. One of the greatest concerns i n studying tenderness is i t s variability.  Paul et a l , (1959)compared  cooking losses  and tenderness of chickens hatched from eggs l a i d by the same hen with those of chickens from eggs of d i f f e r e n t hens i n the same f l o c k .  The use of h a l f - s i b s d i d not reduce v a r i a t i o n  although cooking loss and tenderness were s i m i l a r f o r both groups. Tenderness varies from muscle to muscle within an animal and from animals of the same or d i f f e r e s t species and t h i s v a r i a t i o n may be influenced by both ante- and postmortem events. A symposium i n 1963 (Campbell Soup Company, 1963) dealt with many of the factors then thought to influence muscle tenderness.  Antemortem factors such as breed, sex and  management practices and postmortem factors such as aging and cooking method were discussed.  This chronological sequence of  events overlooked one r e l a t i v e l y short, but highly s i g n i f i c a n t , time period —  that from slaughter to r i g o r onset.  This period  4 varies from 2 - 4 . 5  hours i n poultry and up to 18 - 20 hours  i n beef and i t s importance had been demonstrated by several workers p r i o r to the symposium (Ramsbottom and Strandine, 1949; Koonz et a l . , 1954; deFremery and Pool, 1 9 6 0 ; Locker, 1960). A review of the factors influencing avian tenderness was published by Marion (1967) , Two basic physical changes occur i n pre-rigor postmortem muscle, a shortening or tendency to contract and a loss of e x t e n s i b i l i t y .  Factors which a f f e c t these changes and  t h e i r r e l a t i o n to tenderness have been reviewed by Marsh and Newbold and Harris (1972).  (1972)  Both are excellent reviews of  pertinent l i t e r a t u r e i n t h i s area. Since shortening or the tendency of the muscle to contract a f f e c t s eventual muscle tenderness, i t follows i n the sequence of events that the post-rigor resolution of these parameters must also be important.  G o l l (196 8) reviewed the present  l i t e r a t u r e i n t h i s area dealing, i n p a r t i c u l a r , with the evidence which c l e a r l y indicates that a resolution of r i g o r a c t u a l l y occurs i n postmortem muscle.  The author emphasized the need  for further research on the e f f e c t s of lysosomes and pH changes on postmortem m y o f i b i l l a r proteins i n order to better understand what causes the resolution of r i g o r . Antemortem Tenderness Related Factors Breed and Strain The e f f e c t of breed and s t r a i n on tenderness has been  -  d i f f i c u l t to e s t a b l i s h .  5  -  Shrimpton and M i l l e r  (1960) com-  pared two strains of chickens and found male Leghorns to be less tender than White Rock males and females.  Goodwin (1966)  compared s i x strains of Broad Breasted Bronze turkeys and reported that s t r a i n d i d not s i g n i f i c a n t l y influence shear values. Larmond et a_l. (1968) found that the e f f e c t of breed on goose q u a l i t y was negative f o r the genotypes Moran et a l .  studied.  (1970) and Larmond et a l . (1970)  reported that a Cornish male - White Rock female cross gave better carcass q u a l i t y than the pure strains or r e c i p r o c a l crosses but no f l a v o r or shear differences were evident between sexes or crosses. Sex and Age I t has been generally established that the older the poultry at slaughter the less tender the meat. al.  May et  (1962) found that 72 - week-old chickens were less tender  than 10 - week-old chickens regardless of the time analyzed postmortem or the aging temperature. Goodwin et al.. (1969) studied 12 s t r a i n s of birds grown to 8 weeks of age before processing. No difference was found between commercial s t r a i n s i n the shear values of breast and thigh.  There was, however, a s l i g h t difference  i n tenderness of the sexes with males having lower shear values f o r both breast and thigh muscle.  A sex r e l a t e d tenderness d i f f e r e n c e i n b r o i l e r s a l s o demonstrated  by Larmond e t a l . (1969), but a  was  study of  Large White t u r k e y s r e v e a l e d no s i g n i f i c a n t sex d i f f e r e n c e s in  eating quality  (Larmond ejt a l . , 1971) .  These  authors  a l s o found t h a t tenderness decreased w i t h age a t s l a u g h t e r . Ration The composition o f the d i e t has very l i t t l e or no e f f e c t on tenderness as l o n g as the d i e t p r o v i d e s f o r optimum growth r a t e  (Marsden e t aJU, 1957  a, b; Goerty e t aJL,, 1961).  V a r y i n g the energy l e v e l , however, has been shown t o a l t e r the  body c o m p o s i t i o n , b a s i c a l l y through p r o t e i n and f a t changes  (Donaldson e_t a l _ . , 1956; 1967;  Summers e t a l . , 1965;  Marion e t a l . ,  Goodwin et. a l . , 1969). Shrimpton  on f u l l  and M i l l e r  (1960) showed t h a t b i r d s kept  feed were more tender than b i r d s kept on a r e s t r i c t e d  diet. Muscle Type In most r e p o r t s shear v a l u e s f o r b r e a s t muscle are  h i g h e r than those f o r t h i g h muscle  (1959) found t h a t l i g h t muscle  (dark).  (light)  Peterson et a l .  i n young b i r d s was  significantly  tougher than dark but i n o l d e r b i r d s the r e v e r s e was  found,  van den Berg et, a l . (1963, 1964). found t h a t t e n d e r i z a t i o n i n b r e a s t muscle was  essentially  complete  after  1-2  days p o s t -  mortem, whereas i n leg muscle a second tenderization period occured 2 - 5 Slaughter  days postmortem. and Processing Tenderness Related  Factors  Humane Slaughter Normal slaughtering procedure f o r poultry consists of suspending birds by t h e i r feet, b r i e f e l e c t r i c a l and exsanguination by an external throat cut. can r e s u l t i n a great deal of struggle before stunning  and a considerable  becomes unconscious.  stunning  This procedure electrical  lapse of time before the b i r d  deFremery and Pool  (1958) found that  a r e l a t i o n s h i p existed between struggle at slaughter  and  tenderness whereas Lineweaver (1959) and Dodge and Stadelman (1960) found no r e l a t i o n s h i p between struggling and postmortem tenderization• Anesthetization, by sodium pentobarbital  (Nembutal)  has been used i n an attempt to f i n d a more humane method of slaughter  (May  and Huston, 1959;  Stadelman and Wise, 1961;  Goodwin et a l . , 1961;  deFremery, 1965), Goodwin et a l .  (1961) found that the method of slaughter had no  significant  e f f e c t on breast muscle tenderness but the use of Nembutal produced some detrimental e f f e c t s on tenderness.  Stadelman  and Wise (1961) found that anesthetization with Nembutal lengthened the period of maximum toughness i n chickens.  This  was  l a t e r v e r i f i e d by deFremery (1965) but h i s tenderness findings were contrary to those of Goodwin et a l . (1961),  Landes et a l .  - 8 (1971) also found that turkeys anesthetized with Nembutal were more tender than nonanesthetized controls. Immobilization of turkeys and chickens using carbon dioxide has been demonstrated et al.,1957, 1961).  (Drewniak et a l . , 1955; Kotula  A 75 second exposure to 33 - 36 percent  carbon dioxide concentration was shown to keep b r o i l e r s unconscious, but a l i v e , during shackling, s t i c k i n g and bleeding (Kotula et a l . ,  1961).  Scalding The adverse e f f e c t s of high scalding temperatures on poultry tenderness have long been knov/n.  Present scalding  techniques vary but i n general f a l l within the range of 125 140°F f o r times of from 30 - 150 Shannon et a l .  seconds.  (1957) studied 6 l e v e l s of scald  temperatures f o r 6 d i f f e r e n t times at each l e v e l .  The study  showed that time of scald and temperature of scald s i g n i f i cantly reduced tenderness and time had a greater e f f e c t than temperature.  These findings were v e r i f i e d on turkeys by Klose  et al. (1959) and chickens by Pool et a l , (1959). Wise and Stadelman  (1959) investigated the e f f e c t of  scald time and temperature on tenderness at various depths within chicken P e c t o r a l i s major muscle.  The authors found  that the toughening e f f e c t of high temperature-long time scalding was related to the depth to which the scald heat penetrated the muscle.  These same authors (Wise and  Stadelman,  - 9 1961)  suggested t h a t two a s p e c t s may  the s c a l d i n g e f f e c t on t e n d e r n e s s .  be i m p o r t a n t i n d e s c r i b i n g F i r s t l y , protein denatura-  t i o n a t e l e v a t e d t e m p e r a t u r e s and s e c o n d l y , an u n d e f i n e d e f f e c t caused by h o l d i n g t h e c a r c a s s a t t e m p e r a t u r e s i n e x c e s s o f normal body t e m p e r a t u r e . Klose et a l .  (1971a) and Kaufman e t a l .  (1972)  experi-  mented w i t h a t e c h n i q u e u s i n g a chamber and s u b a t m o s p h e r i c steam i n an e f f o r t t o e l i m i n a t e immersion s c a l d i n g .  The  techni-  que was e f f e c t i v e i n r e d u c i n g p o l l u t i o n and m i n i m i z i n g w a t e r r e q u i r e m e n t s b u t t h e end p r o d u c t had about t h e same s h e l f  life  and degree o f t e n d e r n e s s as immersion s c a l d e d b i r d s . Beating-Picking P i c k i n g machines, w h i c h have s t o u t r u b b e r f i n g e r s on a r a p i d l y r e v o l v i n g drum, have been shown t o produce  muscle  w h i c h i s s i g n i f i c a n t l y t o u g h e r t h a n hand p i c k e d c o n t r o l s (Wise and Stadelman, 1957; P o o l e t a l . , 1 9 5 9 ; K l o s e e t a l . , 1959) . deFremery and P o o l (1960) showed t h a t s e v e r e m e c h a n i c a l h a n d l i n g o f f r e s h c h i c k e n muscle caused r a p i d  loss  o f ATP  also  and a r a p i d drop i n muscle pH. Sayre (1969, 1970)  showed t h a t m e c h a n i c a l p i c k i n g l e d t o a r a p i d drop i n pH and subsequent toughness i n t h e m u s c l e .  The a u t h o r r e p o r t e d t h a t  a c o m b i n a t i o n o f s c a l d i n g and b e a t i n g produced postmortem changes s i m i l a r t o t h o s e produced by s c a l d i n g and p i c k i n g a l o n e .  - 10 Hot  Cutting Lowe  w h i c h was sisted  (1948) f o u n d  cut w i t h i n  even a f t e r  T o u g h e n i n g by et  studied  the  hours of  e t al.  of c u t t i n g . effect  60  and  120  that obtained mortem.  On  the  ing  stub effect  other  breast  c u t made.  shoulder  Miller  particular  They found and  attention  the  specific  the  obtained.  The  authors  hours  cutbreast  twice post-  sawed o f f a t  thereby  s e c t i o n , no  (1967) .  specific  flattening  w i n g was  Koonz  that knife  same p r o c e d u r e a t 22  hand, i f the  by  extensively  at  c u t s made and  joint  to the b r e a s t  a  leaving  the  p r e - r i g o r toughen-  thus concluded  that  for  i n cut-up p o u l t r y c o n s i d e r a t i o n should  t o t i m e p o s t m o r t e m and  l o c a t i o n of  cut  in relation  be to  muscle. Pre-Rigor The  place  -  b r e a s t muscle i n s e r t i o n ,  optimum t e n d e r n e s s given  a l s o been r e p o r t e d  give  per-  cooling.  minutes postmortem gave s h e a r v a l u e s  attached was  subsequent  N i x o n and  muscle  toughness  et a l . (197lb)have  types of  f o l l o w i n g the  p o i n t beyond the wing  and  (1959) and  Klose  the  the  the wings a t the  20,  aging  This  of c u t t i n g p o u l t r y carcasses  m u s c l e s a f f e c t e d by  at  slaughter.  above r e p o r t s d i d n o t  times post-slaughter,  ting  toughness i n b r e a s t  p r e - r i g o r c u t t i n g has  The type  1 hour of  24  a l . (1954) , P o o l  to the  induced  Tenderness Related  b i o p h y s i c a l and  biochemical  Factors changes which  i n p o s t m o r t e m mammalian m u s c l e h a v e b e e n t h e  take  subject  of  -  extensive  research.  a v i a n muscle ian  The  a c c o m p a n i e d by disappearance  into  several basic  and  glycolysis  post-rigor  pertinent Chemical  and  inosinic  pre-rigor  resolution  acid  from  the  stores  changes  (Goll,  the  the the  deamination acid  through  (deFremery,  (Newbold and  1966  Harris,  196 8) h a v e c o v e r e d many o f  the  Changes  o f t h e most i m p o r t a n t  factors  e x t e n t o f t h e pH  the muscle  (deFremery  tenderness  change i n the m u s c l e .  t h e r a t e o f pH  drop b r i n g  about  and  P o o l , 1960;  o f pH  c h a n g e on  i n the  relationship i s the  Treatments  residual  rate  which  toughness  Khan and Nakamura,  in  1970,  1971). The  effect  mined b a s i c a l l y  through  t e n d e r n e s s has been d e t e r -  acceleration,  retardation  o r p r e v e n t i o n of postmortem g l y c o l y s i s . glycolysis death,  i s usually  scalding  accomplished  or mechanical  been d i s c u s s e d i n p r e v i o u s  Acceleration  through  picking.  sections.  and  free  blockage of  struggle  These e f f e c t s  at  have  a).  1972)  areas.  b e t w e e n p o s t m o r t e m c h e m i c a l c h a n g e s and  increase  of  N-phosphorylcreatine;  the accumulation of l a c t i c  r e f e r e n c e s i n these  One  and  stiffening  T h i s phenomenon i s  of muscle glycogen  R e v i e w s on and  change i s the  i n t h e mammal-  c h e m i c a l changes i n c l u d i n g  o f g l y c o g e n , ATP  acid;  same as t h o s e  rigor mortis.  o f ammonia and  adenylic  anerobic  changes which o c c u r i n postmortem  most o b v i o u s  m u s c l e as i t p a s s e s  of  -  are, i n g e n e r a l , the  species.  appearance  The  11  - 12 -  Retardation of g l y c o l y s i s i n poultry muscle has been effected by e l e c t r i c a l stunning or i n j e c t i o n of Nembutal p r i o r to exsanguination (deFremery, 1965;  Sayre, 1969,  1970).  Both  treatments r e s u l t i n high pH values post-slaughter and a subsequent slow decline of muscle pH. The blockage of g l y c o l y s i s may be accomplished  by  antemortem i n j e c t i o n of sodium iodoacetate (deFremery and Pool, 1963;  Sayre 1969,  1970)  hyde dehydrogenase.  to i n h i b i t the enzyme phosphoglyceralde-  Antemortem epinephrine i n j e c t i o n s , to e l i -  minate muscle glycogen, has been widely used as a means of eliminating g l y c o l y s i s  (deFremery and Pool, 1963;  1965; Khan and Nakamura, 1970;  Sayre, 1969,  deFremery,  1970).  These  authors found minimized postmortem g l y c o l y s i s and increased tenderness through i n j e c t i o n of epinephrine. Klose et a l , (1970) found that muscle depleted of glycogen by antemortem epinephrine i n j e c t i o n s did not have lower shear values than normal muscle.  The authors were unable  to explain reasons f o r t h i s discrepancy but did question the o v e r a l l effectiveness of epinephrine i n j e c t i o n s f o r lowering muscle glycogen. The decrease of N-phosphorylcreatine  (PC) and  ATP  i n muscle are c l o s e l y related since the immediate postmortem source of ATP occurs through dephosphorylation of PC and phosphorylation of adenosine diphosphate  (ADP).  The PC i n  chicken breast muscle i s very l a b i l e (deFremery, 1965, 1966a)  - 13 -  and t h e t r a n s i t o r y pH i n c r e a s e i n p o u l t r y muscle  immediately  postmortem has been a t t r i b u t e d t o t h e f r e e c r e a t i n e l i b e r a t e d at slaughter  (Dodge and P e t e r s , 1960) .  Under normal c o n d i t i o n s t h e l e v e l o f ATP i n c h i c k e n b r e a s t muscle i s a p p r o x i m a t e l y  10 u moles/g f r e s h t i s s u e .  T h i s l e v e l remains r e l a t i v e l y h i g h f o r t h e f i r s t 1 - 3 postmortem t h e n  hours  d r o p s r a p i d l y and t h e muscle p a s s e s i n t o  rigor  m o r t i s when t h e ATP l e v e l has f a l l e n t o about 30 p e r c e n t o f i t s i n i t i a l level  (deFremery, 1966a).  P h y s i c a l Changes M u s c l e i n t h e l i v i n g a n i m a l i s s o f t , p l a s t i c and e x t e n s i b l e , b u t i n r i g o r i t becomes r i g i d and r e l a t i v e l y inextensible.  In addition to losing extensibility  muscle s h o r t e n s d u r i n g r i g o r development. Harris rigor  (1972) have e x t e n s i v e l y r e v i e w e d  unrestrained  Newbold and  the aspects o f p r e -  shortening. T h i s s h o r t e n i n g i s g r e a t l y dependent on t e m p e r a t u r e  but n o t a l l muscles show t h e same e x t e n t o f s h o r t e n i n g . and Hagyard  Locker  (1963) d e f i n e d a " c o l d s h o r t e n i n g " phenomenon i n ox  neck muscle and s i n c e t h a t r e p o r t o v i n e 1966), p o r c i n e  (Galloway  (Cook and L a n g s w o r t h ,  and G o l l , 1 9 6 7 ) , H e n d r i c k s  et a l . ,  1971) and a v i a n muscles (Smith e t a l . , 1969) have been r e p o r t e d t o " c o l d s h o r t e n ".  Jungk and M a r i o n (1970) r e p o r t e d t h a t no  " c o l d s h o r t e n i n g " was e v i d e n t i n t u r k e y b r e a s t muscle b u t t h i g h  - 14 -  muscle did exhibit "cold shortening" (Marion, 1971), Marsh and Thompson (1958), Locker and Hagyard (1963) and Marsh and Leet (1966) reported that the amount of "cold shortening" decreased as the period between slaughter and exposure to cold increased. Interesting e f f e c t s on tenderness of beef and lamb carcasses have been effected by changing postmortem hanging practices (Herring et a l . , 1965 a, b; Bouton and Harris, 1972b). D i f f e r e n t points of attachment prevent d i f f e r e n t muscles from shortening leading to an improved tenderness i n these muscles. No work of t h i s nature has been done with avian species.  How-  ever, Hegarty and A l l e n (1972) found that stretching pre-rigor turkey muscles, which had been excised from the carcass, did not s i g n i f i c a n t l y lower shear values and i n some cases the stretched muscles were s i g n i f i c a n t l y tougher than unstretched controls. Klose et a l , ,  (1970) studied the e f f e c t of pre-rigor  contraction on the tenderness of postmortem chicken muscle. E l e c t r i c a l stimulation, beating, freeze-thawing or heating reduced muscle length, i n most cases, to betv/een 40 and 5 0 percent of the o r i g i n a l rest length.  Subsequent shear values  for the contracted, cooked muscles were found to be about onehalf those f o r uncontracted controls.  The authors speculated  that the extreme state of contraction effected changes at the sarcomere l e v e l which resulted i n the m y o f i b r i l s being more susceptible to a shearing s t r e s s .  - 15 Post-Rigor  Resolution  Related  Factors  of Rigor Post-rigor  lution  Tenderness  t e n d e r i z a t i o n i n muscle i n v o l v e s a reso-  of rigor mortis.  The e v i d e n c e  relating  r e s o l u t i o n o f r i g o r was r e v i e w e d b y G o l l evidence begins  were d i s c u s s e d .  t o develop  Firstly,  t o a maximum a t v a r y i n g t i m e s species, clines The  the a b i l i t y  after  second  rigor  after  postmortem.  to maintain  occurs  of evidence  s e v e r a l days,  One rigor  rupture et  suggesting  Similar  lengthen  Regardless  1967; T a k a h a s h i  slowly dereached.  postmortem (Gothard  that  sar-  shortening e t a l . , 1966;  e t a l . , 1967). f o r the observed  resolution  o f Z - l i n e s t r u c t u r e and weakening and e v e n t u a l  o f t h e bonds between t h e I and Z f i l a m e n t s .  muscle  of  that a resolution of  again  possible explanation  i s loss  a l . (1970)  rabbit  d e a t h and i n c r e a s e s  i n postmortem muscle i s t h e o b s e r v a t i o n  Stromer and G o l l ,  of  isometrically  t h e p o i n t o f maximum t e n s i o n h a s b e e n  line  after  Two l i n e s o f  isometric tension  comeres w h i c h have undergone e x t e n s i v e will,  (196 8 ) .  muscle h e l d  t e n s i o n immediately  to the actual  showed t h a t t h e Z - l i n e o f b o v i n e , lost  i t s integrity  during  f i n d i n g s have been r e p o r t e d  T a k a h a s h i e t a l . (1967) b u t S a y r e  muscle.  p o r c i n e and  postmortem  storage.  i n c h i c k e n muscle by  (1969, 1970) f o u n d  w e a k e n i n g t o be more p r o m i n e n t t h a n postmortem c h i c k e n  Henderson  I - Z  Z-line degradation i n  - 16 A second possible cause of the resolution of r i g o r i s the weakening of the actin-myosin i n t e r a c t i o n .  Such weak-  ening may be effected by a very s p e c i f i c and l i m i t e d p r o t e o l y s i s of myosin, a c t i n and/or one of the regulatory proteins 1968) ,  (Goll,  Evidence of such a weakening was f i r s t reported by  Fujimaki et. a l . (1965) . Aging and Frozen Storage The aging period i s considered  the time when a pro-  cessor can most influence the tenderness of chicken and turkey muscle.  The d i f f e r e n t aging requirements f o r red and white  muscle (van den Berg et a l . , 1964) must be taken into considera t i o n , when considering an adequate aging  period.  Marion and Goodman (1967) and Welbourn et a l , (1968) have studied turkey q u a l i t y i n r e l a t i o n to aging, time and c h i l l i n g treatment p r i o r to freezing.  Larger turkeys were  found to require a shorter aging period p r i o r to freezing suggesting that a d d i t i o n a l tenderization occurs i n large  turkeys  during freezing and thawing (Marion and Goodman, 1967), Several chemical changes have been shown to occur i n frozen poultry muscle that may r e l a t e to tenderness (Khan et a l . , 1963;  Khan, 1964).  The change i n protein and nonprotein  s t i t u e n t s of chicken breast muscle was followed during storage.  Nonprotein constituents increased with frozen  i n d i c a t i n g that some p r o t e o l y s i s had occurred.  confrozen storage  This p r o t e o l y s i s  could a f f e c t the s o l u b i l i t y and ion-binding properties of the  - 17 -  protein, and thus a f f e c t tenderness, loss of juiciness and subsequent development of dryness i n the meat. Methods of Measuring Muscle  Tenderness  One of the greatest d i f f i c u l t i e s i n comparing  avail-  able data on avian tenderness i s the tremendous v a r i a t i o n i n procedures used to determine tenderness. emphasized  Marion (1967)  the need to standardize mechanical and sensory  methodology so that i n d i v i d u a l researchers may be able to determine how  t h e i r data compares with researchers i n other  laboratories. Pearson  (1963) presented a review of objective and  subjective methods f o r measuring meat tenderness and pointed out the advantages and l i m i t a t i o n s of each method. Most of the objective methods of determining meat tenderness use some form of a shearing device and record the force required to shear or compress a sample of standard s i z e . The r e l a t i o n s h i p between instrument tenderness values and sensory panels has been widely studied over the l a s t two decades (Deatherage and Garnatz, 1952; Klose et a l , ,  1961;  White et a l . , 196 4; Pangborn et a l . , 1965; Sharrah et a l . , 1965 a, b; Pool and Klose, 1969, Szczesniak et a l . , Larmond and Petrasovits, 1972).  1970;  A comparison of objective  methods has been published by Bouton and Harris  (1972a).  Some of the more recent studies have raised objections on both the t h e o r e t i c a l and p r a c t i c a l aspects of the shear type method  - 18 for determining  meat t e n d e r n e s s  and K l o s e , 1969;  Szczesniak  (Sharrah e t a l . , 1965  b;  Pool  e t a l , , 1970).  A d i f f e r e n t approach t o the measurement o f meat t e n d e r n e s s has been t r i e d by some w o r k e r s .  Nakamura (1972)  measured t e n s i l e s t r e n g t h of muscle f i b e r s i n o r d e r t o postmortem a g i n g of c h i c k e n b r e a s t m u s c l e .  study  S t a n l e y et. a l .  (1972) p e r f o r m e d two b a s i c t y p e s o f o b j e c t i v e measurements on raw p o r c i n e muscle  s h e a r i n g and break s t r e n g t h t e s t s ;  sarcomere l e n g t h , e l a s t i c i t y , s t r e s s r e l a x a t i o n and elongation.  The  and  break  r e s u l t s of t h e s e t e s t s were compared w i t h  t a s t e panel e v a l u a t i o n s of tenderness, count on cooked meat.  e l a s t i c i t y and  Texturized vegetable  chew  p r o t e i n was  used  as a r e f e r e n c e by the p a n e l and p r o v e d u s e f u l i n r e d u c i n g t i o n s between chew count and o b j e c t i v e e v a l u a t i o n .  The  varia-  authors  c o n c l u d e d t h a t t h e r e a r e two m a j o r s t r u c t u r a l c o n t r i b u t i o n s o f raw muscle t o cooked meat t e n d e r n e s s ,  a connective  tissue factor  and a c o n t r a c t i o n f a c t o r , and d i f f e r e n t o b j e c t i v e methods  should  be u s e d f o r t h e i r e v a l u a t i o n . Zachariah  e t a l . (1971) have a l s o t e s t e d a method f o r  p r e d i c t i n g t e n d e r n e s s on raw m u s c l e .  E l e c t r i c a l impedance  measurements made on p o u l t r y tended t o i n d i c a t e t h a t h i g h impedance was  a s s o c i a t e d w i t h t e n d e r b i r d s and  low impedance  w i t h tough b i r d s . I s o m e t r i c T e n s i o n Measurement The  f i r s t s t u d i e s on the use  of i s o m e t r i c t e n s i o n  -admeasurements t o f o l l o w t h e t i m e - c o u r s e  of r i g o r mortis i n  b o v i n e and r a b b i t muscle were r e p o r t e d by Busch e_t a l . (1967) and Jungk e t a l . (1967),  P r i o r t o t h i s time e x t e n s i b i l i t y  measurements were used i n o r d e r t o q u a n t a t i v e l y f o l l o w r i g o r mortis. The measurement o f i s o m e t r i c t e n s i o n p r o v i d e s s e v e r a l unique advantages over e x t e n s i b i l i t y measurements (Busch e t a l . / 1972).  The most i m p o r t a n t advantage i s i t s a b i l i t y t o d e t e c t  changes w h i c h c o r r e s p o n d  t o not only onset o f r i g o r but r e s o -  l u t i o n o f r i g o r as w e l l . Schmidt e t a l . (1968) d e s c r i b e t h e development o f an i s o t o n i c and i s o m e t r i c r i g o r o m e t e r w h i c h a l l o w e d measurement o f i s o m e t r i c t e n s i o n ( s h o r t e n i n g ) and i s o t o n i c t e n s i o n of e x t e n s i b i l i t y ) simultaneously.  These same a u t h o r s  (loss (Schmidt  e t a l . , 1970 a, b) have used t h e r i g o r o m e t e r t o s t u d y some f a c t o r s a f f e c t i n g the time-course muscle.  of r i g o r mortis i n porcine  Jungk and M a r i o n (1970) have d e m o n s t r a t e d i s o m e t r i c  t e n s i o n development and d e c l i n e i n t u r k e y muscle and have e s t a b l i s h e d a l i n e a r r e l a t i o n s h i p between t e m p e r a t u r e and t e n s i o n development i n b r e a s t m u s c l e . Busch e t a l . ( 1 9 7 2 a ) p u b l i s h e d  some improvements i n  t h e p r o c e d u r e f o r m e a s u r i n g postmortem i s o m e t r i c t e n s i o n and have r e p o r t e d e x t e n s i v e d a t a on t e n s i o n development from t h r e e mammalian s p e c i e s  (porcine, bovine,  rabbit).  - 20 Antemortem Stress and Postmortem Muscle Quality Animals are exposed to many forms of stress during growth and i n p a r t i c u l a r during shipment to market and slaughter. These stresses increase the need f o r hormones which are produced, by the adrenal gland. Selye (1956) defines stress as: "the state manifested by a s p e c i f i c syndrone which consists of a l l the n o n - s p e c i f i c a l l y induced changes within a b i o l o g i c a l system". In h i s early work (Selye, 1950) noted that animals exposed to a number of stress-producing  f a c t o r s , such as emotional  excitement, fatigue, cold and i n a n i t i o n , always reacted with an increased secretion of hormones from the adrenal medulla and adrenal cortex.  One e f f e c t of these hormones i s a l t e r a t i o n of  l i v e r and muscle glycogen l e v e l s and changes i n the l a t t e r are of p a r t i c u l a r importance i n r e l a t i o n to postmortem muscle q u a l i t y . The e f f e c t of stress on postmortem muscle q u a l i t y i s exemplified by the Poland China breed of pigs.  These animals  have been shown to be extremely susceptible to antemortem  stress  and y i e l d a high incidence of pale soft exudative (PSE) muscle (Sayre et a l . , 1963 a, b; Briskey, 1964; Kastenschmidt et a l . , 1966, 1968; L i s t e r et a l , , 1970; Sair et al.,1970).  In beef  animals, stress has been implicated i n the incidence of dark cutting beef (Lawrie, 1958, 1966 a,b).  To date, no such stress  e f f e c t has been demonstrated i n poultry muscle although the  - 21 tremendous v a r i a t i o n i n tenderness may,  i n some way, be r e -  l a t e d t o v a r i a t i o n s i n s t r e s s s u s c e p t i b i l i t y i n the a v i a n species. The i n f l u e n c e o f s t r e s s on b o v i n e , p o r c i n e and o v i n e meat q u a l i t y has been reviewed by H e d r i c k  (1965) and Judge  (1969) and on growth and performance by W i l s o n (1971) and S i e g e l poultry  (1971).  (1971) have reviewed the l i t e r a t u r e on  a d a p t a t i o n t o confinement r e a r i n g systems and  and environment r e s p e c t i v e l y . of antemortem  Ringer  stress  However, a study of the e f f e c t s  s t r e s s on postmortem muscle q u a l i t y i n the a v i a n  species i s lacking. Lack o f . i n f o r m a t i o n i n the above mentioned area and the need f o r a comprehensive study o f the r e l a t i o n s h i p between isometric  t e n s i o n development and d e c l i n e and b r o i l e r t e n d e r -  ness prompted the r e s e a r c h which i s p r e s e n t e d i n t h i s t h e s i s .  - 22 MATERIALS AND METHODS  Isometric Tension Experiments Muscle Source The laying hens used i n this study were obtained from the Department of Poultry Science at U.B.C. were approximately  2 year o l d New Hampshires,  The birds  The b r o i l e r s  were obtained from a l o c a l processing plant, transported to the U.B.C. poultry farm and kept i n a range house for 7 - 1 0 days p r i o r to use to allow f o r adjustment to the new surroundings.  The b r o i l e r s were maintained  on a 20 percent  b r o i l e r grower r a t i o n and were slaughtered at 8 - 12 weeks of age. For slaughter, birds were placed i n a metal funnel, exsanguinated  by an outside neck cut and allowed  to bleed f o r about 2 minutes.  The wings and legs were  manually restrained during slaughter i n addition to r e s t r i c tion provided by the funnel. Isometric Tension Measurement Isometric tension development and decline were measured using an E & M 6-channel physiograph isometric transducers.  f i t t e d with  The physiograph was obtained from  Narco-Bio-Systems Inc. formerly E & M Instrument Co., Houston, Texas.  - 23 Muscle f o r tension measurement was obtained immedi a t e l y after exsanguination by cutting the breast skin and excising a 1 cm wide s t r i p of muscle tissue from the anterior portion of the P e c t o r a l i s major.  The s t r i p was cut p a r a l l e l  to the d i r e c t i o n of the muscle f i b e r s and care was taken to prevent stretching of the muscle during excision and subsequent s t r i p preparation.  A regression l i n e was prepared by  c a r e f u l l y measuring the weight and cross-sectional area of 2  several muscle s t r i p s 5 cm i n length and 0.1 - 1.0 cm i n cross section. cut  A l l s t r i p s used i n subsequent studies were  to 5 cm i n length, weighed and the cross-sectional area  determined from the regression l i n e . 2 between 0.15 - 0.25 cm  Most s t r i p s ranged  since t h i s size best f i t t e d the  clamping system used. One end of a muscle s t r i p was clamped i n a battery cable clamp  (Mueller No. 48B) and the other end was attached  to a second clamp.  This second clamp was fixed on a p l e x i -  glass rod within a plexiglass c y l i n d e r , 9.5 cm i n diameter and 20 cm high.  The rod was fixed about 4 cm above the  chamber bottom i n order to permit the use of magnetic ring. the  stir-  The chamber was f i l l e d with enough buffer to cover  muscle s t r i p and top clamp and the muscle s t r i p was  attached to an isometric transducer by means of 6 l b t e s t monofilament f i s h i n g l i n e t i e d to the free clamp.  Approxi-  2  mately 5.0 g/cm  tension was applied to each s t r i p i n order  to a t t a i n some measure of uniformity of s t a r t i n g conditions.  -  The  p h y s i o g r a p h was  was  equivalent  studied  24  c a l i b r a t e d so t h a t a 1 cm  to 5 g tension.  from each b i r d .  Up t o 6 s t r i p s  to attachment of s t r i p s  minutes.  The  1.  from  f r o m one b i r d was  e n t i r e system used i n t h i s  i s shown i n P l a t e  could  The maximum t i m e l a p s e  guination  studies  pen d e f l e c t i o n  and  be exsan20  subsequent  - 25 The E f f e c t of Environment on Tension Pattern Four d i f f e r e n t systems were studied i n order to select the appropriate chamber media f o r the muscle s t r i p s . System 1 consisted of a humid chamber produced by l i n i n g the chambers with moistened chromatography paper, placing about 3 cm of s a l t solution i n the bottom of the chamber and covering the top of the chamber with Saran wrap allowing a small space f o r the attachment of the s t r i p to the transducer.  The other 3 systems consisted of f i l l i n g the chamber  with one of d i s t i l l e d water, phosphate buffer pH 7.2, i o n i c strength 0.15 or Tris-acetate buffer pH 7.1, i o n i c strength 0.22 (Goll e t a l . , 1970). The E f f e c t of pH on Tension Pattern Phosphate buffers of pH 5.8, 6.3, 6.7 and 7.2 were prepared as described by Gomori (1955) .  Six b r o i l e r s  were used i n t h i s study and four s t r i p s were cut from each bird.  One s t r i p was run at each pH and tension measurements  were made at room temperature (22 - 25°C).  The length of  measurements varied between 16 - 20 hours. The E f f e c t of Calcium, Magnesium and EDTA on Tension Pattern Calcium chloride, magnesium chloride and EDTA were  - 26 -  added to the pH 7.2 phosphate buffer.  Solutions were prepared  to contain 10"^, 10""*, 10-"*^ M calcium, lo""* M magnesium, 10""* M EDTA, 10  M calcium + 10  10~^ H EDTA.  J  M EDTA and 10  M magnesium +  Several s t r i p s from b r o i l e r s were run i n each  solution and s t r i p s from 6 laying hens were run i n the buffer _3  plus 10  M calcium.  The E f f e c t of Temperature on Tension |  Pattern  Muscle s t r i p s were run i n phosphate buffer ranging from 0 - 60°C.  The cold temperature s t r i p s were run i n cold-  rooms at about 2 and 5°C and the 0°C readings were obtained by pre-cooling the buffer to 0°C i n a freezer.  Temperatures  above room temperature were attained by placing small, 50 watt aquarium heaters i n the buffer chambers and s t i r r i n g magnetically to maintain even heat d i s t r i b u t i o n .  The heaters  were able to maintain preset temperatures within + 1°C. Temperatures studied were 0, 2, 5, 2 3 , 30, 37, 43, 50 and 60°C. 1  E f f e c t of Processing Techniques on Tension Pattern and Tenderness Five d i f f e r e n t treatments were studied within t h i s experiment. 1.  Exsanguination  + r e s t r i c t e d struggle - control  This Temperature was selected as representative of room temperature which varied between 22 - 25°C.  - 27 -  2,  Exsanguination + r e s t r i c t e d struggle + hot V7ater  3,  scald  Exsanguination + free struggle + hot water scald  4,  Exsanguination + r e s t r i c t e d struggle + pluck  5,  Exsanguination + free struggle + hot water scald + pluck  Exsanguination with r e s t r i c t e d struggle was done as previously described.  Simulation of processing plant conditions was done  by suspending birds by t h e i r feet and allowing them to struggle f r e e l y both before and after exsanguination.  Scalding con-  sisted of 90 second submersion i n water at 60°C and plucking was done on a rotary picker, f i t t e d with p l i a b l e rubber fingers, for 60 seconds.  Six muscle s t r i p s were taken immediately  one side of the breast f o r tension measurement.  from  Three s t r i p s  were taken from muscle close to the skin and three from muscle near the breast bone i n order to study an "inner" and "outer" e f f e c t i n the muscle.  The exposed breast muscle was covered  with Saran wrap, packed i n drained crushed i c e and aged for 24 hours at 2°C after which tenderness measurements were performed  i n a manner s i m i l a r to that reported by deFremery  and Pool (1960).  The excised breast muscle was clamped between  two 1/8 inch aluminum plates f i t t e d with metal spacers so that cooked  muscle approximately 0.7 cm i n thickness was obtained.  The muscle was cooked i n b o i l i n g water f o r 30 minutes and  - 28 cooled i n running tap water f o r 5 minutes.  S t r i p s of p a r a l l e l  f i b r e s , 1.5 cm wide were prepared and sheared using an A l l o Kramer shear press.  A single blade shear c e l l , 250 l b r i n g  and 9 cm/min cross head speed were used f o r a l l shears. A minimum of 10 shears per b i r d was obtained and i n most cases attenuation was set at the 5 percent l e v e l . Epinephrine Experiments Preliminary Experiment The equivalent of 4 mg epinephrine/kg (Sigma Chemical Co., St. Louis, Missouri) body weight was injected into the breast muscle of 6 b r o i l e r s which  were k i l l e d at 3,  6, 9, 12, 15 and 18 hours p o s t - i n j e c t i o n .  Tension and tender-  ness measurements were made as previously described.  Two  control birds were also run. Experiment 1 A t o t a l of 18 male and 18 female b r o i l e r s were used i n t h i s experiment.  A 2 x 3 x 6 randomized complete block design  (Cochran and Cox, 196 4) was used.  Treatments consisted of unin-  jected controls and exsanguination at 2,4, 8, 12 and 16 hours post-injection.  The experiment was run over a 6 day period  and males and females were k i l l e d on separate days.  Injection  was done intramuscularly into the thigh and dosage was as used  - 29  i n the preliminary experiment.  Blood was c o l l e c t e d at death  for blood lactate analysis according to the method of Hadjwassiliou and Rieder (196 8).  Tension and tenderness were  also measured. Experiment 2 The procedure and design of experiment 1 were duplicated except that p o s t - i n j e c t i o n slaughter times of 4, 8,  10, 12 and 24 hours were used.  Muscle samples were taken  within 2 minutes a f t e r exsanguination, frozen i n l i q u i d nitrogen (LN ) and stored i n aluminum f o i l envelopes under 2  for subsequent metabolite analysis. Sample Preparation for Metabolite Assay The samples stored under L N 2 were powdered by the -  method of Borchert and Briskey (1965) as modified by Vanderstoep (1971) .  The frozen samples v/ere pulverized i n a  macro-model V i r t i s homogenizer f o r 1.5 minutes at approximately 11,000 rpm.  The powdered sample was replaced i n aluminum  foil  envelopes and stored under  pH of the muscle samples was determined by modifying the  method of Cassens and Newbold (1967).  1 - 2 g powdered  sample was homogenized i n 10 ml neutralized 0.005 M sodium  - 30 iodoacetate at 2°C.  The s l u r r y was allowed to warm to room  temperature and pK was measured using a Corning Model 10 pH meter. Metabolite Analyses ATP was determined by the method of Lamprecht and Trautschold  (1963) with two modifications.  Two grams of  previously powdered sample were added to 7.5 ml instead of 6.5 ml p e r c h l o r i c acid and 1 cm cuvettes were used instead of 2 cm c e l l s .  This l a t t e r change necessitated a l t e r a t i o n of  the quantities of intermediates, cofactors and enzymes used. Lactate was determined by the method of Hohorst (19G3) and glycogen by the method of P f l e i d e r e r (1963). O p t i c a l density measurements were made using a Unicam SP 800 recording spectrophotometer.  A l l chemicals  were of reagent grade, made up i n glass d i s t i l l e d water. Enzymes, cofactors and intermediates used were obtained from Sigma Chemical Co., St. Louis, Missouri.  Stress Experiments  Commercial  Stress Twenty-eight b r o i l e r s were used i n t h i s experiment.  One male and one female was obtained from a l o c a l processing plant just p r i o r to slaughter, transported to the Food Science  - 31 -  laboratory at U.B.C. and k i l l e d immediately. was repeated on seven d i f f e r e n t days.  This procedure  One control male and  female, from a supply maintained at U.B.C, was k i l l e d on each of these days. Immediately  a f t e r exsanguination, 15 - 20 g breast  muscle was frozen i n LN  2  and subsequently analysed f o r pH and  ATP as previously described.  Tension and tenderness were also  measured as previously described. Keat Stress Twenty female b r o i l e r s were used i n t h i s study. Fourteen birds were placed i n hot a i r at 110°F f o r 3 hours p r i o r to exsanguination.  Seven of these birds were k i l l e d  with r e s t r i c t e d struggle and seven were allowed to struggle freely.  Six birds were k i l l e d as controls. Samples of muscle were excised immediately post-  slaughter and frozen i n LN  2  f o r "0" hour pH and ATP a n a l y s i s .  Tension and tenderness were measured and 24 hour pH was also determined. Cold Stress Twenty-seven female b r o i l e r s were studied i n t h i s experiment.  Eighteen birds were placed i n a 2°C coldroom.  Nine were exsanguinated after 2 hours and 9 a f t e r 6 hours. The remaining nine birds were k i l l e d as controls.  - 32 -  Samples of muscle were excised immediately postslaughter and frozen i n  for subsequent ATP, glycogen and  hexose monophosphate analysis and tension and tenderness were measured.  Cold Shortening Experiments Experiment 1 B r o i l e r s , of mixed sex, were used i n this experiment. The birds were exsanguinated with r e s t r i c t e d struggle and 6 muscle s t r i p s were prepared from each b i r d f o r tension measurement.  Two s t r i p s were run i n buffer at room temperature,  4 s t r i p s were attached to transducers i n a 2°C coldroom then pre-cooled buffer at 2°C was added to the chambers.  These  four s t r i p s were kept i n the coldroom i n order to observe tension development  at t h i s temperature.  Two s t r i p s were removed  from the coldroom at 12, 24 and 36 hours post-maximum tension. The time of maximum tension was determined from the two control s t r i p s run at room temperature.  The 2°C buffer was exchanged  for room temperature buffer and the s t r i p s were attached to isometric transducers at room temperature to observe the a b i l i t y of the s t r i p s to develop tension. was  A similar series of tests  done i n which s t r i p s were attached to transducers at  room temperature, 2°C buffer was added and a f t e r the i n i t i a l "cold shortening" occured the buffer was replaced with room temperature buffer f o r further observation of tension pattern.  - 33 These s t r i p s were designated as " 0 " time samples.  A total  of 15 birds v;as used so that each treatment contained data from 6 d i f f e r e n t b i r d s and 12 d i f f e r e n t muscle s t r i p s . Experiment 2 Six b i r d s were used i n t h i s experiment.  Birds were  exsanguinated with r e s t r i c t e d struggle and a sample of muscle was immediately frozen i n LN » 2  Twelve s t r i p s of muscle,  proportional i n size to s t r i p s used f o r tension measurement, were then prepared.  Eight s t r i p s were placed i n phosphate  buffer at 2°C and after 3 minutes, four were removed, dried r a p i d l y on a paper towel and frozen i n EN2»  T  h  e  o  t  n  e  were removed a f t e r 7 minutes and s i m i l a r i l y frozen.  four  r  The  remaining 4 s t r i p s were placed i n buffer at room temperature at the same time as the eight s t r i p s were placed i n the cold buffer.  These s t r i p s were removed after 7 minutes and  s i m i l a r l y frozen,  ATP,creatine phosphate and hexose monophos-  phate analyses were subsequently performed on the muscle according to the method of Lamprecht and Stein (1963).  samples  - 34 RESULTS AND  DISCUSSION  Isometric Tension Experiments. The E f f e c t of Environment on Tension  Pattern  Ideally, isometric tension pattern should be studied on s t r i p s suspended i n a i r , thereby minimizing  external e f f e c t s .  The isometric tension pattern of several s t r i p s was  studied by  suspending s t r i p s i n chambers maintained at a high r e l a t i v e humidity.  These conditions, however, did not prevent the sur-  face of the muscle s t r i p s from drying and spurious tension patterns were obtained. of Busch et_ a l . (1972 dehydration  These findings are s i m i l a r to those  a) who  found that occasionally, surface  occurred even at 95-98 percent r e l a t i v e humidity.  These same authors also found that the isometric tension pattern of rabbit psoas muscle was  i d e n t i c a l whether the s t r i p s  were suspended i n a i r or i n a s a l i n e b u f f e r .  On the basis of  this f i n d i n g , two d i f f e r e n t buffer systems and d i s t i l l e d water were used as l i q u i d media and t h e i r e f f e c t on b r o i l e r muscle tension pattern was  studied.  The tension patterns obtained i n the Tris-acetate buffer were almost i d e n t i c a l to those obtained buffer  (Figure 1).  Tension maximum was  i n the phosphate  reached i n 4.3  hours  in both buffers compared to 8,3 hours i n the d i s t i l l e d water. The main difference between the two buffer systems was tension decline.  i n the  A f t e r 16 hours postmortem, s t r i p s i n the  Tris-acetate buffer had declined to about 60 percent of the  TIME P O S T M O R T E M Figure  1.  (Hours)  E f f e c t of d i f f e r e n t e x t r a c e l l u l a r i n c u b a t i o n media on i s o m e t r i c t e n s i o n p a t t e r n of b r o i l e r P. major muscle.  - 36 -  maximum tension and were d e c l i n i n g slowly.  S t r i p s i n phosphate  buffer had declined to about 45 percent and were continuing to show a rapid rate of decline.  The Tris-acetate buffer appeared  cloudy a f t e r 16 hours, whether or not sodium azide was added to the b u f f e r , suggesting that some form of exchange may have occurred between the buffer and the muscle.  This may explain  why the rate of tension decline was l e v e l l i n g o f f at t h i s point in time.  In contrast, the phosphate buffer remained c l e a r . The tension pattern obtained i n d i s t i l l e d water, as  expected, was quite d i f f e r e n t from the patterns obtained i n the two b u f f e r s .  The tension developed much slower and a f t e r peak-  ing, tension declined slowly u n t i l about 85 percent maximum tension was reached. t h i s point.  Very l i t t l e decline was observed beyond  This i s probably due to a flow of soluble materials,  i n p a r t i c u l a r s a l t ions, from inside the muscle into the lower ionic  strength water. On the basis of the above f i n d i n g s , phosphate buffer  was selected for use i n a l l subsequent studies. considered  Other points  i n making t h i s s e l e c t i o n were i t s ease and s i m p l i -  c i t y of preparation and i t s previous use by Jungk and Marion (1970) and Marion (1971) f o r tension studies on turkey muscle. The E f f e c t of pH on Tension  Pattern  Average tension patterns f o r s t r i p s maintained i n buffers of varying pH are reported i n Figure 2.  The values  Figure 2.  E f f e c t of e x t r a c e l l u l a r pK on isometric tension pattern of b r o i l e r major muscle.  were obtained by averaging the hourly values f o r tension and time to maximum tension of 6 b r o i l e r s . . The patterns do not d i f f e r s u b s t a n t i a l l y i n rate of tension development or decline. This method of obtaining a tension pattern  does/however, give  misleading values f o r both time to maximum tension (referred to as time henceforth)  and the actual maximum tension developed.  This a r i s e s through the fact that a l l birds do not reach maximum tension at the same time. and time are shown i n Table 1.  The true mean values f o r tension These values were obtained by  averaging the actual values f o r tension and f o r time f o r the s t r i p s from the b r o i l e r s .  Paired comparison t - t e s t s were  done by p a i r i n g the pH 5.8, 6.3 and 6.8 s t r i p s i n d i v i d u a l l y , with the control (pH 7.2)  strips.  TABLE I . MEANS AND STANDARD ERRORS OF TIME AND TENSION DEVELOPMENT FOR STRIPS OF BROILER P^ MAJOR MUSCLE RUN IN PHOSPHATE BUFFER AT FOUR DIFFERENT pH LEVELS. 2 pH  Time, h r  Tension, g/cm  7.2  4.50 + 0.61  40.26 + 2.80  6.7  3.90 + 0.63*  34.75 + 3.92  6.3  3.60 + 0.39*  27.73 + 1.51 **  5.8  3.33 + 0.22*  28.15 + 2.08 *  * S i g n i f i c a n t l y d i f f e r e n t from pH 7.2 (p<0.05). ** p<0.01  39  -  Time v a l u e s f o r pH 6.7 and 7.2 a r e b o t h a p p r o x i m a t e l y 4,3 hours when t a k e n f r o m t h e F i g u r e 2.  T h i s compares t o t r u e  v a l u e s o f 3,9 and 4,5 f o r pH 6.7 and 7.2 r e s p e c t i v e l y .  Simi-  l a r l y , peak t e n s i o n v a l u e s f o r pH 6.7 and 7.2 a r e 31 and 34 2 g/cm  from F i g u r e 2 v e r s u s 34.75 and 40.26 r e s p e c t i v e l y  from  T a b l e 1. A d e f i n i t e t r e n d i s e v i d e n t from t h e pH d a t a .  As  pH d e c r e a s e d so d i d t h e time r e q u i r e d t o r e a c h maximum t e n s i o n and amount o f t e n s i o n . s i g n i f i c a n t l y lower  The t i m e s f o r pH 5.8, 6.3 and 6.7 a r e  (p<0.05) t h a n f o r t h e c o n t r o l , pH 7.2.  The average t e n s i o n o f s t r i p s a t pH 5.8 o r 6.3 was s i g n i f i c a n t l y lower t h a n a t pH 7.2. The  r e s u l t s o b t a i n e d here d i f f e r somewhat from  t h o s e o b t a i n e d by Busch e t a!L. (1972a) who r e p o r t e d no change i n t h e amount o f t e n s i o n i n r a b b i t psoas muscle between pH 5.5 - 7.0.  However, a t pH 5.0, t e n s i o n appeared  t o decrease.  They a l s o found a d e c r e a s e i n t i m e r e q u i r e d t o r e a c h maximum t e n s i o n as t h e pH d e c r e a s e d from 7.0 t o 5.0. o b t a i n e d a t 37°C.  These d a t a were  When t h e experiment was conducted a t 2°C,  the o p p o s i t e r e s u l t was o b t a i n e d i e . d e c r e a s i n g pH from 7,0 t o 5.0 i n c r e a s e d t h e time r e q u i r e d f o r maximum t e n s i o n t o d e v e l o p . The  f a c t t h a t t h e above d a t a were o b t a i n e d u s i n g  r a b b i t muscle and t h a t d i f f e r e n t t e m p e r a t u r e s gave d i f f e r e n t r e s u l t s make i t d i f f i c u l t t o draw a n a l o g i e s t o t h e p r e s e n t d a t a on b r o i l e r muscle w h i c h were o b t a i n e d a t a p p r o x i m a t e l y 25°C.  - 40 -  One s i m i l a r i t y does e x i s t between the two sets of data.  Both  show that decreasing the e x t r a c e l l u l a r pH does not hinder the a b i l i t y of muscle to develop or release isometric tension. The fact that time and tension are altered by decreasing e x t r a c e l l u l a r pH i s d i f f i c u l t to explain,  A p r i l et a l ,  (1968) and Rome (1968) have shown that e x t r a c e l l u l a r pH does not a l t e r i n t r a c e l l u l a r pH to any great extent but does change the selective permeability of the sarcolemma.  This may or may  not be the case i n b r o i l e r muscle as i t appears that i n the lower pH b u f f e r s , anerobic g l y c o l y s i s i s halted e a r l i e r than in control b u f f e r s , thus r e s u l t i n g i n less tension and shorter time to maximum tension.  I f the observed phenomena were due  to a change i n sarcolemmal permeability then a greater change i n the o v e r a l l tension pattern would be expected,due to loss of ions and/or metabolites and co-factors v i t a l to the contract i o n and r e l a x a t i o n phases of the tension pattern. The E f f e c t  of Temperature on Tension Pattern During post-slaughter handling poultry muscle en-  counters temperatures ranging from 60°C i n scald tanks down to near 0°C during i c e - s l u s h cooling and aging.  Because of t h i s a  study was i n i t i a t e d to determine the e f f e c t of temperatures within t h i s range on postmortem isometric tension pattern. Temperatures between 5°C and 20°C were not studied because b r o i l e r s are not exposed to t h i s range during the pre-rigor  - 41 -  p e r i o d and pass t h r o u g h i t q u i t e r a p i d l y on subsequent The r e s u l t s o f t h e s e s t u d i e s on temperature e f f e c t s  cooling.  are p r e -  s e n t e d i n T a b l e I I . The time v a l u e s a r e r e p o r t e d as m i n u t e s i n s t e a d o f hours because o f t h e r a p i d t e n s i o n development i n some o f t h e t r e a t m e n t s . TABLE I I . MEANS AND STANDARD ERRORS OF TIME AND TENSION DEVELOPMENT FOR STRIPS OF BROILER P^ MAJOR MUSCLE RUN IN BUFFERS AT VARIOUS TEMPERATURES. Temperature,  °C  Time, min  T e n s i o n , g/cirr  0  3.1 +  0.2 **  65.37 +  6.5 **  2  3.3 +  0.2 **  38.23 +  3.6 **  5  2.2 +  0.2  17.24 +  2.3  ** S i g n i f i c a n t l y  d i f f e r e n t from 5°C (p<0.01)  23  276.7 + 22.1  46.40 +  2.0  30  217.8 + 82.0  49.73 +  6.5  37  116.5 + 44.4 **  65.46 + 11.7  43  49.3 + 15.6 **  mm  73.75 +  9.4 **  50  8.1 +  1.2 **  316.89 + 19.3 **  60  0.5 +  **  290.18 + 29.2 **  ** S i g n i f i c a n t l y d i f f e r e n t from 23°C (p<0.01)  - 42 -  The d a t a f o r 0 ° , 2° and 5°C show d e f i n i t e l y , c o l d s h o r t e n i n g ^ o c c u r s i n b r o i l e r P_j_ ma j or muscle.  that In f a c t ,  the i n c r e a s i n g e f f e c t of c o l d s h o r t e n i n g i s demonstrated w i t h i n the temperature range from 0 - 5°C,  deFremery  and P o o l  (1960) found t h a t the r a t e o f ATP d e c l i n e i n postmortem muscle was 20°C.  broiler  f a s t e r a t 0°C than a t 10°C and minimal between 10 -  Smith e t a l . (1969) f i r s t  e f f e c t i n a v i a n muscle.  demonstrated a c o l d  shortening  They found t h a t s h o r t e n i n g at 0°C  s i g n i f i c a n t l y g r e a t e r than i n t h e 12 - 18°C range.  was  The above  r e s u l t s are i n c l o s e a c c o r d w i t h the p r e s e n t f i n d i n g s .  The  p r e s e n t d a t a , however, demonstrated a more dramatic c o l d s h o r t e n i n g e f f e c t t h a t was  r e p o r t e d by Smith e t a l . (1969).  These authors found t h a t s h o r t e n i n g was  essentially  complete  a f t e r 3 hours i n b r o i l e r s whereas the p r e s e n t study shows t h a t s h o r t e n i n g i s v i r t u a l l y i n s t a n t a n e o u s and the t e n s i o n developed i s e s s e n t i a l l y a l l abated w i t h i n 15 - 30 minutes a f t e r maximum development.  The d i f f e r e n c e between these d a t a p r o b a b l y r e f l e c t  the f a c t t h a t i s o m e t r i c t e n s i o n as determined i n the p r e s e n t experiment, i s a  much more s e n s i t i v e t e c h n i q u e than the mea-  surement o f l e n g t h determined by Smith e± a l . (1969). The f a c t t h a t the time and t e n s i o n are s m a l l e s t a t 5°C suggests a l s o t h a t a p o i n t of minimal t e n s i o n  development  Cold s h o r t e n i n g i n the l i t e r a t u r e r e f e r s t o the a c t u a l l e n g t h change which o c c u r s i n e x c i s e d muscles s u b j e c t e d to low temperatures. In t h i s t h e s i s , however, c o l d s h o r t e n i n g i s used t o d e s c r i b e the r a p i d t e n s i o n development a t 0 , 2 and 5°C.  - 43 -  i s being approached as suggested by the data of deFremery and Pool (1960) and Smith et a l . (1969).  This cold temperature  e f f e c t w i l l be discussed further i n a subsequent section of this thesis. The time and tension data f o r temperatures of 23°C and above i s consistent with an increase i n g l y c o l y s i s at higher temperatures.  Though time tends to shorten and tension  increase, with increasing temperature, no s i g n i f i c a n t changes are apparent u n t i l 37°C i s reached. were observed at 50 and 60°C.  The most s t r i k i n g r e s u l t s  These temperatures were studied  because the outer layers of breast muscle could e a s i l y reach temperatures i n t h i s range during scalding.  In view of the  previously discussed toughening which occurs due to the scalding procedure, these data provide an insight as to why the toughening occurs. The association between muscle contraction and tenderness has been well established (Herring et a l . , 1965 a; Marsh and Leet, 1966; Howard and Judge, 1968).  The great 2  increase i n tension developed at 50 and 60°C (ca. 300 g/cm ) 2  versus 23°C (ca. 50 g/cm  ) suggests that, i n the outer layers  of b r o i l e r P^ major, contraction would be maximal within a very short period of time.  The increased g l y c o l y t i c rate at  these temperatures would r e s u l t i n a low pH,  A combination of  the low pH and high temperature could lead to denaturation of the highly contracted m y o f i b r i l s thus preventing the normal  - 44 -  tenderization which occurs i n postmortem muscle. showed that actomyosin  Hamm (1966)  s o l u b i l i t y i s greatly decreased by  heating i n the range from 40 - 60°C.  Khan (1971) has shown  that dephosphorylation of ATP at high temperatures  a f f e c t s the  mode or extent of s t i f f e n i n g of the muscular tissue thus preventing tenderization. altered  The present data indicates that the  mode of s t i f f e n i n g could be the r e s u l t of increased  tension (contraction) developed at 50 - 60°C.  This increased  contraction would mean an increase i n actomyosin  formation  which upon denaturation would r e s u l t i n the toughening  observed  in scalded poultry. The combination of low pH and high temperature may also a f f e c t tenderness through a l t e r a t i o n s i n connective t i s s u e . Schaller and Powrie (1972) showed s l i g h t changes i n connective tissue of b r o i l e r P^ major due to heating at 60°C. The E f f e c t of Calcium, Magnesium and EDTA on Tension Pattern Three d i f f e r e n t calcium concentrations were prepared and used i n t h i s study on b r o i l e r and fowl muscle.  The time  and tension data f o r b r o i l e r s and the time data f o r the fowl are presented i n Table I I I . The presence of the 3 l e v e l s of calcium did not s i g n i f i c a n t l y a f f e c t the time to maximum tension f o r the b r o i l e r s _3 or fowl.  The 10  M l e v e l d i d , however, s i g n i f i c a n t l y a f f e c t  the amount of tension developed i n the b r o i l e r muscle (p<0.01).  - 45 -  TABLE I I I . MEANS AND STANDARD ERRORS OF TIME AND TENSION • DEVELOPMENT FOR STRIPS OF BROILER AND FOWL P^ MAJOR MUSCLE RUN IN PHOSPHATE BUFFER AND BUFFER CONTAINING THREE LEVELS OF CALCIUM Calcium Concentration Control  10" M  10" M  10'" M  4.04 + 0.86  3.70 + 0.72  36.43 + 4.63* 45.61 + 4.09  54.89 + 7.10  10.50 + 0.62  10.17 + 0.67  3  4  7  Broiler Time  4.18 + 0.62  Tension  51.71 + 4.32  4.06 + 0.50  Fowl Time  9.63 + 0.53  9.10 + 0.71  ** S i g n i f i c a n t l y d i f f e r e n t from control (p<0.01)  The most noticeable d i f f e r e n c e , with respect to b r o i l e r s versus fowl, i s the difference between the time to maximum tension. The time required i n fowl i s twice that of b r o i l e r s which would indicate a much slower rate of anaerobic g l y c o l y s i s i n the postmortem fowl or considerably higher i n i t i a l l e v e l s of glycogen and  ATP. Although i t i s not possible to accurately compare  tension values for fowl and b r o i l e r s , i t i s possible to obtain a rough estimate.  The cross-sectional area of the f i r s t 3 0  s t r i p s cut a f t e r preparing the c o r r e l a t i o n curve, when averaged, give an i n d i c a t i o n of the average size of muscle s t r i p s being prepared at that time.  If t h i s value i s applied to the average  -  tension is  value  46 -  f o r the fowl  obtained.  This  then approximately  amount i s i n l i n e w i t h  40 g/cm  broiler  tension  control  values. The calcium  strips  4 f o r fowl. in  tension  release  data  f o r c o n t r o l and 10  a r e shown i n F i g u r e  In both  cases,  the e x t r a c e l l u l a r b u f f e r  M  3 f o r b r o i l e r s and F i g u r e  t h e p r e s e n c e o f 10  M calcium  caused  increase i n  a significant  -4 the  rate of tension  M calcium of  caused  tension  ficant  release.  a slight  decline.  and f o w l  60 p e r c e n t .  animals i s l e s s l a b i l e  older et  poultry  i n rate a  signi-  of tension  A t 12 h o u r s  c o n t r o l s had d e c l i n e d  This  difference that  t o 40  c o n t r o l s had  i n tension  release  the Z-line i n older  than the Z - l i n e i n younger animals  T h i s may f u r t h e r r e l a t e t o t h e e s t a b l i s h e d are l e s s tender than b r o i l e r  fact  age p o u l t r y  (Goll,  that (May  ajL., 1962; Larmond e t a l . , 1 9 7 1 ) . The  as  produced  whereas t h e f o w l  may be r e l a t e d t o t h e o b s e r v a t i o n  1970).  i n fowl  control strips.  the b r o i l e r  o f t h e maximum t e n s i o n , to only  a n d 10  i s an o b v i o u s d i f f e r e n c e i n t h e r a t e  post-maximum t e n s i o n ,  declined  10  M was s i m i l a r t o t h e c o n t r o l .  d e c l i n e between b r o i l e r  percent  muscle,  but non-significant increase  The 10""'* M l e v e l  e f f e c t b u t 10 There  In b r o i l e r  -7  e f f e c t o f calcium  on t e n s i o n  development i s n o t  c l e a r c u t a s i t s e f f e c t on t h e r a t e o f t e n s i o n  None o f t h e l e v e l s t e s t e d tension  and o n l y  developed  the 10"  release.  a f f e c t e d t h e t i m e t o r e a c h maximum 3  M level  i n b r o i l e r muscle.  decreased  Since  calcium  t h e amount o f t e n s i o n i s responsible f o r  - 47 -  TIME P O S T M A X I M U M T E N S I O N (Hours) F i g u r e 3.  E f f e c t of 10 M c a l c i u m on t e n s i o n d e c l i n e i n b r o i l e r P. major muscle« C i r c l e s and b a r s are means ± 1 standard e r r o r .  - 48 -  F i g u r e 4.  E f f e c t o f 10 M c a l c i u m on t e n s i o n d e c l i n e i n fov;l major muscle. C i r c l e s and bars are means + 1 standard e r r o r .  -  contraction the  in vivo  49  -  (Hasselbach,  196 4 ) , one  sarcolemma remains impermeable  d u r i n g most o f  the  must assume  to e x t r a c e l l u l a r  pre-rigor period.  The  observed  that  calcium decrease  _3 in  the  amount o f  calcium  tension developed  suggests that  a critical  i n the  presence of  concentration  may  r e a c h e d o r e x c e e d e d t h u s p r o m o t i n g a more r a p i d of the that  10"  muscle the  calcium  i n t o the muscle.  M calcium  3  and  l o s s of  that  developed represented and  l o s s of  These  ability  authors  and  a balance  to maintain  isolated  f r o m r a b b i t m u s c l e and plete  B u s c h e t a l . (1972  a calcium  isometric tension  have  stimulated  been  found  i n r a b b i t psoas  t h a t t h e maximum  between t e n s i o n  a "calcium  b)  process  t e n s i o n a t any  M  penetration  reduced t e n s i o n development  suggested  10  caused  tension  development particular  activated sarcoplasmic  com-  Z - l i n e removal from r a b b i t muscle m y o f i b r i l s i n the  pre-  at  least  concentration  10  M  calcium.  i s i n accord  with  its ability  factor"  to e f f e c t  sence of  demonstrated  time.  This  the  critical  calcium  tension release  findings  _3  which marked  show t h a t t h e increase  not  differ  the  role  Davey and  muscle  of  calcium  Gilbert  calcium  (1969) and  could occur  controls.  case,  to  a  the  been p r o v i d e d  on by  Haga et. a l ,  e x t r a c t i o n of  s i n c e the  sequester  does  data  s t r u c t u r a l weakening  r i g o r mortis  its ability  Further  a l . (1966) .  i o n s promoted  In t h i s after  Haga e t  causes  10""'* M c a l c i u m  i n postmortem m u s c l e has  that calcium  loses  M  i n tension release while  from muscle.  reticulum  10  s u b s t a n t i a l l y from the  (1966) f o u n d actin  presence of  calcium  within  sarcoplasmic at this  time.  - 50 Davey and G i l b e r t (1969) suggested that calcium was for the weakening of muscle structure since EDTA was to s t a b i l i z e muscle f i n e structure during aging.  necessary found  These  findings are consistent with the enhanced tension release i n _3  the presence of 10  M  calcium.  The events which are involved i n loss of isometric tension 1968)  (resolution of rigor) have been categorized  as loss of Z-line structure which leads to  (Gqll,  eventual  rupture of the bonds between the I - Z filaments, and weakening of the actin-myosin i n t e r a c t i o n . Loss of Z-line structure has been demonstrated by several workers using muscle from d i f f e r e n t sources (Stromer and G o l l , 1967, e t a l . , 1970 chicken).  rabbit and porcine;  beef;  Henderson  Takahaski, et a l . , 1967,  In most cases, however, t h i s loss was  demonstrated  by blendorizing aged muscle pieces and examining the fragmented myofibrils.  I t i s extremely d i f f i c u l t , using t h i s technique,  to determine i f the r e s o l u t i o n of r i g o r i s due to breaks at the I - Z junction or loss of Z-line structure.  However, i t  should be noted that loss of Z-line structure has also been demonstrated i n s i t u ,(Henderson et a l . , 1970). Sayre (1969) found that the Z-line i n chicken muscle, aged for 24 hours, was  s t i l l intact.  Upon blendorizing, the  muscle appeared to fragment i n the I-band region and not A-band or Z-line regions.  the  These r e s u l t s are i n agreement with  the r e s u l t s of Fukazawa et a l . (1963) who  found that breaks i n  myofibrils always took place i n the I-band region.  These data  combined with the data of Takahaski et a l . (1967) suggest that  - 51 resolution of r i g o r and tension release, i n poultry muscle, may  be due  to weakening of the muscle structure at or near  I - Z junction.  If t h i s junction i s s t r u c t u a l l y weakened,  then fragmentation  procedures for m y o f i b r i l l a r preparation  would rupture these weakened areas allowing Z-line material to d i f f u s e away.  This would give the appearance of Z-line  d i s i n t e g r a t i o n during postmortem storage. Busch et a l . (1972 sence of l O "  3  a, b) have shown that the pre-  n EDTA or EGTA (calcium chelators) i n the e x t r a -  c e l l u l a r buffer did not i n t e r f e r e with tension development i n rabbit or porcine muscle.  They d i d , however, prevent  the  release of tension for up to 48 hours post-maximum tension i n d i c a t i n g that calcium had been successfully removed from i t s role i n stimulating tension release. The above findings were not observed i n b r o i l e r muscle.  A study of the e f f e c t s of magnesium (necessary i n  contraction process as well as calcium), EDTA and equimolar combinations of calcium-EDTA and magnesium-EDTA on tension development and release i s presented 5.  i n Table IV and Figure  The presence of the above materials i n the e x t r a c e l l u l a r  buffer did not s u b s t a n t i a l l y a l t e r the time to reach maximum tension, further suggesting that the sarcolemma remains v i r t u a l l y impermeable to e x t r a c e l l u l a r materials i n early postmortem muscle.  EDTA and equimolar concentrations of EDTA  and calcium or magnesium s i g n i f i c a n t l y lower the amount of  - 52 -  Figure  5.  E f f e c t o f 1 0 " M magnesium, EDTA a n d c a l c i u m - E D T A on t e n s i o n d e c l i n e i n b r o i l e r P_j_ m a j o r m u s c l e . 3  - 53  TABLE IV. MEANS AND STANDARD ERRORS OF TIME AND TENSION DEVELOPMENT FOR STRIPS OF BROILER Pj. MAJOR MUSCLE IN PHOSPHATE BUFFER AND BUFFER CONTAINING H g , EDTA, C a + EDTA AND Mg + EDTA. TT  + +  ++  Treatment  Time, hr  Tension, g/cm'  5.74 + 0.76  Control (n=ll)  51.25  + 2.36  10" M Mg (n=5)  6.48 + 1.21 (6.44 + 1.13)  10" M EDTA (n=5)  4.70 + 0.96 1.27) (5.39  38,38 + 1.17* (50,12 + 3.79)  4.65 + 0.96  32.57 + 3.73*  3  3  10" M  Ca  3  +  10M (n=5) 3  (6.18  EDTA  10" M M g 3  + +  ++  l  10 M EDTA (n=3)  + 1.48)  a  41.62 + 4.81 (53.12 + 3.79)  (49.22 + 3.97)  4.56 + 0.95  32.90 + 0.95*  (5.77 + 0.89)  (56.14 + 5.40) mmm  * S i g n i f i c a n t l y d i f f e r e n t from control (p<0.05) a  Values within parentheses are averages f o r control s t r i p s run simultaneously with the various treatment s t r i p s and used i n the paired comparison analyses.  tension developed.  Magnesium tended to lower tension somewhat  but not s i g n i f i c a n t l y from control values. The most unexpected finding i n t h i s study was the e f f e c t of these materials on the rate of tension release.  EDTA,  which prevents tension release i n porcine and rabbit muscles,, stimulates tension release i n b r o i l e r P_j_ major muscle.  When  equimolar concentrations of calcium or magnesium were added fco  b u f f e r c o n t a i n i n g 10" on t e n s i o n r e l e a s e  J  M EDTA an a d d i t i v e e f f e c t was observed  (Figure 5 ) ,  Only the r e l e a s e data f o r  calcium-EDTA i s shown because the magnesium-EDTA data were v i r t u a l l y the same.  The r e l e a s e data  f o r s t r i p s run i n  magnesium c o n t a i n i n g b u f f e r , i f superimposed on the c a l c i u m data  i n F i g u r e 3, are again  i d e n t i c a l to calcium.  The r o l e  of magnesium i n t e n s i o n r e l e a s e , though not v e r i f i e d , i s p r o bably act  somewhat d i f f e r e n t than t h a t of c a l c i u m .  Magnesium i o n s  as a p l a s t i c i z e r i n muscle a l l o w i n g a c t i n and myosin t o  s l i p p a s s i v e l y past each o t h e r .  I t i s therefore possible,  t h a t the magnesium s t i m u l a t e s the d i s s o c i a t i o n o f actomyosin r e s u l t i n g i n an i n c r e a s e d r a t e o f t e n s i o n d e c l i n e . The  n a t u r e of the a d d i t i v e e f f e c t s o f calcium-EDTA  and magnesium-EDTA i s not  known.  both e f f e c t i v e l y c h e l a t e d by EDTA with calcium nesium.  C a l c i u m and magnesium a r e ( B l a e d e l and Meloche, 1963)  forming a s l i g h t l y more s t a b l e complex than mag-  One p o s s i b l e e x p l a n a t i o n  f o r the a d d i t i v e e f f e c t on  t e n s i o n r e l e a s e may be t h a t the complex o f EDTA-Ca o r EDTA-Mg, which i n t h i s form i s uncharged, may pass through the sarcolemma with  g r e a t e r ease than e i t h e r o f the i o n s when p r e s e n t  larly.  Once i n s i d e the c e l l ,  i r o n , which d i s p l a c e c a l c i u m  other  i o n s such as z i n c ,  singulead,  and magnesium i n an EDTA complex,  c o u l d b r i n g about a r e l e a s e o f c a l c i u m  and magnesium i o n s  thereby s t i m u l a t i n g a more r a p i d r a t e o f t e n s i o n r e l e a s e . explanation  This  i s p u r e l y s p e c u l a t i v e and a thorough examination o f  muscle s t r i p s , t r e a t e d i n the above manner, i s warranted a t the  - 55 electron microscopic l e v e l .  This study i s of p a r t i c u l a r impor-  tance i n view of the unique transverse tubular system which has been demonstrated i n chicken pectoral muscle  (Mendell,  1971) . The E f f e c t of Processing Techniques on Tension Pattern and Tenderness Processing techniques have been shown to adversely a f f e c t poultry tenderness by several workers (Shannon et a l . 1957;  Pool et al.,1959; Wise and Stadelman, 1959,  1961).  view of these f i n d i n g s , various processing techniques,  In  singu-  l a r l y and i n combination, were applied to b r o i l e r s postmortem i n order to study tension parameters i n r e l a t i o n to tenderness (shear value). The e f f e c t s of the various treatments on tension parameters from the two d i f f e r e n t l e v e l s of P^ major muscle are shown i n Table V.  Only the combination treatment of pre-  slaughter struggle, scalding and plucking produced a s i g n i f i cant difference i n tension parameters between outside and inside breast muscle. Wise and Stadelman (1959) found that shear  was  s i g n i f i c a n t l y r e l a t e d to the depth at which samples were taken, to the temperature of the scald water and to the duration of scald.  Shear value were not determined for d i f f e r e n t muscle  depths, but based on the s i g n i f i c a n t decrease i n time to maximum  tension, i t i s possible that treatment 5 could r e s u l t i n  s i g n i f i c a n t differences between inner and outer l a y e r s .  - 56 TABLE V . MEANS AND STANDARD ERRORS OF TENSION PARAMETERS FOR INNER AND OUTER STRIPS OF BROILER P*. M A J O R MUSCLE SUBJECTED TO VARIOUS POST-SLAUGHTER TREATMENTS,  Treatment  1  2  3  4  5  3  Time, hr  Tension,  g/cm  2  Tension release b a t one hour, %  outer  3.9 + 0.6  33.1 + 1.7  21.3 + 3.5  inner  3.5 + 0.6  35.6 + 1.7  26.1 + 3.7  outer  2.7 + 0.5  67.7 + 6.7  25.0 + 1.7  inner  3.0 + 0.4  56.1 + 2.7  20.7 + 1.7  outer  2.7 + 0.5  43.9 + 4.4  21.4 + 5.1  inner  3.1 + 0.4  53.4 + 3.7  19.0 + 3.7  outer  2.2 + 0.4  41.8 + 4.1  28.1 + 3.2  inner  2.1 + 0.3  47.0 + 3.9  28.4 + 3.2  outer  1.9 + 0.4*  65.6 +10.5  29.5 + 5.1*  3.0 + 0.3  55.0 + 9.6  16.3 + 2.5  inner  t r e a t m e n t s NO.  1 : Control - r e s t r i c t e d struggle 2 : S t r u g g l e , pluck  (n=15)  (n=5)  3 : Restricted struggle, scald 4 : Struggle,  s c a l d (n=7)  5 : Struggle,  s c a l d , pluck  * S i g n i f i c a n t l y d i f f e r e n t from i n n e r s t r i p s  (n=6)  (n=8) (p<0.05)  k Amount o f t e n s i o n r e l e a s e d a t one hour p o s t maximum t e n s i o n .  - 57 The data f o r inner and outer s t r i p s combined and the shear values are presented i n Table VI. basis, only treatment 4 produced to maximum tension.  On an o v e r a l l  a s i g n i f i c a n t change i n time  Treatments 2, 4 and 5 s i g n i f i c a n t l y  increased the amount of tension developed compared to the control.  The shear values indicate an additive response to the  various processing techniques.  The procedures which seem to  have the greatest a f f e c t on the tenderness are free struggle at slaughter and scalding. TABLE VI. MEANS AND STANDARD ERRORS OF POOLED TENSION PARAMETERS AND SHEAR VALUE DATA FOR INNER AND OUTER STRIPS OF BROILER P. MAJOR MUSCLE SUBJECTED TO VARIOUS POST-SLAUGHTER TREATMENTS.  Treatment  a  3.  2  Tension, g/cm  1  3.7 + 0.6  36.8 + 1.5  23.7 + 3.3  4.5 + 0.3  2  2.8 + 0.4  61.9 + 4.6**  22.8 + 2.3  5.6 + 0.3*  3  2.9 + 0.5  48.6 + 3.7**  20.2 + 4.3  6.3 + 0.6*  4  2.2 + 0.3* 44.4 + 3.9  28.3 + 2.9  9.0 + 0.5**  5  2.5 + 0.6  22.9 + 3.5  10.5 + 0.9**  59.8 + 6.2**  Tension Release at one hour,%  b  Time,hr  Shear Value,lbs  For treatment breakdown see Table V.  k Amount of tension released at one hour post maximum tension. * S i g n i f i c a n t l y d i f f e r e n t from control (p < 0.05) ** P < 0.01 The tenderness data are i n accord with results found by other workers (Shannon et a l . , 1957; Pool et a l . , 1959; Wise and  - 58 -  Stadelman, 1959, 1961).  The data also show that tension r e -  lease does not c o r r e l a t e with shear value.  A l l treatments  showed f i r s t hour tension release values i n the range of 20 28 percent and there were no s i g n i f i c a n t differences between treatments  and c o n t r o l s . The  treatments  f a c t that maximum toughening was observed f o r  i n v o l v i n g scalding r e l a t e s to the findings of the  temperature studies discussed e a r l i e r .  The tension values  did not approach those found at 50 and 60°C because the outer layers of breast muscle, which may reach these temperatures, had a p a r t i a l l y cooked appearance and were discarded. I t was noted during shear measurement that a sharp break i n shear peak occurred after the blade had the outer layer of the breast muscle demonstrating  passed through the existence  of a toughened s h e l l around the outer areas of breast muscle probably caused by high temperature-low pH denaturation. Segregation of B r o i l e r Controls on the Basis of Time to Reach Maximum Tension I t was noted during the course of the tension e x p e r i ments that muscle s t r i p s i n c o n t r o l buffer varied considerably i n rate of tension release.  There was a d e f i n i t e pattern be-  tween time to reach maximum tension and the proportion of tension released within 12 hours post-maximum tension. control s t r i p s from 35 birds were segregated  The data f o r  into three groups,  on the basis of time required to reach maximum tension.  The  - 59 -  means and standard deviations f o r the tension parameters of these three groups and f o r the pooled birds are presented i n Table V I I . TABLE VII. TIME AND TENSION MEANS .AND STANDARD DEVIATIONS FOR THREE BROILER GROUPS SEGREGATED ON THE BASIS OF TIME TO REACH MAXIMUM TENSION. Group I  a  (n=10)  II III  (n=15) (n=10)  Pooled (n=35) a  sd  Time, min  b  sd  T e n s i o n , g/cm"^  147.2**  30.3  47.74  234.7  40.3  46.09  8.94  473.1**  74.1  51.88  12.32 •  48.50  12.60  299.3  134.7  15.65  Tension maximum f o r the three groups was observed between: Group I Group II  0 - 3 hours postmortem -  Group I I I -  3 - 6 hours postmortem } 6 hours postmortem  sd Standard Deviation ** S i g n i f i c a n t l y d i f f e r e n t from Group II (p<0.01) Segregation on the above time basis gave three groups of birds which d i d not d i f f e r with regard to amount of tension developed but d i f f e r e d s i g n i f i c a n t l y from each other on the basis of the time required to reach maximum tension.  The ten-  sion release data f o r the three groups are presented i n Figure 6 and the regression l i n e parameters f o r each Group are presented  -  Figure  6,  60  Isometric tension d e c l i n e i n three groups of b r o i l e r s separated on the b a s i s of time r e q u i r e d to reach maximum t e n s i o n .  - 61 -  in Table VIII.  I t can be seen that the Group I b i r d s , which  reached maximum tension i n less than 3 hours, released tension much more r a p i d l y than did Groups II or I I I b i r d s .  Statistical  t-test analysis of difference of means showed that Group I birds released tension at a faster rate (p<0.01) than Groups II and III b i r d s . other  Groups II and I I I d i f f e r e d s i g n i f i c a n t l y from each  (p<0,05) only during the f i r s t 5 hours post-maximum tension.  TABLE VIII. REGRESSION LINE PARAMETERS FOR TENSION RELEASE (INDEPENDENT VARIABLE) VERSUS TIME (DEPENDENT VARIABLE) FROM THREE GROUPS OF BROILER CONTROLS AND FOR THE POOLED GROUPS. Group  R  Intercept  Slope  I (n=10)  80.10  -5.33  0.711  II (n=15)  92.60  -4.56  0.776  III (n=10)  97.66  -4.54  0.849  Pooled (n=35)  90.47  -4.77  0.642  a See The  a  2  footnote for Table VII. tension pattern f o r Group I birds i s almost i d e n t i c a l to  _3 . calcium was added pattern observed when 10 M to the buffer. I t i s possible that the rapid onset of r i g o r ,  the release  as demonstrated by the short time to maximum tension,  stimu-  lated a more rapid or greater release of calcium from the sarcoplasmic  reticulum once r i g o r had occurred.  The difference i n release of tension was obvious at 1 hour post-maximum tension and i t appeared possible to p r e d i c t ,  - 62 with some degree of accuracy, the 12 hour release from the 1 hour value.  In order to test t h i s hypothesis, the 1 hour  release values f o r each group were, correlated with the values for subsequent hourly values.  The groups were analyzed i n d i -  v i d u a l l y and then the data were pooled and a general r e l a t i o n ship was established. The r e s u l t s of these analyses are presented i n Table IX.  The data show that, f o r Group I b i r d s ,  T7-J3LE IX. SIMPLE CORRELATIONS OF ONE HOUR TENSION RELEASE VALUES WITH SUBSEQUENT HOURLY VALUES FROM THREE GROUPS OF CONTROL BROILERS AND FOR THE POOLED DATA FROM THE THREE GROUPS. Time, hr  Group I (n=10)  a  Group II (n=15  Group III (n=10)  Pooled (n=35)  2  .958**  .825**  .564*  .950**  4  .904**  .596*  .475  .850**  6  .838**  .456  .480  .789**  8  .859**  .474  .224  .775**  10  .359**  .367  -.006  .731**  12  .901**  .306  -.088  .699**  See footnote f o r Table V I I . * p<0.05 ** p<0.01 there i s a s i g n i f i c a n t c o r r e l a t i o n  (p<0.01) between 1 hour ten-  sion release and subsequent hourly values up to 12 hours postmaximum tension.  The r e l a t i o n s h i p i s less pronounced f o r Groups  II and I I I . This i s probably due to the larger standard deviations  - 63 in time to maximum tension as demonstrated i n Table VII. The c o r r e l a t i o n between 1 hour release and subsequent hourly values is significant  (p<0.01) when the data f o r the 35 birds i s pooled.  This shows that one could obtain a reasonably accurate pattern of tension release by measuring only the 1 hour tension release. The data presented i n Table X shew that the r e l a t i o n ships between 2 hour values and subsequent hourly values are generally stronger than f o r the 1 hour data. Groups II and I I I , i n p a r t i c u l a r ,  The r values f o r  are improved considerably  as are the r values f o r the pooled data. TABLE X. SIMPLE CORRELATIONS OF TWO HOUR TENSION RELEASE VALUES WITH SUBSEQUENT HOURLY VALUES FROM THREE GROUPS OF CONTROL BROILERS AND FOR THE POOLED DATA FROM THE THREE GROUPS. Time, hr  Group I (n-10)  a  Group II (n=15)  Group I I I (n=10)  Pooled (n=35)  4  .965**  .914**  .866**  .951**  6  .889**  .818**  .767**  .899**  8  .873**  .828**  .689**  .883**  . 10  .845**  .749**  .506  .841**  12  .828**  .695**  .414  .798**  a See footnote f o r Table VII. * p<0.05 ** p(0.01  -  64  -  T h e Relation Between O n e Hour Tension Release, Tine to Maximum Tension and Shear Value Analyses were performed to e s t a b l i s h i f rate of tension release was  s i g n i f i c a n t l y correlated to the time to reach  maximum tension and i f so to e s t a b l i s h the r e l a t i o n s h i p .  The  data from 1 5 0 s t r i p s were f i t t e d to l i n e a r , logarithmic and hyperbolic models i n order to determine the most suitable r e l a t i o n s h i p for the data. mum  I t was  found that the time to maxi-  tension and 1 hour tension release were l i n e a r l y r e l a t e d .  With percent r e l a t i v e tension  (% RT) as the dependent v a r i a b l e  and time as the independent v a r i a b l e , the following equation for the regression l i n e was n«  150,  R  2  =  .462  obtained: % RT = 6 1 . 7 4 + , 4 0 8 Time,  (p<0.01).  Since tension release was more rapid when time to maximum tension was was  shortest and since 1 hour tension release  s i g n i f i c a n t l y r e l a t e d to release for subsequent hours (up  to 1 2 hours post-maximum tension), i t was  decided to determine  the r e l a t i o n between 1 hour tension release and the tenderness observed i n b r o i l e r s .  eventual  Linear, logarithmic and  hyperbolic models were applied to the data f o r 1 hour tension release and shear values from 1 0 0 b r o i l e r s .  One hour tension  release values ranged from 0 - 4 8 percent and shear values ranged from 2 . 5 to 1 4 . 3 pounds. was  No s i g n i f i c a n t r e l a t i o n s h i p  observed for any of the models studied, suggesting  the tension release observed i n i n d i v i d u a l birds i s not i n d i c a t i v e of tenderness.  that  - 65 deFremery and  Pool  -  (1963) e s t a b l i s h e d t h a t treatments  which a c c e l e r a t e r i g o r m o r t i s  r e s u l t i n increased  (shear value) i n b r o i l e r b r e a s t muscle.  The  toughness  present  data  on  the r e l a t i o n s h i p between shear v a l u e , time to maximum t e n s i o n and  one  hour t e n s i o n r e l e a s e r a i s e s some i n t e r e s t i n g q u e s t i o n s  with regard  t o the r e l a t i o n s h i p between t e n s i o n r e l e a s e i n  b r o i l e r P. major muscle and  tenderness of the muscle.  Birds  which e x h i b i t the most r a p i d r a t e of t e n s i o n development a l s o show the most r a p i d r a t e of d e c l i n e even though, i n most the amount of t e n s i o n developed does not d i f f e r The  cases,  significantly.  r a p i d t e n s i o n development i n d i c a t e s a c c e l e r a t e d r i g o r  which should (1963).  l e a d to toughness a c c o r d i n g  to deFremery and  mortis Pool  T h i s however, i s not the case s i n c e a p o s i t i v e r e l a t i o n -  s h i p e x i s t s between t e n s i o n development and between r e l e a s e and  shear  r e l e a s e and  not  value.  Three p o s s i b l e reasons f o r the l a c k of a s i g n i f i c a n t r e l a t i o n s h i p between shear v a l u e and  tension release  are:  sample e r r o r , the s u i t a b i l i t y o f shear measurement f o r a s s e s s i n g o v e r a l l muscle tenderness and was  the d e t e r m i n a t i o n  done o n l y a t 24 hours postmortem.  mortem time may  of shear  T h i s 24 hour  be long enough t o a l l o w a g r e a t e r  of t e n s i o n i n the Group I I and i n l i n e w i t h Group I b i r d s .  values  post-  release  I I I b i r d s thus b r i n g i n g them more  I t would be of i n t e r e s t to study  the t e n s i l e and break s t r e n g t h parameters o f uncooked muscle i n r e l a t i o n t o t e n s i o n parameters and  to study these parameters a t  a f i x e d time post-maximum t e n s i o n f o r each b i r d .  Perhaps i n  - 66 -  t h i s way a better idea of the r e l a t i o n s h i p between tension release, the resolution of r i g o r mortis and tenderization may be  obtained. On the basis of the present data, one can conclude  that v a r i a t i o n s i n tension release, from b i r d to b i r d , are not i n d i c a t i v e of the tenderness of the i n d i v i d u a l birds at 24 hours postmortem.  The o v e r a l l tension pattern f o r a pooled group of  b r o i l e r s i s , however, i n d i c a t i v e of the observed tenderization process i n b r o i l e r s .  Most tenderization i n P^ major muscle  of b r o i l e r s occurs within a few hours post-rigor and during t h i s period 50 percent or more of the isometric tension i s r e leased.  The tenderization phenomenon i n b r o i l e r s i s much more  rapid than i n pork and beef muscle, which show a slower tension development and decline.  I t may be concluded that the tension  pattern i s i n d i c a t i v e of the tenderization phenomenon of a species but tension patterns f o r i n d i v i d u a l s within a species, may or may not r e l a t e to the actual tenderness of the i n d i v i dual animal or muscle. Epinephrine  Experiments  Preliminary Experiment This experiment was conducted to determine the approximate time when the e f f e c t of epinephrine i n the b r o i l e r s being used.  i n j e c t i o n was maximal  deFremery and Pool  (1963) and Sayre  (1969, 1970) used a pre-slaughter i n j e c t i o n time of 16 hours to  - 67 e f f e c t glycogen depletion i n b r o i l e r s , whereas deFremery (1966b) used 18 hours and Klose et, a l . (1970) 15 hours.  Khan and  Nakaraura (1970) found that the epinephrine e f f e c t was maximal at 12 hours p o s t - i n j e c t i o n .  The data obtained i n t h i s p r e l i m i -  nary study are presented i n Table XI.  The data, though limited  to one b i r d per time, suggest that the maximum e f f e c t of epinephrine occurs between 9 and 12 hours  post-injection.  TABLE XI. TENSION PARAMETERS AND SHEAR VALUES FOR P^. MAJOR MUSCLE FROM BROILERS INJECTED WITH EPINEPHRINE AT VARIOUS TIMES PRE-SLAUGHTER. Tension, g/cm^  Pre-slaughter Injection Time, hr  Time, min  Control  399  54.85  4.06  3  213  41.96  4.15  6  38  94.90  6.58  9  27  157.70  7.01  12  43  96.72  7.40  15  92  99.36  4 .62  18  49  37.93  6.53  The injections  Shear Value, lbs  i n t h i s prelimanary experiment were done  intramuscularly into the P_j_ major muscle.  I t was noted during  subsequent tenderness measurements that shear values f o r muscle near the s i t e of i n j e c t i o n were n e g l i g i b l e while values f o r areas away from the s i t e of i n j e c t i o n were generally higher  - 63 than control b i r d s .  In viev; of t h i s l o c a l i z e d epinephrine  e f f e c t , i n j e c t i o n s f o r the subsequent experiments  were done  intramuscularly into the thigh muscle. Epinephrine Experiment 1 The analysis of variance showed that there was a s i g n i f i c a n t treatment e f f e c t f o r a l l parameters studied (Table XII).  Treatment means and the r e s u l t s of Duncan's new multiple  range test are presented i n  Table XIII.  The tension and time  data show an inverse r e l a t i o n s h i p with maximum tension being developed i n the shortest time.  These values also indicate  the e f f e c t of the epinephrine i n j e c t i o n s was maximal at 8 hours post-injection.  This i s somev/hat e a r l i e r than the 12 hour  value found by Khan and Nakamura  (1970) .  TABLE XII. ANALYSIS OF VARIANCE FOR PARAMETERS STUDIED IN EPINEPHRINE EXPERIMENT 1. Source  df Tension  Mean Squares Time Blood Lactate  Shear Value  Sex  1  2505.7  180.0  0.085**  9.28  Treatment  5  11918.4**  32077.0**  0.044**  9.96*  SxT  5  461.0  7149.4  0.011  1.18  Error  24  682.9  7389.5  0.011  3.23  Total  35  * p<0.05 ** p<0.01  69  TABLE XIII. DUNCAN'S NEW MULTIPLE RANGE TEST ON SIGNIFICANT TREATMENT MEANS FROM EPINEPHRINE EXPERIMENT 1. Post-Injecrtion Slaughter Time, hours Control Tension g/cm Time, min  43.4a*  234.5a  12 49.5a  166.5ab  107,9b  65.4bc  161.4  32.3c  16  119.2b  103.6b  107.3bc  93.5bc  Blood Lactate, mM/lOOml  0.33abc  0.51a  0.45ab  0.26c  0.36bc  0.41ab  Shear Value, lbs  2.6a  3.2ab  5.0bc  5.6c  5.5bc  5.3bc  *Means i n the same row with s i m i l a r superscripts do not d i f f e r s i g n i f i c a n t l y (p<0.05) A s l i g h t increase was found i n blood lactate concent r a t i o n i n birds k i l l e d 2 hours after i n j e c t i o n .  This i s pro-  bably due to the rapid breakdown of glycogen to l a c t i c acid which then d i f f u s e s out of the  muscle into the blood  stream.  The lowest l e v e l of blood lactate was found i n the 8 hour group where tension was maximum and time minimum. Results of shear value analysis were contrary to most findings i n that s i g n i f i c a n t toughening was found instead of a tenderization.  Khan and Nakamura (1970) found that muscle from  b r o i l e r s , injected with epinephrine 2 or 6 hours before slaughter , was more tender than control muscle after 24 hours of postmortem  - 70 storage.  The present data shows no s i g n i f i c a n t difference  between control and 2 hour samples and s i g n i f i c a n t  toughening  in 4, 8, 12 and 16 hour samples. deFremery and Pool (1963) and deFremery  (1966b)found  that elimination of postmortem g l y c o l y s i s by epinephrine i n j e c tions gave chicken meat that was tender immediately ter.  post-slaugh-  These authors, however, did not compare the e f f e c t on  tenderness a f t e r 24 hours of aging. In order to determine the r e l a t i o n s h i p between tension, time, blood lactate and shear value, a simple c o r r e l a t i o n analysis was run on the data.  The c o r r e l a t i o n analysis i s presented  i n Table XIV. TABLE XIV. CORRELATION MATRIX FOR PARAMETERS STUDIED IN EPINEPHRINE EXPERIMENT 1. Tension  Time  Time  .711**  Blood Lactate  .315  .196  Shear  .611**  .454**  Blood Lactate  .331*  *p<0.05 ** p<0.01 As expected, the regression analysis showed s i g n i f i cant relationships between the tension developed, the time to maximum tension and shear values.  Blood lactate l e v e l  s i g n i f i c a n t l y related to shear value (p<0.05).  was  - 71 The  a n a l y s i s of v a r i a n c e  (Table XII)  showed t h a t a l l  parameters, except b l o o d l a c t a t e , f a i l e d t o show a sex e f f e c t .  The male b r o i l e r s , w e r e s i g n i f i c a n t l y h i g h e r  females w i t h c o n t r o l l e v e l s b e i n g 0.44 respectively.  The  2 hour treatments versus 0,39  significant  e f f e c t was  and  0.32  m Holes/lOOmls  p a r t i c u l a r i l y n o t i c e a b l e i n the  where males averaged  0,63  m Holes/lOOmls  m Moles/10Omls f o r females.  On  the b a s i s of experiment, i t was  d e c i d e d to r e p e a t  the experiment and i n a d d i t i o n , c o l l e c t data f o r muscle glycogen,  than  pH  and  lactate.  The  times of sampling  ATP,  were changed  somewhat t o t r y to b e t t e r d e f i n e the time of maximal e p i n e p h r i n e effect. E p i n e p h r i n e Experiment 2 The treatment  a n a l y s i s of variance i s presented  means and the r e s u l t of Duncan's new  t e s t are presented i n T a b l e XVI.  As  i n T a b l e XV  and  m u l t i p l e range  i n Experiment 1, the 8  hour p r e - s l a u g h t e r i n j e c t i o n time gave the maximal e f f e c t . Howe v e r , i n a l l c a s e s , t h e r e were no s i g n i f i c a n t d i f f e r e n c e s between 8, 10 and  12 hour p r e - s l a u g h t e r i n j e c t i o n s .  I t v/ould appear  from  t h i s t h a t the time of maximum e f f e c t extends over at l e a s t a 4 hour range and t h a t the number o f b i r d s used i n the t e s t not s u f f i c i e n t t o e s t a b l i s h a more e x a c t Muscle glycogen e p i n e p h r i n e e f f e c t , was  was  time.  l e v e l , which i n d i c a t e s the e x t e n t of the  minimum a t 8 hours and  s l i g h t l y higher at  TABLE XV.  ANALYSIS OF VARIANCE OF PARAMETERS  Source  df  STUDIED IN EPINEPHRINE EXPERIMENT  Mean Squares Tension  Time  ATP  953 .3  9184.0  24.1*  13.3**  0.006  12.8*  10.7**  0.015  34.0 0.06 24.6** ** ** 539.9 0.71 9.7** 124.5  Glycogen  Blood Lactate  Sex  1  Treatment  5  SxT  5  692.3  682.1  1.9  3.8  0.027  Error  24  1122.2  4070.6  4.7  1.1  0.033  Total  35  * p<0.05 ** p<0.01  2.  7920.8** 43361.0**  Tissue Lactate  66.2  pH  Shear Value  0.09  2.2  0.07  2.2  - 73 TABLE XVI. DUNCAN'S NEW MULTIPLE RANGE TEST ON SIGNIFICANT TREATMENT MEANS FROM EPINEPHRINE EXPERIMENT 2. Post-Injection Slauahter Tine, hours  Tension, g/crrr^ Time,  rain  40.19a* 265.2  4  8  78.47a  128.35b  87.5a  45.2a  10  12  123.15b 127.20b 46.1a  50.5a  24 76.44a 119.0a  ATP u Moles/g  5.79ab  5.56ab  3.67b  3.76b  3.10b  6.76a  Glycogen, mg/g  3.38  1.13a  0.27a  0.45a  0.67a  1.52a  Slaughter pH  6.04a  6.19a  6.77b  6.79b  6,62b  6.11a  Tissue Lactate, /u Moles/g Shear Value, lbs  45.0a  4.57a  45.2a  4.69a  28.2b  6.51b  24.6b  7.27b  30.8b  6.84b  44.2a  4.53a  *Means i n the same row with s i m i l a r superscripts do not d i f f e r s i g n i f i c a n t l y (p<0.05) 10 and 12 hours and by 24 hours had recovered to one half of the control l e v e l .  I t i s of i n t e r e s t to note that the ATP l e v e l r e -  mained quite high throughout the e n t i r e time period studied. Since A.TP i s needed f o r shortening, t h i s observation i s consistent with the development of considerable tension i n the 8, 10 and 12 hour muscle s t r i p s .  There was very l i t t l e glycogen  pre-  sent i n the muscles at these time periods, therefore, l i t t l e  - 74  postmortem g l y c o l y s i s .  Consequently,  the time to maximum ten-  i  sion was very short even though tension was high. The pH and tissue lactate values follow a pattern •i  similar to glycogen and time to maximum tension.  The c o n t r o l ,  4 and 24 hour l e v e l s were similar and lactate dropped while pH rose i n the 8, 10 and 12 hour samples. The r e l a t i o n s h i p between shear values and the s i g n i f i c a n t treatment parameters i s shown i n Figures 7, 8 and 9. Shear value has a p o s i t i v e r e l a t i o n s h i p with tension and pH and negative with glycogen, time to maximum tension, tissue lactate and ATP. I t i s of i n t e r e s t to note that no s i g n i f i c a n t blood lactate e f f e c t was obtained i n t h i s  experiment.  A simple c o r r e l a t i o n analysis was performed data from the second experiment presented i n Table XVII.  on the  and the c o r r e l a t i o n matrix i s  I t can be seen that there are s i g n i -  f i c a n t c o r r e l a t i o n s between a l l parameters except blood l a c t a t e . I t i s d i f f i c u l t to explain the difference between blood lactate values from experiments  1 and 2.  The analysis of variance (Table XV) shows that, s i m i l a r to experiment and time.  1, there was no sex difference for tension  Sex differences were observed f o r glycogen, ATP and  shear value.  The s i g n i f i c a n t sex e f f e c t f o r shear value was  not observed i n experiment  1, however, shear values for females  were consistently higher than f o r males.  The shear value average  for control males was 4.4 pounds versus 4.8 pounds for females. In the 10 hour group where shear values were maximum, the males averaged  5.8 pounds to 8.8 pounds f o r the females.  -  Figure  7.  75  -  R e l a t i o n betv/een t e n s i o n , time to maximum t e n s i o n and shear v a l u e i n major muscle from e p i n e phrine t r e a t e d b r o i l e r s .  -  Figure  8.  76  -  R e l a t i o n between muscle glycogen and ATP l e v e l s and shear v a l u e i n major from e p i n e p h r i n e t r e a t e d  -  6 n! ° 0  1  4  POST  F i g u r e 9.  *  8  I N J E C T I O N  77  -  1  12  1  1  16  S L A U G H T E R  20 TIME  1 24  (Hours)  R e l a t i o n betv/een pH, muscle l a c t a t e and shear v a l u e i n P. major muscle from e p i n e p h r i n e t r e a t e d b r o i l e r s .  TABLE XVII.  CORRELATION MATRIX FOR PARAMETERS STUDIED IN EPINEPHRINE EXPERIMENT 2. Tension  Time  ATP  Glycogen  pH  Blood Lactate  Time  .781**  ATP  .705**  .587**  Glycogen  .542**  .689**  .437**  pH  .731**  .598**  .631**  .475*  .068  .010  .100  .115  .049  .610**  .466**  .479**  ,404*  .816** .149  .762**  .570**  .826**  .454**  .770** .020  Blood Tissue  Lactate Lactate  Shear Value  * p<0.05 ** p<0.01  Tissue Lactate  .647**  - 79 The greatest sex difference i n glycogen l e v e l s found i n the control birds where values of 6.07  and 1.70  tissue were found f o r males and females respectively.  was mg/g  In spite  of t h i s great difference i n control l e v e l s , both males and females showed minimum glycogen levels (0.32 and 0.23mg/g tissue respectively) at 8 hours.  The ATP l e v e l s for females  remained lower than f o r males throughout a l l of the treatment times.  Both l e v e l s d i d , however, approach equality at 8 hours  where the males averaged 3.8 and females 3.5 u Moles/g t i s s u e . After 8 hours the ATP l e v e l i n males began r i s i n g while the l e v e l i n females continued to drop reaching a minimum of 1.6 p Moles/g tissue at 12 hours. In general the sex differences seem to be related to differences i n l e v e l s present i n control b i r d s . as i f females may do males.  I t also appears  react somewhat d i f f e r e n t l y to epinephrine than  This i s p a r t i c u l a r l y noticeable i n the ATP and ten-  derness data. The data from a l l the epinephrine experiments, i n cluding the preliminary experiment, show that depletion of glycogen induces toughness i n b r o i l e r s examined at 24 hours postmortem.  This i s i n contrast to the data of Khan and  Kakamura (19 70) but the r e s u l t s obtained f o r the various parameters show why  toughness may be expected.  Sayre (1969) found that shear values from chickens, injected pre-slaughter with epinephrine, did not change appre-  - S o -  c i a b l y during the aging period.  He suggested that t h i s muscle  becomes inextensible quickly due to lack of ATP, but due to the high pH and possible i n t e g r i t y of the endoplasmic reticulum, there may be no great stimulus f o r contraction or tension development.  The present data shows that t h i s i s not so.  There i s ample ATP remaining i n the muscle, even when glycogen has been e s s e n t i a l l y depleted, and considerable tension i s developed.  The fact that the muscle becomes inextensible  quickly i s v e r i f i e d by the present data which demonstrated that the time required to reach maximum tension decreased to 45 minutes when the epinephrine e f f e c t was maximal.  The fact that the  epinephrine injected birds develop a great deal of tension postmortem may explain why the toughening was observed.  This a b i l i t y  to develop tension may also explain the observed tenderness i f epinephrine treated birds are cooked without aging.  Marsh and  Leet (1966) found i n beef neck muscle that 20 percent contract i o n was associated with a " f a i r " degree of tenderness; between 20 - 40 percent contraction was associated with a rapid decrease i n tenderness to a minimum and between 40 - 60 percent contraction gave increased tenderness approximating that observed at 20 percent contraction. /vlthough most workers have found an increase i n tenderness i n epinephrine treated b i r d s , Klose et_ a l . (1970) d i d not f i n d the expected lower shear values.  They questioned  the a b i l i t y of epinephrine to deplete muscle glycogen but Cori  - B l and Cori (1928) have shown that under proper conditions, t h i s technique depletes muscle glycogen p r i o r to slaughter.  Further-  more, the present data and that of Khan and Makamura (1970) show c l e a r l y that glycogen l e v e l s are depleted by  pre-slaughter  epinephrine i n j e c t i o n s . The epinephrine  experiments were carried out to study  the response of the b r o i l e r under a severe stress s i t u a t i o n . An apparent adverse reaction, i n the form of tougher muscle, resulted from these studies and because females appeared to react more adversely than males a l l subsequent stress experiments except for the "commercial s t r e s s " , were applied to females only. Stress Experiments The r e s u l t s from the study on b r o i l e r s , exposed to antemortem commercial handling,(Table  XVIII) show that there  are no s i g n i f i c a n t differences between "stressed" and control birds for any of the parameters studied except time required to reach maximum tension. The f i c a n t l y longer  signi-  (p<0.05) than t h e i r control counterparts  reach maximum tension. difference was  "stressed" females required  to  Though males showed the same trend, the  not s i g n i f i c a n t .  On a combined sex basis  "stressed" birds were s i g n i f i c a n t l y d i f f e r e n t from controls (p<0.05).  For the most part, the differences between control  and "stressed" males are negligable.  Although only the time  difference i s s i g n i f i c a n t i n the females, most other parameters  TABLE XVIII. MEANS AND STANDARD ERRORS OF PARAMETERS OF P. MAJOR MUSCLE FROM BROILERS IN THE COMMERCIAL STRESS EXPERIMENT Female Stress Time, hr  4.81+0.7*  Male Control  3.02+0.7  44.3 +3.4  35.3 +2.8  Shear V a l u e , lbs  4.60+0.4  4.05+0.3  ATP, u Moles/g  7.98+0.5  pH  5.99+0.05  Tension, g/cm  Stress  6.25+1.2 39.8 + 1.3  Combined Sexes Control  Stress  Control  4.49+0.4  5.53+0.7*  3.76+0.4  40.7 +5.3  42.0 +1.8  38.0 +3.0  4.05+0.3  4.88+0.3  4.33+0.3  3.97+0.2  5.92+0.8  8.48+0.9  8.46+0.9  8.23+0.4  7.19+0.7  5.77+0.09  5.92+0.07  5.93+0.05  5.95+0.04  5.85+0.06  2  * S i g n i f i c a n t l y d i f f e r e n t from corresponding c o n t r o l  (p<0.05)  approached s i g n i f i c a n c e at the p<0.0 5 l e v e l .  The most s t r i k i n g  of these differences i s the difference i n muscle ATP l e v e l s . These data suggest a possible sex related difference i n r e s i s tance or adaptation to commercial handling The  conditions.  r e s u l t s for female b r o i l e r s subjected to a thermal  stress p r i o r to slaughter  (Table XIX) suggest that the birds were  affected by the heat treatment and that the e f f e c t was i n t e n s i f i e d by allowing the birds to struggle f r e e l y during The  slaughter.  time to maximum tension was not shortened s i g n i f i c a n t l y  by the heat treatment alone but the free struggle at slaughter apparently  accelerated g l y c o l y s i s so that the time d i f f e r e n c e  v/as s i g n i f i c a n t  (p<0,05).  The amount of tension was increased  s i g n i f i c a n t l y by both "stress" treatments.  The s i g n i f i c a n t  differences between " s t r e s 5 e d " - f r e e struggle birds and control birds for time to maximum tension and 1 hour tension release are consistent with data reported e a r l i e r on the e f f e c t s of commercial processing techniques  on tension parameters.  They  also confirm the lack of r e l a t i o n s h i p between tension release and tenderness within the range of parameters studied. The r e s u l t s for the "cold stress" experiment are presented  i n Table XX.  there v/as a lengthening tension.  As i n the commercial stress experiment, of the time required to reach maximum  This e f f e c t was accompanied by a tendency for tension,  shear value, ATP and glycogen concentration to be high and hexose monophosphate to be lower i n "cold-stressed" b i r d s .  - 34 -  TABLE XIX. MEANS AND STANDARD ERRORS OF PARAMETERS OF P^ MAJOR MUSCLE FROM BROILERS IN THE HEAT STRESS EXPERIMENT. Control, RS  Parameter Time, hr  a  4.77 + 1.1  Tension, g/cm^  38.2 ;t  1  .7  Stres!3, RS  Stre:S 3 ,  3.12 + 0.6  2.14 + 0.2*  48.1  + 4.1*  S  b  + 4.2**  52.6  Shear Value, lbs  5.06 + 0.4  5.50 + 0.5  5.10 + 0.4  ATP, u Moles/g  7.26 + 1.0  6.11 + 0.6  5.69 + 0.7  pH, "0" hr  6.14 + 0.04  6.05  5.96 + 0.03*  pH, "24" hr  5.64 + 0.03  5.61 + 0.02  1 Hour b Tension Release, % a  22.6  + 2.3  33.4  i  0.05  + 4.0  5.68 + 0.03 + 2.3*  38.5  RS - Restricted struggle at slaughter S - Free struggle at slaughter  * S i g n i f i c a n t l y d i f f e r e n t from control (p^O.05) ** p<0.01 Amount of tension released at one hour post maximum tension. The birds subjected to 2°C f o r 2 hours were s i g n i ficantly  tougher (p<0.05) than control b i r d s .  Although the  values do not d i f f e r s i g n i f i c a n t l y i n most cases, the cold stress e f f e c t appeared to be maximal at 2 hours.  - 85 TABLE XX. MEANS AND STANDARD ERRORS OF PARAMETERS OF P. MAJOR MUSCLE FROM BROILERS III THE COLD STRESS EXPERIMENT.  Parameter  Control  Stress 2 hr at 2°C  Time, hr  5.59 + 0.5  Tension, g/cm  49.06 + 3.3  2  7.73 + 0.8* 51.99 + 3.2  6 hr at 2°C 8.29 + 1.2 46.86 + 4.4  Shear Value, lbs  5.91 + 0.3  6.97 + 0.4*  6.11 + 0.3  ATP, u Holes/g  6.08 + 0.9  6.66 + 0.4  6.34 + 0.5  Glycogen, rcg/g  4.53 + 0.4  5.60 + 0.6  5.04 + 0.7  HMP  6 .96 + 0.3  6.12 + 0.5  6.42 + 0.5  a  cl  HMP - Hexose Monophosphate * S i g n i f i c a n t l y d i f f e r e n t from control (p<0.05) The most s u r p r i s i n g e f f e c t i n the "cold stress" study was the e f f e c t  on time to maximum tension.  The 6  hour birds had the longest time to maximum tension but since the v a r i a t i o n was large, the values d i d not d i f f e r s i g n i f i c a n t l y from the controls.  Three of the nine birds i n this group, however,  took from 11 - 12 hours to reach maximum tension.  This i s a  r e l a t i v e l y high incidence when compared to the fact that only 1 b r o i l e r , i n over 100 control b r o i l e r s studied i n t h i s project,  - 86 -  required as long as 12 hours to reach maximum tension. The most important agents which have been proven to be stressors to the fowl are temperature extremes, handling, shaking, food and/or water deprivation and debeaking, 1971).  (Freeman,  In the i n i t i a l "alarm phase", which r e s u l t s after ex-  posure to a stressor, adrenalin or epinephrine i s released from the  adrenal medulla causing the passage of potassium from the  muscles to the blood and the breakdown of l i v e r and muscle glycogens to glucose and l a c t i c acid (Lawrie, 1966). I f the e f f e c t of the stressor were severe enough, one would expect a l t e r a t i o n s i n postmortem muscle due to depletion of muscle glycogen.  The r e s u l t s from the epinephrine experi-  ments, reported e a r l i e r i n the t h e s i s , v e r i f y t h i s e f f e c t . The r e s u l t s from the stress experiments, however, are somewhat ambiguous and varied.  This may be due, i n part, to the fact  that none of the stressors studied was severe enough to e l i c i t the  response observed by the actual i n j e c t i o n of epinephrine. The data from the "commercial stress" and "cold  stress" experiments show a d i f f e r e n t trend than the data from the  "heat stress" experiment.  These findings are i n accord  with Seigel (1971) who found that d i f f e r e n t environmental stimuli produced evidence of "stress response" i n birds but often several c r i t e r i a of response had to be evaluated since responses to a p a r t i c u l a r stimulus may single response.  contradict or mask a  Such masking or contradiction of responses  - 87 may  be of p a r t i c u l a r importance i n s t u d y i n g a s o - c a l l e d  "commercial  s t r e s s " which  involves several potential  stressors  (heat, c o l d , h a n d l i n g , crowding). The apparent l e n g t h e n i n g of the time t o reach maximum  t e n s i o n observed i n the "commercial  and c o l d  stress"  experiments suggests t h a t glycogen l e v e l s have not been d i s turbed and t h a t the p e r i o d o f postmortem g l y c o l y s i s has, i n some manner, been lengthened.  T h i s e f f e c t has not been p r e -  v i o u s l y observed i n b r o i l e r s and i s d i f f i c u l t Lawrie  to explain.  (1966) suggested t h a t the d i f f e r e n c e i n bovine response  to p r e - s l a u g h t e r f a s t i n g or e x e r c i s e , as compared t o other' s p e c i e s , may muscle  r e l a t e t o the g r e a t e r c a p a c i t y o f the  to g a i n energy by d i r e c t c a t a b o l i s m of f a t t y  thereby c o n s e r v i n g c a r b o h y d r a t e . may  ruminant acids,  The p o s s i b i l i t y t h a t p o u l t r y  be a b l e t o e l i c i t t h i s response, under  certain  stress  s i t u a t i o n s , cannot be o v e r l o o k e d . The commercial obvious.  The  i m p l i c a t i o n s o f such a phenomenon i s  study on commercial  processing techniques,  r e p o r t e d e a r l i e r , showed t h a t postmortem muscle  parameters  were s i g n i f i c a n t l y a l t e r e d by the v a r i o u s procedures.  It is  t h e r e f o r e e v i d e n t , t h a t any change which a f f e c t e d postmortem g l y c o l y s i s would be m a g n i f i e d by the p r o c e s s i n g t e c h n i q u e s . In the case o f the " c o l d and commercial  s t r e s s e d " b i r d s , the  apparent i n c r e a s e i n time to maximum t e n s i o n should have a b e n e f i c i a l e f f e c t on the u l t i m a t e muscle  quality.  Conversely,  -  the shortened  33  time to maximum tension, observed i n "heat  stressed" birds would be magnified by the processing  proce-  dures and the muscle q u a l i t y should be adversely affected. Bovine, ovine and porcine species when subjected to stressors p r i o r to slaughter, usually have lower muscle glycogen, higher postmorten pH, increased water holding capacity and improved tenderness and j u i c i n e s s  (Hedrick, 1965),  However, under c e r t a i n conditions postmortem q u a l i t y i s adversely affected i n bovine and porcine muscles.  This i s evidenced by  the occurence of "dark cutting" beef and "pale, s o f t ,  exudative"  pork which have been studied by several workers (Lawrie, 1958, 1966 a, b; Sayre e t a l . , 1963 a b; L i s t e r et a l , , 1970) The only adverse q u a l i t y a t t r i b u t e observed during the study of avian muscle was the s l i g h t increase i n shear value i n the 2 hour cold stressed b i r d s .  This may be related  to the fixed 24 hour aging period given a l l birds post-slaughter rather than the actual cold treatment.  Control birds reached  maximum tension at 5,6 hours post-slaughter whereas the 2 hour birds peaked at 7,7 hours post-slaughter.  This shows that the  2 hour birds would have, on the average, a shorter aging time than the control b i r d s . Cold Shortening  Studies  During the study of the e f f e c t s of temperature on isometric tension pattern, a cold shortening phenomenon was observed which appeared to increase i n i n t e n s i t y at 5°C down  -  to  0°C,  strips The  The e f f e c t to develop  15 b r o i l e r s  89 -  of this  further  studied  s h o r t e n i n g on t h e a b i l i t y  tension  i n this  t e n s i o n o f 30.9 g/cm ' w i t h i n -  s i o n was d e v e l o p e d  through  i s demonstrated  experiment  3 minutes  cold  as r a p i d l y  strips  had r e t u r n e d t o t h e o r i g i n a l after  as i t d e v e l o p e d  attachment  Mien  an  average  this  ten-  s h o r t e n i n g , i t v/as r e l e a s e d  almost  minutes  muscle  i n T a b l e XXI.  developed  a t 2°C.  of  so t h a t  i n most c a s e s t h e  starting  point within  15  to the transducers.  TABLE X X I . MEANS AND STANDARDS ERROR OF TENSION PARAMETERS OF BROILER P j . MAJOR MUSCLE SUBJECTED TO VARIOUS POST-SLAUGHTER TEMPERATURE TREATMENTS.  Treatment  Tension,  Room T e m p e r a t u r e , control  61.31 + 2.7  C o l d S h o r t e n i n g , 2°C  30.94 + 5.9  "0"  43.57 + 8.1  time  a  g/cm  331.67 + 23.5 2.93 +  0.3  261.33 + 42.0 63.16 + 11.8  + 0.03  102.67 + 35.5  PMT  2 4 hours  PMT  7.93  36 h o u r s  PMT  1.77 + 0.8  a  Time, min  12.62 + 0.03  12 h o u r s  b  2  40.5 + 10.3  " 0 " t i m e r e f e r s t o s t r i p s p l a c e d i n b u f f e r a t 2°C t o o b s e r v e the c o l d s h o r t e n i n g e f f e c t then immediately s u b j e c t e d t o b u f f e r a t room t e m p e r a t u r e t o o b s e r v e f u r t h e r t e n s i o n development. T h e s e t h r e e t i m e s r e f e r t o m u s c l e s t r i p s h e l d i n b u f f e r a t 2°C f o r v a r i o u s l e n g t h s o f t i m e post-maximum t e n s i o n (PMT), t h e n p l a c e d i n b u f f e r a t room t e m p e r a t u r e t o o b s e r v e t e n s i o n d e v e l o p ment. The t i m e t o maximum t e n s i o n f o r t h e s e s t r i p s v/as d e t e r m i n e d f r o m c o r r e s p o n d i n g c o n t r o l s t r i p s r u n a t room t e m p e r a t u r e .  - 90 -  When s t r i p s were allowed to shorten at 2°C, then brought up to room temperature by changing the buffer, they s t i l l developed a considerable amount of tension during the course of a normal tension pattern.  The time to reach maximum  tension was about one hour shorter than f o r control s t r i p s and the amount of tension was only about two-thirds that of the controls.  I f the tension developed on cold shortening i s added  to the subsequent tension developed at room temperature, then the t o t a l exceeds that developed by controls. Holding muscle s t r i p s i n buffer at 2°C f o r periods of 12, 24 and 36 hours demonstrated a decreasing a b i l i t y of the s t r i p s to develop isometric tension subsequently.  At 3 6 hours  post-maximum tension, the s t r i p s had e s s e n t i a l l y l o s t t h e i r a b i l i t y to develop tension.  This indicates that g l y c o l y s i s had continued  i n the s t r i p s at 2°C but the rate was probably too slow to e f f e c t a tension development,  other than the i n i t i a l cold shortening  tension, at t h i s temperature. The mechanism of the cold shortening phenomenon i s somewhat obscure.  Locker and Kagyard  (1963) showed that cold  shortening, i n beef muscle, started within a few minutes of commencement  of cooling and was almost complete within one hour.  Smith e t al_. (1969) demonstrated a cold shortening e f f e c t i n turkey and chicken  major and found that shortening was maxi-  mal at 0°C. This shortening was e s s e n t i a l l y complete after 3 hours i n chickens and 5 hours i n turkeys.  The v a r i a t i o n between  - 91 these s t u d i e s and may  be due  at 2°C  the p r e s e n t  to the use  s t u d i e s on b r o i l e r P. major  o f s m a l l s t r i p s of muscle i n a b u f f e r  as opposed t o whole muscles cooled  temperature e q u i l i b r i u m would be  i n a i r a t 0°C.  The  a t t a i n e d much f a s t e r i n the  s t r i p s of muscle thereby accounting  f o r the more r a p i d  shorten-  i n g observed. The  toughening, as a r e s u l t o f c o l d s h o r t e n i n g ,  c r i b e d by Newbold and  Karris  (1972) and  l i k e l y to occur i n p o u l t r y muscle.  Marsh  a f t e r the c o l d s h o r t e n i n g In order shortening,  has  (1972) i s not  This i s evident  the a b i l i t y of the s t r i p s t o r e l a x to i n i t i a l  through  l e v e l s immediately  reached i t s peak.  t o b a t t e r understand the nature of the c o l d  a second study was  of c o l d s h o r t e n i n g  on  pounds i n muscle.  The  i n i t i a t e d to measure the e f f e c t  some of the energy r i c h phosphate come f f e c t of c o l d s h o r t e n i n g  on the  ATP  concentration  i s of p a r t i c u l a r i n t e r e s t s i n c e s h o r t e n i n g  o n l y when ATP  i s present  study ara  i n the muscle.  The  r e s u l t s of  occurs this  shown i n T a b l e X X I I . The  ATP  l e v e l s were lowered somewhat by  s t r i p s of muscle to b u f f e r at 2°C freezing i n l i q u i d nitrogen also evident  subjecting  f o r 3 or 7 minutes  for analysis,  A lower ATP  before level  was  i n muscle s t r i p s h e l d i n b u f f e r at room temperature  f o r 7 minutes. and  des-  S i g n i f i c a n t d i f f e r e n c e s between c o l d - t r e a t e d  c o n t r o l s t r i p s were found but  cold-treated strips did  not  d i f f e r from s t r i p s h e l d f o r 7 minutes i n b u f f e r a t room tempera-  ture.  This lac3c of a s i g n i f i c a n t decrease i n ATP levels i s i n  accord with Busch et. a l . (1967) who observed only a small change in ATP l e v e l during large tension development at 2°C. I t i s evident, however, that a s i g n i f i c a n t amount of ATP need not be hydrolyzed to e f f e c t the cold shortening.  This i s more  p l a u s i b l e when one considers that a normal tetanic contraction in muscle i s capable of developing 2 - 3 kg tension/cm (Huxley, 1958),  muscle  The 30.9 g/cm^ obtained during cold shortening  represents only about 1 percent of the p o t e n t i a l tetanus, therefore ATP levels may not change s i g n i f i c a n t l y .  The pre-  sence of adequate l e v e l s of ATP subsequent to shortening would explain why the muscle i s able to relax immediately a f t e r cold shortening since ATP also acts as a p l a s t i c i z e r i n muscle allowing actin and myosin to s l i d e f r e e l y past each other, TABLE XXII. MEANS AND STANDARD ERRORS OF THE ATP, HHP AND CP CONTENT OF BROILER P. MAJOR MUSCLE SUBJECTED TO VARIOUS TEMPERATURE TREATMENTS, a  Treatment  HMP  ATP  CP  Control  6.95 + 0.68  9.23 + 0.64  2.02 + 0.4  3 min at 2°C  4.48 + 0 .56**  8.40 + 0.49  2.23 + 0.24  7 min at 2°C  4.17 + 0.52**  8.06 + 0.51*  2.52 + 0.25  7 min at 25°C  5.35 + 0.36  8.56 + 0.55  2.44 + 0.21  Abbreviations used are: HMP - hexose monophosphate ATP - adenosine triphosphate CP - creatine phosphate * S i g n i f i c a n t l y d i f f e r e n t from control (p<0.05) ** p<0.01  -  Harsh  93  -  (1966) p o s t u l a t e d t h a t c o l d s h o r t e n i n g ,  like  thaw r i g o r , r e s u l t e d from i n a c t i v a t i o n of a r e l a x i n g f a c t o r by  c a l c i u m r e l e a s e , t h i s b e i n g the r e s u l t of a s a l t  Such a s a l t  " f l u x " may  r a t e s of d i f f u s i v e and  "flux".  be e x p l a i n e d i n terms of the  relative  chemical  temperature  processes  s i n c e the  c o e f f i c i e n t of d i f f u s i o n i s c o n s i d e r a b l y lower than t h a t of chemical  reaction, B  Y  a p p l y i n g the above p o s t u l a t i o n to the c o l d  s h o r t e n i n g phenomenon observed i n b r o i l e r muscle, i t i s p o s s i b l e to suggest a sequence of events o c c u r i n g i n the muscle when subjected to c o l d b u f f e r , from the s a r c o p l a s m i c fibrillar  A s a l t " f l u x " of c a l c i u m i o n s , r e l e a s e d reticulum  (SR), would s t i m u l a t e the myo-  adenosine t r i p h o s p h a t a s e  (myosin) to s p l i t ATP,  e f f e c t i n g shortening or c o n t r a c t i o n .  The  amount of c o n t r a c t i o n  would be p r o p o r t i o n a l to the c o n c e n t r a t i o n c f the s a l t which a p p a r e n t l y salt "flux"  may  " c o l d shock" and  v a r i e s s u b s t a n t i a l l y between 5°C and  i t would appear t h a t a f t e r having  c a l c i u m pump r e v e r s e s sequestered  amount of ATP  c a l c i u m , the SR and  by the SR.  present  lost  The  the the  again becomes o p e r a b l e .  Since t h e r e i s s t i l l  The  a  considerable  to a c t as a p l a s t i c i z e r , the muscle r e l a x e s I f h e l d at or near 0°C,  the  strips  a slow r a t e o f g l y c o l y s i s which i s not r a p i d enough to  e f f e c t a f u r t h e r t e n s i o n development. near 0°C,  0°C.  c a l c i u m i s removed from the m y o f i b r i l s  to i t s o r i g i n a l r e s t l e n g t h . maintain  "flux"  be a temporary phenomenon r e s u l t i n g from  a b i l i t y to sequester  and  thereby  s u f f i c i e n t g l y c o l y s i s has  A f t e r 36 hours, at o r  o c c u r r e d w i t h i n the muscle  s t r i p s to eliminate any further a b i l i t y to develop tensipn even i f the s t r i p s are brought to room temperature. The decrease i n hexose monophosphate l e v e l s may  result  from an increased phosphorylation of fructose-6-phosphate to fructose-1, 6-diphosphate which i s catalyzed by phosphofructokinase.  This however, i s speculative and warrants further  study as does the apparent increase i n creatine phosphate  levels.  -  95  -  SUMMARY AND CONCLUSIONS  The e f f e c t s of buffer, pH, temperature and various ions were studied i n r e l a t i o n to tension development and decline i n broiler  major muscle.  A tension pattern, s i m i l a r  to those reported f o r turkey, porcine, bovine and rabbit muscle, v/as observed using phosphate buffer as an incubation media. Tension maximum v/as attained i n control b r o i l e r s at approximately 4 . 5 hours postmortem  and an average of 4 5 g tension/cm  muscle v/as obtained. Changing the pH or temperature of the buffer d i d not a f f e c t the a b i l i t y of the b r o i l e r muscle to develop or release tension but both factors i n some instances, altered the amount of tension developed and the time required to reach maximum tension. ably.  The e f f e c t of temperature v/as found to vary consider-  Temperatures i n the range of those used i n commercial  scalding were shown to cause a 6 - 7 f o l d increase i n tension development within a very short time.  Such tension develop-  ment may be r e l a t e d to the toughening which r e s u l t s from scalding of b r o i l e r s . -3  The presence of 10  II calcium or magnesium ions i n  the incubation buffer produced a of tension release.  marked  change i n the rate  Their e f f e c t on tension development v/as  minimal i n d i c a t i n g that the sarcolemma of postmortem  muscle  may be impermeable to e x t r a c e l l u l a r materials for a short  - 96 p e r i o d o f time postmortem.  C h e l a t i o n o f the c a l c i u m  o r mag-  nesium with EDTA produced an a d d i t i v e e f f e c t on t e n s i o n suggesting and  t h a t non-charged complex may r e a d i l y e n t e r  release  the muscle  t h a t a displacement o f c a l c i u m o r magnesium from the complex  may then take p l a c e thereby r e l e a s i n g these i o n s t o e f f e c t a more r a p i d t e n s i o n d e c l i n e . A p a t t e r n was observed i n c o n t r o l s t r i p s run i n phosphate b u f f e r .  Three groups o f b r o i l e r s were c a t e g o r i z e d  on the b a s i s o f time r e q u i r e d t o reach maximum t e n s i o n . r a t i o n on t h i s b a s i s r e v e a l e d  Sepa-  t h a t b i r d s r e a c h i n g maximum  t e n s i o n i n l e s s than 3 hours postmortem had a s i g n i f i c a n t l y g r e a t e r r a t e o f t e n s i o n r e l e a s e than b i r d s i n the 3 - 6 or g r e a t e r than 6 hour c a t e g o r i e s . s t r i p s from the 0 - 3  The r a t e o f r e l e a s e f o r  hour group c o i n c i d e d w i t h the r a t e o f  r e l e a s e f o r s t r i p s run i n b u f f e r c o n t a i n i n g 10 suggesting  hour  J  M calcium,  a d i f f e r e n c e i n c a l c i u m r e g u l a t i o n i n t h i s group  of b i r d s . I t was found p o s s i b l e t o p r e d i c t t h e p r o p o r t i o n o f maximum t e n s i o n r e l e a s e d a t 12 hour post-maximum t e n s i o n from the p r o p o r t i o n r e l e a s e d at 1 o r 2 hours. was  The one hour  value  a l s o s i g n i f i c a n t l y c o r r e l a t e d t o the time r e q u i r e d t o reach  maximum t e n s i o n .  Tenderness and 1 hour t e n s i o n r e l e a s e  value  were n o t s i g n i f i c a n t l y r e l a t e d i n d i c a t i n g t h a t the r a t e o f t e n s i o n r e l e a s e from b i r d to b i r d i s n o t i n d i c a t i v e o f subsequent t e n d e r n e s s . The  e f f e c t of v a r i o u s p r o c e s s i n g  treatments on t e n s i o n  - 97 -  parameters and b r o i l e r tenderness was studied.  An additive  response v/as observed f o r the d i f f e r e n t combinations studied with the combined commercial process of free struggle at slaughter, hot water scalding and mechanical plucking y i e l d i n g the greatest changes and s i g n i f i c a n t l y toughening b r o i l e r breast muscle. The e f f e c t of pre-slaughter epinephrine i n j e c t i o n s on postmortem tension parameters, tenderness and various compounds r e l a t e d to postmortem g l y c o l y s i s i n muscle v/as studied.  The  maximum e f f e c t of epinephrine i n j e c t i o n occurred between.8-12 hours p o s t - i n j e c t i o n .  At t h i s time, muscle glycogen l e v e l s  were e s s e n t i a l l y depleted but muscle ATP v/as s t i l l  sufficient  to e f f e c t considerable tension development during the extremely short period of postmortem g l y c o l y s i s .  This a b i l i t y to develop  considerable tension appeared to be the cause of the toughening observed i n the muscle from epinephrine injected b i r d s . The e f f e c t of several antemortem stressors on postmortem b r o i l e r muscle v/as studied.  The stressors studied  (commercial, cold and heat) d i d not s i g n i f i c a n t l y a l t e r muscle quality.  A difference i n response to the heat stress, as com-  pared to the commercial and cold stresses, v/as observed.  The  response of birds to a s t r e s s f u l s i t u a t i o n i s characterized by release of epinephrine.  I t i s evident that the situations  studied i n t h i s thesis v/ere not severe enough to e l i c i t the magnitude of response observed from the actual i n j e c t i o n of t h i s hormone.  -  98  -  A c o l d s h o r t e n i n g phenomenon was observed i n the range from 0 - 5°C and the magnitude  o f the s h o r t e n i n g  as the temperature decreased towards 0 ° C . at 2°C showed t h a t a f t e r the i n i t i a l  Subsequent  cold shortening  studies further  t e n s i o n development  d i d not o c c u r a t t h i s temperature.  t e n s i o n development  d i d o c c u r i f the 2°C b u f f e r was  f o r b u f f e r a t room temperature.  increased  Further  exchanged  A h o l d i n g p e r i o d o f 36 hours  at 2°C was n e c e s s a r y t o e l i m i n a t e f u r t h e r t e n s i o n  development  whan b u f f e r temperature was r a i s e d t o room temperature.  The  c o l d s h o r t e n i n g which o c c u r r e d a t 2°C d i d not s i g n i f i c a n t l y a l t e r muscle c o n c e n t r a t i o n s o f h i g h energy phosphate  compounds.  - 99 LITERATURE CITED A p r i l , E., Brandt, P.W., Reuben, J.P. and Grundfest, H. 1968. Muscle contraction: the e f f e c t of i o n i c strength. Nature 220:182. Blaedel, W.J. and Meloche, V.W. 1963. Elementary Quantitative Analysis. Theory and P r a c t i c e . 2nd ed. Harper and Row, Publishers, New York, Evanston and London. Borchert, L.L. and Briskey, E.J. 1965. Protein s o l u b i l i t y and associated properties of porcine muscle as influenced by p a r t i a l freezing with l i q u i d nitrogen. J . Food S c i . 30:138. Bouton, P.E. and H a r r i s , P.V. 1972a. A comparison of some object i v e methods used to assess meat tenderness. J . Food S c i . 37:218. Bouton, P.E. and H a r r i s , P.V. 1972b. The e f f e c t of some postslaughter treatments on the mechanical properties of bovine and ovine muscle. J . Food S c i . 37:539. Briskey, E.J. 1964. E t i o l o g i c a l status and associated studies of pale s o f t exudative procine musculature. Adv. Food Res. 13. Academic Press, New York. Busch, W.A., P a r r i s h , F.C. J r . and G o l l , D.E. 1967. Molecular properties of post-mortem muscle. 4. E f f e c t of temperature on adenosine triphosphate degradation, isometric tension parameters and shear resistance of bovine muscle. J . Food S c i . 32:390. Busch, W.A., G o l l , D.E. and P a r r i s h , F.C. J r . 1972a. Molecular properties of postmortem muscle. Isometric tension development and decline i n bovine, porcine and rabbit muscle. J . Food S c i . 37:289. Busch, W.A., Stromer, M.H., G o l l , D.E. and Suzuki, A. 1972b. Ca - s p e c i f i c removal of Z l i n e s from rabbit s k e l e t a l muscle. J . C e l l B i o l . 52:367. + 2  Campbell Soup Company, 1963. Proceedings Meat Tenderness Symposium, p.2. Cassens, R.G. and Newbold, R.P. 1967. E f f e c t of temperature on the time course of r i g o r mortis i n ox muscle. J . Food S c i . 32:269. Cochran, W.G. and Cox, G.M. 1964. Experimental Designs. 2nd ed. John Wiley & Sons Inc. New York, London. Cook, C F . and Langsworth, R.F. 1966. The e f f e c t of preslaughter environmental temperature and post-mortem temperature upon some c h a r a c t e r i s t i c s of ovine muscle. 1. Shortening and pH. J . Food S c i . 31:497. C o r i , C F . and C o r i , G.T. 1928. action. 1. The influence of drate metabolism of f a s t i n g formation of carbohydrates.  The mechanism of epinephrine epinephrine on the carbohyr a t s , with a note on new J . B i o l . Chem. 79:309.  - 100 -  Davey, C L . and G i l b e r t , K.V. 1969. Studies on meat tenderness, 7. Changes i n the f i n e structure of meat during aging. J . Food S c i . 34:69. Deatherage, F.E. and Garnatz, G. 1952. A comparative study of tenderness determination by sensory panel and by shear strength measurements. Food Technol. 6:260. deFremery, D. and Pool, M.F. 1958. Biochemical studies with chicken muscle as related to r i g o r mortis and tenderizat i o n . Poultry S c i . 37:1198. deFremery, D. and Pool, M.F. 1960. Biochemistry of chicken muscle as related to r i g o r mortis and tenderization. Food Research 25:73. deFremery, D. and Pool, M.F. 1963. The influence of postmortem g l y c o l y s i s on poultry tenderness. J . Food S c i . 28:173. deFremery, D. 1965. The e f f e c t of anesthesia during slaughter on some biochemical properties of chicken breast muscle. Poultry S c i . 44:1370. deFremery, D. 1966a. Some aspects of postmortem changes i n poultry muscle, i n The Physiology and Biochemistry of Muscle as a Food. Briskey, E.J., Cassens, R.G. and Trautman, J.C. (eds.) p. 205. Univ. of Wisconsin. deFremery, D. 1966b. Relationship between chemical properties and tenderness of poultry muscle. Agr. Food Chem. 14:214. Dodge, J.W. and Stadelman, W.J. 1960. V a r i a b i l i t y i n tenderness due to struggling. Poultry S c i . 39:672. Dodge, J.W. and Peters, F.E. 1960. Temperature and pH changes i n poultry breast muscle at slaughter. Poultry S c i . 39:765. Donaldson, W.E., Combs, G.F. and Romoser, G.L. 1956. Studies on enery l e v e l i n poultry r a t i o n s . 1. The e f f e c t of c a l o r i e to-protein r a t i o of the r a t i o n on growth, nutrient u t i l i z a t i o n and body composition of chicks. Poultry S c i . 35:1100. Drewniak, E.E., Baush, E.R. and Davis, L.L. 1955. Carbon dioxide immobilization of turkeys before slaughter. U.S.D.A. C i r c u l a r 958. Freeman, B.M. 1971. Stress and the domestic fowl: a p h y s i o l o g i c a l appraisal. World's Poultry S c i . J . 27:263. Fujimaki, M., Arakawa, N., Okitani, A. and Takagi, D. 1965. The changes of "myosin B" ("actomyosin") during storage of r a b b i t muscle. I I . The d i s s o c i a t i o n of "myosin B" into myosin A and a c t i n , and i t s i n t e r a c t i o n with ATP. J . Food S c i . 30:937. Fukazawa, T., Hashimoto, Y. and Tonomura, Y. 1963. I s o l a t i o n of single sarcomere and i t s contraction on addition of adenosine triphosphate. Biochem. Biophys. Acta 75:234.  -  101  -  Galloway, D.E. and G o l l , D.E. 1967. E f f e c t of temperature on molecular properties of post-mortem porcine muscle. J . Anim. S c i . 26:1302. Goertz, G.E., Weathers, B., Harrison, D.L. and Sanford, P.E. 1961. Tenderness scores and Warner Bratzler shears f o r b r o i l e r s and B e l t s v i l l e White turkeys fed d i f f e r e n t cereal grains. Poultry S c i . 40 (2) :488. G o l l , D.E. 1968. The resolution of r i g o r mortis. Proc. 21st A n n . Recipr. Meats Conf. p. 16. National Livestock and Meat Board, Chicago, I l l i n o i s . G o l l , D.E. 1970. i n The Physiology and Biochemistry of Muscle as a Food. 2. Briskey, E.J., Cassens, R.G. and Marsh, B.B. (eds.) p. 823. Univ. of Wisconsin. G o l l , D.E., Arakawa, N., Stromer, M.H., Busch, W.A. and Robson, R.M. 1970. Chemistry of muscle proteins as a food, i n The Physiology and Biochemistry of Muscle as a Food. 2. Briskey, E.J., Cassens, R.G. and Marsh, B.B. (eds.) p. 755. Univ. of Wisconsin. Gomori, G. 1955. Preparation of buffers f o r use i n enzyme studies. Methods i n Enzymology 1:138. Goodwin, T.L., Mickelberry, W.C. and Stadelman, W.J. 1961. The influence of humane slaughter on the tenderness of turkey meat. Poultry S c i . 40:921. Goodwin, T.L. 1966. The influence of s t r a i n on the tenderness of twenty-six-week-old turkeys. Poultry S c i . 45:594. Goodwin, T.L., Andrews, L.D. and Webb, J.E. 1969. The influence of age, sex and energy l e v e l on the tenderness of b r o i l e r s . Poultry S c i . 48:548. Gothard, R.H., Mullins, A.M., Boulware, R.F. and Hansard, S.L. 1966. H i s t o l o g i c a l studies of post-mortem changes i n sarcomere length as related to bovine muscle tenderness. J . Food S c i . 31:825. Hadjwassiliou, A.G. and Rieder, S.V. 1968. The enzymatic assay of pyruvic and l a c t i c acids. A d e f i n i t e procedure. C l i n . Chem. Acta 19:357. Haga, T., Yamamoto, N., Maruyama, K. and Noda, H. 1966. The e f f e c t of myosin and calcium on the s o l u b i l i t y of F a c t i n from muscle mince. Biochem. Biophys. Acta 127:128. Hamm, R. 1966. Heating of muscle systems, i n The Physiology and Biochemistry of Muscle as a Food. Briskey, E.J., Cassens, R.G. and Trautman, J.C. (eds.) p. 363. Univ. of Wisconsin. Hasselbach, W. 1964. Relaxing factor and the relaxation of muscle. Progr. Biophys. Mol. B i o l . 14:167. Hedrick, H.B. 1965. Influence of ante-mortem stress on meat p a l a t a b i l i t y . J . Anim. S c i . 24:255.  - 102 Hegarty, P.V.J, and A l l e n , C.E. 1972. Rigor-stretched turkey muscles: E f f e c t of heat on f i b e r dimensions and shear values. J . Food S c i . 37:652. Herring, H.K., Cassens, R.G. and Briskey, E.J. 1965a. Sarcomere length of free and restrained bovine muscles at low temperature as related to tenderness. J . S c i . Food Agric. 16:379. Herring, H.K., Cassens, R.G. and Briskey, E.J. 1965b. Further studies on bovine muscle tenderness as influenced by carcass p o s i t i o n , sarcomere length and f i b e r diameter. J . Food S c i . 30:1049. Henderson, D.W., G o l l , D.E. and Stromer, M.H. 1970. A comparison of shortening and Z-line degradation i n post-mortem bovine, porcine and rabbit muscle. Amer. J . Anat. 128:117. Hendricks, H.B., L a f f e r t y , D.T., Aberle, E.D., Judge, M.D. and Forrest, J.C. 1971. Relation of porcine muscle f i b e r type and size to post-mortem shortening. J . Anim. S c i . 32:57. Hohorst, H.J. 1963. L-(+)-Lactate. Determination with l a c t i c dehydrogenase and DPN. i n Methods of Enzymatic Analysis. Bergmeyer, H.U. (ed.) p. 265. Academic Press, New York,1965. Howard, R.D. and Judge, M.D. 1968. Comparison of sarcomere length to other predictors of beef tenderness. J . Food S c i . 33:456. Judge, M.D. 1969. Environmental stress and meat q u a l i t y . Anim. S c i . 28:755.  J.  Jungk, R.A., Snyder, H.E., G o l l , D.E. and McConnell, K.G. 1967. Isometric tension changes and shortening i n muscle s t r i p s during post-mortem aging. J . Food S c i . 32:158. Jungk, R.A. and Marion, W.W. 1970. Post-mortem isometric tension changes and shortening i n turkey muscle s t r i p s held at various temperatures. J . Food S c i . 35:143. Kastenschmidt, L.L., Briskey, E.J. and Hoekstra, W.G. 1966. Metabolic intermediates i n s k e l e t a l muscles with f a s t and slow rates of post-mortem g l y c o l y s i s . Nature 212:151. Kastenschmidt, L.L., Hoekstra, W.G. and Briskey, E.J. 1968. G l y c o l y t i c intermediates and co-factors i n " f a s t " and "slow" glycolysing muscle of the p i g . J . Food S c i . 33:151. Kaufman, V.F., Klose, A.A., Bayne, H.G., Pool, M.F. and Lineweaver, H. 1972. Plant processing of sub-atmospheric steam scalded poultry. Poultry S c i . 51:1188. Khan, A.W., van den Berg, L. and Lentz, C P . 1963. E f f e c t s of frozen storage on chicken muscle proteins. J . Food Sci.28:425. Khan, A.W. 1964. Changes i n nonprotein nitrogenous constituents of chicken breast muscle stored at below-freezing temperatures. Agr. Food Chem. 12:378.  - 103  -  Khan, A.W. and Nakamura, P. 1970. E f f e c t s of pre- and postmortem g l y c o l y s i s on poultry tenderness. J . Food S c i . 35:266. Khan, A.W. 1971. E f f e c t of temperature during post-mortem g l y c o l y s i s and dephosphorylation of high enery phosphates on poultry meat tenderness. J . Food S c i . 36:120. Khan, A.W. and Nakamura, R. 1971. Quality and biochemical changes during frozen storage of meat from epinephrine-treated and untreated chickens. J . Food S c i . 37:145. Klose, A.A., Pool, M.F., Wiele, M.B., Hanson, H.L. and Lineweaver, H. 1959. Poultry tenderness 1. Influence of processing on tenderness of turkeys. Food Technol. 13:20. Klose, A.A., Campbell, A.A., Hanson, H.L. and Lineweaver, H. 1961. E f f e c t of duration and type of c h i l l i n g and thawing on tenderness of frozen turkeys. Poultry S c i . 40:683. Klose, A.A., Luyet, B.J. and Menz, L.J. 1970. E f f e c t of contract i o n on tenderness of poultry muscle cooked i n the prerigor state. J . Food S c i . 35:577. Klose, A.A., Kaufman, V.F. and Pool, M.F. 1971a. Scalding poultry by steam at subatmospheric pressures. Poultry S c i . 50:302. Klose, A.A., Sayre, R.N. and Pool, M.F. 1971b. Tenderness changes associated with cutting up poultry shortly a f t e r warm e v i s e r a t i o n . Poultry S c i . 50:585. Koonz, C.H., Darrow, M.I. and Essary, E.O. 1954. Factors influencing of p r i n c i p a l muscles composing the poultry carcass. Food Technol. 8:97. Kotula, A.W., Drewniak, E.E. and Davis, L.L. 1957. E f f e c t of carbon dioxide immobilization on the bleeding of chickens. Poultry S c i . 36:585. Kotula, A.W., Drewniak, E.E. and Davis, L.L. 1961. Experimentation with i n - l i n e carbon dioxide immobilization of chickens p r i o r to slaughter. Poultry S c i . 40:213. Lamprecht, W. and Stein, P. 1963. Creatine phosphate, i n Methods of Enzymatic Analysis. Bergmeyer, H.U. (ed.) p. 610. Academic Press, New York, 1965. Lamprecht, W. and Trautschold, I. 1963. Adenosine-5-triphosphate, Determination with hexokinase and glucose-6-phosphate dehydrogenase. i n Methods of Enzymatic Analysis. Bergmeyer H.U. (ed.) p. 543. Academic Press, New York, 1965. Landes, D.R., Dawson, L.E. and P r i c e , J.F. 1971. Protein e x t r a c t a b i l i t y of turkey breast muscle e x h i b i t i n g d i f f e r e n t rates of g l y c o l y s i s . J . Food S c i . 36:122.  -  104 -  Larmond, E., Petracovits, A., K e r r i t , E.S. and Tape, N.W. Frozen geese q u a l i t y as affected by sex and breed. J . Food S c i . 33:349.  1968.  Larmond, E. and Koran, E.T. 1969. Eating q u a l i t y of chicken b r o i l e r s as influenced by age and sex. Can Inst. Food Technol. J . 2:185. Larmond, E,, Koran, E.T. and Kim, E.I. 1970. Eating q u a l i t y of two basic breeds of b r o i l e r chickens and t h e i r crosses. Can Inst. Food Technol. J . 3:63. Larmond, E., Petrasovits, A. and Moran, E.T. 1971. Eating q u a l i t y of Large White turkeys as influenced by age and sex. Can Inst. Food Technol. J . 4:75. Larmond, E. and Petrasovits A. 1972. Relationship between. Warner-Bratzler and sensory determination of beef tenderness by the method of paired comparisons. Can. Inst. Food S c i . Technol. J . 5:138. Lawrie, R.A. 1958. Physiological stress i n r e l a t i o n to darkcutting beef. J . S c i . Food Agric. 9:721. Lawrie, R.A.  1966a. Keat Science, Permagon Press Ltd., Oxford.  Lawrie, R.A. 1966b. Metabolic stresses which a f f e c t muscle, i n The Physiology and Biochemistry of Muscle as a Food. Briskey, E.J., Cassens, R.G. and Trautman, J.C. (eds.) p. 137. Univ. of Wisconsin. Lineweaver, H, 1959. as c i t e d by Dodge, J.W. and Stadelman, W.J. 1960, V a r i a b i l i t y i n tenderness due to struggling. Poultrv S c i . 39:672. L i s t e r , D., S a i r , R.A., W i l l , J.A,, Schmidt, G.R., Cassens, R.G., Hoekstra, W.G. and Briskey, E.J, 1970. Metabolism of s t r i a t e d muscle of stress-susceptible pigs breathing oxygen or nitrogen. Am. J . Physiol. 218:102. Locker, R.H. 1960. Degree of muscular contraction as a factor i n tenderness of beef. Food Research 25:304. Locker, R.H. and Hagyard, C.J. 1963. A cold shortening e f f e c t i n beef muscle. J . S c i . Food Agric. 14:787. Lowe, B. 1948. Factors a f f e c t i n g the p a l a t a b i l i t y of poultry with emphasis on h i s t o l o g i c a l postmortem changes. Adv. i n Food Research. 1:203, Marion, J.E., Boggess, T.S. J r . and Woodroof, J.G. 1967. E f f e c t of dietary f a t and protein on l i p i d composition and oxidat i o n i n chicken muscle. J . Food S c i . 32:426.  - 105 Marion, W.W. 1967. Meat tenderness i n the avian species. World's Poultry S c i . J . 23:6. Marion, VJ.W, and Goodman, H.M. 1967. Influence of continuous c h i l l i n g on tenderness of turkey, Food Technol, 21:89. Marion, W.W. 1971. Turkey tenderness and associated physiochemical parameters. Feedstuffs, A p r i l 3, p. 24, Marsden, S.J., Alexander, L.M., Lamb, J.C. and Linton, G.S. 1957a. Relationships among d i e t composition, f l e s h i n g , fatness and edible q u a l i t y of female roasting turkeys.1. Fish products i n starters and growers. Poultry S c i , 36:635. Marsden, S.J., Alexander, L.M., Lamb, J.C. and Linton, G.S, 1957b, Relationships among d i e t composition, f l e s h i n g , fatness and edible q u a l i t y of female roasting turkeys. 2. Fish products i n s t a r t e r s ; cereal grains and oilcake meals i n growers. Poultry S c i , 35:646, Marsh, B,B. and Thompson, J.F. 1958. Rigor mortis and thaw r i g o r i n lamb. J . S c i . Food Agric. 9:417. Marsh, B.B., 1966 Relaxing factor i n muscle, i n The Physiology and Biochemistry of Muscle as a Food. BrTskey, E . J . , Cassens, R.G. and Trautman, J.C, (eds.) p. 225, Univ. of Wisconsin. Marsh, B.B. and Leet, N.G. 1966. Studies i n meat tenderness. 3. The e f f e c t s of cold shortening on tenderness. J . Food S c i . 31:450, Marsh, B.B. 1972. Post-mortem muscle shortening and meat tenderness. Proc. Meat Ind. Res. Conf. p. 109. May, K.N. and Huston, T.M. 1959. Observations on the e f f e c t of sodium pentobarbital on the ease of handling and processing chickens. Poultry S c i . 38:1225. May, K.N., S a f f l e , R.L., Downing, D.L. and Powers, J . J . 1962. I n t e r r e l a t i o n s of post-mortem changes with tenderness of chicken and pork. Food Technol. 16:72. Mendell, J.R. 1971. Unusual features of the T-system of the p e c t o r a l i s muscle of the chicken. J . Ultrastructure Res. 37:333. Moran, E.T., Orr, H.L. and Larmond, E. 1970. Dressing, grading and meat y i e l d s with b r o i l e r chicken breed. Food Technol. 24:73. Nakamura, R. 1972. Measurement of t e n s i l e strength of muscle f i b e r s and i t s change during postmortem aging of chicken breast muscle. J . Agr. Food Chem. 20:809.  -  106  -  Newbold, R.P, and H a r r i s , P.V, 1972. The e f f e c t of pre-rigor changes on meat tenderness. A review. J . Food S c i . 37:337. Nixon, D.M. and K i l l e r , B.F. 19G7. Evaluation of turkey boning techniques. Poultry S c i . 46:1088. Pangborn, R.M. , Sharrah, 11., Lewis, K. and Erant, A.W. 1965 Sensory and mechanical measurements of turkey tenderness. Food Technol. 19:126 8. Paul, P.C., Sorenson, C.I. and Abplanalp, H. 19 59. V a r i a b i l i t y i n tenderness of chicken. Food Research 24:205. Pearson, A.M. 1963. Objective and subjective measurements f o r meat tenderness. Proc, Meat Tenderness Symposium, Campbell Soup Company, Camden, N.J. p. 135, Peterson, D,W,, Simone, M,, L i l l y b l a d e , A.L.and Martin, R. 1959. Some factors a f f e c t i n g the i n t e n s i t y of flavor and toughness of cooked chicken muscle. Food Technol. 13:304. P f l e i d e r e r , G. 1963. Glycogen. Determination of D-glucose with hexokinase, pyruvic kinase and l a c t i c dehydrogenase, iri Methods of Enzymatic Analysis. Bergmeyer, H.U. (ed.) p. 59, Academic Press, New York, 196 5. Pool, M.F., deFremery, D., Campbell, A.A. and Klose, A.A. 1959. Poultry tenderness. 2, Influence of processing on tenderness of chickens. Food Technol, 13:25, Pool, M.F. and Klose, 7i.A, 196 9, The r e l a t i o n of force to sample dimensions i n objective measurement of tenderness of poultry meat. J , Food S c i . 34:524. Ramsbottom, J.M. and Strandine, E.J, 1949. I n i t i a l physical and chemical changes i n beef as related to tenderness. J . Anim. S c i . 8:398. Ringer, R.K. 1971. Adaptation of poultry to confinement systems. J . Anim. S c i . 32:589.  rearing  Rome, E, 1968. X-ray d i f f r a c t i o n studies of the various filament l a t t i c e of s t r i a t e d muscle i n various bathing media. J . Mol. B i o l . 37:331. S a i r , R.A., L i s t e r , D., Moody, W.G., Cassens, R.G,, Hoekstra, W.G., and Briskey, E.J. 1970. Action of curare and magnesium on s t r i a t e d muscle of stress-susceotible pigs. Am, J , P h y s i o l . 218:108. Sayre, R.N., Briskey, E.J. and Hoekstra, W.G. 1963a. A l t e r a t i o n of post-mortem changes i n porcine muscle by preslaughter heat treatment and d i e t modification. J . Food S c i . 28:292. Sayre, R.N., Briskey, E.J. and Hoekstra, W.G. 1963b. Comparison of muscle c h a r a c t e r i s t i c s and post-mortem g l y c o l y s i s i n three breeds of swine, J . Anim. S c i . 22:1012.  - 107 -  Sayre, R.N. 1969. Fragmentation of chicken m y o f i b r i l s , Proc, 22nd Ann. Recipr. Heats Conf. p. 230. Sayre, R.N. 1970. Chicken m y o f i b r i l fragmentation i n r e l a t i o n to factors influencing tenderness. J , Food S c i . 35:7. S c h a l l e r , D.R. and Powrie, W.D. 1972. Scanning electron microscopy of heated beef, chicken and rainbow trout muscles. Can. Inst. Food S c i . Technol. J . 5:184, Schmidt, G.R., Cassens, R.G. and Briskey, E.J. 1968. Development of an isotonic-isometric rigorometer. J . Food S c i . 33:239. Schmidt, G.R., Cassens, R.G. and Briskey, E.J. 1970a. Changes i n tension and certain metabolites during the development of r i g o r mortis i n selected red and white s k e l e t a l muscles. J . Food S c i . 35:571. Schmidt, G.R,, Cassens, R.G, and Briskey, E.J. 1970b. Relationship of calcium uptake by the sarcoplasmic reticulum to tension development and r i g o r mortis i n s t r i a t e d muscle. J . Food S c i . 35:574. Selye, H. 1950. The Physiology and Pathology of Exposure to Stress. A.cta Inc., Montreal. Selye, H. 1956. Stress of L i f e . McGraw H i l l Book Co., New York. Shannon, W.G., Marion, W.W. and Stadelman* W.J. 1957. E f f e c t of temperature and time of scalding on the tenderness of breast meat of chicken. Food Technol. 11:284. Sharrah, N., Kunze, M.S. and Pangborn, R.H,1965a, Beef tendernessSensory and mechanical evaluation of animals of d i f f e r e n t breeds. Food Technol, 19:233, Sharrah, N,, Kunze, M.S. and Pangborn, R.M. 1965b. Beef tendernessComparison of sensory methods with the Warner-Bratzler and L.E.E. Kramer shear presses. Food Technol. 10:238. Shrimpton, D.H. and M i l l e r , W.S. 1960. Some causes of toughness i n b r o i l e r s (young roasting chickens) I I . E f f e c t s of breed, management and sex. B r i t i s h Poultry S c i , 1:111, S i e g e l , H.S. 1971. Adrenals, stress and the environment. World's Poultry S c i . J . 27:327. Smith, M.C., Judge, M.D. and Stadelman, W.J. 1969. A "cold shortening" e f f e c t i n avian muscle. J . Food S c i , 34:42, Stadelman, W.J, and Wise, R.G, 1961. Tenderness of poultry meat. 1, E f f e c t of anesthesia, cooking and i r r a d i a t i o n . Food Technol, 15:292.  - 108 Stanley, D.W., McKnight, L.M., Hines, W.G.S., Usbourne, W.R. and deMan, J.M, 197 2, Predicting meat tenderness from muscle t e n s i l e properties. J , Textural Studies.3:51, Stromer, M.H, and G o l l , D.E, 1967. Molecular properties of post-mortem muscle, 3. Electron Microscopy of M y o f i b r i l s . J. Food S c i . 32:386, Summers, J.D, Slinger, S.J. and Ashton, G.C. 1965. The e f f e c t of dietary energy and protein on carcass composition. Poultry S c i . 44:501. Szczesniak, A.S., Humbaugh, P.R. and Block, H.W. 1970. Behavior of d i f f e r e n t foods i n the standard shear compression c e l l of the shear press and the e f f e c t of sample weight on peak area and maximum force. J . Textural Studies 1:356, Takahashi, K,, Fukazawa, T. and Yasui, T, 1967, Formation of m y o f i b r i l l a r fragments and r e v e r s i b l e contraction of sarcomeres i n chicken pectoral muscle. J , Food S c i . 32:409. van den Berg, L., Khan, A.W. and Lentz, C.P. 1963. Biochemical and q u a l i t y changes i n chicken meat during storage at above freezing temperatures. Food Technol. 17:91. van den Berg, L., Lentz, C.P. and Khan, A.W. 1964. Post-mortem changes i n tenderness and water-holding and ion-binding properties of poultry leg and breast meat. Food Technol. 18:5 Vanderstoep, J . 1971. Post-mortem g l y c o l y t i c and physical changes i n turkey breast muscle, PhD. t h e s i s . Univ. of B r i t i s h Columbia. Welbourn, J.L,,Harrington, R.B. and Stadelman, W.J. 1968, Relationships among shear values, sarcomere lengths and cooling procedures i n turkeys, J , Food S c i . 33:450. White, E.D., Hanson, H.L., Klose, A,A, and Lineweaver, H, 1964. Evaluation of toughness differences i n turkeys. J , Food S c i . 29:673. Wilscn, W.O. 1971. Evaluation of stressor agents i n domestic animals. J . Juiim. S c i . 32:573. Wise, R.G. and Stadelman, W.J. 1957. E f f e c t of beating by mechanical pickers on the tenderness of poultry meat. Poultry S c i . 36:1169. Wise, R.G. and Stadelman, W.J. 1959. Tenderness at various muscle depths associated with poultry processing techniques. Food Technol. 13:689.  -  109 -  W i s e , R.G. and S t a d e l m a n , W.J. 1961. T e n d e r n e s s o f p o u l t r y meat. 2. E f f e c t o f s c a l d i n g p r o c e d u r e s . P o u l t r y S c i . 40:1731. Z a c h a r i a h , G.L., Haugh, C.G. and S t a d e l m a n , W.J. 1971. T e n d e r n e s s m e a s u r e m e n t s b a s e d on t h e e l e c t r i c a l p r o p e r t i e s o f p o u l t r y . P a p e r p r e s e n t e d a t t h e 1971 a n n u a l m e e t i n g . A m e r i c a n S o c i e t y o f A g r i c u l t r u a l E n g i n e e r s . A.S.A.E. S t . J o s e p h , Michigan.  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0101137/manifest

Comment

Related Items