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Thiamine degradation in a luncheon-type ham product thermally processed in retort pouches and cans Young, Kirsten Emily 1984

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THIAMINE DEGRADATION IN A LUNCHEON-TYPE HAM PRODUCT THERMALLY PROCESSED IN RETORT POUCHES AND CANS by KIRSTEN EMILY YOUNG B.Sc. Honors, U n i v e r s i t y of Guelph, 1981 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Department of Food Science) We accept t h i s t h e s i s as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA Duly, 1984 © K i r s t e n Young, 1984-In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the University of B r i t i s h Columbia, I agree that the Libr a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I further agree that permission for extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head of my department or by h i s or her representatives. I t i s understood that copying or publ i c a t i o n of t h i s t h e s i s f o r 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 1956 Main Mall Vancouver, Canada V6T 1Y3 Date July 3, 1984 ABSTRACT Thiamine i s an e s sent i a l nutr ient and meat products can serve as an important source of t h i s v i tamin . I t i s thermally l a b i l e and thus s i g n i f i c a n t des t ruct ion can occur during the commercial s t e r i l i z a t i o n of foods. This study inves t iga ted the thermal degradation k i n e t i c s of thiamine i n a luncheon-type ham product . In a d d i t i o n , thiamine reten-t i o n fo l lowing processing of the product i n r e to r t pouches and metal cans at two re tor t temperatures was evaluated. Degradation of thiamine i n the luncheon-type ham product was described by f i r s t order react ion k i n e t i c s for temperatures between 100 and 1 4 0 ° C , and temperature dependence of the reac t ion followed the Arrhenius equat ion. The a c t i v a t i o n energy was 105 k3/mol and the reac t ion rate constant at a reference temperature of 1 2 1 ° C was 2.03x10~ 2 m i n " 1 . Thiamine re tent ion was determined fo l lowing processing of 397 g quant i t i e s of the luncheon-type ham product i n 300x407 cans and 159 mm by 229 mm r e t o r t pouches re s t ra ined to 19 mm th ickness . Retort tempera-tures of 1 1 5 . 6 ° C ( 2 4 0 ° F ) and 1 2 6 . 7 ° C ( 2 6 0 ° F ) were used to obtain minimum process l e t h a l i t i e s of 6.0 min. As w e l l , for a c o n t r o l , 184 g of product was processed at 1 1 5 . 6 ° C i n the 307x111.5 cans used commer-c i a l l y . A l l cans were s t e r i l i z e d i n pure steam whereas a 75/25 steam/ a i r mixture was used for the re tor t pouch processes. A n a l y s i s of variance ind ica ted s i g n i f i c a n t d i f ferences i n thiamine re tent ion among the package and processing temperature combinations i i i (p<0.001). Student-Newman-Keuls mul t ip le comparisons procedure showed that a l l treatments were s i g n i f i c a n t l y d i f f e r e n t from one another (p<0.05). The luncheon-type ham product processed i n re tor t pouches required process times 61 and 75% shorter than processes of equivalent center-point l e t h a l i t y for cans at 115.6 and 1 2 6 . 7 ° C . As a consequence, the products i n r e to r t pouches reta ined 16 and 26% more thiamine than t h e i r canned counterparts at the two re tor t temperatures. The higher r e t o r t temperature for cans resu l ted i n a k% decrease i n thiamine re tent ion compared to the lower temperature, while for re tor t pouches there was a 6% increase i n thiamine re ta ined . The product processed i n the smaller cont ro l cans at 1 1 5 . 6 ° C had a l e v e l of thiamine re tent ion intermediate between that processed i n r e t o r t pouches and the l a rger cans. i v TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS iv LIST OF TABLES v i LIST OF FIGURES v i i i ACKNOWLEDGEMENTS ix INTRODUCTION 1 LITERATURE REVIEW 3 A. Thermal Degradation of Thiamine 3 B. Retort Pouches 9 C . Thermal Process ing of Cans and Retort Pouches 13 1. Process ing Media 13 2. Temperature Measurement 15 3. Process Determination 19 D. Qual i ty of Thermally Processed Products 21 1. Basic Considerat ions 21 2. E f fec t of Container Shape 24 3. E f fec t of Processing Temperature 30 4 . Goals of This Research Pro ject 35 EXPERIMENTAL 38 A. The Luncheon-Type Ham Product 38 1. Product Desc r ip t ion 38 2. Moisture Content 38 B. Thiamine Ana lys i s 39 C . K i n e t i c s of the Thermal Degradation of Thiamine 41 D. Process Determination 44 1. The Retort 45 2. Processing Condit ions 46 3. Temperature Measurement and F i l l i n g of Containers . . . 48 4. Process Times „ 50 5 . Process C a l c u l a t i o n 50 E . Processing for Thiamine Retention Evaluat ion 53 1. Process ing 54 2. Sampling and Product Ana lys i s 54 3. Data Ana lys i s 57 RESULTS AND DISCUSSION 60 A . K i n e t i c s of the Thermal Degradation of Thiamine 60 1. Reaction Rate 60 2. Temperature Dependence of Degradation 69 B. Process Determination 69 1. Process Times 69 2. Process L e t h a l i t y 76 V Page C. Process ing for Thiamine Retention Evaluat ion 77 1. pH 77 2. Thiamine Retention 77 a) Ana lys i s of variance 77 b) Treatment d i f ferences 80 c) Amount of thiamine reta ined 84 3. Process L e t h a l i t y 87 CONCLUSIONS 95 LITERATURE CITED 96 APPENDICES 104 v i LIST OF TABLES Page Table 1. Studies of thermal degradation of thiamine i n food systems 7 Table 2 . Thermal re s i s tance of various food const i tuents 22 Table 3. Heating schedule for thiamine k i n e t i c s work 43 Table 4 . Process ing condi t ions used for cans and r e t o r t pouches 47 Table 5. Process times used i n the process determination phase of the work 51 Table 6 . Process times used i n the thiamine re tent ion eva l -uat ion phase of the work, ca lcu la ted by Stumbo's method using heat penetrat ion data obtained i n three process runs for each treatment 55 Table 7 . Out l ine of ana lys i s of variance used for thiamine re ten t ion a f ter processing assuming that t rea t -ments were f ixed 58 Table 8. Reaction rate constants for the thermal degrada-t i o n of thiamine i n a luncheon-type ham product at temperatures between 100 and 1 4 0 ° C for three rep-l i c a t i o n s 66 Table 9. Reaction rate constants at 1 2 1 ° C and a c t i v a t i o n energies for thiamine i n a luncheon-type ham pro-duct heated at 100 to 1 4 0 ° C for three r e p l i c a t i o n s . . . 71 Table 10. Heating and coo l ing curve parameters for a luncheon-type ham product obtained during process determination work i n three process runs 72 Table 11. Process times and estimated F 0 values when these process times are used, ca l cu la ted with Stumbo's method for three process runs per treatment i n the process determination work for a luncheon-type ham product 74 Table 12. Ana ly s i s of variance for thiamine re tent ion i n a luncheon-type ham product a f ter processing i n re tor t pouches and cans 78 v i i Page Table 13. Thiamine re tent ion i n a luncheon-type ham product a f t e r processing i n re tor t pouches and cans, with treatment d i f ferences tested using Student-Newman-Keuls m u l t i p l e comparisons procedure (n=12) . 81 Table 1*. Thiamine concentrat ion (wet basis) i n a luncheon-type ham product a f ter processing i n r e t o r t pouches and cans (n=12) 85 Table 15. Process l e t h a l i t y values for a luncheon-type ham product processed i n r e t o r t pouches and cans with three process runs for each treatment and c a l c u l a -t ions done using Stumbo's method 88 Table 16. Heating and coo l ing curve parameters for a luncheon-type ham product processed i n r e t o r t pouches and cans with three process runs per treatment 89 Table 17. Volume of cook-out l i q u i d obtained fo l lowing pro-cess ing of a luncheon-type ham product i n r e t o r t pouches and cans (n=12 unless otherwise indicated) . . . 91 v i i i LIST OF FIGURES Page Figure 1. Degradation of thiamine i n a luncheon-type ham product at 1 0 0 ° C for three r e p l i c a t i o n s 61 Figure 2. Degradation of thiamine i n a luncheon-type ham product at 1 1 0 ° C for three r e p l i c a t i o n s 62 Figure 3 . Degradation of thiamine i n a luncheon-type ham product at 1 2 0 ° C for three r e p l i c a t i o n s 63 Figure 4. Degradation of thiamine i n a luncheon-type ham product at 1 3 0 ° C for three r e p l i c a t i o n s 64 Figure 5. Degradation of thiamine i n a luncheon-type ham product at 1 4 0 ° C for three r e p l i c a t i o n s 65, Figure 6 . Arrhenius r e l a t i o n s h i p for the degradation of thiamine i n a luncheon-type ham product heated at 100 to 1 4 0 ° C for three r e p l i c a t i o n s 70 Figure 7. Treatment by r e p l i c a t i o n i n t e r a c t i o n for thiamine r e t e n t i o n i n a luncheon-type ham product processed i n re tor t pouches and cans 79 ix ACKNOWLEDGEMENTS The author wishes to express her gra t i tude to Dr . Marvin Tung, her research supervisor for h i s encouragement, support and guidance through-out the course of t h i s research p r o j e c t . She wishes to thank the members of the research committee: Dr . W. Powrie, Dr. 3. Richards , Dr. 3. Le i ch te r and Dr . 3. Vanderstoep for t h e i r advice during the research phase of t h i s pro ject and i n the review of t h i s manuscript. Spec ia l thanks are extended to Trudi Smith for her help with the thermal processing aspects of t h i s project and the use of the process c a l c u l a t i o n programs she had wr i t t en ; to Sherman Yee for his a s s i s tance with the thiamine ana ly s i s and laboratory equipment and to Dr . H. S. Ramaswamy for his advice on the operation of the r e t o r t . The help provided by several other students and s t a f f wi th in the Department of Food Science during the course of the research i s g rea t ly apprec ia ted . Thi s study was made poss ib le by a 1967 Science and Engineering Scholarship to the author and f i n a n c i a l support from the S t r a t eg i c Grants Program of the Natural Sciences and Engineering Research Counci l of Canada. - 1 -INTRODUCTION Thermal processes f ind wide a p p l i c a t i o n i n the food industry for extending the s h e l f - l i f e of foods. Included among these processes i s commercial s t e r i l i z a t i o n . In t h i s process , a heat treatment i s appl ied to destroy microb ia l vegetat ive c e l l s and spores which upon anaerobic storage could endanger the health of the consumer or cause d e t e r i o r a t i o n of the product . T r a d i t i o n a l containers for these products are the metal can and glass j a r . F l e x i b l e laminates s table at high temperatures have been introduced i n recent years for use i n producing various containers inc lud ing the re tor t pouch. Heat i s used i n thermal processing i n order to i n a c t i v a t e the microb ia l populations and achieve a safe product . However, concomitant with t h i s i s the des t ruc t ion of q u a l i t y a t t r i b u t e s such as co lour , texture , f lavour and n u t r i t i v e q u a l i t y which can de ter iora te as a r e s u l t of the heat treatment. The processor wishes to provide the consumer with a safe product, and within economic cons t ra int s one e x h i b i t i n g the maximum poss ib le re tent ion of q u a l i t y a t t r i b u t e s . The concern for producing high q u a l i t y products has led to inves-t i g a t i o n s i n which d i f f e r e n t processes , that accomplish the major ob jec t ive of safety , have been compared on the basis of q u a l i t y a t t r i -bute r e t e n t i o n . High temperature, short time processes have been used to achieve these ob ject ives with convect ion-heat ing products and i n a sep t i c processing (Lund, 1979). However, with conduction-heating products processed i n t r a d i t i o n a l c y l i n d r i c a l cans, changes i n process - 2 -temperature provide no major improvement. V a r i a t i o n s i n container geometry provide greater promise for improved q u a l i t y r e t e n t i o n . A s i g n i f i c a n t increase i n the n u t r i t i o n a l value of a thermally processed food i s poss ib le with the use of container geometries which allow more r ap id heat penetrat ion compared to conventional cans (Te ixe i ra et a l . , 1975). Retort pouches provide for a favourable change i n geometry compared to conventional c y l i n d r i c a l containers for q u a l i t y a t t r i b u t e r e t e n t i o n . The i r t h i n p r o f i l e al lows rapid heat penetrat ion and thus process times can be reduced by one- third to one-half r e l a t i v e to cans conta in ing the same amount of product ( R i z v i and Acton, 1982). With th in p r o f i l e conta iners , changes i n re tor t temperature may of fer l a rger improvements i n nutr ient re tent ion compared to conventional cans (Te ixe i ra et a l . , 1975). - 3 -LITERATURE REVIEW A. Thermal Degradation of Thiamine Qual i ty a t t r i b u t e s , inc lud ing some n u t r i e n t s , may degrade as a r e su l t of the a p p l i c a t i o n of heat. Thiamine i s one of the thermally l a b i l e vitamins which, along with ascorbic a c i d , has received a t t ent ion i n inve s t i ga t ions of processing e f fects on n u t r i t i v e value of foods (Lamb et a l . , 1982). Thermal des t ruct ion of thiamine can re su l t from cleavage of the methylene bridge between the t h i a z o l e and pyrimidine moieties of the molecule. The p r i n c i p a l products formed are 4~methyl-5-(f3-hydroxy-e t h y l ) t h i a z o l e and a pyrimidine d e r i v a t i v e which i s probably 2-methyl-A-amino-5-hydroxymethyl pyrimidine (Dwivedi and A r n o l d , 1972, 1973). A second degradation reac t ion involves breakdown of the t h i a z o l e por t ion of the molecule to y i e l d hydrogen s u l f i d e along with smaller amounts of other such compounds (Dwivedi and Arno ld , 1972, 1973). Dwivedi and Arnold (1972) inves t iga ted the thermal degradation of thiamine i n phosphate buf fer . Below pH 6 .0 , heating of thiamine so lu-t ions resul ted i n cleavage of the methylene bridge of the thiamine molecule. These authors concluded that above pH 6 .0 , hydrogen s u l f i d e was formed due to the breakdown of the th i azo le r ing of a l t e rna te forms of thiamine (the pseudobase and t h i o l forms) which are present i n small amounts along with free thiamine i n t h i s pH range. It was suggested that a lower a c t i v a t i o n energy favours breakdown of the t h i a z o l e r ing of the a l te rnate forms of thiamine over cleavage of the methylene bridge above pH 6 .0 . - 4 -Much of the published work about thiamine degradation presents information on re tent ion of the vitamin fol lowing treatment of a given food with a p a r t i c u l a r set of c o n d i t i o n s . Although t h i s i s useful for descr ib ing e f fec t s of a given treatment, determination of k i n e t i c para-meters allows for an improved d e s c r i p t i o n of the degradation process. Desc r ip t ion of the ef fect of a thermal treatment requires two k i n e t i c parameters: 1) the rate of nutr ient des t ruct ion at a reference tempera-ture and 2) the dependence of the rate of des t ruct ion on temperature (Lund, 1975). Once determined, these parameters allow comparison of d i f f e ren t food products and can be used i n models to pred ic t thiamine re ten t ion r e s u l t i n g from a s p e c i f i e d procedure (Farrer , 1955; Lund, 1982). F i r s t order reac t ion k i n e t i c s have been used to descr ibe the rate of degradation of nutr ients i n foods (Thompson, 1982). Such a model may descr ibe the k i n e t i c s of the r e a c t i o n , but does not neces sar i ly i n d i c a t e the mechanism of the reac t ion (Lenz and Lund, 1980). F i r s t order k i n e t i c s have been appl ied to thermal degradation of thiamine i n both model systems and foods (Greenwood et a l . , 1944; Rice and Beuk, 1945; F a r r e r , 1955; F e l i c i o t t i and Esse len , 1957; Mulley et a l . , 1975a; Fox et a l . , 1982; SkjOldebrand et a l . , 1983). In some cases, devia t ions from f i r s t order k i n e t i c s have been observed i n food systems (Rice and Beuk, 1945; Bendix et a l . , 1951). The rate of a f i r s t order reac t ion i s propor t iona l to the f i r s t power of the concentrat ion of one reactant . The rate expression i s : - 5 -d[A] — — = k[A] [1 ] dt where [A] i s the concentrat ion of the reactant , t i s time and k i s the r eac t ion rate constant with uni t s of r e c i p r o c a l time. This expression can be rearranged and then integrated between time l i m i t s of 0 and t corresponding to reactant concentrat ions of [ A ] 0 and [A] r e s p e c t i v e l y : r [ A ] « ™ j —— = -k J dt [2] [ A ] Q [ A ] 0 ln[A] - l n [ A ] Q = -kt [3] By transposing the i n i t i a l concentrat ion term to the r i gh t hand s i d e , the reactant concentrat ion can be shown to be a semilogarithmic funct ion of time: ln[A] = l n [ A ] Q - kt [4] kt or log[A] = log[A] - [5] 0 2.303 An a l t e rna te way to descr ibe the reac t ion rate i s with the decimal reduct ion time (D) . The D value i s defined as the time required at constant temperature for the reactant concentrat ion to decrease by 90% (Lund, 1977). Temperature dependence of the reac t ion rate has most commonly been described using the Arrhenius equation (Labuza and Riboh, 1982; Thompson, 1982): k = k e o [6] where k 0 i s the pre-exponential factor or frequency f ac tor , R i s the gas constant (8 .314 3 / ° K m o l ) , T i s the absolute temperature ( ° K ) and E a i s the a c t i v a t i o n energy (3/mol) . Thi s equation ind ica te s that a p l o t of the logarithm of k versus r e c i p r o c a l absolute temperature w i l l y i e l d a s t r a ight l i n e with a slope of negative a c t i v a t i o n energy d iv ided by the product of the gas constant and 2.303. Thus, the a c t i v a t i o n energy can be used to describe the temperature dependence of the reac-t i o n rate (Lund, 1977). The increase i n rate of thiamine des t ruc t ion by heat with increas ing temperature has been succes s fu l ly described with the Arrhenius equation for both model systems and foods (Farrer and Morr i son, 1949; F a r r e r , 1955; F e l i c i o t t i and Esse len , 1957; Mulley et a l . , 1975a). Another term used to descr ibe the temperature dependence of a reac t ion rate i s the z -va lue . I t represents the temperature change required to change the reac t ion ra te , expressed as D, by one order of magnitude (Lund, 1977). A summary of k i n e t i c data for the des t ruct ion of thiamine i n food systems i s presented i n Table 1. Studies included are those per ta in ing to temperatures normally used for thermal processing of canned low-acid foods. Thus a reference temperature of 2 5 0 ° F ( 1 2 1 ° C i s the approximate equivalent) i s used for the reac t ion rate constant . Only those s tudies which presented information on the system considered and included a reference reac t ion rate at 1 2 1 ° C ( k 1 2 1 ) a r , d a n a c t i v a t i o n energy (or s u f f i c i e n t information to allow t h e i r c a l c u l a t i o n ) are i n c l u d e d . Table 1. Studies of thermal degradation of thiamine i n food systems. Food product pH Temperature range, °C k j ^ l 1 ! m i n " 1 E 1 , k3/mol Reference Beans, green puree 5.8 109 to 149 1.52x10- 2 113 F e l i c i o t t i and Esselen (1957) Beef l i v e r puree 6 . 1 , 109 to 149 1.92x10"* 113 F e l i c i o t t i and Esselen (1957) puree nat 121 to 138 8.96x10" 3 115 Mulley et a l . (1975a) Carrot puree 6.1 109 to 149 1.48x10" 2 113 F e l i c i o t t i and Esselen (1957) Lamb puree 6.2 109 to 149 1.81x10~2 113 F e l i c i o t t i and Esselen (1957) Pea puree 6.8 109 to 149 1.47x10" 2 113 F e l i c i o t t i and Esselen (1957) puree nat 121 to 138 8.27x10-;* 115 Mulley et a l . (1975a) i n brine puree nat 121 to 138 1.02x10" 2 113 Mulley et a l . (1975a) whole nat 104 to 132 1.66x10- 2 89 Bendix et a l . (1951) Pork puree 6.2 109 to 149 1.58x10" 2 113 F e l i c i o t t i and Esselen (1957) luncheon meat nat 99 to 127 1.3 x10" 2 93 Greenwood et a l . (1944) Spinach puree 6.7 109 to 149 1.86x10- 2 113 F e l i c i o t t i and Esselen (1957) In cases where k i 2 i and/or E a were not provided by the authors , these values were derived by regress ion of the logarithm of k values on rec iproca l absolute temperature for the data provided. 2 N a t u r a l pH. - 8 -A var i e ty of factors may a f fect the thermal degradation of t h i a -mine. Temperature, time and pH are bel ieved to be the most important (Far rer , 1955; Dwivedi and Arno ld , 1973). Thiamine i s less s table at a l k a l i n e pH values than at ac id pH va lues . Experiments conducted with phosphate buffer systems have shown an increased rate of thiamine des t ruct ion with increas ing pH over the range of 4.5 to 7.0 ( F e l i c i o t t i and Esse len , 1957; Mulley et a l . , 1975b). The most dramatic change i n the react ion rate occurred between pH 6.0 and 6 .5 . Dwivedi and Arnold (1972) have l inked t h i s change to the two poss ib le degradation mechan-isms previous ly d i scussed . Other factors which may a f fect thermal degradation of thiamine include the e l e c t r o l y t e system, metal ions , none lec t ro ly tes and the s ta te of the vitamin (Far rer , 1955). Thiamine i n food systems i s more re s i s t an t to breakdown than i s the vitamin i n aqueous or buffer so lu-t ions (Farrer , 1955; F e l i c i o t t i and Esse len , 1957; Mulley et a l . , 1975a). Prote ins and s tarch have been shown to protect thiamine (Dwivedi and A r n o l d , 1973). F e l i c i o t t i and Esselen (1957) inves t iga ted thermal degradation of thiamine i n a v a r i e t y of food systems inc lud ing both vegetable and animal products . Based on the r e s u l t s obtained, these researchers suggested that the v a r i a t i o n i n rate of thiamine des t ruct ion i n foods could be dependent on an i n t e r r e l a t i o n s h i p between pH and the proport ion of combined thiamine present . Combined thiamine may be present as cocarboxylase (thiamine pyrophosphate) as the major form, but poss ib ly a l so as protein-bound thiamine or i n other forms (Far rer , 1955). - 9 -Cocarboxylase i s less s table to heat than free thiamine (Farrer , 1955; Mulley et a l . , 1975b). F e l i c i o t t i and Esselen (1957) suggested that a r e l a t i v e l y low pH i n a product could counteract a higher r e l a t i v e pro-port ion of combined thiamine. Mulley et a l . (1975b) inves t iga ted the e f fec t of cocarboxylase concentrat ion i n cocarboxylase-thiamine hydro-c h l o r i d e mixtures i n phosphate buffer heated at 2 6 5 ° F ( 1 2 9 . 4 ° C ) . They found that with concentrat ions of up to 35% cocarboxylase i n the mixture, there was no inf luence on the rate of thiamine des t ruct ion at 2 6 5 ° F i n the pH range of 4.5 to 6 .5 . Thi s range of cocarboxylase concentrat ions and pH covers most food products . The authors concluded that i f these r e s u l t s could be extended to food, that the amount of cocarboxylase genera l ly found i n foods would not a f fect the k i n e t i c s of thiamine d e s t r u c t i o n . Di f ferences i n food composition may in part account for other v a r i a t i o n s noted i n the thermal des t ruc t ion of thiamine. Such v a r i a -t ions would be product dependent. Researchers who tested d i f f e r e n t food products have reported s i m i l a r des t ruc t ion behaviour which ind ica te s that composition d i f ferences play a r e l a t i v e l y minor r o l e (Far rer , 1955; F e l i c i o t t i and Esse len , 1957; Mulley et a l . , 1975a). B. Retort Pouches The re tor t pouch i s a food package made of a f l e x i b l e laminate which i s capable of withstanding the thermal processing required to achieve commercial s t e r i l i z a t i o n (Mermelstein, 1978). Items packed i n re tor t pouches have been compared to both canned, and frozen b o i l - i n - b a g - 10 -products . L i k e the can, the pouch i s hermet ica l ly sealed and thermally processed to achieve commercial s t e r i l i t y . As for b o i l - i n - b a g products , there i s a s i m i l a r t h i n p r o f i l e and reheating can be accomplished by immersion of the unopened package i n b o i l i n g water (Lampi, 1977). The U .S . Army Natick R&D Command (Nat ick , MA) with c o l l a b o r a t i o n from Cont inenta l F l e x i b l e Packaging (Chicago, IL) and Reynolds Metals Inc . (Richmond, VA) c a r r i e d out much of the development work on the re tor t pouch (Lampi, 1977; Mermelstein, 1978; Tuomy and Young, 1982). Thi s work, commencing i n the l a t e 1950's went through various stages i n a progression from exploratory inve s t i ga t ions to r e l i a b i l i t y s tudies required to make the re tor t pouch a commercial r e a l i t y . Summaries of the development work have been presented by Lampi (1977) and Mermelstein (1978). Su i t ab le f l e x i b l e packaging mater ia l s had to be developed i n order for the r e t o r t pouch to succeed. The mater ia l s must be capable of with-standing thermal processing temperatures as wel l as providing exce l l en t b a r r i e r propert ies for extended she l f l i f e , phys ica l strength to with-stand handling and d i s t r i b u t i o n abuse and the a b i l i t y to form an hermetic sea l (Lampi, 1977; Cage and C l a r k , 1980). Laminates i n use today genera l ly cons i s t of three l a y e r s , s t a r t i n g from the out s ide : po lyes te r , aluminum f o i l and an inner layer of polypropylene or poly-o l e f i n . The outer layer of polyester f i l m provides p r i n t a b i l i t y and s t rength . Aluminum f o i l serves as a moisture, l i g h t and gas b a r r i e r . The inner l ayer i s heat sea lable and provides an i n e r t food-contact surface (Mermelstein, 1978; Cage and C l a r k , 1980; He in tz , 1980). - 11 -P o t e n t i a l advantages of r e t o r t pouches compared to conventional packaging methods have been l i s t e d by many authors inc lud ing Mermelstein (1978) and Heintz (1980). The t h i n p r o f i l e of the r e t o r t pouch provides greater surface area than a c y l i n d r i c a l can of the same volume. This permits r ap id heat penetrat ion and thus reduces process t ime. With the use of shorter process times, improved food q u a l i t y , both sensory and n u t r i t i o n a l , i s to be expected as compared to s i m i l a r products packaged i n conventional cans. The re tor t pouch i s convenient for the consumer i n that i t can be stored without requ i r ing r e f r i g e r a t i o n for long periods of t ime. The product can be heated by immersion of the unopened pouch i n b o i l i n g water. The pouch can be e a s i l y torn or cut open, and once empty, i t can be f la t tened or burned for d i sposa l and there are no dangerous sharp edges. T o t a l package mater ia l costs are lower for a re tor t pouch and outer carton than for a three-piece s t ee l can. Both empty and f u l l r e t o r t pouches take less space and weigh le s s than metal cans. Studies have reported that less t o t a l energy i s required to provide the same product ready-to-eat from a r e t o r t pouch than from a can (Steffe et a l . , 1980; Wil l iams et a l . , 1982, 1983) as wel l as i n d i c a t i n g t o t a l cost benef i t s when using the re tor t pouch. Retort pouches are present ly used i n Canada, Europe, 3apan and the United S ta tes . Commercial production i n Europe and 3apan began i n the ear ly 1960's on a l i m i t e d sca le (Lampi, 1980). Mermelstein (1978) reported annual marketing f igures at that time of approximately 350 m i l l i o n pouches i n Dapan and 50 m i l l i o n i n England. In North America, the m i l i t a r y forces are major users of re tor t pouch packaged food. The - 12 -annual peacetime requirement for m i l i t a r y ra t ions i n the United States i s estimated at 40 m i l l i o n r e t o r t pouches of food (Heintz , 1980). The Canadian armed forces a l so use r e t o r t pouches for r a t ions (Morr i s , 1981). Retort pouches were f i r s t introduced to the North American r e t a i l market by Swan V a l l e y Foods of Vancouver, BC (Peters , 1975) i n November, 1974. In Canada, two firms c u r r e n t l y provide re tor t pouch foods (Magic Pantry Foods I n c . , Hamilton, ON and 3 .B . Empaquetage I n c . , S t . Hyacinthe, PQ). Although the pioneering work was c a r r i e d out i n the United States , the re tor t pouch has been slow to become es tab l i shed i n the r e t a i l market there . Approval by the Food and Drug Admini s t ra t ion and the United States Department of A g r i c u l t u r e for the use of r e t o r t pouches was not obtained u n t i l 1977 (Davis , 1981). Other drawbacks have slowed in t roduc t ion of the r e t o r t pouches on a large s c a l e . Major investments must be made for new production f a c i l i t i e s , whereas good f a c i l i t i e s are c u r r e n t l y in place for more t r a d i t i o n a l packaging forms (Davis , 1981). F i l l i n g and sea l ing equipment for the r e t o r t pouches operate at r e l a t i v e l y slow speeds (Will iams et a l . , 1983). The high c a p i t a l cost and slow production l i n e speeds have led to higher f in i shed product costs when compared to the same product packaged i n cans. As w e l l , consumers do not appear to be f u l l y aware of the advantages offered (Davis , 1981). In recent years , severa l companies i n the United States have introduced foods packed i n re tor t pouches to r e t a i l markets. These i n c l u d e : Hormel, I n c . , A u s t i n , MN; ITT Cont inenta l Baking C o . , Rye, NY; - 13 -Kra f t I n c . , Glenview, IL and Spec i a l ty Seafoods, Anacortes , WA (Heintz , 1980). C. Thermal Processing of Cans and Retort Pouches 1. Process ing Media Three media have been used for processing of f i l l e d containers i n r e t o r t s : steam; water immersion/overpressure systems and steam/air mixtures . Cans are t r a d i t i o n a l l y processed i n steam. Pure steam has the advantages of provid ing a high heat t rans fer rate to the containers with rapid r e t o r t response, and the process can be c o n t r o l l e d by a s i n g l e f ac tor , medium temperature or pressure (Wilson, 1980). Genera l ly , r e tor t pouches are processed with over r id ing pressure . Pouch seals are weakened by heating and are unable to withstand the same pressure d i f f e r e n t i a l s that may be sustained by metal cans (Lampi, 1977). In te rna l pressure i n re tor t pouches and cans increases during the re tor t cook cyc le due to the increased product temperature which causes: 1) increased vapour pressure of water i n the product; 2) increased pressure due to expansion of a i r i n the headspace; 3) re lease of a i r from the product due to decreased gas s o l u b i l i t y ; and 4) thermal expansion of the food product (Davis et a l . , 1960). This pressure may cause the pouch to expand even when product f i l l and re s idua l a i r are c o n t r o l l e d , due to v a r i a t i o n s i n external pressure caused by f l u c t u a -t ions i n process cond i t ions , and seal rupture can re su l t (Davis et a l . , 1960; Goldfarb , 1970; Whitaker, 1971). The over r id ing a i r pressure helps to counteract the tendency of noncondensible gases wi th in the - 14 -pouch to expand, which could reduce the o v e r a l l heat t rans fer c o e f f i -c ient at the food surface due to the presence of a gas l ayer (Goldfarb, 1970; Whitaker, 1971). During the coo l ing cyc le which fol lows the cook, the medium surrounding the container w i l l have a lower temperature than the food w i t h i n , and at t h i s stage, overr id ing pressure i s required to prevent burst ing of r e to r t pouches. In Oapan, pure steam has been used for processing of r e t o r t pouches with a high processing temperature to achieve very rapid heating so as to maintain a higher pressure external to the pouch than i s developed i n t e r n a l l y . These short processes must be c a r e f u l l y con-t r o l l e d with a i r introduced during coo l ing to counteract high i n t e r n a l pressures (Tsutsumi, 1979a, b and c ) . In order to provide over r id ing a i r pressure, r e to r t pouches are usual ly processed i n steam/air mixtures or water immersion/overpressure systems (Lampi, 1977). When processing with steam/air mixtures, both temperature and pressure of the media must be c o n t r o l l e d because heat t rans fer rates decrease with increas ing a i r content of the mixture (Ramaswamy, 1983). Moreover, adequate mixing must be provided to avoid accumulation of a i r pockets that would exh ib i t poor heating (Lampi, 1977; Wilson, 1980). Mixing can be achieved by a p o s i t i v e flow system i n which there i s continuous vent ing , or by using a fan (Pflug and Borrero , 1967; Lampi, 1977; M i l l e v i l l e , 1981). L ike steam/air mixtures , with water immersion/overpressure systems, both medium temperature and pressure must be c o n t r o l l e d . With water, heat t rans fer rates are lower than for pure steam and good c i r c u l a t i o n must be maintained to prevent - 15 -temperature s t r a t i f i c a t i o n (Lampi, 1977; Wilson, 1980). In conventional r e t o r t s , extra time i s required for heating of water i n the re tor t at the s t a r t of the cook (Pflug et a l . , 1963); however i n s p e c i a l water immersion r e t o r t s , the come-up time can be reduced by using preheated water (Lampi, 1977). Water hardness may re su l t i n s o i l e d pouches and bui ld-up of scale on separat ion p la te s , and excessive v i b r a t i o n s may be caused by improper or rapid add i t ion of steam (Pflug et a l . , 1963). When processing re tor t pouches, care must be exercised to obta in reproducib le and small amounts of headspace a i r i n the pouches, to confine pouches during processing so they have a known maximum th ick-ness, and to allow for e f f i c i e n t c i r c u l a t i o n of the heating medium between layers of pouches (Beverly et a l . , 1980; Ramaswamy, 1983). Residual gas i n unconfined pouches w i l l cause increased thickness of the pouch during processing because of thermal expansion of the gas, and longer process times w i l l be requ i red . In confined pouches as wel l as i n cans, r e s idua l a i r may cause product q u a l i t y degradation due to ox ida t ive react ions (Beverly et a l . , 1980). When used proper ly , a l l three media can be e f f e c t i v e l y employed to process r e to r t pouches (Pflug et a l . , 1963; Lampi, 1979), with each of the media having i t s own proponents. Pure steam i s genera l ly used for processing metal cans because of i t s r e l a t i v e s i m p l i c i t y and high heat t rans fer r a te . 2. Temperature Measurement Data obtained from heat penetrat ion tes t s conducted on containers of food during processing can be used to c a l c u l a t e the process time - 16 -required for that product. Temperature measurements are made at the slowest heating point (cold spot) in the f i l l e d conta iner . Procedures for conducting such heat penetrat ion tes t s have been described by Als t rand and Ecklund (1952), Pf lug (1975) and Bee and Park (1978). In cans, Ecklund Type-T r i g i d thermocouples (O .F . Ecklund I n c . , Cape C o r a l , FL) have been the primary means used to obtain temperature measurements for heat penetrat ion work (Bee and Park, 1978). Spec i a l receptacles and connectors are a v a i l a b l e for use with these thermo-couples from the same company. Ecklund (1956) reported that errors associated with the conduction of heat into the product from receptac les which pro ject in to cans could be taken in to account by adjust ing the lag factor ( j) i n 307 (87 mm) and smaller diameter cans of conduction-heating product . (Thermal processing abbreviat ions and terminology are presented i n Appendix I .) The lack of r i g i d i t y associated with the r e t o r t pouch has required development of devices to ensure l o c a t i o n of a thermocouple i n the des i red p o s i t i o n (Pflug et a l . , 1963). Several methods have been proposed for i n s e r t i o n of thermocouple leads into pouches. The wires may be introduced separately by heat sea l ing them into one of the pouch seals (Pflug et a l . , 1963), or by threading them through small holes i n the pouch wal l which are sealed with s i l i c o n e rubber (Spinak and Wiley , 1982). Placement of the wire through the seal area may weaken the sea l and cause wide seals which can d i s t o r t pouch dimensions (Davis et a l . , 1972). In e i ther case, these methods are labourious and time consuming (Pflug et a l . , 1963; Spinak and Wiley , 1982). - 17 -A second method for i n s e r t i o n of a thermocouple in to a re tor t pouch involves the use of a spec i a l packing gland which has a compres-s ion f i x t u r e to achieve a seal around the thermocouple wire (Pflug et a l . , 1963). These glands are convenient and r e l a t i v e l y easy to use (Pflug et a l . , 1963; Davis et a l . , 1972) but may i n t e r f e r e with th ick-ness r e s t r i c t i o n s provided by the re tor t racks or the normal geometry of the pouch (Berry, 1979). Kopetz et a l . (1979) ind ica ted that the use of these packing glands could lead to er ror s due to conduction of heat from the metal gland to the thermocouple j u n c t i o n . D e t a i l s of the experiment were not presented. Spinak and Wiley (1982) found that no s i g n i f i c a n t e r ror s were introduced when an Ecklund packing gland was 1.5 i n (38 mm) from the thermocouple junct ion in a conduction-heating product (banana puree) as compared to sea l ing the wires through the pouch wal l with s i l i c o n e rubber sea lant . A t h i r d p o s s i b i l i t y for i n s e r t i o n of a thermocouple i s to use a receptac le which allows the p o s i t i o n i n g of a r i g i d thermocouple in a manner s i m i l a r to those used i n cans. An angle bracket i s mounted outside the pouch with a t h r o u g h - f i t t i n g on the receptac le to help p o s i t i o n the thermocouple and determine pouch th ickness . A rubber spacer d i s c placed on the r i g i d thermocouple a short d is tance from the sensing j u n c t i o n , rests on the bracket to ensure proper p o s i t i o n i n g of the thermocouple t i p . Receptacles and packing glands for r e t o r t pouches are a v a i l a b l e from O . F . Ecklund, Inc . Once inser ted into the pouch, the thermocouple must be held at the des i red p o s i t i o n . For s o l i d food mater ia l s which contain s l i c e s or - 18 -chunks, the thermocouple can be placed within a piece or between s l i c e s (Pflug et a l . , 1963). In l i q u i d and semi- l iqu id products , the thermo-couple can be located at the center of a c o i l spr ing with the same i n t e r n a l diameter as the thickness of the pouch to be used. Food can be forced in to the spring i f requi red , to completely surround the sensing t i p (Davis et a l . , 1972; P f l u g , 1975). Pf lug et a l . (1963) reported success with these same types of products using a p l a s t i c "saddle" to pos i t i on the thermocouple. Another p o s s i b i l i t y i s to use an i n t e r n a l folded V-shaped gusset made of the same mater ia l as the pouch and heat-sealed to the walls of the pouch to hold the wire . The gusset i s designed to keep a fine-gauge thermocouple centered i n the pouch regardless of pouch th ickness , as long as i t s length i s not exceeded (Pflug et a l . , 1963). In l i q u i d products a wooden s t i c k may be located d iagonal ly i n the pouch with the thermocouple s tapled to the s t i c k (P f lug , 1975). The choice of method for p o s i t i o n i n g a thermocouple i n a pouch has l a r g e l y been determined by p r a c t i c a l cons idera t ions . There i s l i t t l e information a v a i l a b l e which compares the various methods. Berry (1979) used 16 gauge copper c o i l spr ings , 18 gauge s tee l c o i l springs and a gusset as prev ious ly described to center thermocouple wires i n r e t o r t pouches conta ining cream of ce lery soup. He reported d i f ferences i n the c a l c u l a t e d process l e t h a l i t i e s (FQ) determined using the same process c o n d i t i o n s . These d i f ferences were thought to be due to conduction of heat to the product through the c o i l s . However, t h i s report did not provide d e t a i l s on the degree of v a r i a t i o n encountered or the s t a t i s t i -ca l s i g n i f i c a n c e of the observed d i f f e rence s . - 19 -3. Process Determination Thermal process times are determined to ensure that the product rece ives a heat treatment s u f f i c i e n t to destroy expected spoi lage organ-isms. Various c a l c u l a t i o n methods have been developed for process time determination and have been proven s a t i s f a c t o r y with years of use for metal cans and glass j a r s . The concepts re la ted to mic rob ia l s u r v i v a l have d i r e c t a p p l i c a b i l i t y to process determination for foods i n re to r t pouches s ince mic rob ia l h i s t o r i e s and growth condi t ions are the same (Lampi, 1977). The reported experience has ind ica ted that the standard mathematical formulas for process c a l c u l a t i o n s may be used when f^ (heating rate index) and j n (heating lag factor) can be used to descr ibe the heat penetrat ion data . When a semi-logari thmic heating p lot shows no s t r a i g h t - l i n e sect ion the general method i s suggested for use (Lampi, 1977). The general method i s the most accurate method for c a l c u l a t i o n of process l e t h a l i t y . However, t h i s method provides l i t t l e f l e x i b i l i t y i n al lowing mathematical determination of process changes when v a r i a t i o n s i n condi t ions occur . The formula methods allow increased f l e x i b i l i t y and reduce the amount of c a l c u l a t i o n required to determine process times (Stumbo, 1973). B a l l ' s formula method i s the most commonly used formula method i n the food industry for process c a l c u l a t i o n s (Spinak and Wiley , 1982). Spinak and Wiley (1982) compared B a l l ' s formula method with the general method for determination of process times using three products packed i n re tor t pouches (banana puree, steak s t r i p s and diced white - 20 -potatoes i n b r i n e ) . These researchers found B a l l ' s formula method could be improved to agree with the shorter process times determined by the general method by inc lud ing the come-up c o n t r i b u t i o n to l e t h a l i t y and the ac tua l coo l ing lag factor ( j c ) rather than assuming a value of 1.41 as i s done i n B a l l ' s f n / U versus g t ab le s . For the cold spot, U represents the equivalent i n minutes at r e to r t temperature of a l l l e t h a l heat received and g i s the number of degrees below re tor t temperature at the end of the heating per iod . With these changes, the c a l c u l a t i o n method becomes the procedure re ferred to as Stumbo's method (Stumbo, 1973). No improvement was noted when the actua l coo l ing rate index was used instead of assuming f c = ^ h * With the recommended changes to B a l l ' s formula method, process times predicted for the slowest heating and fastest coo l ing pouch(es) tested were within one minute of those determined with the general method (Spinak and Wiley , 1982). Stumbo's method has been succes s fu l ly used for metal cans as w e l l . Smith and Tung (1982) used a f i n i t e d i f ference s imulat ion tech-nique to generate temperature h i s t o r y curves for conduction-heat ing foods i n c y l i n d r i c a l conta iners of a v a r i e t y of s i zes processed under a range of c o n d i t i o n s . The de l ivered l e t h a l i t y ca lcu la ted by f i v e formula methods was compared to that determined using the general method with numerical in teg ra t ion and small time i n t e r v a l s . Of the formula methods te s ted , Stumbo's method was found to provide the most accurate estimates of process l e t h a l i t y over a l l condi t ions t e s t ed . - 21 -D. Quality of Thermally Processed Products 1. Basic Considerat ions Thermal processes are used i n conjunction with other preservat ion techniques to extend the she l f l i f e of foods. The treatment received by the product i s designed to reduce the a c t i v i t y of undesirable components such as enzymes and microorganisms i n the food product to achieve com-mercia l s t e r i l i t y . Such a heat treatment w i l l i n a c t i v a t e microorganisms or t h e i r spores which could grow and cause spoi lage or a heal th hazard under the condi t ions of s torage. Containers inc lud ing metal cans, g lass j a r s and re tor t pouches may be used to provide an hermet ica l ly sealed, anaerobic environment (Lund, 1977). Concomitant with the thermal des t ruct ion of mic rob ia l populat ions i s the degradation of q u a l i t y a t t r i b u t e s of a food. The q u a l i t y a t t r i -butes include both sensory and n u t r i t i o n a l propert ies (Lund, 1977; Tung and Smith, 1980). Processes which are equivalent i n terms of accom-p l i shed l e t h a l i t y do not neces sar i ly r e s u l t i n the same re tent ion of q u a l i t y a t t r i b u t e s (Lund, 1977). The thermal processor wishes to provide the consumer with a safe product, yet one e x h i b i t i n g good reten-t ion of q u a l i t y a t t r i b u t e s (Te ixe i ra et a l . , 1975; Lund, 1977; Tung and Smith, 1980). Thermal res i s tance of the food components of concern must be considered to develop s t r a teg ie s for maximizing re tent ion of q u a l i t y a t t r i b u t e s . Representative values are presented i n Table 2. Examina-t i o n of these data i n d i c a t e severa l important po in t s . The temperature dependence for vulnerable q u a l i t y a t t r i b u t e s , both sensory and n u t r i -t i o n a l are s i m i l a r . Thus, opt imiza t ion for one q u a l i t y a t t r i b u t e w i l l - 22 -Table 2 . Thermal res i s tance of various food cons t i tuent s . Const i tuent k i 2 i , m i n - 1 E . kO/mol a Vitamins 0.002-0.02 80-130 Colour , texture , f lavour 0.005-0.5 40-130 Enzymes 0.2-2 50-400 Vegetat ive c e l l s 100-1000 400-500 Spores 0.5-20 220-350 Based on Lund (1977). - 23 -genera l ly optimize the re tent ion of a l l q u a l i t y a t t r i b u t e s (Lund, 1975, 1979; R i z v i and Acton, 1982). Spores are more heat r e s i s t e n t than vege-t a t i v e c e l l s ; there fore , thermal processes to obtain commercial s t e r i l -i t y are based on spore des t ruct ion when product composition and storage condi t ions can allow growth of the spores of concern (Stumbo, 1973). At a given temperature, q u a l i t y factors are genera l ly much more r e s i s t a n t to thermal des t ruc t ion than spores or vegetat ive c e l l s (Lund, 1977, 1979; Tung and Smith, 1980). As a consequence microb ia l popula-12 t ions can be reduced by factors of 10 by thermal processes without rendering the product unacceptable or n u t r i t i o n a l l y worthless (Lund, 1977). The temperature s e n s i t i v i t i e s of thermal des t ruc t ion rates for q u a l i t y factors are less than for spores (Lund, 1977; Tung and Smith, 1980). The combination of these factors suggest that by increas ing the temperature used, the reduced time required to achieve the des i red l e v e l of l e t h a l i t y w i l l r e s u l t i n greater re tent ion of nutr ient s (Lund, 1975). However, t h i s w i l l be true only when i t can be assumed that each volume element receives approximately the same l e t h a l heat treatment. This assumption can be made for convect ion-heat ing foods or those processed i n e f f i c i e n t heat exchangers. In e i ther case, any p a r t i c u -la tes must be s t e r i l e in the i n t e r i o r . Under these cond i t ions , high temperature short time (HTST) processes w i l l genera l ly r e s u l t i n maximum re tent ion of q u a l i t y a t t r i b u t e s (Jackson and Benjamin, 1948; Lund, 1977). In conduction-heating products and convect ion-heat ing products which contain p a r t i c l e s that are not s t e r i l e i n the i n t e r i o r , heating to the co ld spot takes place r e l a t i v e l y s lowly . Each volume element - 24 -rece ives a d i f f e ren t temperature h i s t o r y . In order to determine the o v e r a l l re tent ion of a q u a l i t y a t t r i b u t e , the ef fect of the thermal treatment must be integrated for every point wi th in the container (Lund, 1977). The remainder of t h i s d i scus s ion on q u a l i t y re tent ion i n products thermally processed to achieve commercial s t e r i l i t y w i l l concentrate on two factors which have been studied for t h e i r e f fect on the re tent ion of q u a l i t y f ac tor s : container shape and processing temperature. Emphasis w i l l be placed on conduction-heating products , and nutr ient re tent ion as an i n d i c a t o r of q u a l i t y re tent ion due to t h e i r d i r e c t a p p l i c a t i o n to t h i s research p r o j e c t . 2 . E f fec t of Container Shape Each point within the container must rece ive a heat treatment s u f f i c i e n t to destroy the mic rob ia l populat ion of concern i n order to produce a safe product . In conduction-heating products , the rate of temperature response within the product i s l i m i t e d by the dis tance within the food through which the heat must penetrate and by the thermal d i f f u s i v i t y of the product . The thermal d i f f u s i v i t y i s a mater ia l property for a p a r t i c u l a r product, but the thickness of mater ia l through which the heat must penetrate can be changed by a l t e r i n g the container geometry (Te ixe i r a et a l . , 1975). By reducing the dis tance required for heat penetra t ion , process times required to achieve a safe product can be reduced and re tent ion of q u a l i t y a t t r i b u t e s improved (Te ixe i ra et a l . , 1975; Tung and Smith, 1980; R i z v i and Acton, 1982). - 25 -T e i x e i r a et a l . (1975) used a f i n i t e d i f ference computer model to c a l c u l a t e temperature h i s t o r i e s at many loca t ions wi th in conta iner s , coupled with m i c r o b i a l spore and thiamine degradation k i n e t i c s to pred ic t thiamine re tent ion i n conduction-heating foods processed at 2 5 0 ° F ( 1 2 1 . 1 ° C ) i n d i f f e r e n t c y l i n d r i c a l can s izes r ece iv ing the same s t e r i l i z a t i o n e f f e c t . A 307x409 can (87 mm diameter by 116 mm high) was used as a reference and cans with the same volume but lower and higher length to diameter r a t i o s (L/D) were cons idered . For an L/D of approxi-mately 0.1 ( f l a t disk geometry), thiamine re tent ion was 68% compared to 41% re tent ion for the re ference . With the opposite extreme tested (L/D=10) improvement i n thiamine re tent ion of the same order of magni-tude was found. A s i m i l a r type of study was conducted by Ohlsson (1980a), who used d i f f e r e n t can s i ze s which provided d i f f e r e n t volumes. The integrated e f fect on q u a l i t y was expressed as the cook va lue . His r e s u l t s a l so showed that improved q u a l i t y could be obtained by using cans which provided a minimum dis tance for heat penetrat ion to the center . Tung and Smith (1980) a l so used f i n i t e d i f ference modell ing of heat t r ans f e r . They compared the integrated e f fect on q u a l i t y for number 10 cans (603x700; 100 oz; 157 mm diameter by 178 mm h igh) , h a l f - s i z e steam table t rays and i n s t i t u t i o n a l - s i z e d r e t o r t pouches containing conduction-heating food and processed at 1 2 1 ° C to obta in equivalent center point l e t h a l i t y . Qual i ty factor degradation was less for both the pouch and steam table tray than for the can. The same e f fec t was observed when 400 g pouches and cans were compared over a - 26 -process ing temperature range of 115 to 1 3 5 ° C . Computer s imulat ion was used by Adams et a l . (1983) to consider the p o s s i b i l i t y of processing tuna i n re tor t pouches. Thiamine re tent ion and process times were p r e d i c t e d . The shorter process times required for r e t o r t pouches of 1.25 i n (32 mm) thickness resu l ted i n the product r e t a i n i n g more t h i a -mine when processed at e i ther 2 4 0 ° F ( 1 1 5 . 6 ° C ) or 2 5 0 ° F ( 1 2 1 . 1 ° C ) than approximately the same amount of product processed i n 603x408 (157 mm diameter by 114 mm high) cans. Other researchers have c a r r i e d out actual processing experiments to compare r e t o r t pouches and .cans for q u a l i t y a t t r i b u t e r e t e n t i o n . Greene (1979) demonstrated that the r e ten t ion of thiamine and r i b o f l a v i n i n sweet potato puree was s i g n i f i c a n t l y improved and process time reduced when 12 oz (340 g) of product was processed at 2 4 0 ° F ( 1 1 5 . 6 ° C ) or 2 5 0 ° F ( 1 2 1 . 1 ° C ) i n r e t o r t pouches as compared to cans. The d i f f e r -ences i n thiamine and r i b o f l a v i n re tent ion were 21 and 12%, respec-t i v e l y . The ef fect of these processes on beta-carotene was n e g l i g i b l e . The q u a l i t y of cream s t y l e corn processed i n cans i n both s t i l l and continuously agi tated r e t o r t s , and i n re tor t pouches was evaluated by Tung et a l . (1975). Sensory evaluat ions a f ter two weeks of room temperature storage showed no d e f i n i t e q u a l i t y advantages for the product i n r e t o r t pouches. The researchers suggested that the pouches were probably overprocessed due to process times being es tab l i shed for a pouch thickness of 38 mm, while the average depth was 19 mm. Pere i ra (1980) processed cherry pie f i l l i n g i n r e t o r t pouches and cans with heating times determined for peroxidase i n a c t i v a t i o n . This - 27 -was an ac id product so the processes were r e l a t i v e l y m i l d . The ef fects of varying pouch th ickness , superimposed a i r pressure during processing and pouch vacuum were evaluated for t h e i r e f fects on end-product qual-i t y . On an o v e r a l l bas i s , a scorbic ac id content of cherry pie f i l l i n g processed i n cans d id not d i f f e r from that of the pouch treatments when measured one week a f ter process ing . None of the pouch treatments tested gave s i g n i f i c a n t l y higher a scorbic ac id content compared to the canned product . Texture and colour were a lso evaluated. Comparison of r e su l t s for r e to r t pouches and cans was made d i f f i c u l t by the v a r i e t y of r e to r t pouch processing treatments t e s ted . Other researchers have s tudied vegetable and f r u i t products packed with br ine or syrup. These f l u i d s are added to canned p a r t i c u l a t e products to provide for heat t rans fer from the container wal l throughout the product f i l l during heat ing . However, the f l u i d a lso leaches water so lub le nutr ient s from the product and cons t i tu te s a d d i t i o n a l weight during t ranspor ta t ion and storage. With re tor t pouches, the shorter d i s tance required for heat penetra t ion , and co l l apse of the pouch around the s o l i d product by vacuum packing has permitted a reduct ion or e l i m i n -a t ion of the added f l u i d while s t i l l a l lowing reduced processing times and providing a high q u a l i t y product . Leaching of nutr ient s can a l so be reduced ( R i z v i and Acton, 1982). Thus, reductions i n both process time and amount of br ine or syrup may lead to improved nutr ient re tent ion for products packed with l i q u i d s i n pouches as compared to cans. Uribe-Saucedo and Ryley (1982) reported greater a scorbic ac id losses for both the t o t a l package and s o l i d s on ly , when Jersey new pota-toes were processed i n cans as compared to pouches. Abou-Fadel and - 28 -M i l l e r (1983) found that green beans packed i n cans reta ined s i g n i f i -cant ly less thiamine and ascorbic ac id and were l i g h t e r i n co lour , more yellow and sof ter than those processed i n re tor t pouches of the same volume. Vitamin B-6 losses were not s i g n i f i c a n t l y af fected by the process ing method. Chen and George (1981) a l so evaluated the q u a l i t y of green beans, but used home-processing c o n d i t i o n s . Beans processed i n cans contained s l i g h t l y more ascorbic a c i d , but had poorer texture and lower o v e r a l l acceptance than those processed i n pouches. Heat penetra-t i o n data were not obtained i n t h i s study to allow comparison of process l e t h a l i t i e s . The researchers suggested that the beans packed i n r e t o r t pouches were probably overprocessed due to the slow cool ing procedure used to prevent pouches from b u r s t i n g . They f e l t that the texture d i f f e rence may have been re la ted to the combination of a shorter process time and the presence of a lower amount of brine i n the pouched product compared to the canned product . Abou-Fadel and M i l l e r (1983) a l so studied Royal Ann c h e r r i e s . The cherr i e s processed i n re tor t pouches contained s i g n i f i c a n t l y more ascorbic a c i d , were more in tense ly red and firmer than those processed i n cans, although vitamin B-6 re tent ion was not s i g n i f i c a n t l y af fected by the processing method. Meat and f i s h products have a lso been s tud ied . Lyon and Klose (1981) used a t ra ined panel to evaluate the texture and o f f - f l a v o u r of chicken from 29 oz (822 g) cans, cooked fowl meat processed i n r e t o r t pouches (4-54 g ) , uncooked fowl meat processed i n re tor t pouches (463 g) and simmered fowl meat as a c o n t r o l . Process ing i n r e t o r t pouches provided for adequate t e n d e r i z a t i o n , but unl ike the canned product, - 29 -overcooking d id not occur to the extent that meat chunks were reduced to f ib rous , shredded or s t r ingy components. The smaller amount of product packed i n the r e t o r t pouches compared to the cans may have favoured the texture advantage shown by the re tor t pouch (pouch thickness was not repor ted) . Of f - f l avour development was found to be re la ted to precook-ing of the meat p r i o r to thermal process ing . Pf lug (1964) found that beef processed i n r e t o r t pouches was preferred by a sensory panel over that processed i n cans. Seafood items were processed by Adams et a l . (1983) i n large re tor t pouches with a thickness of 1 i n (25 mm) at 2 5 0 ° F ( 1 2 1 . 1 ° C ) . The products tested were red snapper, Spanish mackerel, blue crab (body and claw), shrimp (125 and 35 count/ lb) and flaked ye l lowf in tuna. Optimal l e v e l s of added water, s a l t , c i t r i c ac id and ethylene diamine t e t r a -a c e t i c ac id were determined based on pre l iminary t e s t s . The products processed i n r e t o r t pouches were compared to the same products processed i n 307x113 cans (87 mm diameter by 46 mm high) according to published schedules . A l l of the products processed i n pouches were i n general judged by sensory pane l i s t s to be as good as or superior to the products processed i n much smaller cans. Rainbow t r o u t , pol lock and shrimp were processed i n re tor t pouches and cans without added l i q u i d by Chia et a l . (1983). The products processed i n pouches reta ined more thiamine (di f ferences of 17%, 9% and 15% re tent ion for rainbow t r o u t , po l lock and shrimp, r e s p e c t i v e l y , on a drained weight basis) compared to the products processed i n cans. In a l l cases products i n pouches were f irmer and had a l i g h t e r colour than did the canned products . In - 30 -sensory eva luat ions , the products i n pouches were scored higher i n most cases for co lour , f lavour and o v e r a l l a c c e p t a b i l i t y . Two groups of researchers have s tudied stew-type products . Oimenez et a l . (1976) evaluated ascorbic ac id and thiamine re tent ion as wel l as sensory q u a l i t y of beef stew processed i n cans and r e t o r t pouches. The reheated stew which had been processed i n r e t o r t pouches reta ined more ascorbic ac id and thiamine than stew processed i n cans. These researchers suggested that reheating of the canned stew i n an open pan exposed to oxygen compared to immersion of a sealed pouch i n b o i l i n g water may have i n part led to the d i f ference noted i n ascorbic ac id r e t e n t i o n . There was a cons i s tent preference shown for the product processed i n re tor t pouches compared to that processed i n cans. Ur ibe-Saucedo and Ryley (1982) evaluated ascorbic ac id and thiamine re tent ion i n pork casserole processed i n cans and re tor t pouches. Retention of both nut r i ent s was greater for the product processed i n r e t o r t pouches than for product processed i n cans. Thus, a change in container geometry o f fer s the p o s s i b i l i t y of improving re tent ion of q u a l i t y a t t r i b u t e s . For such improvements to be observed, i t would appear that ca re fu l c o n t r o l of processing condi t ions must be maintained to ensure that overprocessing does not occur . 3. E f f ec t of Process ing Temperature As mentioned p r e v i o u s l y , to consider the ef fect of changing the process temperature for conduction-heating foods, the e f fect of the thermal treatment must be integrated for every point wi th in the - 31 -conta iner . Various computer s imulat ion s tudies have been used to pred ic t the e f fects of changing process temperature on both c y l i n d r i c a l and rectangular shaped conta iner s . T e i x e i r a et a l . (1969) used f i n i t e d i f ference modell ing to predic t thiamine re tent ion i n a conduction-heat ing product processed i n a c y l i n -d r i c a l conta iner . These researchers showed that p red ic t ions favouring high temperature, short time processes based on a comparison of rate data w i l l not always hold for conduction-heating products . In f ac t , thiamine re tent ion may decrease with increas ing temperature. The product receives a r e l a t i v e l y severe heat treatment at the outer surfaces in order to heat the food s u f f i c i e n t l y at the center and t h i s r e s u l t s i n lower thiamine re tent ion o v e r a l l . I t was demonstrated that the optimum temperature w i l l vary depending upon the condi t ions under s tudy. A heat l a b i l e factor with a r e l a t i v e l y low z value (high E a) showed optimum re tent ion with a r e l a t i v e l y low process temperature compared to a high z value q u a l i t y factor for which re tent ion was favoured by a higher temperature process . The poss ib le undesirable e f fect s on product q u a l i t y as a r e su l t of increas ing process temperature for c y l i n d r i c a l conta iners of conduction-heating food were a l so demon-s trated by Tung and Smith (1980) for 400 g cans. Ohlsson (1980a) used a s i m i l a r type of study to p red ic t the integrated e f fect on q u a l i t y (cook value) i n conduction-heating foods i n c y l i n d r i c a l cans. The i r r e s u l t s showed the same trends as d id those of' T e i x e i r a et a l . (1969). Also tested were the e f fects of changing can s i z e , process l e t h a l i t y (F 0 ) and i n i t i a l temperature on the optimum - 32 -process temperature required for the minimum cook value . Increas ing the can s i ze sh i f ted the optimal temperature to lower va lues . The research-ers suggested that for normal can s i z e s , optimal temperatures were i n the range of 117 to 1 1 9 ° C , and that only for s u b s t a n t i a l l y smaller can diameters or heights would s t e r i l i z a t i o n at a higher temperature be an advantage. For s t e r i l i z a t i o n to higher F 0 va lues , the optimal temper-ature was increased . The optimal temperature range d id not change when i n i t i a l temperature was a l t e r e d . The s h i f t i n optimal temperature range predicted by Ohlsson (1980a) for a change i n can s i ze would lead one to suggest that for f l a t conta iners the e f fect of increas ing process temperature on q u a l i t y a t t r i b u t e re tent ion might be d i f f e r e n t than for standard c y l i n d r i c a l conta iner s . This has been shown to be the case. T e i x e i r a et a l . (1975) used computer s imulat ion to pred ic t t h i a -mine re tent ion i n a c y l i n d r i c a l can shaped l i k e a f l a t disk (L/D=0.1) containing the same volume of conduction-heating product as a 307x409 can. The processing temperatures evaluated were 2 5 0 ° F ( 1 2 1 . 1 ° C ) and 2 6 5 ° F ( 1 2 9 . 4 ° C ) . The thiamine re tent ion predicted increased with the increase i n processing temperature (68% to 77% r e t e n t i o n ) . Adams et a l . (1983) used a s i m i l a r technique to predic t thiamine re tent ion i n tuna processed i n i n s t i t u t i o n a l s ized r e t o r t pouches of three d i f f e r e n t th icknesses . At a l l th icknesses , an increase i n process temperature from 2 4 0 ° F ( 1 1 5 . 6 ° C ) to 2 5 0 ° F ( 1 2 1 . 1 ° C ) resul ted i n an increase i n thiamine r e t e n t i o n . - 33 -Tung and Smith (1980) predicted the integrated ef fect on q u a l i t y i n a conduction-heating food product processed i n a 400 g pouch. Process ing temperatures i n the range of 115 to 1 3 5 ° C were tested using computer s i m u l a t i o n . Improvements i n q u a l i t y a t t r i b u t e re tent ion were noted up u n t i l approximately 1 2 5 ° C with re tent ion remaining steady when the processing temperature was increased fur ther . These researchers a l so predicted process times for s p e c i f i e d center point l e t h a l i t i e s . The use of higher process temperatures reduced required process times and thus throughput could be increased with poss ib le energy savings . Using process temperatures from 115 to 1 3 5 ° C for 400 g conta iner s , i t was found that process times for pouches were reduced considerably as temperature increased up to 125 or 1 3 0 ° C , but further process tempera-ture increases re su l ted i n l i t t l e ga in . Process time decreased through-out the e n t i r e temperature range tested for cans of the same s i z e . Ohlsson (1980b) predicted optimal process temperature for minimum cook value for f l a t conta iner s . The e f fec t s of z va lue , F 0 and i n i t i a l temperature on optimal process temperature showed the same trends as for c y l i n d r i c a l containers (previous ly d i scussed) . Increas ing the thickness increased the cook value for a given set of process c o n d i t i o n s . Adams et a l . (1983) predicted a s i m i l a r trend for thiamine re tent ion i n tuna i n i n s t i t u t i o n a l pouches of d i f f e r e n t th icknesses . Each product and container must be evaluated separately to o p t i -mize process temperature for q u a l i t y a t t r i b u t e re tent ion (Tung and Smith, 1980). Di f ferences i n k i n e t i c parameters and container geometry can change the d i r e c t i o n and/or magnitude of the change r e s u l t i n g when the process temperature i s a l t e r e d . - 34 -Greenwood et a l . (1944) evaluated thiamine, r i b o f l a v i n , n i a c i n and pantothenic ac id re tent ion i n pork luncheon meat processed i n 12 oz (340 g) and 2.5 lb (1.13 kg) cans at 2 2 5 ° F ( 1 0 7 . 2 ° C ) , 2 3 5 ° F ( 1 1 2 . 8 ° C ) and 2 4 5 ° F ( 1 1 8 . 3 ° C ) . Approximately equivalent amounts of B vitamins were re ta ined when the process temperature was changed. There was an i n d i c a -t i o n that the 2 4 5 ° F process was i n f e r i o r compared to the 225 and 2 3 5 ° F processes for re tent ion of thiamine. These researchers demonstrated that nutr ient re tent ion var ied with l o c a t i o n i n the 2.5 l b can. Reten-t i o n of a l l vitamins increased through the l o a f of meat from the outer edge to the center . Sweet potato puree processed i n 12 oz (340 g) r e t o r t pouches and cans at temperatures of 2 4 0 ° F ( 1 1 5 . 6 ° C ) and 2 5 0 ° F ( 1 2 1 . 1 ° C ) was evalu-ated for nutr ient re tent ion by Greene (1979). No s i g n i f i c a n t d i f f e r e n -ces i n the re tent ion of thiamine, r i b o f l a v i n or beta-carotene were found between the two process temperatures. With the increase i n process temperature thiamine and r i b o f l a v i n re tent ion decreased for the cans, while thiamine re tent ion increased for the re tor t pouch. The thermal treatments had a n e g l i g i b l e e f fect on beta-carotene content i n a l l processes and there was no d i f ference i n r i b o f l a v i n re tent ion between the two temperatures when the product was processed i n r e t o r t pouches. Thus, there i s p o t e n t i a l to improve q u a l i t y re tent ion i n thermally processed foods by a l t e r i n g the container geometry and/or process temperature. Of the two, changes i n container geometry can provide a l a rger improvement (Te ixe i r a et a l . , 1975). The magnitude of the d i f fe rences and optimum process temperature w i l l depend on the product - 35 -and container tes ted , as wel l as the thermal degradation k i n e t i c s of the q u a l i t y a t t r i b u t e under i n v e s t i g a t i o n . 4 . Goals of Th i s Research Pro jec t In t h i s p ro j ec t , thiamine re tent ion i n a luncheon-type ham product processed i n cans and re tor t pouches was evaluated. A l i m i t e d number of s tudies have been conducted to compare q u a l i t y of meat products pro-cessed i n re tor t pouches and cans. As previous ly d i scussed , nutr ient re tent ion has been evaluated i n stew-type products by two groups of researchers (Jimenez et a l . , 1976; Uribe-Saucedo and Ryley, 1982). Lyon and Klose (1981) evaluated sensory a t t r i b u t e s of a conduction-heating meat product with some added f l u i d . Chia et a l . (1983) evaluated nutr ient re tent ion i n f i s h products which were packed without l i q u i d . None of these s tudies considered the e f fect of a change i n process temperature. This lack of s tudies on meat products i s despi te the fact that most of the products c u r r e n t l y being processed i n r e t o r t pouches i n North America for r e t a i l d i s t r i b u t i o n are meat-based. The one study found which used actual processing tests i n cons ider ing the effect of changing the process temperature for products packed i n r e t o r t pouches was that of Greene (1979) i n which sweet potato puree was t e s ted . The thermally l a b i l e nutr ient s se lected to evaluate the ef fect of heating have most commonly been ascorbic ac id and/or thiamine. Meat, poul t ry and f i s h contr ibute s i g n i f i c a n t l y to our thiamine in take . Data a v a i l a b l e from the U .S . Department of A g r i c u l t u r e for 1974 i n d i c a t e that 28.1% of the thiamine suppl ies a v a i l a b l e for c i v i l i a n consumption were - 36 -provided by t h i s group of products (Karmas, 1975). Pork products have much higher thiamine contents than do other meats. For example, i n roast ham there i s approximately 0.5 mg of thiamine per 100 g, while i n roast beef there i s approximately 0.06 mg per 100 g (Health and Welfare Canada, 1979). The use of a luncheon-type ham product as the tes t product provided a conduction-heating mater ia l that was r e l a t i v e l y homogeneous. Conduction-heating products would be expected to show q u a l i t y a t t r i b u t e benef i t s of the pouch because of the very slow heat penetrat ion rate through such products . Convection currents are not set up to the same degree i n a r e t o r t pouch as i n a can (Pf lug , 1964) and thus l a rger gains i n process time reduct ion can be expected for conduction-heating products r e l a t i v e to those products where convection currents play a ro le when comparing re tor t pouches to cans. The ob jec t ives for t h i s research pro ject were: 1) to consider i f f i r s t order k i n e t i c s could be used to descr ibe the thermal degradation of thiamine i n a luncheon-type ham product . The rate of degradation (k) at s p e c i f i c temperatures (100 to 1 4 0 ° C ) as wel l as the temperature dependence of degradation rate (E a ) were of i n t e r e s t ; 2) to compare thiamine re tent ion i n a luncheon-type ham product processed i n r e t o r t pouches to that packaged i n c y l i n d r i c a l containers f i l l e d with the same amount of product (397 g or 14 o z ) . In a d d i t i o n , the cans used commercially for t h i s product (184 g or 6.5 oz) were chosen to serve as a c o n t r o l ; and 3) to consider the e f fect of changing the process temperature on thiamine re tent ion i n the ham product . The two temperatures se lected - 37 -were 1 1 5 . 6 ° C ( 2 4 0 ° F ) and 1 2 6 . 7 ° C ( 2 6 0 ° F ) . The lower temperature repre-sented a reasonable lower l i m i t of process temperatures commonly used i n indus t ry , while the higher temperature represented an approximate upper l i m i t . Moreover, the upper temperature was chosen based on pred ic t ions made by Tung and Smith (1980) with respect to gains expected i n process time reductions and nutr ient re tent ion improvement with increased process temperature for t h i s s i ze of r e t o r t pouch. - 38 -EXPERIMENTAL A. The Luncheon-Type Ham Product 1. Product D e s c r i p t i o n A luncheon-type ham product was obtained i n a ready-to-process s ta te from a l o c a l processor as requ i red . For t h i s product, raw pork, water, s a l t , sodium phosphate, sodium erythorbate , sodium n i t r i t e and smoke f lavour were mixed together to create a meat emulsion. Pieces of lean raw pork were then blended i n , as a 1:1 r a t i o with the emulsion. The mixture was cured for 48 h while being held at 3 2 - 3 6 ° F ( 0 - 2 . 2 ° C ) . A l l product used i n t h i s study was obtained fo l lowing the cure p e r i o d . In commercial product ion, the product was co ld f i l l e d in to 307x111.5 two-piece t i n f r e e s t ee l cans with a meat release enamel (American Can Company, Vancouver, BC). The f i l l e d cans were mechanically vacuum-sealed and then processed i n a s t i l l r e tor t at 2 4 0 ° F ( 1 1 5 . 6 ° C ) . The f i n a l fat content of the ham product was approximately 9%. 2. Moisture Content Moisture was determined for each batch of raw ham on which thiamine ana lys i s was performed ( t o t a l of 6 batches) . The AOAC vacuum oven method for meat and meat products (AOAC, 1980, Sect ion 24.002) was used. Ham for a l l analyses i n t h i s i n v e s t i g a t i o n was ground i n approxi-mately 200 g l o t s in a Waring blendor using four to s ix blending periods of 6 to 8 s each. Samples (9 g) were weighed accurate ly into s ix pre-d r i e d , de s i cca tor -coo led , weighed aluminum pans (60 mm diameter by 18 mm - 39 -deep). The pans conta ining samples were placed i n a vacuum oven at 1 0 0 ° C and 100 kPa for 6 h . Samples were cooled i n a des iccator conta in-ing s i l i c a gel and then weighed q u i c k l y . The samples were returned to the oven for an a d d i t i o n a l hour, cooled and reweighed. Samples showed a n e g l i g i b l e change i n weight ( le s s than 2 mg) on the second weighing. The loss of weight on drying was considered to be the moisture content . The mean moisture content for a l l samples analyzed was 75.12% with a standard dev ia t ion of 0.46%. B. Thiamine A n a l y s i s A l l thiamine analyses were done according to the AOAC procedure (AOAC, 1980, Sect ions 43.024-43.030). In t h i s method, ac id ex t rac t ion was used to d i s so lve the thiamine. Thi s was followed by an enzymatic treatment to hydrolyze phosphate esters of thiamine and then a chromato-graphic procedure with an ion exchange r e s i n for p u r i f i c a t i o n . The thiamine was oxidized to thiochrome which was f luorescent , and sample f luorescence was compared to that of a standard to determine the amount of thiamine present . In t h i s i n v e s t i g a t i o n , f luorescence was measured with an Aminco-Bowman spectrophotofluorometer (American Instruments C o . , I n c . , S i l v e r Spr ing , MD). The ana ly s i s was performed on wet samples. Thiamine concentrat ions reported were based on using a thiamine hydro-c h l o r i d e standard. For t h i s research p ro j ec t , severa l changes were made i n the AOAC procedure. The enzyme used to provide phosphorolyt ic a c t i v i t y was Mylase 100 (United States Biochemicals C o r p . , C leve land , OH) and incuba-t i o n was c a r r i e d out at 3 5 - 3 7 ° C as recommended by MacBride and Wyatt - 40 -(1983). The ion exchange mater ia l used for p u r i f i c a t i o n , suggested by E l l e f s o n et a l . (1981), was Bio-Rex 70 (Bio-Rad Laborator ie s , Richmond, CA) . These changes were made because the mater ia l s s p e c i f i e d i n the AOAC procedure were no longer a v a i l a b l e . Ex t rac t ion and enzyme hydroly-s i s steps were modified as fol lows to reduce the number of t ransfers required and to s impl i fy the procedure. A smaller sample than suggested i n the AOAC procedure was used. Fol lowing ac id e x t r a c t i o n , pH was adjusted to approximately 4.5 and the enzyme incubat ion was then c a r r i e d out . The pH was not adjusted to 3.5 as i n the AOAC procedure fo l lowing enzyme incubat ion and p r i o r to f i l t r a t i o n . This sequence of steps have been appl ied i n a very s i m i l a r manner previous ly (Assoc ia t ion of Vitamin Chemists, 1966; E l l e f s o n et a l . , 1981). The e l u t i o n volume from the p u r i f i c a t i o n columns was 50 mL rather than 25 mL. Pippen and Potter (1975) have succes s fu l ly employed t h i s increased e l u t i o n volume. The complete thiamine ana ly s i s procedure used i n t h i s i n v e s t i g a t i o n i s presented i n Appendix I I . Pre l iminary t e s t i n g was c a r r i e d out to ensure s a t i s f a c t o r y recovery of thiamine from each step of the method and to test recovery of added thiamine hydrochlor ide and thiamine pyrophosphate from the ham. Based on the recovery experiments conducted, e r ror s of up to approximately 5% would be expected. Tests on the e f fect of f reez ing at - 1 8 ° C for 5 days on the thiamine content of the ham product ind ica ted r e l a t i v e l y small changes. There was a n e g l i g i b l e d i f f e rence when a canned sample was tested and a small increase (6.4%) when a fresh sample was te s ted . - 41 -Thiamine-modifying factors have been found i n severa l products inc lud ing pork (Porzio et a l . , 1973). H i l k e r (1976) found that heme prote ins react with thiamine i n some way so as to i n t e r f e r e with the ana lys i s of thiamine. Using a hemin-thiamine reac t ion product, feeding t r i a l s were conducted with r a t s . The d e r i v a t i v e formed was e i ther a c t i v e as thiamine or thiamine was regenerated during d i g e s t i o n . I f such a reac t ion occurred i n t h i s study, the thiamine concentrat ions reported would be lower than the actua l concentra t ions . However, recovery s tudies with thiamine hydrochlor ide and thiamine pyrophosphate added to the ham product showed good recover ies with no evidence of a thiamine-modifying e f f e c t . As w e l l , H i l k e r (1976) reported that pork had considerably less thiamine-modifying a c t i v i t y than e i ther beef or Skipjack tuna. C. Kinetics of the Thermal Degradation of Thiamine Thermal degradation k i n e t i c s of thiamine were studied using small ham samples heated at d i f f e r e n t temperatures between 100 and 1 4 0 ° C over var ious periods of time. Thiamine ana ly s i s fo l lowing heating allowed for the determination of the rate of nutr ient degradation at each of the temperatures te s ted . The ef fect of temperature on the rate of thiamine degradation was a l so cons idered . The ham was heated i n 127 mm by 4.8 mm i n t e r n a l diameter s t a i n l e s s s tee l tubes with Swagelok f i t t i n g s (Crawford F i t t i n g s (Canada), L t d . , Niagara F a l l , ON) at each end. In order to f i l l the tubes, the ham was ground i n a Waring blendor as for ana lys i s purposes. A 10 mL syringe - 42 -was used to i n s e r t the ground ham product into the tubes. Some ham was removed with a glass rod to leave approximately 25 mm of headspace. Each tube then contained approximately 1.2 g of product. For each test temperature, 21 tubes were prepared with fresh ground ham product and then held in an ice-water bath p r i o r to the heat treatment. A Haake B c i r c u l a t i n g o i l bath equipped with a Haake N3 c o n t r o l l e r (Haake, B e r l i n , West Germany) was used to heat the tubes according to the schedule presented i n Table 3. This schedule was based on guidelines suggested by Lenz and Lund (1980). Five tubes were removed at the end of each of the s p e c i f i e d time periods and immediately cooled i n an ice-water bath. To compensate for thiamine destruction which occurred during the heat-up and cool-down of the tubes, those tubes representing zero time were heated to approach the test tempera-ture and then cooled i n an ice-water bath. Timing for the remaining portion of the schedule was started when the zero time tubes were removed from the o i l bath. Preliminary work was c a r r i e d out to determine the time required for a sample to heat to within 1 to 2 C° of the test temperature. A r i g i d needle-type Ecklund thermocouple (O.F. Ecklund Inc., Cape Coral, FL) was c a l i b r a t e d against an ASTM thermometer at each test temperature with both immersed i n the o i l bath. This thermocouple was inserted with Swagelok f i t t i n g s into the center of a f i l l e d tube and a D i g i t e c 1268 data logger (United Systems Corp., Dayton, OH) was used to monitor the increase in product temperature a f t e r immersion of the tube in the o i l bath. Three tubes f i l l e d with ham product were tested at each tempera-ture. The mean time, plus three standard deviations, to heat the - 43 -Table 3 . Heating schedule for thiamine k i n e t i c s work. Temperature, °C Time, min 100 O1 100 200 300 110 O1 45 90 135 120 O1 20 40 60 130 O1 10 20 30 140 O1 5 10 15 Zero time represented heating i n the o i l bath for 70 s at the test temperature followed by cooling i n an ice-water bath to compensate for the degradation of thiamine which occurred during heat-up and cool-down. _ 44 -samples to within 2 C° of the test temperature was 64.4 s. Seventy seconds of heating was chosen to represent the zero time treatment. This time was convenient for use; moreover a l l samples tested heated to within 1 C° of the test temperature within 70 s. One f i l l e d tube containing a thermocouple was heated during each of the test runs to ensure that heating to within 2 C° of the test temperature occurred within 70 s. Fresh ham product ready-to-process was obtained from the processor and held r e f r i g e r a t e d (1°C) u n t i l used. Heating of the tubes was done on that day and the following day. Test samples that had been heated and cooled were held r e f r i g e r a t e d u n t i l thiamine analysis was c a r r i e d out. The complete schedule was c a r r i e d out three times, with each of these r e p l i c a t i o n s using a d i f f e r e n t batch of fresh ham product. The reaction rate constant was calculated assuming a f i r s t order k i n e t i c model using l e a s t squares regression of the logarithm of thiamine concentration on time for each temperature tested (slope= -k/2.303, see equation 5). The temperature dependence of the thiamine degradation rate was evaluated by regressing the logarithm of k on r e c i p r o c a l absolute temperature, and the a c t i v a t i o n energy was calcu-l a t e d (slope=-E a/2.303R, see equation 6). D. Process Determination Heat penetration data were obtained for the ham product packed and processed under the conditions to be used i n the f i n a l processing experiments. The data obtained were used to determine process times which were calculated on the same basis for each treatment. The product - 45 -to be used for process determination runs was obtained ready-to-process and then frozen i n appropriate s ized l o t s at - 1 8 ° C . The ham was thawed at 1 ° C for 24 hours p r i o r to packing the containers for process ing . 1. The Retort A l l processing was c a r r i e d out i n a v e r t i c a l p i l o t plant r e t o r t which could be operated with 100% steam or with steam/air mixtures . Construct ion d e t a i l s for t h i s r e to r t have been reported elsewhere (Tung, 1980). An homogeneous steam/air mixture was obtained by using a pos i -t i v e flow method i n which there was continuous vent ing . Steam input was through a propor t iona l valve which was c o n t r o l l e d by a temperature s e t p o i n t . This was the only cont ro l system used during the cook cyc le with 100% steam. With steam/air mixtures , a second setpoint was the maximum re tor t pressure . This was c o n t r o l l e d by using a propor t iona l valve on the vent l i n e . The propor t iona l valves were regulated by a Taylor fulscope recording temperature and pressure c o n t r o l l e r (Taylor Instruments L t d . , Toronto, ON). A i r was added at a constant rate to the steam l i n e when steam/air mixtures were employed. Steam or the steam/air mixture was introduced through a cross-spreader at the bottom of the r e t o r t . Venting of the steam/air mixture was through a ring-shaped manifold which contained holes on the lower surface, and was located near the top of the r e t o r t . The flow rate of the medium was maintained at 40 standard cubic feet per minute (1.88 x 10" m s - at standard condi t ions of temperature and pressure) by ad just ing the a i r flow rate through a c a l i b r a t e d Flowrator flow meter - 46 -(F i scher and Porter (Canada) L imi ted , Downsview, ON). Thi s flow rate was found to be e f f e c t i v e by Ramaswamy (1983) and was approximately equivalent to f i v e complete changes of the r e t o r t environment per minute. Fol lowing both steam and steam/air process ing , coo l ing was achieved by the a d d i t i o n of cold water from near the bottom of the r e t o r t . A i r flow was s tar ted fo l lowing 100% steam process ing , and main-tained fo l lowing steam/air processing to allow for pressure c o o l i n g . The propor t iona l valve on the vent l i n e was allowed to operate during cool ing to c o n t r o l maximum re tor t pressure. 2 . Process ing Condi t ions The processing condi t ions and container dimensions (treatments) used are out l ined i n Table 4. The 307x111.5 cans (87 mm diameter by 44 mm high) were those used commercially for the product . The 300x407 cans (76 mm diameter by 113 mm high) with C enamel (Cont inental Group of Canada L t d . , Burnaby, BC) and S t e r i l i t e r e t o r t pouches (DRG Packaging L t d . , Toronto, ON), with outs ide dimensions of 159 mm by 229 mm and in s ide dimensions of 145 mm by 210 mm, were packed with the same amount of product (397 g ) . Ten containers were processed together i n each run. Cans were packed i n a metal c r a t e . The re tor t pouches were or iented i n the v e r t i -c a l d i r e c t i o n and res t ra ined to 19 mm thickness using a s t a i n l e s s s t ee l rack s i m i l a r to that described by Davis et a l . (1972). Channels were provided between the layers of pouches to provide for c i r c u l a t i o n of the heating medium. Table Processing condit ions used for cans and re tor t pouches. Process abbrevia t ion CTRL CAN-115.6 CAN-126.7 PCH-115.6 PCH-126.7 Container 307x111.5 can 300x407 can 300x407 can 159 mm x 229 mm pouch 1 19 mm th ick 159 mm x 229 mm pouch 1 19 mm th ick Amount of product, g 184 397 397 397 397 Process temperature, °C 115.6 115.6 126.7 115.6 126.7 Heating medium steam steam steam 75% steam in steam/air mixture 75% steam i n steam/air mixture Outside dimensions. - 48 -With steam/air mixtures, a v a r i e t y of steam contents have been te s ted . Seventy f i v e percent i s a common mixture used commercially for processing r e t o r t pouches. Ramaswamy (1983) reported that steam/air mixtures for processing of r e to r t pouches should contain more than 60% steam (with respect to d e l i v e r i n g the des ired surface heat t rans fer c o e f f i c i e n t ) and less than 85% (with respect to preserving package i n t e g r i t y ) . 3. Temperature Measurement and F i l l i n g of Containers A l l thermocouples were c a l i b r a t e d against the re tor t thermometer at the same condi t ions as to be used during processing runs. Ten thermocouples of 24 AWG ' t e f lon- in su l a ted Type T s o l i d copper/constantan wire (Omega Engineer ing , I n c . , Stamford, CT) with soldered t i p s were used to monitor environment temperature in the r e t o r t . This same type of wire was used as thermocouple lead wire for the cans. The thermo-couple wires for the re tor t pouches had soldered t i p s and were made from Type T copper/constantan 7/0.2 mm stranded wire insu la ted with t e f l on ( L a b f a c i l i t y L t d . , Hampton, Middlesex, England) . Thermocouple wires for the r e t o r t pouches were anchored with copper wire i n the center of 19 mm (outside diameter) h e l i c a l metal c o i l s 50 to 70 mm i n length to allow p o s i t i o n i n g of the thermocouple i n the center plane of the pouch in the slowest heating zone. The wires were sealed in to the pouches by i n s e r t i n g them through Ecklund packing glands . Extra wire was fed in to the pouch to allow product to be forced i n t o the c o i l around the thermocouple j u n c t i o n . The c o i l was then pul led back into the pouch and the packing gland t ightened down on the - 49 -wire , leav ing approximately 70 to 80 mm of wire in s ide the pouch. The re tor t pouches were then f i l l e d to contain 397 g of ham product . The pouches were vacuum sealed using a Mult ivac vacuum sea ler (Sepp Haggenmliller KG, A l l g a u , West Germany). Ecklund needle-type r i g i d thermocouples of the appropriate s i ze were used with cans. Locking ' receptacles and connectors from O . F . Ecklund were used to hold the thermocouple i n the can and to attach the lead thermocouple wire . The thermocouple t i p s were located at the center of the can so as to be pos i t ioned i n the slowest heating zone (Pf lug , 1975). The cans were then f i l l e d to contain the des ired weight of product and were seamed a f ter introducing steam from a k e t t l e in to the headspace above the product . This treatment was used to develop a p a r t i a l vacuum upon c l o s i n g . The f i l l e d containers were held at 1 °C overnight , and were pro-cessed the fo l lowing day. The r e t o r t was loaded as qu ick ly as poss i -b l e . The temperature data from a l l thermocouples during processing were logged at one minute i n t e r v a l s using a Kaye Ramp II Scanner/Processor (Kaye Instruments I n c . , Bedford, MA). There were three r e p l i c a t i o n s c a r r i e d out for each of the processes. Fol lowing process ing , four containers from each run were opened and the cook-out l i q u i d drained in to a graduated c y l i n d e r and measured. Retort pouches were cut open and the ham c a r e f u l l y removed from the c o i l so that any displacement of the thermocouple t i p from the midplane could be measured. - 50 -4 . Process Times Process ing of the ham product was done f i r s t i n 307x111.5 cans for 75 min at 1 1 5 . 6 ° C . A l l process times were operator ' s process times ( P t ) ; that i s the length of the heating period fo l lowing come-up. The process time for the 307x111.5 cans was based on that used commer-c i a l l y . The process times for the other treatments were ca l cu la ted with the heating and coo l ing parameters obtained with cor rec t ions made for container s i ze and shape and re tor t temperature as required (Stumbo, 1973). Stumbo's method was used i n a l l c a l c u l a t i o n s . The procedures used are discussed in the fo l lowing s e c t i o n . The process times used i n the process determination phase of the work are presented i n Table 5. 5. Process C a l c u l a t i o n Recorded time-temperature data were used i n Stumbo's method for process time c a l c u l a t i o n (Stumbo, 1973). A l l c a l c u l a t i o n s were per-formed using programs developed for an Apple II Plus personal computer (Apple Computer I n c . , Cupert ino, CA) . The parameters fh and jh from the heating curve and f c and j c from the coo l ing curve for each conta iner were determined using regress ion a n a l y s i s . For determination of these parameters, the mean environment temperature during the l a s t 10 minutes of the process was taken as the re tor t temperture, except for PCH-126.7. For t h i s treatment, the l a s t 7 min of the process was used because t h i s i s when s t a b i l i z a t i o n occurred . The r e t o r t temperature ca l cu la ted i n t h i s manner was representat ive of the temperature i n the e n t i r e process and i t i s at the end of the cook that errors i n the - 51 -Table 5. Process times used i n the process determination phase of the work. Process Process t ime, min CTRL 75 CAN-115.6 112 CAN-126.7 63 PCH-115.6 45 PCH-126.7 18 - 52 -d i f f e rence of r e to r t temperature and container center temperature are most c r i t i c a l . The cool ing water temperature was taken from the co ld water tap. Using the determined heating and cool ing parameters, the process temperature required to achieve an F 0 value of 6.0 min was determined for each i n d i v i d u a l conta iner . An F 0 value of 3 min using a z value of 10 C° i s considered to be the minimum cook for C lo s t r id ium botulinum (Pflug and Odlaug, 1978). This microorganism i s the c h i e f pub l i c health hazard i n low-acid foods (foods with a pH greater than 4 . 6 ) . By using an F 0 value of 6 min, the so -ca l l ed "double-bot" cook w i l l be obtained. An i n i t i a l temperature of 5 ° C was used i n the process c a l c u l a -t i o n s . Based on pre l iminary work, t h i s temperature was found to be the minimum i n i t i a l temperature. Come-up times were 5 min for pure steam processing and 6 min with steam/air process ing . An example of the heating and coo l ing curves and parameters provided i n the computer output i s presented i n Appendix I I I . The j values for the 300x407 cans were corrected using the appropriate factor presented by Ecklund (1956) to account for the metal nut of the packing gland protruding within the can. The c a l c u l a t i o n procedures used were e s s e n t i a l l y those of Stumbo's formula method when the c a l c u l a t i o n s are performed manually. A number of features were a v a i l a b l e i n the computer-based procedure used. F i r s t , values for Stumbo's f ^ /U r e l a t i o n with g for var ious j c values at z=10 C° were provided by means of a table look-up method. A l i n e a r r e l a t i o n s h i p between g and j c for each f^ /U was assumed and l i n e a r - 53 -i n t e r p o l a t i o n was used between success ive values of f ^ / U . A second feature allowed c o r r e c t i o n of and j c values for e r ror s i n pos i -t i o n i n g of the thermocouple at the midplane of re tor t pouches. The corrected j values were ca lcu la ted using the r e l a t i o n s h i p published by Olson and Oackson (1942) for an i n f i n i t e s l ab . The process times determined for use in the f i n a l phase of the work for each of the treatments was the mean time plus three standard d e v i a t i o n s . Use of t h i s procedure assures a small p r o b a b i l i t y of a container rece iv ing le s s than a l e t h a l i t y of F o=6.0 min at the cold spot (the exact p r o b a b i l i t y w i l l depend on the actua l number of conta in-ers t e s t ed ) . Tung and Garland (1978) reported on the use of t h i s type of procedure; however, these researchers considered only the v a r i a t i o n i n f^ i n c a l c u l a t i n g the process time to be used. That i s , process times were ca l cu l a ted with heating rates three standard devia t ions above the mean. In the present procedure, o v e r a l l v a r i a t i o n i n the heating and coo l ing parameters was accounted for by c a l c u l a t i n g the process time required for each container te s ted . The F 0 value obtained for each of the containers with the f i n a l predic ted process time was a l so c a l c u -l a t e d . An example of the computer output for the c a l c u l a t i o n of process times i s provided i n Appendix IV. E. Processing for Thiamine Retention Evaluation The process determination work provided process times for use i n t h i s phase of the work. The ham product was processed using each of the treatments prev ious ly out l ined and the re tent ion of thiamine determined. - 54 -1. Process ing Fresh ham product, ready-to-process , was obtained from the l o c a l processor . On the same day, a l l containers for a complete r e p l i c a t i o n (5 treatments) were packed. There were 10 containers processed i n each of the treatments, f i v e of which had thermocouples. Thermocouples were inser ted and containers f i l l e d i n the same manner as prev ious ly out-l i n e d . Two extra containers were packed for each treatment for sampling to determine i n i t i a l thiamine content i n the product . The f i l l e d con-t a iner s were stored at 1 °C u n t i l processed. The processes were c a r r i e d out on the two days fo l lowing packing of the containers i n random order using the condi t ions prev ious ly out-l i n e d (Table 4 ) . The process times are presented i n Table 6. Three r e p l i c a t i o n s were conducted with each r e p l i c a t i o n using ham product from a d i f f e ren t batch. The F 0 de l ivered to each container having a thermocouple was determined using Stumbo's method. The i n i t i a l temperature was taken as the mean thermocouple reading at the time of steam on for the conta iners of that run. The r e t o r t temperature was ca l cu la ted as i n the process determination work. C a l c u l a t i o n s were performed by means of programs for an Apple II Plus personal computer, as before. 2. Sampling and Product Ana lys i s The two extra containers were sampled immediately p r i o r to pro-i cess ing i n order to obtain the i n i t i a l thiamine content of the product. One-quarter of the meat from each container was blended together in a Waring blendor. Two samples were prepared i n t h i s manner. - 55 -Table 6 . Process times used i n the thiamine re tent ion evaluat ion phase of the work, c a l cu l a ted by Stumbo's method using heat penetra-t i o n data obtained i n three process runs for each treatment. Number of i n d i v i d u a l Process conta iners tested Process t ime, min CTRL 28 73 CAN-115.6 28 99 CAN-126.7 29 61 PCH-115.6 29 39 PCH-126.7 26 15 - 56 -Two cans of the processed ham product were sampled for thiamine ana lys i s immediately fo l lowing the thermal treatment. P r i o r to opening these cans and two others , a vacuum gauge was used to measure the vacuum obta ined. This was approximately 2 i n Hg (6.7 kPa) . These vacuum read-ings were low compared to readings of over 20 i n Hg obtained when the product was sealed commercially using a mechanical vacuum c l o s i n g machine. For these four cans, the cook-out l i q u i d was drained from the can in to a graduated c y l i n d e r and measured. For the two samples to be analyzed for thiamine content i n the processed ham product, the l i q u i d was reserved and the ham product was removed as a loa f from each can. The l o a f was b i sected through a v e r t i c a l midplane. The ha l f loaves were macerated i n a Waring blendor along with ha l f of the cook-out l i q u i d drained from the can. Two re tor t pouches were sampled for thiamine a n a l y s i s . A f t e r d ra in ing the cook-out l i q u i d , the pouch was cut away from the contents . The slab was cut i n ha l f along i t s long cen t ra l a x i s . The meat and l i q u i d were macerated together as for the cans. A t h i r d container a l so had the volume of cook-out l i q u i d measured. Two of the re tor t pouches had the volume of r e s idua l a i r measured by a de s t ruc t ive method (Shappee and Werkowski, 1972). In t h i s method, a pouch was cut open while being held under water and the escaping gas was d i rec ted through a funnel in to an inverted graduated c y l i n d e r . The volume of a i r remaining i n the r e t o r t pouches (corrected to atmospheric pressure) var ied from approxi-mately 20 to 40 mL. pH was determined on parts of the raw and processed ham product from each treatment i n the f i r s t r e p l i c a t i o n as well as on raw ham i n - 57 -the second and t h i r d r e p l i c a t i o n s . The pH values were determined on s l u r r i e s made from 12 g of ground ham product and 60 mL of d i s t i l l e d water blended together with a Po ly t ron Kinemetica homogenizer (Brinkmann Instruments, Rexdale, ON). Two s l u r r i e s were made for each sample. A l l samples were stored i n polyethylene bags at - 1 8 ° C u n t i l t h i a -mine ana lys i s was performed. One of the samples taken before processing from each treatment was analyzed i n t r i p l i c a t e . A sample from each of the two test containers within each treatment was analyzed i n d u p l i c a t e . 3. Data A n a l y s i s Examination of the r e s u l t s for thiamine content p r i o r to process-ing showed no trend for container type or order of process ing . There-fore , a mean value of the raw ham thiamine content for a l l processes wi thin one r e p l i c a t i o n was used i n c a l c u l a t i o n s of percent re tent ion of thiamine fo l lowing thermal process ing . Ana lys i s of variance procedures (Steel and T o r r i e , 1980) were used to p a r t i t i o n the t o t a l v a r i a t i o n of the data . Rep l i ca t ions and conta in-ers were considered random and treatments f i x e d . The containers and dupl i ca te s wi th in conta iners were treated as subsamples and subsub-samples, r e s p e c t i v e l y . An o u t l i n e of the ana lys i s of variance table i s presented i n Table 7. This table inc ludes the sources of v a r i a t i o n , as well as degrees of freedom (df) and mean square (MS) used as the denominator for c a l c u l a t i n g each F-va lue . S i g n i f i c a n t treatment d i f ferences (p<0.05) were tested using Student-Newman-Keuls mul t ip l e comparisons procedure (Steel and T o r r i e , - 58 -Table 7. Out l ine of ana ly s i s of variance used for thiamine retent ion a f t e r processing assuming that treatments were f i x e d . Source of v a r i a t i o n df F-value denominator MS Rep l i ca t ions 2 Container e r r o r Treatments Experimental e r r o r Experimental e r ror 8 Container e r r o r Container er ror 15 Dupl ica te e r r o r Dupl ica te er ror 30 T o t a l 59 - 59 -1980). A l l of these s t a t i s t i c a l c a l c u l a t i o n s were performed using a program package, UBC MFAV (Le, 1978), a v a i l a b l e on the UBC Amdahl 470 V/8 computer. - 60 -RESULTS AND DISCUSSION A. Kinetics of the Thermal Degradation of Thiamine 1. Reaction Rate The f i r s t order reac t ion rate constant for the degradation of thiamine i n a luncheon-type ham product at each tes t temperature was determined using leas t squares regress ion of the logarithm of thiamine concentrat ion (wet weight basis) on time. These thermal des t ruct ion curves are presented i n Figures 1 through 5. Both actua l data points and leas t squares regress ion l i n e s are shown. The ca l cu l a ted k values and c o e f f i c i e n t s of determination (r ) for the l i n e s are included i n Table 8. The information presented i n Figures 1 through 5 and i n Table 8 i s based on the assumption of f i r s t order k i n e t i c s . Other reac t ion orders (0 .5 , 1.5 and 2) were considered by examining the leas t squares regres-s ion ana lys i s of the appropriate concentrat ion versus time r e l a t i o n s h i p s (Capellos and B i e l s k i , 1972). The r values were genera l ly the highest for an order of 1.5. However, given the amount of data obtained i n the present experiments, i t i s d i f f i c u l t to make a statement on the exact order of the r e a c t i o n . Examination of the p lo t s presented i n Figures 1 through 5 ind ica te s that f i r s t order k i n e t i c s described the degradation of thiamine i n t h i s i n v e s t i g a t i o n with reasonable accuracy. As w e l l , r values for the l ea s t squares regress ion l i n e s assuming f i r s t order k i n e t i c s (Table 8 ) , were a l l greater than 0.98. As mentioned previous-l y , other researchers have genera l ly been successful i n using f i r s t order k i n e t i c s to descr ibe the thermal degradation of thiamine i n foods. - 61 -Figure 1. Degradation of thiamine i n a luncheon-type ham product a 100°C f o r three r e p l i c a t i o n s . - 62 -9 4 5 90 1 3 5 TIME, min Figure 2. Degradation of thiamine in a luncheon-type ham product 110°C for three replications. - 63 -20 40 60 TIME, min F i g u r e 3. Degradation of thiamine i n a luncheon-type ham product 1 2 0 ° C for three r e p l i c a t i o n s . 9 - 64 -_ l _ 0 10 20 30 TIME, min F i g u r e 4. Degradation of thiamine i n a luncheon-type ham product 1 3 0 ° C for three r e p l i c a t i o n s . g - 65 -Repl icat ion 0 5 10 15 TIME, m i n F i g u r e 5 . Degradation of thiamine i n a luncheon-type ham product 140°C f o r three r e p l i c a t i o n s . Table 8. Reaction rate constants for the thermal degradation of thiamine i n a luncheon-type ham product at temperatures between 100 and 1 4 0 ° C for three r e p l i c a t i o n s . Temperature, ° C 2 (r for regression k, min" 1 of log thiamine concentrat ion on time) Mean k, m i n - 1 Repl ica t ion 1 Rep l i ca t ion 2 R e p l i c a t i o n 3 100 3.34x10" 3 3.54x10~3 3.41x10- 3 3.43x10" 3 (0.992) (0.996) (0.983) 110 7.13x10- 3 7.98x10" 3 8.15x10" 3 7.75x10" 3 (0.990) (0.988) (0.991) 120 1.82x10" 2 1.88x10" 2 1.93x10" 2 1.88x10" 2 (0.995) (0.996) (0.997) 130 4.00x10- 2 4.04x10" 2 4.06x10- 2 4.03x10- 2 (0.996) (0.986) (0.999) 140 9.01x10- 2 9.56x10" 2 9.26x10" 2 9.28x10" 2 (0.996) (0.999) (0.992) - 67 -I t i s to be expected that heat was the major factor in f luenc ing the degradation of thiamine i n t h i s i n v e s t i g a t i o n . However, other f ac tor s may have played a r o l e , such as the presence of oxygen or cur ing ingred ien t s . These factors could have af fected the rate or mechanism of degradat ion. There are numerous environmental factors and product const i tuents which may inf luence the mechanism and/or rate of thiamine degradation (Dwivedi and A r n o l d , 1973). Model systems have been used i n much of the work conducted to test the e f fec t s of such factors on thiamine degradation. E f f e c t s observed i n one model system do not neces sar i ly i n d i c a t e those that are to be expected i n other model systems or i n foods. From the review of thiamine degradation chemistry by Dwivedi and Arnold (1973), i t i s apparent that e f fect s of factors can depend upon the s p e c i f i c compound being tested and the system i n which i t i s present . Fa r re r and Morrison (1949) found that oxygen (present i n a i r or as pure oxygen in the headspace of test ampoules) accelerated the thermal de s t ruc t ion of thiamine i n phosphate buffer at temperatures greater than 9 0 ° C . The observed e f fects were a l t e red when c i t r i c acid-phosphate or phosphate-phthalate buffers were used, and no oxygen ef fect was noted when so lut ions of yeast extract were te s ted . In the present i n v e s t i g a -t i o n , no measures were taken to c o n t r o l oxygen presence i n the headspace of the tubes used. Greenwood et a l . (1943) studied the e f fect of meat cur ing ingre-dients ( s a l t , sodium n i t r a t e , sodium n i t r i t e , sucrose and dextrose) i n aqueous so lu t ions and i n ground lean pork on the amount of thiamine - 68 -de s t ruc t ion which occurred as a r e s u l t of heating at 9 8 ° C for one hour. The meat curing ingredients were used at concentrat ions t y p i c a l l y found i n cured meats, with d i f f e r e n t l e v e l s of s a l t and sodium n i t r i t e being t e s t ed . The extent of thiamine des t ruc t ion i n aqueous so lu t ions was found to be dependent upon pH, and the nature and concentrat ion of added i n g r e d i e n t s . The add i t ion of e i ther s a l t or sodium n i t r i t e increased the amount of thiamine destroyed. When the cur ing ingredients were added to ground pork, the amount of thiamine des t ruct ion was less than i n the aqueous s o l u t i o n s . Di f ferences i n the amount of thiamine des-troyed among various combinations of cur ing ingredients tested or i n t h e i r absence, were wi th in the l i m i t s of experimental e r ror for thiamine determinat ion, both for meat heated immediately a f ter the add i t ion of cur ing ingredients or heated a f ter a l lowing the product to cure for 10 days at 0 - 2 ° C . Thus, for the condi t ions te s ted , curing ingredients had no e f fect on the extent of thiamine degradation. Ex t rapo la t ion of these re su l t s to the present i n v e s t i g a t i o n may not be v a l i d , because of d i f fe rences i n cur ing ingred ient s and heating condi t ions used. Kaya (1977) provided an example of a change i n the mechanism of thiamine degradation as a r e s u l t of a change i n a system component. Destruct ion products of thiamine i n a pH 5.6 acetate buffered s o l u t i o n i n the presence of sodium n i t r i t e included elemental su l fur and t h i o -chrome when the s o l u t i o n was heated at 7 5 ° C for 60 min. These two products were not produced when sodium n i t r i t e was absent. - 69 -2 . Temperature Dependence of Degradation Temperature dependence of the degradation rate of thiamine i n the luncheon-type ham product was evaluated by l ea s t squares regress ion of the logarithm of k on r e c i p r o c a l absolute temperature (Arrhenius r e l a -t ionsh ip ) for each r e p l i c a t i o n . These r e l a t i o n s h i p s are presented i n Figure 6. The a c t i v a t i o n energies for each r e p l i c a t i o n were ca l cu l a ted from the slopes of the l i n e s . As a reference p o i n t , k was evaluated at 1 2 1 ° C . The k i 2 i and E a values are presented i n Table 9 . The E a and k i 2 i values for thiamine i n the ham product were comparable to those previous ly reported i n the l i t e r a t u r e (Table 1) . Greenwood et a l . (1944) found a k ^ i value of 1.3x10" 2 and an E a value of 93 kO/mol for pork luncheon meat. L i k e the ham product used i n t h i s study, the luncheon meat was made from pork which had been cured . Both the mean k i 2 i value of 2.03x10" and the mean E a value of 105 kO/mol found i n t h i s study were somewhat higher than those reported by Green-wood et a l . (1944). F e l i c i o t t i and Esselen (1957) found a k 1 2 i value of 1 .6x10 - 2 m i n - 1 and an E a value of 113 k3/mol for fresh pork puree. I t would be expected that both d i f fe rences i n product composition and experimental technique could lead to d i f ferences i n the values repor ted . B . Process Determination 1. Process Times Process times were determined to obta in F o=6.0 min for each conta iner tested using Stumbo's method. The heating and coo l ing para-meters determined from the heating and cool ing curves are presented i n Table 10. These parameters were used i n the c a l c u l a t i o n of process - 70 -F iqure 6. Arrhenius r e l a t i o n s h i p for the degradation of thiamine i n a luncheon-type ham product heated at 100 to 1 4 0 ° C for three r e p l i c a t i o n s . - 71 -Table 9. Reaction rate constants at 1 2 1 ° C and a c t i v a t i o n energies for thiamine i n a luncheon-type ham product heated at 100 to 1 4 0 ° C for three r e p l i c a t i o n s . R e p l i c a t i o n ^121* min - E , kO/mol r 1 1.96.X10"2 106 0.9984 1 2 2.07x10" 2 105 0.9988 3 2.06x10- 2 105 0.9996 Mean 2.03x10" 2 105 For regress ion of log k on r e c i p r o c a l absolute temperature. - 72 -Table 1 0 . Heating and coo l ing curve parameters for a luncheon-type ham product process obtained runs. during process determination work i n three Mean value (standard devia t ion) Process V min fc> min Jh j c CTRL 28.5 (1.6) 36.0 (1.6) 1.72 (0.24) 1.52 (0.06) CAN-115.6 40.7 (1.3) 56.1 (1.9) 2.40 (0.11) 1.55 (0.09) CAN-126.7 39.6 (1.3) 52.7 (1.8) 2.30 (0.12) 1.66 (0.06) PCH-115.6 11.5 (0.6) 14.3 (0.7) 0.95 (0.12) 1.96 (0.29) PCH-126.7 10.0 (1.0) 14.7 (1.2) 1.02 (0.23) 1.87 (0.36) f - 73 -t imes . The process time for use i n the f i n a l processing work was determined (mean plus three standard deviat ions) and the mean F 0 value estimated when t h i s process time was used for each treatment (Table 11). In a l l cases, f c was greater than f n . Stumbo's method does not consider the ac tua l f c i n the c a l c u l a t i o n procedure, but instead assumes f c=^h* Since f c was greater than f n , there was an addi-t i o n a l margin of safety i n the process times used. For each treatment, the ca l cu la ted process time was greater than the process time required for any i n d i v i d u a l container to obtain an F 0 value of 6.0 min. Thus, the method used to determine process times provided a greater safety margin compared to the t r a d i t i o n a l approach of basing the process on the slowest heating container (P f lug , 1975). This method also provided an i n d i c a t i o n of the v a r i a b i l i t y among conta iners i n heating and coo l ing behaviour. Moreover, the process time determined i n t h i s way was associated with a s t a t i s t i c a l l y based l e v e l of p r o b a b i l -i t y that a l e t h a l i t y greater than the target value would be de l ivered to the conta iner s . In t h i s i n v e s t i g a t i o n the p r o b a b i l i t y was greater than 0.995. The required process times decreased as the dis tance required for heat penetrat ion to the co ld spot decreased and as temperature increased (Table 11). For the same amount of product, the process time was decreased by 61% for a r e t o r t temperature of 1 1 5 . 6 ° C and by 75% with a temperature of 1 2 6 . 7 ° C when re tor t pouches were compared to cans. R i z v i and Acton (1982) stated that process times required to achieve equiva-lent l e t h a l i t i e s with s t i l l processing were genera l ly one- th i rd to - Ik -Table 11. Process times and estimated F 0 values when these process times are used, c a l cu l a ted with Stumbo's method for three process runs per treatment i n the process determination work for a luncheon-type ham product . Number of i n d i v i d u a l Process Process containers tested time, min Mean F , min CTRL 28 73 7.3 (OA1) CAN-115.6 28 99 l.k (0.5) CAN-126.7 29 61 10.2 (1.6) PCH-115.6 29 39 7.0 (0.3) PCH-126.7 26 15 13.0 (3.0) Standard dev ia t ion of F( - 75 -one-hal f less for r e t o r t pouches compared to cans containing the same volume of product . The actua l d i f f e rence i n processing times for the two containers w i l l depend on the heating c h a r a c t e r i s t i c s of the product, the container geometries being compared and the processing c o n d i t i o n s . Conduction-heating products have been studied by Chia et a l . (1983) and Greene (1979). Rainbow t r o u t , po l lock (both with 170 g f i l l ) and shrimp (150 g f i l l ) were considered by Chia et a l . (1983). Compared to canned products , r e t o r t pouch processing allowed for process time reductions of 32-37% with a r e to r t temperature of 2 5 0 ° F ( 1 2 1 . 1 ° C ) . Greene (1979) found that 12 oz (340 g) of sweet potato puree processed i n re tor t pouches required approximately one-half the time required for the same product processed i n cans when a r e t o r t temperature of 2 4 0 ° F ( 1 1 5 . 6 ° C ) was used. When processing was done at 2 5 0 ° F ( 1 2 1 . 1 ° C ) , there was a t h r e e - f o l d d i f f e r e n c e . Computer s imulat ion work by Tung and Smith (1980) for 400 g cans and pouches ind ica ted that as r e to r t temperature increased from 115 to 1 3 5 ° C , the percentage d i f ference i n processing times for the two conta iners increased . The trend for a l a rger percen-tage d i f f e rence i n process times for r e t o r t pouches compared to cans with increas ing process temperature was a lso demonstrated i n the present i n v e s t i g a t i o n . With the same conta iner , increas ing the r e t o r t temperature decreased the process time required to provide equivalent l e t h a l i t y . The l e t h a l e f fec t of heat expressed as l e t h a l rate increases as the temperature i s r a i s e d . With an increase i n r e t o r t temperature, the - 76 -temperature reached at the cold spot i s higher and the time to reach a given process l e t h a l i t y i s reduced (Stumbo, 1973). 2 . Process L e t h a l i t y The estimated mean F 0 values and t h e i r standard devia t ions for a l l processes c a r r i e d out at 1 1 5 . 6 ° C were very s i m i l a r (Table 11). The mean values of F Q for the processes c a r r i e d out at 1 2 6 . 7 ° C were greater than for those c a r r i e d out at 1 1 5 . 6 ° C . The l e t h a l e f fect of heat increases as the temperature i s increased . One minute of heating at 1 1 5 . 6 ° C contr ibutes approximately 0.3 min to F 0 , whereas one minute at 1 2 1 . 1 ° C represents F0=1 min and one minute at 1 2 6 . 7 ° C i s FQ=3.6 min (Stumbo, 1973). Although CAN-115.6 and CAN-126.7 treatments gave s i m i l a r r e su l t s for the heating and cool ing parameters, the mean F Q obtained and i t s standard dev ia t ion were greater for CAN-126.7. At the end of the cook, the co ld spots of the cans i n treatment CAN-126.7 were at a r e l a t i v e l y high temperature and thus l e t h a l i t y was being accumu-la ted qu ick ly leading to a higher mean F 0 and greater v a r i a t i o n of F D . Both the mean value and standard dev ia t ion of F 0 for PCH-126.7 were greater than for any other process . Thi s could be accounted for by both the high v a r i a t i o n i n heating and cool ing parameters (on a r e l a t i v e basis) and the high r e t o r t temperature used. The r e t o r t pouch has a th in p r o f i l e and heating occurs q u i c k l y . Thus, the center temperature at the end of the cook was the highest obtained compared to the other processes . - 77 -C. Processing for Thiamine Retention Evaluation The luncheon-type ham product was processed using the heating times ca lcu la ted i n the process determination work. Thiamine content of the ham product was evaluated both before and a f ter process ing . Three r e p l i c a t i o n s were c a r r i e d out . V. p_H The pH values of the ham product s l u r r i e s from before and a f ter processing i n the f i r s t r e p l i c a t i o n ranged from 6.0 to 6 .5 . The mean value was 6 .31. There was no o v e r a l l trend for an e f fect of processing on the pH. The raw samples tested from the second and t h i r d r e p l i c a -t ions had pH values within the same range. Thus, i t would be expected that nei ther processing nor the d i f f e r e n t batches used would play a r o l e i n the degradation of thiamine which occurred as a r e su l t of a pH e f f e c t . 2. Thiamine Retent ion a) Ana ly s i s of var iance Ana lys i s of variance procedures were used to p a r t i t i o n the t o t a l v a r i a b i l i t y of the data . These r e s u l t s are presented i n Table 12. There were no s i g n i f i c a n t d i f ferences among r e p l i c a t i o n s . The F - r a t i o for experimental e r ror ( r e p l i c a t i o n by treatment i n t e r a c t i o n ) was s i g n i -f i cant at the 5% l e v e l . This would i n d i c a t e that the treatments did not respond i n the same manner wi thin each r e p l i c a t i o n , or the r e p l i c a t i o n s did not show the same response wi th in each treatment. F igure 7 i l l u s -t ra te s t h i s i n t e r a c t i o n and ind ica te s that r e p l i c a t i o n s d id not respond - 78 -Table 12. Ana ly s i s of variance for thiamine re tent ion i n a luncheon-type ham product a f ter processing i n r e t o r t pouches and cans. Source of v a r i a t i o n df MS F - r a t i o Rep l i ca t ions 2 0.241 0.04493 ns Treatments 4 1422.5 89.419 *** Experimental e r ror 8 15.908 2.964 * Container error 15 5.367 3.369 ** Dupl icate er ror 30 1.593 T o t a l 59 ns not s i g n i f i c a n t (p>0.05); * * * s i g n i f i c a n t at p<0.01; * * * s i g n i f i c a n t at p<0.05 s i g n i f i c a n t at p<0.001 5 • - 79 -F i g u r e 7. Treatment by r e p l i c a t i o n I n t e r a c t i o n f o r thiamine r e t e n t i o n i n a luncheon-type ham product processed i n r e t o r t pouches and cans. I - 80 -i n the same way within each treatment. Despite the s i g n i f i c a n t in terac-t i o n , the order of treatment means was the same within each r e p l i c a t i o n , and the mean thiamine re tent ion wi th in each experimental uni t did not overlap among treatments. The s i g n i f i c a n t F - r a t i o for container error ind ica ted that the mean square for container error was s i g n i f i c a n t l y greater than for dup l i ca te e r r o r . That i s , there was greater v a r i a t i o n between conta in-ers wi th in an experimental unit than between dupl ica tes wi th in a con-t a i n e r . It would be expected that r e s u l t s obtained on dup l i ca te samples from within the same container would show less v a r i a t i o n than samples from d i f f e r e n t conta iner s . b) Treatment d i f fe rences S i g n i f i c a n t d i f ferences among treatments i n re tent ion of thiamine were ind ica ted by ana lys i s of variance (Table 12). Di f ferences among the i n d i v i d u a l treatment means were tested using the Student-Newman-Keuls mul t ip l e comparisons procedure. The mean percent re tent ion of thiamine for each treatment and the r e s u l t s of t h i s test are presented i n Table 13. A l l f i v e treatments were s i g n i f i c a n t l y d i f f e r e n t from one another when tested at the 5% l e v e l , and a l l except CAN-115.6 and CAN-126.7 were s i g n i f i c a n t l y d i f f e r e n t from each other when tested at the 1% l e v e l . The luncheon-type ham product processed i n re tor t pouches showed s i g n f i c a n t l y greater thiamine re tent ion at both temperatures compared to product processed i n cans (Table 13). The t h i n p r o f i l e of the re tor t - 81 -Tab le 13. Thiamine re tent ion i n a luncheon-type ham product a f ter pro-cess ing i n r e t o r t pouches and cans, with treatment d i f f e r e n -ces tested using Student-Newman-Keuls m u l t i p l e comparisons procedure (n=12). Thiamine r e t e n t i o n , % M u l t i p l e comparisons test Process Mean (standard deviat ion) pOO.05 1 pOO.01 1 CTRL 47.2 (1.9) c b CAN-115.6 40.0 (2.1) b a CAN-126.7 35.7 (1.3) a a PCH-115.6 55.6 (2.2) d c PCH-126.7 62.2 (2.9) e d Treatments not l a b e l l e d with the same l e t t e r wi th in a column are s i g n i -f i c a n t l y d i f f e r e n t when tested at the l e v e l i n d i c a t e d . - 82 -pouches provides a r e l a t i v e l y short d is tance for heat penetrat ion to the cold spot . As a r e s u l t , shorter process times were required and o v e r a l l q u a l i t y re tent ion was greater than for the same amount of product processed i n standard c y l i n d r i c a l conta iner s . This e f fect of package geometry was predicted for conduction-heating products by T e i x e i r a et a l . (1975), Tung and Smith (1980) and Adams et a l . (1983) and demon-s t ra ted i n ac tua l processing work by Greene (1979) and Chia et a l . (1983). These s tudies were discussed previous ly i n the L i t e r a t u r e Review. The greater re tent ion of thiamine when using the r e t o r t pouch compared to the can of equivalent volume was approximately 16% for a r e t o r t temperature of 1 1 5 . 6 ° C and 26% for 1 2 6 . 7 ° C . Thi s represented increases of 39 and 75% r e s p e c t i v e l y . Ham product processed i n the 307x111.5 cans at 1 1 5 . 6 ° C had a l e v e l of thiamine re tent ion intermediate between that processed i n larger cans and i n r e t o r t pouches (Table 13). The d i f ference between CTRL and CAN-115.6 was approximately 7% thiamine re tent ion and between CTRL and PCH-115.6, approximately 8%. The intermediate value for re tent ion was expected, because the dis tance required for heat penetrat ion to the co ld spot was greater than for the pouch and l e s s than for the t a l l can. The e f fect of temperature change was d i f f e ren t for the r e t o r t pouch and can. For the can, the increase i n processing temperature resul ted i n a decrease in thiamine re tent ion (d i f ference of approxi-mately 4% re tent ion corresponding to an 11% decrease) , while for the re tor t pouch there was an increase i n thiamine re tent ion (6% re tent ion - 83 -corresponding to a 12% i n c r e a s e ) . As previous ly mentioned, for conduction-heating products , the ef fect of the thermal treatment must be integrated for a l l points wi th in the conta iner . The increase i n process temperature for the can must have caused the product near the outer surfaces of the container to have received a r e l a t i v e l y severe process , which resul ted i n s u f f i c i e n t thiamine degradation to overcome the shorter process time required to achieve the same l e t h a l i t y at the center . The net re su l t was an o v e r a l l decrease in thiamine r e t e n t i o n . For the r e t o r t pouch, the t h i n p r o f i l e would promote r e l a t i v e l y rapid heating at the cold spot, the surface degradation e f fec t s would be reduced and a higher o v e r a l l thiamine re tent ion would be expected. The trends observed for the e f fect of processing temperature were expected based on pred ic t ions made by T e i x e i r a et a l . (1969 and 1975), Ohlsson (1980a and b) , Tung and Smith (1980) and Adams et a l . (1983) when using computer s imulat ion techniques . In te s t s with sweet potato puree processed i n cans and re tor t pouches, Greene (1979) showed the same trends for thiamine re tent ion when cons ider ing r e t o r t temperatures of 2 4 0 ° F ( 1 1 5 . 6 ° C ) and 2 5 0 ° F ( 1 2 1 . 1 ° C ) . However, the e f fect of process temperature was not s i g n i f i c a n t for e i ther the can or r e to r t pouch. For cans, Greenwood et a l . (1944) showed a trend for decreased thiamine re tent ion with increas ing process temperature for both 12 oz (340 g) and 2.5 lb (1.13 kg) cans (300x308 or 76 mm diameter by 89 mm high and 404x510 or 108 mm diameter by 143 mm high , r e spec t ive ly ) of pork luncheon meat with re tor t temperatures of 2 2 5 ° F ( 1 0 7 . 2 ° C ) , 2 3 5 ° F ( 1 1 2 . 8 ° C ) and 2 4 5 ° F ( 1 1 8 . 3 ° C ) . Thomas et a l . (1981) a l so showed t h i s - 84 -trend for canned pork i n 404x309 cans (108 mm diameter by 90 mm high) processed at 1 1 6 ° C and 1 2 1 ° C . The greatest thiamine re tent ion reported (PCH-126.7) does not necessar i ly ind ica te the optimum re tent ion poss ib le with the container geometries te s ted . Computer s imulat ion studies could be used perhaps to pred ic t optimum processing condi t ions for maximum thiamine r e t e n t i o n . Another point to consider i s that , although maximum thiamine re tent ion i s de s i red , other product c h a r a c t e r i s t i c s must be evaluated before a f i n a l dec i s ion i s made on the process to use. For ins tance , a c e r t a i n degree of cook may be required to produce the des ired texture i n the product (Ohlsson, 1980c). c) Amount of thiamine re ta ined To compare the r e s u l t s obtained with those reported i n other s tud ie s , the percent re tent ion of thiamine as wel l as the ac tua l thiamine concentrat ion can be cons idered . The thiamine concentrat ions a f te r processing for each of the treatments are ind ica ted i n Table 14. The data presented by Schweigert and Lusbough (1960) i n d i c a t e d that the re tent ion of thiamine i n canned meats ranges from 15 to 55 percent . Comparison of d i f f e r e n t studies i s d i f f i c u l t , because of the d i f f e r e n t products , container s i zes and shapes, and processing condi-t ions used. The U.S . Department of A g r i c u l t u r e (USDA, 1980) l i s t e d a thiamine content of 5.35 ng/g for canned chopped ham. Reedman and Buckby (1943) inves t iga ted the re tent ion of thiamine i n canned pork luncheon meat (a cured product) processed i n 6 l b (2.72 kg) rectangular - 85 -Table 14. Thiamine concentrat ion (wet basis) i n a luncheon-type ham product a f ter processing i n r e t o r t pouches and cans (n=12). Thiamine concentra t ion , ug/g Process Mean (standard deviat ion) CTRL 3.39 (0.14) CAN-115.6 2.87 (0.14) CAN-126.7 2.56 (0.08) PCH-115.6 3.99 (0.15) PCH-126.7 4.46 (0.25) - 86 -conta iners at 2 3 0 ° F ( 1 1 0 . 0 ° C ) . The mean thiamine content found i n the processed product was 6.3 ug/g which represented 52.7% r e t e n t i o n . These researchers a l so tested commercially a v a i l a b l e luncheon meat from 12 oz (340 g) cans. The mean thiamine content for d i f f e r e n t l o t s ranged from 5.48 to 7.56 i>ig/g. Rice and Robinson (1944) processed cured ground pork i n 6 lb (2.72 kg) cans at 2 3 5 ° F ( 1 1 2 . 8 ° C ) and i n 12 oz (340 g) cans at 2 3 2 ° F ( 1 1 1 . 1 ° C ) . These researchers reported 67% re tent ion of thiamine i n the 12 oz cans and 43% re tent ion i n the 6 lb cans. Er ickson and Boyden (1947) processed pork l o i n , and uncured ham and shoulder i n glass j a r s (385 g f i l l ) at 2 5 0 ° F ( 1 2 1 . 1 ° C ) . Percent re tent ion of thiamine fo l lowing processing was 27.5% for l o i n , 18% for ham and 23% for shoulder . The thiamine content i n the processed meat was 2.60 ug/g for l o i n , 1.82 ug/g for ham and 1.76 ug/g for shoulder . None of the s tudies jus t discussed reported the l e t h a l i t y achieved with the processes used. Greenwood et a l . (1944) processed pork lunch-eon meat under condi t ions which have already been d i scussed . In the 12 oz cans, thiamine re tent ion ranged between 73 and 76% with thiamine content i n the processed product between 4.1 and 4.4 ug/g . For the 2.5 l b cans thiamine re tent ion var ied between 46 and 60% with thiamine content i n the processed product between 2.6 and 3.5 ug/g . These researchers used much lower F 0 values than i n the present inves t i ga -t i o n . For the 12 oz cans the center value was 0.08 min and for the 2.5 lb cans the values ranged from 0.24 to 0.29 min. Using 2 3 5 ° F as the process temperature, these researchers increased the F 0 values to 1.85 min for the 12 oz cans and to 2.2 for 2.5 l b cans, which resu l ted i n 56 - 87 -and 36% thiamine r e t e n t i o n , r e s p e c t i v e l y . Thomas et a l . (1981) processed ground pork with added s a l t , sodium tr ipolyphosphate and water i n 404x309 (108 mm diameter by 90 mm high) cans at 116 and 1 2 1 ° C to achieve an F 0 value of 6 min. The pork processed at 1 1 6 ° C retained 12% of the o r i g i n a l thiamine, while that processed at 1 2 1 ° C reta ined 9%. Thus, depending on the exact condi t ions used, wide v a r i a t i o n i n thiamine re tent ion may be expected when pork products are thermally processed. The contents and percent re tent ions of thiamine reported i n t h i s i n v e s t i g a t i o n f a l l wi th in the range of those which have been previous ly observed for pork products . 3. Process L e t h a l i t y Process l e t h a l i t y values were ca l cu l a ted using Stumbo's method for each container having a thermocouple. These r e s u l t s are presented i n Table 15. Comparison of the F 0 values from t h i s tab le with those predic ted (Table 11) ind ica ted that for the cans the values obtained were lower than those p red i c t ed , while for the re tor t pouches, the values were c lo ser to those p red ic ted . The heating and coo l ing para-meters used for c a l c u l a t i o n of F 0 values are presented i n Table 16. The apparent heating c h a r a c t e r i s t i c (represented by f n ) was greater than that found i n the process determination work for the canned t rea t -ments (Table 10), which ind ica ted that heating took place at a slower rate i n the cans during t h i s por t ion of the i n v e s t i g a t i o n compared to the process determination work. The mean f n values for the re tor t pouches obtained during t h i s por t ion of the work were wi thin one standard dev ia t ion of those obtained i n the process determination work. - 88 -Table 15. Process l e t h a l i t y values for a luncheon-type ham product processed i n r e t o r t pouches and cans with three process runs for each treatment and c a l c u l a t i o n s done using Stumbo's method. Number of i n d i v i d u a l °-Z Process containers tested Mean (standard devia t ion) CTRL 14 6.4 (0.4) CAN-115.6 14 6.4 (0.3) CAN-126.7 11 6.5 (1.1) PCH-115.6 11 7.6 (0.2) PCH-126.7 15 13.2 (3.0) - 89 -Table 16. Heating and coo l ing curve parameters for a luncheon-type ham product processed i n r e t o r t pouches and cans with three process runs per treatment. Mean value (standard devia t ion) Process min min Jh Jc CTRL 31.1 (1.1) 38.4 (1.5) 1.64 (0.11) 1.52 (0.08) CAN-115.6 44.5 (1.2) 63.0 (2.4) 2.17 (0.07) 1.61 (0.04) CAN-126.7 43.9 (1.4) 61.7 (1.9) 2.13 (0.09) 1.67 (0.06) PCH-115.6 10.9 (0.4) 15.5 (1.5) 0.85 (0.07) 1.91 (0.29) PCH-126.7 10.6 (0.8) 14.3 (1.0) 0.94 (0.07) 1.94 (0.29) - 90 -The volume of cook-out l i q u i d was greater (by approximately two times) for the product used i n the process determination work compared to that used i n the f i n a l processing experiments. The volumes of l i q u i d are compared i n Table 17. The process times used for processing the product during thiamine re tent ion evaluat ion work were 2 to 13 min shorter than those used i n the process determination work (Tables 5 and 6 ) . The longer heating times used i n the process determination work may have p a r t l y accounted for the r e l a t i v e l y large volume of cook-out l i q u i d observed compared to the f i n a l processing experiments. Mulley et a l . (1975c) reported that for beef puree, l i q u i d separat ion became more pronounced with extended process t imes. The large d i f fe rences i n volume of cook-out l i q u i d observed i n t h i s experiment would not have been expected, given the small d i f ferences between the process t imes. The ham product used i n the process determination work had been f rozen , whereas that used i n the ac tua l processing was f r e s h . The f reez ing of the ham product may have played a ro le i n causing the large volume of l i q u i d loss from the product . The d i f ferences i n the volume of cook-out l i q u i d may have i n part l e d to the d i f ferences noted i n the apparent heating r a t e . Thi s e f f e c t , i f present, was observed for the cans but not for the r e t o r t pouches. In the cans, the meat appeared to shr ink away from the s ides and top and s e t t l ed down in the can. The l i q u i d at the sides may have increased the rate of heat penetrat ion to the can center . The d i f f e rence i n apparent heating rate was not observed with the re tor t pouches. Perhaps t h i s was due to the way the l i q u i d was d i s t r i b u t e d i n the pouches. Because of - 91 -Table 17. Volume of cook-out l i q u i d obtained fo l lowing processing of a luncheon-type ham product i n r e to r t pouches and cans (n=12 unless otherwise i n d i c a t e d ) . Mean volume of cook-out l i q u i d , mL (standard devia t ion) Process Process determination work Actua l processing work CTRL 55 (6) 25 (8) CAN-115.6 96 (3) 45 (8) CAN-126.7 98 (3) 52 (7) PCH-115.6 111 (5) 60 (8) 1 PCH-126.7 115 (5) 59 (3) 1 - 92 -the higher surface area any l i q u i d layer may have been thinner or , poss ib ly with more rapid heating due to the th in p r o f i l e , the ef fect of the l i q u i d was not observed. Mulley et a l . (1975c) suggested that for beef puree the increased thermal d i f f u s i v i t y and more rapid heat t rans fer observed compared to that predicted was due to a channeling ef fect within the s o l i d s lab of pureed meat caused by the formation of a broth wi th in the can. These researchers found that the presence of such a l i q u i d could lead to inaccurac ie s i n the p r e d i c t i o n of thiamine concentrat ion a f ter process-ing when mathematical models for conduction-heating products were used. The accuracy was found to vary with the s ever i ty of the process . Inves-t i g a t i o n s would be required to determine i f the c u r r e n t l y a v a i l a b l e models for conduction-heat ing products could be appl ied to the luncheon-type ham product . The processes for the cans would have required extension by between 3 and 4 min to achieve the o r i g i n a l l y intended process l e t h a l -i t y . I f the processes had been lengthened, the re tent ion of thiamine would have been decreased and thus the re tor t pouch versus can d i f f e r -ences i n thiamine re tent ion at e i ther process temperature would have been expected to be l a rger than those reported . Comparison of CAN-115.6 and CAN-126.7 treatments with extended process times requires cons idera t ion of the order of r e a c t i o n , because at the end of the processes used, one would expect to f ind a thiamine concentrat ion gradient i n the cans and, except i n a zero order r e a c t i o n , the rate of react ion i s dependent on the reactant concentra t ion . With - 93 -f i r s t order k i n e t i c s , the proport ion of the o r i g i n a l thiamine present which i s degraded i n a given time period i s independent of the o r i g i n a l thiamine concentrat ion and increases as the reac t ion rate constant increases (Capel los and B i e l s k i , 1972). The center point of the cans i n the CAN-115.6 treatment had almost reached re tor t temperature at the end of the cook. Thus, one would expect that the e n t i r e can contents were at a r e l a t i v e l y constant temperature and that , had the process been extended, no further large increases i n product temperature would have occurred . Given a r e l a t i v e l y constant temperature, the reac t ion rate constant for thiamine degradation would have been r e l a t i v e l y constant throughout the product. At the higher process temperature (CAN-126.7) the center of the can d id not reach the re tor t temperature (at the end of the process used the temperature was approximately 1 2 1 ° C ) . The temperature at the cold spot of the cans in the CAN-126.7 treatment was greater than the temperature reached i n the CAN-115.6 treatment. I f the process had been extended, the center temperature of the cans in the CAN-126.7 treatment would have increased , thus further increas ing the react ion rate constant . The smallest proport ion of thiamine destroyed i n the product i n the CAN-126.7 treatment i f the process had been extended, would have been in the slowest heating zone (center) s ince the other port ions of the can would have been at higher temperatures, with higher reac t ion rate constants . I f the processes for both CAN-115.6 and CAN-126.7 treatments were extended by the same length of t ime, a greater proport ion of the thiamine remaining i n the CAN-126.7 would have been expected to be degraded than i n the CAN-115.6 treatment. C a l c u l a t i o n s - 9k -c a r r i e d out with the determined k i n e t i c parameters (Table 9) and the percent re tent ion of thiamine fo l lowing the processes used (Table 13) ind ica ted that i f both processes were extended by 3 or k min the d i f f e r -ence between the thiamine re tent ion values for CAN-115.6 and CAN-126.7 would increase . The c a l c u l a t i o n s apply only for the circumstances described above and experimental work would be required to confirm the p r e d i c t i o n of an increased d i f ference i n percent thiamine re tent ion between the two treatments. - 95 -CONCLUSIONS Thermal des t ruct ion of thiamine i n the luncheon-type ham product tes ted could be described by f i r s t order reac t ion k i n e t i c s and the 2 1 Arrhenius equation. The k±2\ value was 2.03x10- min - and E a was 105 k3/mol. The re tent ion of thiamine fo l lowing thermal processing of the luncheon-type ham product i n r e t o r t pouches and cans was evaluated. The process times for the luncheon-type ham product processed i n r e t o r t pouches were 61 and 75% shorter for r e to r t temperatures of 115.6 and 126.7°C r e s p e c t i v e l y , compared to the same amount of product processed i n c y l i n d r i c a l cans. The shorter process times resu l ted i n increases of 16 and 26% thiamine re tent ion for the two re tor t temperatures. The increase i n r e t o r t temperature for the cans resu l ted i n a 4% decrease i n thiamine r e t e n t i o n , while for the re tor t pouches there was an increase of 6% r e t e n t i o n . The re su l t s of th i s i n v e s t i g a t i o n demonstrate that process times for conduction-heating foods packaged i n r e t o r t pouches may be shortened and re tent ion of thiamine may be s i g n i f i c a n t l y increased when compared to commercial s t e r i l i z a t i o n i n conventional c y l i n d r i c a l cans. As w e l l , the choice of processing temperature may a f fect thiamine r e t e n t i o n . However, for conduction-heating products , the e f fect of the thermal treatment must be integrated for every point i n the conta iner . 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The future i s in our hands: C r i t i c a l factors i n r e to r t pouch thermal process assurance. A c t i v i t i e s Rep. of the R&D Associates for M i l i t a r y Food and Packaging Systems, Inc. 31(2) : 49. Labuza, T . P. and Riboh, D. 1982. Theory and a p p l i c a t i o n of Arrhenius k i n e t i c s to the p r e d i c t i o n of nutr ient losses i n foods. Food Technol . 36(10): 66. Lamb, F . C , Farrow, R. P. and E l k i n s , E . R. 1982. E f fec t of process-ing on n u t r i t i v e value of food: Canning. In "Handbook of N u t r i t i v e Value of Processed Food. Volume I . Food for Human Use , " M. R e c h c i g l , J r . ( E d . ) , p. 11. CRC Press , I n c . , Boca Raton, F L . Lampi, R. A . • 1977. F l e x i b l e packaging for thermoprocessed foods. Adv. Food Res. 23: 305. Lampi, R. A . 1979. F l e x i b l e packaging for thermoprocessed foods. In "Fundamentals of Food Canning Technology," J . M. Jackson and B. M. Shinn ( E d . ) , p. 144. 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S. 1983. Heat t rans fer s tudies of steam/air mixtures for food processing i n r e t o r t pouches. Ph .D. t h e s i s , Un iver s i ty of B r i t i s h Columbia, Vancouver, BC Reedman, E . 3. and Buckby, L . 1943. The vitamin B^ content of canned pork. Can. 3. Res. 21: D262. R i c e , E . E . and Robinson, H. E . 1944. N u t r i t i v e value of canned and dehydrated meat and meat products . Am. 3. P u b l i c Health 34: 587. R i c e , E . E . and Beuk, 3. F . 1945. Reaction rates for decomposition of thiamin i n pork at various cooking temperatures. Food Res. 10: 99. R i z v i , S. S. H. and Acton, 3. C . 1982. Nutr ient enhancement of thermostabi l ized foods i n r e t o r t pouches. Food Technol . 36(4) : 105. Schweigert , B. S. and Lushbough, C . H. 1960. E f f ec t s of processing on meat products . In " N u t r i t i o n a l Eva luat ion of Food P r o c e s s i n g , " R. S. Har r i s and H. von Loesecke ( E d . ) , p. 261. John Wiley and Sons, New York, NY. Shappee, 3. and Werkowski, S. 3. 1972. Study of a nondestructive te s t for determining volume of a i r i n f l e x i b l e food packages. Tech. Rep. 73_i|._GP. U .S . Army Natick Labora tor ie s , Nat i ck , MA. Skjaldebrand, C , Anas, A . , Oste, R. and S j o d i n , P. 1983. P r e d i c t i o n of thiamine content i n convect ive heated meat products . 3. Food Technol . 18: 61. Smith, T . and Tung, M. A . 1982. Comparison of formula methods for c a l c u l a t i n g thermal process l e t h a l i t y . 3. Food S c i . 47: 626. Spinak, S. H. and Wiley , R. C . 1982. Comparisons of the general and B a l l formula methods for r e t o r t pouch process c a l c u l a t i o n s . 3. Food S c i . 47: 880. S t e e l , R. G. D. and T o r r i e , 3. H. 1980. " P r i n c i p l e s and Procedures of S t a t i s t i c s . A B iometr i ca l Approach," 2nd ed. McGraw-Hill Book Company, New York, NY. S t e f f e , 3. F . , Wi l l i ams , 3. R . , Chhinnan, M. S. and Black , 3. R. 1980. Energy requirements and costs of r e to r t pouch vs can packaging systems. Food Technol . 34(9) : 39. Stumbo, C . R. 1973. "Thermobacteriology i n Food P r o c e s s i n g , " 2nd ed. Academic Press , New York, NY. T e i x e i r a , A . A . , Dixon, 3. R. , Zahradnik, 3. W. and Zinsmei s ter , G. E . 1969. Computer opt imizat ion of nutr ient re tent ion i n the thermal processing of conduction-heated foods. Food Technol . 23: 845. - 102 -T e i x e i r a , A . A . , Z insmeis ter , G. E . , Zahradnik, 3. W. 1975. Computer s imulat ion of va r i ab le r e to r t cont ro l and container geometry as a pos s ib le means of improving thiamine re tent ion i n thermally processed foods. 3. Food S c i . 40: 656. Thomas, M. H . , Atwood, B. M . , W i e r b i c k i , E . and Taub, I . A . 1981. E f fec t of r a d i a t i o n and conventional processing on the thiamin content of pork. 3. Food S c i . 46: 824. Thompson, D. R. 1982. The chal lenge i n pred ic t ing nutr ient changes during food process ing . Food Technol . 36(2): 97. Tsutsumi, Y. 1979a. Producing pouches and trays to s u i t p a r t i c u l a r needs. In "Using the Retort Pouch Worldwide - Focus on the Present with a Look to the Future " , p. 24. Proc . of the Conference, held i n Ind ianapo l i s , IN. Sponsored by the Food Sciences I n s t . , Purdue U n i v . , March 14-15. Tsutsumi, Y. 1979b. New technology appl ied to pouches and future t rends . In "Using the Retort Pouch Worldwide - Focus on the Present with a Look to the F u t u r e , " p . 67. Proc . of the Conference, held i n Ind ianapo l i s , IN. Sponsored by the Food Sciences I n s t . , Purdue U n i v . , March 14-15. Tsutsumi, Y. 1979c. S t e r i l i z a t i o n methodology appl ied to pouches and t r a y s . In "Using the Retort Pouch Worldwide - Focus on the Present with a Look to the Future " , p. 86. Proc . of the Conference, held i n Ind ianapo l i s , IN . Sponsored by the Food Sciences I n s t . , Purdue U n i v . , March 14-15. Tung, M. A . 1980. Thermophysical s tudies for improved food pro-cesses . A F i r s t Quarter Rep. (16th Oune to 15th S e p t . ) . DSS F i l e No. 35SZ.01804-9-0001, prepared for the A g r i c u l t u r e Canada PDR Program, Ottawa, ON. Tung, M. A . , Garland, M. R. and Campbell , W. E . 1975. Quality compari-son of cream s t y l e corn processed i n r i g i d and f l e x i b l e conta iner s . Can. Ins t . Food S c i . Technol . 0. 8: 211. Tung, M. A. and Garland, T . D. 1978. Computer c a l c u l a t i o n of thermal processes . 3. Food S c i . 43: 365. Tung, M. A . and Smith, T . 1980. Innovations i n thermal process ing . In "Process ing 2000 Symposium", p. 103. MacDonald Col lege of M c G i l l U n i v e r s i t y , Montreal , PQ. Tuomy, 3. M. and Young, R. 1982. Retort-pouch packaging of muscle foods for the armed forces . Food Technol . 36(2): 68. Uribe-Saucedo, S. M. and Ryley, 3. 1982. A comparative study of a scorb ic ac id and thiamine re tent ion i n pouch s t e r i l i z a t i o n and canning. In s t . Food S c i . and Technol . (U.K.) Proc . 15(3): 120. - 103 -USDA. 1980. "Composition of Foods. Sausages and Luncheon Meats. Raw. Processed. Prepared, A g r i c u l t u r e Handbook No. 8 -7 . " Science and Education Admin i s t r a t ion , United States Department of A g r i c u l t u r e , Washington, DC. Whitaker, W. C. 1971. Process ing f l e x i b l e pouches. Mod. Pack. 44: 83. Wi l l i ams , 3. R . , S te f fe , 3. F . and Black , 3. R. 1982. Economic compar-ison of canning and r e t o r t pouch systems. 3. Food S c i . 47: 284. W i l l i a m s , 3. R . , S te f fe , 0. F . and Black , 3. R. 1983. S e n s i t i v i t y of se lected factors on costs of r e t o r t pouch packaging systems. Food Technol . 37(4) : 92. Wil son , D. C . 1980. T h e o r e t i c a l problems i n pouch process ing . Paper presented at 1980 Winter Meeting of the Amer. Soc. of A g r i c u l t u r a l Engineers , Chicago, IL , Dec. 2-5. - 104 -APPENDIX I . Thermal Processing Terminology f - The time required for the straight l i n e portion of the semi-logar-ithmic heating or cooling curve to tranverse one log c y c l e . f - Cooling rate index. The negative r e c i p r o c a l slope of the cooling curve (log m versus time). f ^ - Heating rate index. The negative r e c i p r o c a l slope of the heating curve (log g versus time). F - Process l e t h a l i t y . The equivalent, in terms of minutes at 250°F (121.1°C), of a l l l e t h a l heat received by the cold spot i n a container. This l e t h a l i t y i s calculated with a z value of 18 F° (10 C°). g - The difference in degrees between the r e t o r t temperature and the product temperature at any point. When r e f e r r i n g to the f n/U versus g r e l a t i o n s h i p , g i s that attained at the end of the heating period. j - A number representing the curved section before the semi-logarith-mic heating or cooling curve assumes s t r a i g h t l i n e c h a r a c t e r i s t i c s . j - Cooling lag factor. The j of the semi-logarithmic cooling curve. j ^ - Heating lag f a c t o r . The j of the semi-logarithmic heating curve. m - The diffe r e n c e in degrees between the cooling water temperature and the product temperature. P t - Operator's process time. The time from when the ret o r t reaches processing temperature u n t i l the steam i s turned o f f and cooling started. U - The equivalent, in minutes at r e t o r t temperature, of a l l l e t h a l heat received by a designated point in a container. z - The number of degrees for the thermal destruction curve (logarithm of thermal destruction time versus temperature) to traverse one log cy c l e . In t h i s research project, the product temperature i n a l l cases ref e r s to the temperature measured in the cold zone. Additional d e t a i l s for the der i v a t i o n and use of these terms can be found i n Stumbo (1973). - 105 -APPENDIX I I . Thiamine Analysis Procedure The procedure used for thiamine analysis was based on the AOAC method (AOAC, 1980). A l l chemicals used were reagent grade unless otherwise s p e c i f i e d . Contrad 70 (Canlab, Vancouver, BC) was used to clean a l l glassware. I t was reported to rinse cleanly and be su i t a b l e for fluorescence work. Following cleaning, a l l glassware was rinsed with tap water 8 to 10 times and then with d i s t i l l e d water 5 times. Contact of reagents with p l a s t i c , stopcock grease, cork and rubber was avoided to prevent the introduction of fluorescent impurities (Guibault, 1973). A l l water used was d i s t i l l e d unless otherwise s p e c i f i e d . Reagents and Supplies 1. Enzyme s o l u t i o n . A 10% aqueous sol u t i o n of Mylase 100 (United States Biochemical Corp., Cleveland, OH) was prepared in the amount required on the day i t was to be used (MacBride and Wyatt, 1983). 2. Base exchange s i l i c a t e . Bio-Rex 70 50-100 mesh ion exchange material (Bio-Rad Laboratories, Richmond, CA) was activated to convert the sodium form to the hydrogen form. To a c t i v a t e , 300 mL of 2N hydrochloric acid (HC1) was added, t h i s was s t i r r e d for 15 min and then decanted. This step was repeated a second time. Then, 300 mL of water was added and the mixture s t i r r e d 1 min and then decanted. The water rinses were repeated u n t i l the pH of the water was 4.5 to 7.0 ( E l l e f s o n et a l . , 1981). The re s i n was stored at approximately 2°C u n t i l used. Reactivation of the r e s i n was done in the same manner as the f i r s t a c t i v a t i o n . 3. Chromatographic columns. Separation tubes for vitamin B were obtained from Fisher S c i e n t i f i c Ltd. (Vancouver, BC). The t i p s of the columns were cut back so as to obtain a flow rate of approxi-mately 1 mL/min from the f i l l e d columns. A plug of glass wool was placed in the bottom of the column. The column was f i l l e d to the bottom of the rese r v o i r with water and activated r e s i n i n water suspension was poured into the columns. Resin was allowed to s e t t l e by gravity and enough r e s i n was used to f i l l the column and leave approximately a 2 mm layer i n the bottom of the r e s e r v o i r . 4. 2N sodium acetate. Two hundred and seventy two grams of NaC2H302*3H20 was disolved i n water and d i l u t e d to 1 L. 5. Neutral potassium chloride s o l u t i o n . Two hundred and f i f t y grams of KC1 was dissolved i n water and d i l u t e d to 1 L. 6. Acid potassium chloride solution (acid-KCl). Eight and one-half m i l l i l i t e r s of concentrated HC1 was added to 1 L of neutral potas-sium chloride s o l u t i o n . 7. 15% sodium hydroxide solution (15% NaOH). F i f t e e n grams of NaOH was dissolved i n water and d i l u t e d to 100 mL. - 106 -8. Potassium f e r r i c y a n i d e s o l u t i o n (1%). One gram of K 3 Fe(CN) 6 was d i s so lved i n water and d i l u t e d to 100 mL. This was prepared fresh d a i l y and held protected from l i g h t . 9 . O x i d i z i n g reagent. Four m i l l i l i t e r s of potassium f e r r i c y a n i d e so lu t ion was d i l u t e d to 100 mL with 15% NaOH s o l u t i o n . I t was held protected from l i g h t and used wi th in 4 h . 10. Stock thiamine s o l u t i o n (approximately 100 yg/mL). F i f t y m i l l i -grams of USP thiamine hydrochlor ide reference standard (U.S. Phar-macopeial Covention, I n c . , R o c k v i l l e , MD) that had been dr ied to constant weight over phosphorus pentoxide i n a des icca tor was qu ick ly weighed out. Thi s was d i s so lved i n 20% ethanol (made from 95% ethanol d i l u t e d with water) a c i d i f i e d to pH 3.5-4.3 with 0.1N HC1 and then d i l u t e d to 500 mL with the a c i d i f i e d a l c o h o l . The so lu t ion was stored re f r i ge ra ted ( 2 ° C ) i n a g lass-s toppered, aluminum f o i l covered glass b o t t l e . 11. Intermediate thiamine s o l u t i o n (approximately 10 yg/mL). F i f t y m i l l i l i t e r s of stock thiamine so lu t ion was d i l u t e d to 500 mL with 20% ethanol adjusted to pH 3.5-4.3 with HC1 (prepared as described for stock thiamine s o l u t i o n ) . This was stored re f r i ge ra ted in a g lass-s toppered, aluminum f o i l covered glass b o t t l e . 12. Working thiamine s o l u t i o n (approximately 1 yg/mL). Ten m i l l i l i t e r s of intermediate thiamine so lu t ion was d i l u t e d to 100 mL with 0.1 N HC1. This was prepared fresh d a i l y . 13. Stock quinine su l f a te s o l u t i o n . One hundred mil l igrams of quinine su l fa te was d i s so lved i n 0.1N s u l f u r i c ac id ( H 2 S O 4 ) and d i l u t e d to 1 L with the same solvent (Assoc ia t ion of Vitamin Chemists, 1966). This was stored re f r i ge ra ted i n a g lass-s toppered, aluminum f o i l covered glass b o t t l e . 14. Working quinine su l f a t e s o l u t i o n . Three m i l l i l i t e r s of stock quinine su l fa te so lu t ion was d i l u t e d to 1 L with 0.1N H 2S0 i 4 (Asso-c i a t i o n of Vitamin Chemists, 1966). This was prepared fresh d a i l y and held protected from l i g h t . 15. I sobutyl a l c o h o l . This was not r e d i s t i l l e d . High grade g las s d i s t i l l e d Omni-Solv i sobuty l a l coho l from BDH (BDH Chemicals , Vancouver, BC) was used. This was reported to be s u i t a b l e for f luorescence work. 16. 0.1N HC1. E ight and one-half m i l l i l i t e r s of concentrated HC1 was d i l u t e d to 1 L with water. 17. 0.1N H2SO4. Two and e ight- tenths m i l l i l i t e r s of concentrated H2S04 was d i l u t e d to 1 L with water. 18. 2N HC1. One hundred and seventy m i l l i l i t e r s of concentrated HC1 was d i l u t e d to 1 L with water. - 107 -P r o c e d u r e 1 . A t h o r o u g h l y g r o u n d sample w h i c h c o n t a i n e d 10 t o 30 ug o f t h i a m i n e was we ighed i n t o a 100 mL v o l u m e t r i c f l a s k . When w o r k i n g w i t h l a r g e amounts o f m a t e r i a l a s y r i n g e was used t o p l a c e t h e sample i n t o t h e f l a s k . I f t h e r e was a s m a l l amount o f sample m a t e r i a l ( i n t h e k i n e t i c s t u d y ) a s p a t u l a was u s e d . A p p r o x i m a t e l y 40 mL o f 0 .1N HC1 was added and m i x i n g was a c c o m p l i s h e d by v i g o r o u s s h a k i n g . The w a l l s o f t h e f l a s k were washed down w i t h a d d i t i o n a l 0 .1N HC1 so a t o t a l o f 75 mL was a d d e d . Up t o 10 samples were p r e p a r e d . 2 . Two s t a n d a r d s were p r e p a r e d . Twenty m i l l i l i t e r s o f w o r k i n g t h i a m i n e s o l u t i o n was p i p e t t e d i n t o a 100 mL v o l u m e t r i c f l a s k and 55 mL o f 0 .1N HC1 was a d d e d . 3 . The samples and s t a n d a r d s were p l a c e d i n a b o i l i n g w a t e r b a t h . They were h e a t e d f o r 30 m in w i t h f r e q u e n t s h a k i n g . k. The f l a s k s were c o o l e d t o 40°C o r l o w e r . Seven m i l l i l i t e r s o f 2N sod ium a c e t a t e s o l u t i o n was added t o a d j u s t t h e pH t o a p p r o x i m a t e l y 4 . 5 . F i v e m i l l i l i t e r s o f enzyme s o l u t i o n was added and i n c u b a t i o n was c a r r i e d o u t a t 35-37°C f o r 3 h . 5 . The f l a s k s were c o o l e d t o room t e m p e r a t u r e . The c o n t e n t s were d i l u t e d t o 100 mL w i t h w a t e r , m ixed t h o r o u g h l y and t h e n f i l t e r e d t h r o u g h Whatman #1 f l u t e d f i l t e r paper I n t o 125 mL e r y l e n m e y e r f l a s k s . The f l a s k s were c o v e r e d w i t h P a r a f l l m ( A m e r i c a n Can Company, G r e e n w i c h , CT) and s t o r e d o v e r n i g h t a t a p p r o x i m a t e l y 2 ° C , p r o t e c t e d f r o m l i g h t . 6 . Columns were p r e p a r e d . Twenty f i v e m i l l i l i t e r s o f sample was p i p e t t e d o n t o t h e c o l u m n s . T h i s was a l l o w e d t o d r a i n t h r o u g h . I m p u r i t i e s were c l e a n e d o f f t h e co lumns w i t h t h r e e 5 mL p o r t i o n s o f a l m o s t b o i l i n g w a t e r . The t h i a m i n e was e l u t e d f r o m t h e co lumns i n t o 50 mL v o l u m e t r i c f l a s k s w i t h f i v e 10 mL p o r t i o n s o f a l m o s t b o i l i n g a c i d - K C l . The s o l u t i o n s were c o o l e d and t h e n d i l u t e d t o 50 mL w i t h a c i d - K C l . 7 . The o x i d a t i o n was c a r r i e d o u t i n C o r n i n g 50 mL round b o t t o m g l a s s -s t o p p e r e d c e n t r i f u g e t u b e s ( o b t a i n e d f r o m W e s t e r n S c i e n t i f i c S e r v i c e s L t d . , R ichmond, B C ) . The re were f o u r t u b e s per sample o r s t a n d a r d and 16 t u b e s were worked w i t h a t one t i m e . The t u b e s were h e l d p r o t e c t e d f r o m l i g h t . A p p r o x i m a t e l y 1.5 g sod ium c h l o r i d e (1 mL f r o m a m e a s u r i n g spoon) was p l a c e d I n each o x i d a t i o n t u b e and t h e n 5 mL o f sample o r s t a n d a r d s o l u t i o n was p i p e t t e d I n t o each o f f o u r t u b e s . Tubes were h a n d l e d I n g r o u p s o f f o u r . For t h e f i r s t two t u b e s o f t h e - g r o u p , t h e r e q u i r e d r e a g e n t was 3 mL o f o x i d i z i n g r e a g e n t , and f o r t h e l a s t two 3 mL o f 15% NaOH. The r e a g e n t s were p remeasured I n t o s m a l l g l a s s t u b e s . The I s o b u t y l a l c o h o l was d i s p e n s e d f r o m an O x f o r d A u t o m a t i c P l p e t t o r b o t t l e ( o b t a i n e d f r o m F i s h e r S c i e n t i f i c - 108 -L t d . , Vancouver, BC). The required reagent was added to the f i r s t tube and i t was swir led gent ly . Immediately, 13 mL of i sobuty l a l c o h o l was added and the tube shaken for 15 s. The a d d i t i o n of reagent and i sobuty l a lcohol was repeated for the next three tubes. The four tubes were shaken for 2 min and then centr i fuged at low speed for 2 min while the reagents and i sobuty l a lcohol were added to the next 4 tubes. The centr i fuge was stopped and the procedure continued u n t i l a l l tubes were completed. 8. Pasteur p ipet tes were used to t ransfer the i sobuty l a lcohol l ayer to te s t tubes which were held protected from l i g h t . Fluorescence measurement was ca r r i ed out on the i sobuty l a l coho l l a y e r s . Working quinine su l f a te so lu t ion was used to standardize and set the sens i -t i v i t y of the instrument each time i t was used. The spectrophoto-fluorometer was a l so checked between readings with the working quinine su l fa te s o l u t i o n . Samples to which 15% NaOH was added were blanks , those to which o x i d i z i n g reagent was added provided sample or standard readings . Amount of thiamine i n sample (\ig/g) Mean sample reading Mean sample blank reading |j.g thiamine i n f i n a l standard soln x 40 x Mean standard reading Mean standard blank reading g of ham used - 109 -APPENDIX III. Example Heating and Cooling Curves Heating curve (logarithm of g versus time) f o r a 300x407 can c o n t a i n i n g a luncheon-type ham product processed at 115.6°C. 1. e - l - I f c i 8 10 2© 3 0 4 6 5 8 6 0 7 8 8 8 •fh=37.85: j c h = 2 . 2 5 S r-so,= . 9998 9 8 Cooling curve (logarithm of m versus time) f o r a 300x407 can c o n t a i n i n g a luncheon-type ham product processed at 115.6°C with c o o l i n g water at 10°C. - 110 -APPENDIX IV. Example Process time Calculation Results P r o c e s s t i m e r e q u i r e d t o a c h i e v e F o = 6 . 0 min f o r 307x111 .5 cans c o n t a i n i n g a l u n c h e o n - t y p e ham p r o d u c t p r o c e s s e d a t 1 1 5 . 6 ° C . **Ther«al P r o c e s s a n a l y s i s - ESTIMATION OF PROCESS TIME** **Usin-9 Stumbo' s method f o r simple heat i n s c u r v e s ** T a r s e t Fo = 6.8 min R e t o r t temperature = 115.6 degrees Process time Sample ID f h f c J c h Jcc J c h Jcc I n i t i a l lemp exp c o r r 5.8 °C C21-R2 SMALLCAN 27.43 37.61 1.68 1.58 1.68 1.50 66.8 C22-R2 SMALLCAN 29.86 36.68 1.47 1.47 1.47 1.47 68.5 C23-R2 SMALLCAN 38.87 35.31 1.55 1.51 1.55 1.51 63.2 C24-R2 SMALLCAN 28.52 38.13 1.88 1.41 1.88 1.41 63.8 C25-R2 SMALLCAN 23.86 38.28 1.57 1.48 1.57 1.48 68.8 C26-R2 SMALLCAN 28.88 36.14 1.63 1.58 1.63 1.58 68.4 C27-R2 SMALLCAN 23.83 35.85 1.58 1.52 1.58 1.52 63.1 C23-R2 SMALLCAN 38.25 38.14 1.61 1.45 1.61 1.45 78.3 C38-R2 SMALLCAN 38.17 34.73 1.52 1.60 1.52 1.68 68.8 C21-R4 SMALLCAN 27.56 36.88 1.77 1.52 1.77 1.52 66.8 C22-R4 SMALLCAN 23.54 38.68 1.66 1.43 1.66 1.43 63.4 C23-R4 SMALLCAN 38.87 36.86 1.64 1.56 1.64 1.56 63.8 C24-R4 SMALLCAN 28.34 35.83 1.66 1.55 1.66 1.55 67.2 C26-R4 SMALLCAN 38.41 36.71 1.63 1.54 1.63 1.54 78.9 C27-R4 SMALLCAN 23.83 35.32 1.61 1.43 1.61 1.43 63.8 C28-R4 SMALLCAN 23.38 36.33 1.64 1.43 1.64 1.43 68.8 C23-R4 SMALLCAN 23.81 34.46 1.54 1.64 1.54 1.64 67.8 C38-R4 SMALLCAN 27.74 34.75 1.81 1.57 1.81 1.57 67.2 C21-R5 SMALLCAN 22.74 33.15 2.78 1.43 2.78 1.43 63.6 C22-R5 SMALLCAN 26.72 33.43 1.73 1.56 1.73 1.56 65.4 C23-R5 SMALLCAN 27.83 34.83 1.83 1.56 1.83 1.56 67.6 C24-R5 SMALLCAN 27.34 37.47 2.81 1.45 2.81 1.45 68.2 C25-R5 SMALLCAN 23.35 34.77 1.72 1.53 1.72 1.53 63.1 C26-R5 SMALLCAN 27.77 33.78 1.57 1.53 1.57 1.53 65.5 C27-R5 SMALLCAN 27.42 38.23 1.76 1.46 1.76 1.46 66.7 C28-R5 SMALLCAN 28.63 36.33 1.57 1.55 1.57 1.55 67.8 C23-R5 SMALLCAN 26.85 35.88 1.85 1.58 1.85 1.58 66.8 C38-R5 SMALLCAN 27.88 34.77 1.83 1.63 1.83 1.63 67.6 Averages 28.51 36.83 1.72 1.52 1.72 1.52 St. Dev. 1.68 1.55 8.24 8.86 8.24 8.86 Average e s t i m a t e d p r o c e s s time* min 67.3 Standard d e v i a t i o n * min 1.68 Average + 3 s t a n d a r d d e v i a t i o n s * min 72.3 - 111 -P r e d i c t e d F 0 values obtained i f the recommended process was used for 307x111.5 cans c o n t a i n i n g a luncheon-type product. **Thermal Process A n a l y s i s - CONFIRMATION OF PROCESS** **Using Stumbo's method For simple heating curves ** Target Fo = 6.0 min Retort temperature = 115.6 degree-: I n i t i a l Temperatures: 5.0 Process times* min : 72.S F o Sample ID f h f c •jch • j c c Jch Jcc I n i t i a l Temp e XP corn 5.U °C C21-R2 SMflLLCflN 27.43 37.61 1.68 1.50 1.68 1.50 -? -?ci-f . !' J C22-R2 SMflLLCflN 23.86 36.60 1.47 1.47 1.47 1.47 7 15C23-R2 SMflLLCflN 30.07 35.31 1.55 1.51 1.55 1.51 6.35 C24-R2 SMflLLCflN 1 I I £Z.~t 38. 13 1.80 1.41 1.80 1.41 7.01 C25-R2 SMflLLCflN 23.86 38.28 1.57 1.48 1.57 1.48 7.28 C26-R2 SMflLLCflN i.'b". 80 36. 14 1.68 1.50 1.69 1.50 7. 18 C27-R2 SMflLLCflN 23.83 35.05 1.58 1.52 1.58 1.52 6.33 C29-R2 SMflLLCflN 30.25 38.14 1.61 1.45 1.61 1.45 6.67 C30-R2 SMflLLCflN 30. 17 34.73 1.52 1.60 1.52 1.60 7.06 C21-R4 SMflLLCflN 27.56 36.08 1.77 1.52 1.77 1.52 7.56 C22-R4 SMflLLCflN 23.54 38.60 1.66 1.49 1.66 1.43 6.31 C23-R4 SMflLLCflN 30.07 36.86 1.64 1.56 1.64 1.56 6.79 C24-R4 SMflLLCflN 28.34 35.03 1.66 1.55 1.66 1.55 7.48 C26-R4 SMflLLCflN 30.41 36.71 1.63 1.54 1.63 1.54 6.53 C27-R4 SMflLLCflN 23.83 35.32 1.61 1.43 1.61 1.43 6.80 C28-R4 SMflLLCflN 23.30 36.33 1.64 1.49 1.64 1.43 7.06 C23-R4 SMflLLCflN 23.01 34.46 1.54 1.64 1.54 1.64 7.52 C30-R4 SMflLLCflN 27.74 34.75 1.81 1.57 1.81 1.57 7.47 C21-R5 SMflLLCflN 22.74 33.15 2.7y 1.43 2.78 1.43 8.51 C22-R5 SMflLLCflN 26.72 33.43 1.73 1.56 1.73 1.56 7.94 C23-R5 SMflLLCflN 27.83 34.83 1.83 1.56 1.83 1.56 7.36 C24-R5 SMflLLCflN 27.34 37.47 2.01 1.45 2.01 1.45 7.21 C25-R5 SMflLLCflN 23.35 34.77 1.72 1.59 1.72 1.53 6.38 C26-R5 SMflLLCflN 27.77 33.70 1.57 1.59 1.57 1.53 7.83 C27-R5 SMflLLCflN 27.42 38.23 1.76 1.46 1.76 1.46 7.58 C28-R5 SMflLLCflN 28.63 36.33 1.57 1.55 1.57 1.55 7.54 C29-R5 SMflLLCflN 26. 85 35.88 1.85 1.58 1.85 1.58 7. 73 C30-R5 SMflLLCflN 27.80 34.77 1.83 1.63 1.83 1.63 7.37 Average de 1 iveri ed Fo* min 7.30 

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