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Temperature and heat transfer studies in a water immersion retort Morello, Gerry F 1987

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TEMPERATURE  AND HEAT TRANSFER STUDIES IN A WATER IMMERSION RETORT by GERRY F.  MORELLO  B. Sc., University of British Columbia, 1981  A THESIS SUBMITTED THE  IN  PARTIAL  REQUIREMENTS  FOR THE  MASTER OF  FULFILMENT DECREE  OF  SCIENCE  in THE  FACULTY  OF GRADUATE  STUDIES  Department of Food Science  We  accept this thesis as conforming to the required standard  THE  UNIVERSITY O F  BRITISH  COLUMBIA  November 1987  © GERRY F. M O R E L L O , 1987  OF  In  presenting  degree freely  this  in partial  fulfilment  at the University of British  Columbia,  available  copying  of  department publication  this or  thesis  for reference thesis by  of this  and study.  for scholarly  his or thesis  her  of  f^O&b  SUEAlCg  DE-6(3/81)  gain  agree  that that  shall  It  is  for an  the Library shall permission  may be granted  representatives.  for financial  The University of British C o l u m b i a 1956 Main Mall Vancouver, Canada V6T 1Y3  I agree  I further  purposes  permission.  Department  of the requirements  make  it  for extensive  by the head  understood  advanced  that  not be allowed without  of my  copying  or  my written  ABSTRACT Temperature were  and  performed. The  stability  of  the  heat  transfer  temperature  retort  during  the  retort was  uniformity within  sterilizing  calculated retort  conditions  for  the  (115  and  in  a pilot-scale water  investigated  cook  period.  based on  the  The  immersion retort  temperature  distribution  investigation  heating and cooling  of  heat  the  retort  Variable 125°C)  was  retort and  determined  operating  three  weir  from  transfer  uniformity  process  conditions heights  and  parameters calculated  of food-simulating teflon transducers. The  within  transducers.  temperatures  study  the  from the heat penetration curves of  studies  lethalities  consisted  (29.2,  of  two  31.2 and 34.6  cm).  Mean  standard  deviations  of  distribution during the cook period gradients the  were  entrance  found and  regions  of  water  hottest  locations  between  exit  channels (the  ranged from  the  regions  thermocouple  of  upper water  entrance  and  exit  0.19 to  and  lower  channels.  1 and 2) averaged  readings  of  temperature  0.22 C ° . Slight  water  The  channels  coldest  approximately  region  indicating  water  temperature  and  locations  0.6 C °  channel  between (the  exit  than  the  the  exit  lower  11 and  region of water channel 10).  Mean stability  standard  during  the  deviations  cook  ranged  from  readings  0.10 to  entrance and exit regions of water channels displayed similar stability.  was  indicated. A  retort  heat  transfer  temperature  of  variability 125°C  ii  channel 11, which  within  temperature  0.20 C ° . Temperature  The  of  channels, except  indicating  uniform  existence  all water  thermocouple  was  The  between  period  of  the  produced  water  was  less stable.  immersion  smaller f^  and  stability  f  retort values  than  115°C.  between  trays.  trays. Weir for  Variations Weir  height  a significantly  cm)  created  widest  in  weir  height  2  influenced  cm)  exhibited  1 (29.2 cm) exhibited  most  for  variability  the  the  uniform  uniform f^  very top  between  tray  distribution values  values between  tray.  Although  levels,  of  weir  fj  values  between  all trays,  weir  height  height  all  except 3 (34.6  1 displayed  the  range of f^ values.  More period.  variability  Weir height  the range of f  Within  in  f  trays,  a  and  gradient  positions.  In  comparison, the  positions  of  trays  positions of trays  variations  in  between  tray  values  between  trays  was  shown  during  values between  values between trays was similar for all three weir  exit  Weir  values  2 displayed the most uniform f  entrance,  larger  (31.2  larger value  the  heipht  middle  1  positions, with  and  largest f^  10.  The  1  and  height  had  2  and  f  the  smallest values found  values  largest  produced  no  influence  levels was shown, with with  f^  values  were  f  was  found  values  however,  heights.  found  in the  were  trays,  cool  between in the  the  entrance  exit  and  middle  in  the  middle  found  1 and 3 and the middle and exit positions of tray 10.  heights weir  of  the  lower  trays.  smaller on  j  values values.  than  A  gradient  smaller values associated with  Smaller  and  j  values  weir  were  height  of  3,  values  upper  trays  and  associated  with  the  entrance positions of trays than with the middle and exit positions.  A comparison with  steam processing  immersion process and larger f  indicated larger  fj  values  for the  water  values for the cooling method used with the steam  process.  Calculation  of  process  lethalities  indicated  iii  variability  of  sterilizing  conditions  within the trays. the  retort.  Larger  Within trays,  F  larger  middle and exit  values were  0  F  associated with upper trays than with  values were  0  positions. The  found  largest  F  0  in the  tray  values were  positions of the middle to upper trays, while the  entrance  exhibited  lower  positions in the  than  entrance  smallest values were  found  in the  stability  cook  period,  middle and exit positions of the bottom trays.  Retort  pressure  however,  during  the  occurred,  which  the  studies  indicated  initial minutes retort  of  corrected.  pressure the  cool  Pressure  target pressure was re-established.  iv  during  the  period,  a significant  stability  was  pressure  maintained  once  drop the  TABLE OF CONTENTS Abstract  ii  List of Tables  vii  List of Figures  x  Nomenclature  xi  Acknowledgements  xii  I.  INTRODUCTION  1  II.  LITERATURE REVIEW  4  A. HISTORICAL B A C K G R O U N D B. THERMAL STERILIZATION SYSTEMS 1. Development of the Retort 2. Conventional Thermal Processing Systems C. THERMAL PROCESSING FLEXIBLE CONTAINERS 1. Heating M e d i a 2. Media Circulation 3. Retort Pressure 4. Racking Design D. C O M M E R C I A L STERILIZERS FOR P O U C H PROCESSING  4 5 5 6 8 8 11 12 13 14  III.  EXPERIMENTAL A. RETORT SYSTEM 1. F M C 500W Laboratory Sterilizer 2. Retort Operating Procedure B. PROCESSING C O N D I T I O N S C. DATA C O L L E C T I O N 1. Temperature Distribution and Stability 2. Heat Transfer Distribution a. Heat Transfer b. Teflon Transducers c. Comparison With Steam Processing 3. Process Lethality Calculation 4. Retort Pressure  18 18 18 20 21 24 24 25 25 28 32 33 33  IV.  RESULTS A N D DISCUSSION A. RETORT TEMPERATURE 1. Temperature Distribution 2. Temperature Stability B. HEAT TRANSFER 1. Heating Rate Index (f^)  35 35 45 51 56 56  2. C o o l i n g Rate index (f ) ° c 3. Heating Lag Factor (j, )  62 68  v  4. C o o l i n g  Lag Factor (j^)  75  5. Comparison With Steam Processing C. LETHALITY DISTRIBUTION D. RETORT PRESSURE V. VI.  CONCLUSIONS  80 83 89 ;  LITERATURE CITED  93 97  vi  LIST O F TABLES  Table  1:  Estimated total water flow rates through retort car and corresponding  flow through each paired water channel  23  Table 2: Thermocouple locations in the retort  27  Table 3: Transducer locations in the retort  30  Table 4: Some thermophysical properties of teflon  31  Table 5: Sample computer output of retort temperature histories  36  Table  6:  Table  thermometer temperatures 7: Range and mean of overall temperature during the entire cook period  Comparison of  overall  mean  retort  car  temperatures  with  reference 43  uniformity (26  thermocouples)  Table 8: Analysis of variance for overall standard deviations of temperature Table  44  9: Range of temperature uniformity at each minute interval, the average uniformity during the cook period, and the range of times for the retort to stabilize  Table 10: Analysis of variance for p o o l e d mean thermocouple temperatures 11: Duncan's multiple range test comparing p o o l e d mean temperatures of different weir heights  thermocouple  Table  12: Duncan's multiple range test comparing p o o l e d mean temperatures of different water channels  thermocouple  Table  13:  and  mean  of  standard  deviations  of  temperature  for  53  Table  15:  range  test  comparing mean  temperature  stabilities  Table  of different weir heights 16: Duncan's multiple range  test  comparing mean  temperature  stabilities  of different water channels and the reference thermometer  Duncan's  multiple  range  test  comparing f^  different trays for weir height 1  54 55  Table 17: Analysis of variance for heating rate indices 18a:  50  52  Table 14: Analysis of variance for temperature stability  Table  49  each  ' thermocouple during the entire cook period  Duncan's multiple  46 47  Table  Range  44  58 values  associated  with 60  vii  Table  Table  Table  18b: Duncan's multiple range different trays for weir height  test 2  comparing  18c: Duncan's multiple range different trays for weir height  test 3  comparing  19:  test  comparing  Duncan's  multiple  range  values  associated  with 60  f^  values  associated  with 61  f^  values  associated  with  different tray positions  61  Table  20: Analysis of variance for cooling rate indices  Table  21a: Duncan's multiple range test different trays for weir heig ht 1  comparing  f  values  associated  with  Table  21b: Duncan's multiple range different trays for weir height  test 2  comparing  f  values  associated  with  21c: Duncan's multiple range different trays for weir height  test 3  comparing  22:  test  comparing  Table  Table  Duncan's  multiple  range  ...63  65 65 f  values  associated  with 66  f  values  associated  with  different tray positions  66  Table  23: Analysis of variance for heating lag factors  Table  24: Duncan's multiple different weir heights  Table  Table  Table  Table  range  test  comparing  test 1  comparing  25b: Duncan's multiple range different trays for weir height  test 2  comparing  25c: Duncan's multiple range different trays for weir height  test 3.  comparing  26:  test  comparing  multiple  values  associated  with 72  25a: Duncan's multiple range different trays for weir height  Duncan's  70  range  values  associated  with 72  values  associated  with 73  values  associated  with 74  values  associated  with  different tray positions  74  Table  27: Analysis of variance for cooling lag factors  Table  28a: Duncan's multiple range different trays for weir height  test 1  comparing  j  values  associated  with  Table  28b: Duncan's multiple range test different trays for weir height 2  comparing  j  values  associated  with  28c: Duncan's multiple range different trays for weir height  comparing  Table  test 3  76  78 78 j  values  associated  with 79  viii  Table  Table  Table  Table  Table  Table  Table  Table  Table  29: Duncan's multiple different tray positions  range  test  comparing  j  values  associated  79  30: Comparison of heating and cooling parameters calculated using steam and water immersion processes at 125°C 31: Analysis of formula method  variance  with  for  lethality  values  calculated  using  pure 81  Stumbo's 84  32: Duncan' multiple range test comparing associated with different weir heights  Stumbo's  lethality  85  33a: Duncan's multiple range test comparing Stumbo's associated with different trays for weir height 1  lethality  33b: Duncan's multiple range test comparing Stumbo's associated with different trays for weir height 2  lethality  33c: Duncan's multiple range test comparing Stumbo's associated with different trays for weir height 3  lethality  34: Duncan's multiple range test comparing associated with different tray positions  lethality  Stumbo's  values 87 values 87 values 88  35: Summary of retort pressure data during cook and cool periods  ix  values  values 88 91  LIST O F  Figure  1: Cross section retort design  of  F M C 500W  FIGURES  Laboratory Sterilizer showing the  Figure 2: Schematic drawing to show thermocouple (not to scale). Figure 3: Schematic drawing to show transducer (not to scale)  locations in the  26  locations in the  retort 29  4: Sample plot of temperatures monitored the retort during the cook period  Figure  5: Sample plot of mean and standard deviations of temperature thermocouples at each recorded time during the cook period  Figure  6: Sample plot of the mean and its standard thermocouple location over the entire cook period Example pressure  at  different  histories of an experimental run  x  19  retort  Figure  Figure 7:  basic  locations  deviation  inside  for all  at  each  39  40  41 92  NOMENCLATURE  a  Half-length of a rectangular brick-shaped transducer,  b  Half-width of a rectangular brick-shaped transducer,  c  Half-thickness of a rectangular brick-shaped transducer.  Cp  Specific heat capacity.  f c  C o o l i n g rate ° .  index. .  f^  Heating rate  index.  F  Process lethality at the centerpoint  0  j  of a package,  C o o l i n g lag factor. Heating lag factor,  k  Thermal  p  Probability level for testing statistical significances.  T.  Transducer  temperature at start of cool period.  T.^  Transducer  temperature at start of heating period.  Tp-  c  conductivity.  Pseudo-initial temperature of the transducers at start of cooling  period.  ^pih  Pseudo-initial temperature of the transducers at start of heating period.  T^  Retort temperature.  T  C o o l i n g water  a  Thermal  p  Specific gravity.  temperature.  diffusivity.  xi  ACKNOWLEDGEMENTS The  author wishes to  for his advice throughout  He William  also  D.  Department  wishes  Powrie of  of  express  the course of this research  to the  thank  Bio-Resource  technical  wishes  to  the  members  Department  Canada, for their constructive  He  his sincere appreciation to  of  Engineering  Food and  especially  assistance. Special thanks  thank  Ian  are  also  J.  his  Science,  criticism and review  Marvin A. Tung  project.  of  Dr.  Dr.  Allan  research Dr. T.  K.  committee:  Victor  Paulson  of  Lo  of  Dr. the  Agriculture  of this thesis.  Britt  for  extended  to  his  invaluable  Agnes  advice  Papke and  R.  and Alex  Speers. Financial  support  was  provided  the Natural Sciences and Engineering  in  part  by  the  Strategic  Research Council of Canada.  xii  Grants  Program  of  1. I N T R O D U C T I O N Commercial sterilization processes in hermetically sealed containers organisms, thus attaining food time.  Flexible  sterile  shelf  packages,  in order to  inactivate pathogenic  stability at room  metal  stable food  apply thermal treatments to  cans  products  and  and  temperature  glass  food  jars  are  packaged  and other spoilage  for extended  available  processors  foods  may  as  periods  containers  choose  from  a  of for  variety  of retort systems to meet their specific needs.  Conventional as  the  heating  different  will  and  with  if  processing  exceeds  greater  than  in  been the  immersion/air overpressure coefficient  compared with water  Once  the  water  retort a  with  pouch  present  (Pflug  internal  because  internal  several  processors  containers  particularly  pouches  have  transfer  is  Steam/air or  steam/air processes  heat  rigid  This  flexible  packages, however,  processing, the  it  burst.  process.  pressure  Flexible  rises during  may  cooling for  those  increase  package  media.  from  temperature  retort systems utilize saturated steam, steam/air mixtures or  et  problem  have  pressures  States  systems. The values  reported  within  by  too  air overpressure they  the  U.S. by  Pflug  the flexible  package  great early  to  during  in Canada,  shown  concern  product  the  ability  a  As  problems  the  systems  achieved  have  processing  1963).  during  commercially accepted  United  al.,  pressure  pressure  heat  a  degree, stage  are  for  the  of  the  recommended  maintain a  retort  processing.  While  Europe  and  Japan,  preference  for  water  seems to be the lower (1964)  water  steam/air  surface  mixtures  as  immersion heating.  a retort system has been chosen, the sterilizing efficacy of each  must be assessed, under the specific operating conditions to be used, before be used commercially. Uniformity  retort it can  and stability of heating and cooling within a retort  1  ?  is  critical  to  Currently,  its  ability  retorts  and  to  their  provide  safe,  operating  but  not  procedures  excessive  are  usually  thermal  evaluated  processes.  by  collecting  temperature  distribution information from thermocouples placed at various  positions in  the  retort.  Heat  determining  the  ability  the  process.  Yamano,  of  transfer  the  heating  suggested  ensure  heat transfer  proper  information  medium  Several researchers  1976)  necessarily  distribution  to  (Pflug,  that  distribution. At  uniformly  of  present,  be  release  valuable  or  in  absorb  enthalpy  1964; Ramaswamy, 1983; Tung  temperature  distribution  would  uniformity  the  there  heating is no  within  a  medium to  et  al., 1984a;  retort provide  standard methodology  during  does a to  uniform measure  heat transfer distribution and stability in thermal processing systems, however, researchers  (Peterson  and  Adams,  used food-simulating transducers  1983; Ramaswamy,  to  calculate heating  1983; Weintraub,  rate indices which  not  several  1986)  have  indicate heat  transfer conditions.  Two heating  thermal  rate  process  index  (f^)  penetration  curve.  portion  the  heat  while  the  of  difference, heating steam,  rate.  The  With  parameters  and  the  lag  heating rate penetration lag factor  sufficient  the  surface  heat  conductivity  of the  product;  factor  index curve  is the to  are  of  for  coefficient  one  the  the  large  below  changes  in f^  a and  critical  level,  the  product  no  values are observed which  log  to  describe  for  the  longer identify  cycle  of  (1923),  to  heat line  temperature a  processing  compared  a  the  straight  establishing  when  product's  geometric form limit the heat transfer to its centerpoint. reduced  Ball  used  lag in  example  is very only  by  time required  change  transfer,  and therefore  developed  (j^),  is a measure  heat  transfer  originally  the  uniform in  pure  thermal  thermal properties  and  However, if heat transfer is is  the  limiting  factor  changes in heat transfer.  and  3 The  f^  centerpoint A  retort  and  parameters  lethalities (F ) 0  providing  overprocessing  a  experienced  large  some  of  may  be  used  by the product  variability  the  also  in  product  lethal  load,  to  calculate  in various  rate  parts of the  distribution  resulting  in  differences  may  decreases  be in  in  retort. severely  nutritional,  sensor)' and functional properties.  A weir for flexible medium, overall weir.  type  pressurized  water  retort is one water processing system available  pouches. This system employs water  with  water Other  coefficients,  solid  aluminum trays  flow  proceeds  than  recent  no  other  by  work  literature  for  pouch  gravitational by has  restraint  flow  McCinnis been  under  and  (1986)  found  pressure  as the  and water  flow  is regulated  by  studying  discussing  heat  control. an  surface the  transfer  adjustable  heat  thermal  The  transfer  processing  capabilities of this particular system.  This  investigation  the following 1.  To  studied  a pilot-scale weir type  pressurized  water  retort  with  objectives:  study  the effects of the process variables, temperature  and weir height,  on  the temperature distribution of the retort during heating and cooling. 2.  To  study  the  effects  of  the  above  process  variables  on  the  heat  transfer  distribution of the retort during heating and cooling. 3.  4.  To  study  the  effects  of  the  above  lethality distribution of the  retort.  To  responses  compare  environments  the  thermal  at the same temperature.  of  process  this  variables  water  on  system  the  with  centerpoint  pure  steam  II. LITERATURE  A.  HISTORICAL  The of  heat  BACKGROUND  discovery  processing  of the principle of heat sterilizaton and the initial practices  the early 19th century. at this  (Appert, subject  the  1810),  length the  is  credited  Although  early stage, Appert  in terms of  REVIEW  of  first  of  Nicolas  he did not  learned the  to  the  four  was  and  Benjamin  (1948)  cited  Ball (1938),  De  Kruif (1926) and Tanner  of  history  the  canning  of  1937; Deming,  process.  1902; May,  as dealing with the development in certain areas of machinery.  Coldblith  and technology  The  the  United  (1971,  A  1937; Stare,  major  of  reviews  industry  the  non-acid  foods  Appert's  book  on  the  Can  Company  good  coverage  (Anonymous,  cited  or the  on  in  process  literature  American  1949) are  States or the w o r l d ,  work  1971).  by  of the canned foods  1972a) concentrated  1938).  (1932) as providing  number  this  science of the  (Ball,  only  literature  (1947),  Bitting,  the  did  acid and  of thermal processing for over 70 years (Coldblith,  Jackson  the  between  time required  editions,  who  understand the  distinction  processing  Appert,  development  by  1960;  Goldblith  (1971)  as a whole, canning  development  development  of  canning  of the science  of canning in relation to the social character of the times.  next  major  stage  in  the  development  of  thermal  processing  was  the  scientific discoveries of  Pasteur in 1860. Pasteur was able to prove and establish the  basic  Appert's  applied  science to  publication,  behind  the  study  even though  of  processes  thermal  of  processing  food until  millions of cases of f o o d  during this time (Coldblith,  1971).  4  preservation. 85  years  Science after  was  not  Appert's  first  had been packed and consumed  5 The of  contributions  major  the  importance.  causative  than the  of  Underwood  Among  agents  of  boiling point  their  canned  Prescott  spoilage  and  is needed to  importance of heat penetration  in the  accomplishments, they  food  of water  and  19th century  showed  heating  achieve  in canned foods  late  to  that  20th  century  Bigelow and co-workers,  has  seen  process  THERMAL  STERILIZATION  1. D e v e l o p m e n t of the Goldblith retort first  and to  "digester"  the  (1972b) key  use  the  as  "an  quite  apparatus  and the importance of cooling; and  dangerous  pressure, more  did  gave  pot  a detailed  involved.  common  grow  for  thermobacteriology  Ball and Stumbo,  which  quickly  in  cooking.  had  processing  a  cover  the in  foods  that  and  by  improvements  food  (1938)  could  to  of  the  be  the  described  be  to  using a modified version  of  the  clamped  Papin's down  Consequently, at  development  1681, is thought  pressure.  in regulating  popularity.  canned  under  early  Ball  circa 1831, began  difficulty in  of  Papin,  canned  the  account  Denys  principle  cooking  because of  not  by  in  1972a).  SYSTEMS  pressure  for  the  1972a).  withstand moderate pressure". Appert, Papin's  greater  Retort  people  iron  are  sterilization; demonstrated  advancements  technology  in processing equipment (Goldblith,  B.  major  bacteria  temperatures  were the first to recommend the use of incubation tests (Goldblith,  The  were  This  fire  and  salt  temperatures  early  equipment,  resulting  water above  steam  baths the  were boiling  temperature of water.  improvements  in  safety  features  and  operating  methods  continued  and  in  6 1852  Raymond Chevallier-Appert  gauge  (Ball,  1938).  The  patented  retort  was  (France) a retort equipped with  able  to  reach  140°C  and  the first designed specifically for food conservation (Goldblith,  The States  by  forerunner A.K.  of the vertical retorts  Shriver  boiler, was fitted with large  iron  major  crates  research  1874.  His  for  the  the  open  used  gauge top  the  design  (Ball,  of  a steam  of  supply  newer  and  As  in the  from  a  United separate  and handled cans in  1938; Goldblith, retorts.  as  1972b).  and thermometer,  commercial use  progressed,  documented  used today was patented  retort  a safety valve,  through  breakthrough  transfer  in  was  a pressure  1971).  This  microbiological  improved  thermal  was  and  a  heat  processing  equipment followed.  2. C o n v e n t i o n a l  Thermal  Conventional  Processing  and  aseptic  commercial  sterilization of  conduction  heated and viscous  meet the specific needs continuous, the  heat  employ transfer  foods,  of  Systems thermal  with  processing  conventional  Direct  flame  and  available  better  may  be  for  suited  for  systems  to  batch-type  or  of conventional  use steam,  microwave  are  being  For example, systems  still or agitation techniques, or medium.  systems  foods. There is a variety  processors.  systems  steam/air or water as  energy  thermal  about  1950,  processing  systems are also available.  Still continuous horizontal saturated  retorts  were  agitating or  vertical  used  systems and  almost  became  batch  exclusively more  operated.  steam as the heating medium,  with steam/air or water when  overpressure  until  common. These  however,  The  systems  still  retorts  generally  after  which  are  either  operate  they may be modified to  is required.  with  operate  7 Ball  and  described systems.  and Bigelow  penetration  Olson  (1957),  discussed  a  foods  agitating  by Lopez (1981). O n e be applied when  A  direct  documented principles  of  sterilization.  HTST  containers to  let  the  waveguide (1974) using  use is  and/or  that agitation of the  water  et  al.  system (1961).  processing (1975)  and  Lopez  agitating  container  (1981)  steam  retort  accelerated  heat  corn.  processing  systems  are  also  covered  in using water systems is that air overpressure  sterilization  in  was  connection  discussed  design  bursting.  developed  Leonard  et  in  al.  with  parameters  may  France  (1975)  in  1957  and  on  the  reported  the  mechanisms  and  operating  of  flame  characteristics  sterilizer.  of  microwave  a relatively products  (Rosenberg  documented microwave  (1975)  processing flexible containers susceptible to  Casimir  The  continuous  non-agitating  advantage  Beauvais  of a flame spin  of  Fennema  such as cream-style  and  flame  by  (1971),  number  et al. (1920) found  in viscous  Several  Brody  pass  systems  sterilization by microwave  in  area. The  through  and  energy.  Harper,' 1967; Landy,  new  energy  Bogl, for  They  a  thermal  basic principle  microwave  1987).  Kenyon  continuous  also  cited  sterilization large  et al., 1966).  in  a conveyor  belt  et  al.  (1971)  Ayoub  processing  patents  as  sealed  scale sterilization  on  energy in either batch or continuous  1965; Long  food  field  thermal  several  of  of  and of  food  discussing  or  is  in et  a al.  pouches  methods  systems (Jeppson  of and  8 C. THERMAL  PROCESSING  Flexible for  packages,  commercially  commercial  of  container,  however,  associated  with  of  the  metal cans  flexible  Areas  of  must  packages  containers.  and  glass jars  foods.  product  retort pouches  pouch.  CONTAINERS  shelf-stable  the  rigid  of  rigid  sterile  sterility  development  FLEXIBLE  The  be  concern  same  satisfied  present  available  basic  as  of  the  processing  (1976,  1978)  containers  requirements  regardless  some  Mermelstein  and  are  for  type  of  problems  discussed  not  the  early  Lampi (1977)  gave  an excellent  in-depth  review  include:  type  of  medium,  media  the  heating  circulation, retort pressure, and racking design.  1. H e a t i n g  Media  Steam, media  available for  superior  in  containers high  steam/air  terms  (Pflug,  internal  latter stages  to  pouch  gases  within  water  processing cooling.  with has  come-up  process  time,  water retort  the  pouches.  temperature  Borrero,  can  are  exceed  1967), the  potential The  conventional ' heating  use  of  distribution  and  steam,  although  heating  rate  is least feasible, however,  retort  pressure,  especially  in the transition from the heating to  the  of  because  during  cooling  the  cycle.  be the ideal medium during the early stages of heating if it was all non-condensible  al., 1963). the  processing  pressures  remove  et  and  1964; Pflug and  of the  (Pflug  or  thermal of  Pure steam would possible  mixtures  However,  pouch  can  superimposed been  the  be  gases  pressure  from  differentials  counteracted air  attempted  pressure. for  inside the  heating  by  caused  processing  Some  high  pouches  pouch by  with  before  non-condensible  steam/air  temperature followed  sealing  by  pure  mixtures steam  overpressure  9 It was water with  and  concluded  steam/air  water  is  Japan, Europe were the  1960's  both  in  be  the  views  as  to  can  to  use.  be  1964; Pflug and  Borrero,  used  pouches.  effectively States,  for  while  retort  steam/air  1981; Milleville, 1980).  whether  steam/air  Although  made  (Pflug,  United  and Canada (Lopez,  system  conclusions  could  preferred  conflicting better  in the  or  comparisons  since  each  is  Beverly  1967),  Processing  more  popular  (1980) stated  with  air overpressure  have  been  made,  has  certain  no  in  there  water  medium  that  was  definitive  advantages  and  disadvantages.  Processing standard  pouches  procedure Yamano  and  and  Pflug  (1964)  steam/air,  (1976)  reported  reported  water,  water  f^  and  compare  longer  come-up  times,  but  smaller  values  were  lowest  for  steam/air.  Lopez  (1981)  75%  theoretical  calculations found  steam/air mixtures  to  by be  the  well  reason for the  to  7 5 % steam/air were air in  may be one  to  models  water  of  on  identical  bentonite  based  percentage  essentially  used  coefficients and  is  for glass containers, which  preference. water,  in  heating f^  1 0 0 % steam, listed  596  values  for  followed  overall  increases, the  and  overall  American  in steam/air  for 2  transfer  90%  transfer  497 W / m K . heat  water.  by  heat  Pflug (1964). Coefficients 965,  known  steam, As  the  coefficient  decreases significantly (Tung et al., 1984b).  Tsutsumi have  high  and  even  reported  (1979b)  stated  that  air contents, water with heat that  amounts of  Pflug  penetration,  processing  in water  air are present  et  al.  thus  (1963)  in  when high  heating  below  overpressures  avoiding may be  low more  120°C  could  steam/air effective  be  used  ratios. than  or  when to  pouches  attain rapid  Weintraub  steam/air when  (1986) large  pouches.  listed  several  disadvantages  of  processing  pouches  in  10 water:  long  process  water;  water  many  horizontal  rapid  steam  times  hardness  result  may  retorts  injection  soil  are  to  the  resulting mechanical shock. in a separate (Lampi,  reservoir,  not  from  longer  pouches  and  designed  water  thus  negating  build  for  may  Process water  come-up  in  can be  the  cool-down  scale  on  separation  processing,  pouch  rapid c o m e - u p  and  damage  pre-heated  to  times  for  plates;  improper  because  process  of  or the  temperatures  rate advantage  of steam/air  1977).  Steam/air processing water  processing.  reported  using  The  it to  seems to  use  of  retort  lack most of the  steam/air  glass  mixtures  containers.  steam and air and steam/air distribution  Processing Tsutsumi  retort  (1979a).  pouches  The  high  with  pure  that  inside  due  since to  steam  within  the  changes successful pouches.  quick greatly  retort.  disadvantages monitor  the  of  cook in  foods  no  enhances Air  these  times  pure  heating,  the  air  the  high  is  temperature  ensure  after  pressure  the  prolonged  processing  at  in  time  as  of  Parcell  proper  of  is  Japan  reported  high  pouch  processes  and  the  storage.  Roop  115.6°C  of  and  to  than  the  heating,  thus  the  and  bentonite  distribution cycle.  necessity  avoid Nelson  (1979b)  higher  cooling  the  by  temperature  temperature  include  lethality  is  during  for  of  requirements.  was  ultra  necessary  efficiency  (1930)  retort are critical during  and  the  with  mixing  135°C and 150°C. Tsutsumi  necessary  proper  new,  in the  steam  outside  heating  overpressure  to  steam  on  not  associated  which fulfills these  temperature-short  pressure  disadvantages  maintenance  to all points  systems he discussed, employed temperatures of stated  is  The  processing. Milleville (1980) described a procedure  pure  up  water  result  and  to  The closely  possible  physical  (1981)  reported  dispersions  in  confined  11 2. M e d i a  Circulation  The heat  objective  transfer  of  media  distribution  circulation  throughout  the  is  to  retort  load.  manipulated in terms of flow pattern and flow  Pflug  and  relative  rate  heating  containers.  with Some type,  heating  100% steam, factors  of  They  containers  found  but  affecting  (1967) noted  was the  that  even  heating  the more  uniform  The  temperature  media circulation  and  can  be  flow pattern in a retort affects  the  velocity.  that the and  a  the  location  flow  pattern  critical  medium flow  of  the  was  for  important  water  pattern  fastest  or  and  slowest  when  heating  steam/air  and velocity  processes.  are the  retort  racking system design, container loading patterns and container size.  The containers. reduced  velocity For  during  containers the  of  Borrero  attain  of  example, contact  may result  containers  the  heating when  with  water  cold  (National  Food  heating  model.  is  reproducible  rate  of  medium,  its  velocity  of  and subsequently  Association,  determined  the  Insufficient  flow rate on  important not only-i for the maintenance of consistent,  heating  gradient  Processors  They  the  containers.  in a temperature  (1983) studied the effect of water conduction  medium can affect  1985).  heat transfer  to  temperature  is  water  slower  Peterson  past heating  and  the of  Adams  heat penetration parameters using a that  the  water  retort temperature, but  circulation  rate  is  also for obtaining  heat penetration parameters and process times. The  f^  values  decreased and heat transfer coefficients increased with increasing flow rates.  When  steam/air is the  heating  medium, the  condensation of steam from the mixture when Insufficient  medium velocity  results  in poor  steam proportion  is reduced  releasing heat to containers  of  by  food.  movement and mixing of the steam and  12 air,  thus  producing  consequently studied  differences  the  containers transfer  composition  effect and  of  in  coefficients  for  that  and  of  and  fj  turbulent  different  heat  steam/air values  (1967)  mixtures  have  made  recognized  conditions  the  the  retort.  essential  to  heating  found  to  that  rate  velocities.  Heat  with  circulation  Adequate  systems  the  et al., 1984b).  may  of  circulation  flow system or a powerful  Water  (1961) glass  induced  effect.  and  of  increase  1963; Tung  for  retort  Blaisdell  increasing  need  by a positive  the  and  the  with  to  of  Pflug  on  been  recommendations  within  parts  transfer.  decreased  mixtures  of steam/air media can be achieved create  of  in  and Peterson, 1982; Blaisdell,  Borrero  steam/air and water  rate  steam/air  medium flow rate (Adams  Pflug  the  velocities  concluded  variations  use  fan to  circulation  pumps or air agitation.  3. Retort  Pressure  A  retort  containers of can  during  heating  and  create  1960), which exceed  the  pouch  could  surpass outer 0.1  kg/cm  overpressure  2  during  will  result  retort  the  cooling  high in  period.  internal pouch  pressure.  Toyo  withstand  outer  pressures,  pouch  (1.4  maintain  thermal processing, with the  extremely  Whitaker overpressure  is  or  during  seal damage  Seikan  pressure  free  of  integrity  being  product  these  if these  Kaisha Ltd.  by  seal  critical periods  Expansion  pressures  the  internal  but  breakage might occur even  and  periods  (1973b)  expansion,  the  of  flexible  latter  stages  residual (Davis  gases et  pressures  stated when  that  at pressure  greatly  their  inner  al.,  RP-F  pressures  differences  of  psi).  (1971)  during  gave  a detailed  processing  under  description  specific  and  conditions.  example Various  as  to  the  overpressure  use  of  levels  13 have  been  suggested  recommended stated  that  by  different  sources.  Pflug et  34.47-68.95 kPa (5-10 psi) overpressure. in  general,  an  overpressure  of  ± 6 . 8 9 kPa ( ± 1  recommended  of  an  in order  overpressure to  provide  et al. (1972) suggested prevent  Design  The  racking  practices  (Wilson,  confinement,  products  of  1980).  Good  are generally  when  processing  Badenhop, not  design  1980).  properly  Pouch controlled  thickness  through  Badenhop,  pouches  can  racking  Badenhop  (1980)  is  specified  and  (7.1-12.8  2  psi)  containing  when  85 to  processing  7 5 % steam.  to  protect  at  Davis  seals  and  If  processed  a vertical by  confinement 1980).  reach  this known thickness.  The  the  during  the  to  good  provide  thermal  proper  rack.  is used,  processing  pouch  position, except  pouches  Racking  during the  and  will  (Berry,  support,  will bulge  designs  value  of  the  should  process,  for a  few  1979; Milleville  heating and cooling  racking design  spacing  processing  horizontal  plane is advantageous  sterilization  by the rack  designs  in the  design  and overlapping  affects  is critical  orientation.  in a vertical  supported  containers from moving  and  psi)  89.63 kPa (13 psi)  a retort system  media circulation and  Pouches  if  kg/cm  of  (10  (1971)  psi). Toyo Seikan Kaisha Ltd. (1973a)  a steam/air mixture  an overpressure  kPa  Coldfarb  rupturing.  4. Racking  and  0.5-0.9  and  Milleville and  68.95  should be controlled to within  120°C  al. (1963)  at the also  base  prevent  cycles.  but  can  be  (Beverly et al., 1980; Milleville  determine  a sterilization  the process  maximum can  be  thickness based  on  14 It ensure  is  important  uniform channels  circulate  through.  on  design  the  heating  on  this  racking  temperature  provide  The  that  both  can  heat  sides  also  media flow.  orientation.  and  et  allow  transfer  of  orient  Davis  Tung  designs  the  an  throughout  containers  pouches al. (1972)  al.  (1984b)  found  found  load.  the  or  circulation Proper  heating  horizontally  process heat  medium  the  for  vertically  et  even  times  transfer  in  to  designs  medium  to  relation  to  varied  depending  coefficients  to  be  affected by the orientation of a flat brick-shaped test model in steam/air studies.  D.  COMMERCIAL  A  number  processing from water or  of  or  of  retort  American,  traditional the  their  results were  batch  steam/air or water horizontal  maintained  for  a  batch  Japanese  processors This  both  led  encouraging  retorts  retort  temperature  PROCESSING  and  continuous  and  uniformity  and  These  Nelson  to suggest  the  diagrammed of  modified  cans without  significant  example of was  systems  exist  retorts  systems  for are  thermal available  operate  must make large capital investments  enough  require  or  manufacturers.  Roop  pouches  systems. An  steam/air  POUCH  Specifically designed  and  equipment.  Traditional  a  pouches.  European  equipment  FOR  conventional  steam/air; however,  modify  found  STERILIZERS  ±0.56  (1981) retort  further  basic piping  C°  F°)  investigate  buy using  modifications.  They  them  to  and instrumentation  for  Milleville (+ 1  to  study.  modifications  by  to  using  to  convert  (1980). when  This  operated  system at a (  steam/air mix of 75/25 at 122.2°C (252°F).  The  Lagarde  Company  of  France produces  a steam/air system used by  Magic  15 Pantry  Foods,  Inc.  at  Hamilton,  ON  Milleville (1981) diagrammed the circulate the  steam/air. Magic  pouch/retort  capacity.  heat rotary  distribution  for  Lagarde  Automatic  Seikan  Kaisha  Overpressure  their  RP-F retort  than  and  had  a  Ltd.  at  temperature  temperature.  The  three  operated  120°C  retort  fan and  efficiency  hot-water  other  Anacortes, W A  Andres horizontal water  at  of  Japan  steam/air  within  had  a  described  retort  (248°F) with  was  1.5  ±2  capacity  down  water per  retort minute  used (400  and had a temperature  capacity varied from 2016 to  between  tiers  of  of  (±3.6  in  the  Foods  pouches  a weir  Milleville, 1981).  FMC  to  a 2000 uniform 1982).  A  United  States.  operated  at  depending  claimed the  Sterilizer" system system  their to  psig)  F°)  at  "Fully process  pressure; sterilization  Lampi  (1977)  processing. Specialty Seafoods  of  1981).  (1973) briefly described a  an  distribution of within 2688,  detail  1944 pouches.  (1973) and Gee  gpm),  "Convenience using  (Anon.,  (21.3  2  available from  bar over the pouches in the racks prevented  FMC  ducts  more  documented  kg/cm  C°  in  Delta, BC (Milleville,  and Duxbury (1972), A n o n .  1514 litres  The  1981;  systems were  and Brett & Associates of  batch-type  kPa (35 psig) pouch  steam/air retort  and  retorts  gave further details of a modified version for high temperature Two  side  1981).  product agitation.  (1973a) This  1981; Morris,  at 121.1 °C (250°F) for  energy  conventional  distribution  car  uses a turbo  greater  provide  Retort".  pouches  Foods  claimed  steam/air  1982; Milleville,  system which  Pantry  retort is also available to  Toyo  (Anon.,  This  retort  circulated  air pressure  of 241.3  ±1.11  on the  C° ( ± 2  product,  F°).  The  and a clamp  floating.  was (Anon.,  designed  to  1979b;  Anon.,  minimized c o m e - u p  circulate  water  1982; Lopez,  and  cool-down  16 times  and achieved efficient uniform  containers  of  plates  maintain a constant  to  pre-heat  than  ±0.56  Stock  modified  improve  the  handle  rate as  rotation  the  of  "Rotomat"  to  controversy  of  A  to  (1975)  load  models  described  process pouches  was  was  temperature reported  Pinto  (1978)  system  to  Goldfarb  retort  F°).  a  pouches.  and  not  reduce  used  1500 and  Lampi  transport  within (1977)  rotated  retort  cook  time,  withstand 1981).  could  however,  a  version  1981)  batch  pouches  with  through  was  stresses;  improved  was  also  has to  some  therefore,  tray feature  marketed  entree-size  pouches/load,  retort  Continental  by  for  the  (±0.5  first  this  Hydrolock  chambers  (1971) described a Robins Hydrolock  three  and  Anon.  which  could  pouches. The by  F°) (Lampi,  used  in  1200/batch.  steam/air circulated  C°  have of  be there  rotational An  to  pouch capacities.  load  2000  +0.28 to  a reservoir  The  (Anon.,  process  two  1982).  horizontal  to  distribution  described  used  may also be suitable for processing  designed  by  system  between  retort,  in water or steam/air at a capacity of  retorts  confined  circulating water  (Milleville,  retort  unique  were  between  a horizontal  could  in 1982 (Anon.,  1000,  Pouches  available in four different  1981),  pouches  water  of  Continuous "Hydrolock"  (Lopez,  whether  rectangular  production  was  (±1  maximum thickness. The  heating  pouches was introduced  a  C°  process water and models were  The been  less  heat transfer for temperature variations  system  against the  a fan to  1977).  system.  of  achieve  Lawler  Lopez  which flow  Rexham  (1967)  (1981)  used  and  a  carrier  process  water.  which was very similar to the Rexham  steam/air model.  A  modified  Stork  "Storklave"  system  (Anon.,  1979a;  Lopez,  1981)  was  17 reported  to  continuous pallet-type  be  able  vertical  retort  with  hydrostatic  The  but  was  featured  basically  system, specifically for retort pouches and apparently shipped  to  the system in a continuous  a  a  by  through  systems,  system  movement  travelled  to  pouches.  of  Japan in 1975 (Gerrish, that  similar  retort  system.  A hydrostatic  reported  handle  set  carriers which  a conveying  to  FMC  air overpressure  was  1975), was rated at 450 pouches/minute. developing  a hydrostatic  system  using  and Lampi (1977) mentioned other systems.  Gerrish hot-water  (1975) also processing  III.  A.  RETORT  SYSTEM  1. F M C 500W  The  Laboratory  retort  Sterilizer  (FMC  Science  pilot  Sterilizer  investigated  Corporation, plant,  pilot-scale version system employs  in this Santa  University  of a weir  type  which heat  inside  study  Clara,  of  a retort  British  pressurized  exchanger  as heat  of  water  Model  at the The  500W  FMC  500W  from  of  through  the water  to  the trays  a of  over-riding  air  control, are  a flow  Basically, the system  is  type  restraint and water flow travels  Food  retort  processing system. This  medium tray.  Laboratory  Department  as the heating medium with  each  is transferred  FMC  located  used for pouch  part  an  Columbia.  car and the water  makes up the lower  was  CA)  steam-injected hot water  pressure. Solid aluminum trays, stacked  EXPERIMENTAL  channel  is a plate-type by  convection  and then to the pouches by conduction.  In this F M C 500W system, water filling the retort end,  car. Hot water  is distributed  by  enters  a perforated  is initially pre-heated in a reservoir the top of the car where  plate  and flows  horizontally  prior to  it travels to one through  the  flow  channels of the stacked trays to the opposite e n d . Water exiting the channels turns 90°  and moves  the  bottom  of  upwards the retort  past a steam injection Figure  to a weir  over which  shell where  portal  and back  it flows to  it exits  the car. The water  through  an outlet  the retort  falls to  and is circulated  car by a recirculation  pump.  1 is a cross sectional diagram showing the basic design of the retort.  Cooling  is  achieved  by  simultaneously  18  adding  cold  water  from  the  main  Water Inlet  Retort Shell  - 4  —> 1  <-  -~>  f ~  ——  * -• ....  1  <~  1  -->  ->  .  1 - >  < -  —)  \  - 4  \  Water Distribution Plate  1 1  -y s.  Reference  Water Channel  Water Outlet  Figure 1  Cross section of  1 1  <^  Thermometer  4 - - >  4 -—>  <~ 1  1  <-  <— —> 1  ~>  F M C 500W Laboratory Sterilizer showing basic design.  Retort Water Level  20 water  supply  portion water,  of  and draining the  the  total flow that  a portion  to the reservoir  equivalent  of  the  is not  while  circulating  that  being drained. As a means of  conserving  hot  displaced and  retort  the  310 kPa (45 psig). The  same specifications. The  324 mm. Eleven trays  11 trays  19 mm. There  are  waters  may  although  the  is 176 (16/tray)  provided  by  1524 mm long, with reservoir  dimensions of  are provided,  11 pairs of  system were  hot water  inside  to the transducer thickness, with capacity of  mixed  retort,  be  shunted  using the recirculation pump during the early stages of  is 610 mm in diameter and  pressure of  from the  partially  Some specifications for this retort The  flow  only  the  cooling.  the  manufacturer.  a maximum operating  located above retort  the  car are  10 were  used  retort  water  with  channels when  the using  has  1048 x 402 x  in this study  dimensions 1041 x 397 x 19 m m . The for pouches  back  due  pouch  dimensions 120 x 184 x 10 trays, with  individual  cross-section dimensions 177.8 x 6.35 mm (7 x 0.25 in).  2. Retort O p e r a t i n g P r o c e d u r e In followed. cooling  general, the  Each experimental period. The  (53 psig). The 1.  consisted of operated with  is a brief  provided  by  the  manufacturer  was  a 50 minute heating and a 25 minute a steam supply  outline of the  pressure  of  365.4 kPa  procedure:  and pre-heat  to  10 C ° above  the  target  temperature to reduce the come-up time.  Pressurize  Open  run  procedure  tank 2/3 full with water  the  reservoir  water to the retort 3.  operation  retort was  following  Fill reservoir retort  2.  retort  tank  to  206.8  kPa (30  psig)  to  aid  the  transfer  of  at steam-on.  and close the appropriate valves and set the controls  prior to steam-on.  21 The  process  water  and  tempernture  for the  target temperature  115°C.  The  process  of  overshoot  125°C  pressure  and  controller  controllers  242°F for the was  set  at  to  retort.  were  set  at  260°F  target temperature  25  psig  to  of  maintain  a  retort pressure of 172.4 kPa . 4.  At steam-on, transfer water from reservoir  5.  W h e n water transfer is complete, close retort vent, open retort air supply,  and  open steam bypass valve. 6.  When  retort  temperature  mercury  thermometer  (approximately  9-10  reaches  minutes  within  after  2  C°  steam-on),  of  close  the  target  steam  bypass  valve. 7.  Prepare reservoir for cool cycle by  8.  At  9.  cool  start,  close  releasing air pressure.  main steam valve,  open  high  tranfer some hot process water to reservoir  tank.  At  end  flow  of  cold  hot  water  water  valve  transfer, 2.5  flow  close  high  flow  cold  and  stop  hot  water  turns  cold  water  water  valve,  transfer.  valve  and  open  low  on  level  Turn  controller and adjust drain valve to maintain constant retort water level. 10.  At end of cool cycle, drain retort water and release air pressure.  B. PROCESSING  Retort combinations  CONDITIONS  operating of  conditions  conditions  which  were might  varied be  when  utilized  feasible  in the  to  represent  normal operation of  the the  retort system.  During steam  pressure  experimentation, at  275.79  kPa  U.B.C. (40  Physical psig).  Plant  Practice  operated runs  the  indicated  main this  campus condition  22 provided  insufficient  Physical  Plant  the  Ideally,  a high  temperatures  experimentation.  extremes  heat  steam  a  fully  loaded  pressure  pressure  to  steam  retort  365.42  supply  of  car.  kPa  Upon  (53  413.69  request,  psig)  kPa (60  during psig)  or  be more desirable for retort operation.  Retort during  to  increased  experimentation. greater would  enthalpy  at which  uncontrollable  of  115°C  These  the  temperatures  retort  and therefore  (239°F)  might  be  and  were  125°C  chosen  operated.  to  Cooling  ranged from approximately  (257°F)  were  represent  water  targeted  temperature  temperatures  were  8 to 15°C.  Weir heights of 29.2 cm (11.5 in), 31.1 cm (12.0 in) and 34.6 cm (13.6 in), hereafter  referred  Two  weir  two  lowest  weir  plate.  plate.  to  plates  were  settings The  These  as weir  available,  represent  highest  weir  height one  the  setting  heights  1, 2 and adjustable  and  set  the  during  other  chosen  the to  only  height  represent  of  the  experimentation.  non-adjustable.  minimum and maximum heights represents  were  3, were  of the the  The  adjustable  non-adjustable  extremes  in  available  settings.  Peterson and Adams (1983) showed the  heat transfer coefficient and  water  flow  re-circulation the  rate  during  pump.  The  overall water flow  during water  cooling  was  heating flow  inlet valve. The  consequently was  capacity  rate could not  controlled overall  by  the  governed of  the  process by  pump  combined  lethalities. In  the  be varied during  cooling flow  cold water inlet valve, however,  that variability in water flow rate affected  flow was  capacity  not  of  the  adjustable,  heating. The  re-circulation  rate could  this system,  water  pump  be varied by  and  the  water  therefore flow  rate  the  cold  manipulating the  it was kept constant during experimentation.  23 TABLE 1 Estimated total water flow rates through retort car and corresponding each paired water channel.  Source  Total Flow Rate (liters/minute)  Recirculation  8.8  Low flow valve  150  13.6  High flow  290  26.4  247  22.5  Flow  +  Low flow  rate  estimations of  valve  meters  the  and  during  a specific length  water  were  measuring the  the  retort  channels  pump,  the  water  inlet  total  heating  volume  of  water  in  uniform  cold  (fully  water  open)  and cooling  flow  inlet  flow  valve  the  rates  flow  retort  system,  rates were  which  circulation  and  this  1 shows  car and corresponding  flow  valve  available  of time. Table  (assuming  low  not  heating and cooling water  valves  through  valve  through  Flow Rate/Channel (liters/minute)  97  Pump  pump  flow  collected  therefore  calculated by  in an  empty  crude opening  retort  car  the estimated total water flow rate rate through  patterns) (open  combined  used were  each  supplied  by  2.5 turns), pump  and  estimated to  of  the  the  the  be  paired  re-circulation  high  low  11  flow  flow  cold  valve.  The  97 and  247 liters  per minute.  A consistent  constant head  an overpressure.  retort  pressure  pressure for  the  of  172.37  re-circulation  fully  pump  psig) to  act  was  set  to  against and  maintain a to  provide  Weintraub (1986) found no significant difference (p>0.05) in heating  rate indices of unpackaged teflon transducers  A  kPa (25  loaded  retort  car was  resulting from variable retort  used during  the  experimental  runs  pressures.  to  simulate  24 the  worst  conditions  load consisted Bros., for  Ltd.,  pressure  hundred  NB)  could  fluctuations  brackets  trays holding  of  were  expected  the  pairs of  Canadian  purchased  locally.  withstand  bursting;  operate  Sardines Cans  repeated  sardines would to  prevent  sardine  of  thermal  two  cans  be  the  cans were  of  loaded  in  The  soya oil  (or  side  (Connors chosen  cans by  could  side  had  a filled pouch);  and  many  cans  ballast  were  processing;  placed  similar to  pairs  under.  sardines  foods.  from  as ballast,  and 16 pairs on the 4 trays holding  Rectangular  separating.  14 pairs on  no  One the 6  transducers.  COLLECTION  1. T e m p e r a t u r e D i s t r i b u t i o n  The  temperature  under  extremes  and  Stability  distribution  different  operating  in temperature  heating and cooling  and  stability  conditions. to which  Engineering,  Inc.,  locations.  were  logged  using  a  at  The  (Kaye one  Columbia  the  fully  Thermocouple  loaded  retort  locations were  might  be exposed  car  chosen during  was to the  cycles.  Stamford,  Scanner/Processor  of  containers  Twenty-eight teflon-insulated 24 A W G  selected  to  Brunswick  without  used  transducers  C. DATA  represent  be  the same dimensions as the teflon transducers  forty-eight  studied  would  cans of  cans  thermal properties  aluminum  retort  Harbour,  reasons:  approximately the  100 g  Black's  several  withstand  of  the  CT)  with  minute  300D  fused  thermocouples Instruments  Digital  sensing  were  Inc.,  intervals.  copper/constantan  The  Cartridge  data  junctions  connected  Bedford,  MA) were  Recorder  thermocouples were  to  and  a the  recorded  (Columbia  (Omega  placed Kaye  in  Ramp  temperature  the II data  on  magnetic  tape  Data  Products  Inc.,  25 Columbia, were  MD)  for  subsequent  pre-calibrated  Saddle  Brook,  NJ)  corrections were  Figure  in  a  analysis  Haake  against  N3-B  an  2 shows the thermocouple  temperature  exited  control  thermocouple were  and  with  the  sensor.  Figure  regions  water,  adjacent indicates  2.  In  in  hollow  in order  pieces  of  to firmly secure  Instruments  thermometer  rubber  to  the  the  retort  specific  general, o d d  and even  of the water channels. Thermocouples  sandwiched  (Haake  and  Inc.,  appropriate  also located at positions adjacent to  2  located in the entrance regions  bath  thermocouples  data.  car . and  to  oil  All  locations in the entrance and exit areas of  were  Table  reference  microcomputer.  mercury-in-glass  made to the temperature  entered  a  circulating  ASTM  the water channels. Thermocouples water  using  where  thermometer location  numbered  and  of  each  thermocouples  numbered thermocouples  in the  exit  positioned in the water channels  tubing,  with  the  their position and to  junctions  exposed  prevent the sensing  were  to  the  junctions  from contacting the tray surface.  2. Heat Transfer  a. Heat  Transfer  The  heat transfer uniformity  different  operating  heating.  Eighteen  placed  Distribution  in  containers  conditions teflon  selected might  be  fully  solid  teflon  using  food-simulating  locations exposed  at the geometric center  of the  of  to  transducers  transducers  represent  during  loaded retort car was studied  heating  the transducers  (150  extremes and during  in  x  to 111 heat  cooling. The  simulate x  conduction  21.7 mm)  transfer  under  to  temperature  heating and cooling were  were which  histories logged  26  Retort Car  Water Channel  Therpiocouple  11 10  33:  3L  Exit End  Entrance End  Side View  ©C  ™  Thermocouple  a t e r  ,  Channel  ©A  Bo  Top  Schematic  DO  View  FIGURE 2 drawing to show thermocouple locations in the (not to scale)  retort.  27  Thermocouple  Thermocouple  Number  TABLE 2 locations in the retort.  Water  Channel  Position  19 20 21 22  1 1 2 2  A B A B  23 24 25 26  3 3 4 4  C D C D  27 28 29 30  5 5 6 6  A B A B  31 32 33 34  6 6 7 7  C D C D  35 36 37 38  8 8 9 9  A B A B  39 40 41 42  10 10 11 11  C D C D  43 44 45 46  Adjacent Adjacent Adjacent Adjacent  to to to to  water inlet water exit thermometer thermometer  28 at for  one  minute  further  using  analyses. Two  indices  (f)  1942),  were  heating  intervals  and  heat  lag factors  calculated  and  transducers.  The  (j)  of  datalogger  penetration  these  behavior  effect  Kaye  parameters,  at  location  data  using  the  centerpoint  within  a  the  positions  3 shows  transducer  of selected trays. Table  in reference to  fa. Teflon  placements  which  of  materials  affect  thermal  (Peterson  and  have  been  of  the  car  to  using these  the  rate  and lackson, describe  teflon  on  tape  cooling  1957; Olson  microcomputer  at the  processing  Adams,  of  used  1983; Pflug,  (Ramaswamy  and  Tung,  used as food-simulating  Table the  4  the  brick-shaped ability  of  the  and  exit  parameters.  entrance,  middle  transducer  The  similar  to  teflon many  no  than  transducers  apparent slight  been  characteristic  thermal  food  have  model  systems  products. 1964),  For  bricks  for  comparing  example, of  metal  and  nylon  and  nylon  bricks  were  (Mantell,  1958)  1986) and silicone rubber  used.  In  this  study,  bentonite  teflon  transducers.  lists some  calculated  figures.  1986)  in  food  1983), bricks of teflon (Weintraub,  other  and  3 indicates the specific location of each  (Ramaswamy,  reported  heating  magnetic  Figure 3.  variety  suspensions  and  on  Transducers  A factors  the  recorded  the  retort  heating medium to transfer enthalpy was compared  Figure  and  (Ball, 1923; Ball and Olson,  from  cooling  the  diffusivity heat  products thermal  warping  of  by  listed  thermal (Leniger  bricks  and  conduction by  degradation the  properties  Tung or  after  of  Beverloo,  and their et  al.  permanent repeated  teflon  1975)  thermal  (1984a).  these  diffusivities  Weintraub  modification  high  using  to  temperature  are  (1986)  properties processing.  29  Retort Car  Tray  Transducer  10 / /  8  Entrance End  VIA /  /  /  /  Exit End  Side View  D  F  E Tray  Transducer  A  C  B  Top  View  FIGURE 3 Schematic drawing to show transducer locations in the (not to scale)  retort.  30  Transducer  Transducer  The  TABLE 3 locations in the  Number  Tray  retort.  Number  Position  1 2 3  1 1 1  A B C  4 5 6  3 3 3  D E F  7 8 9  5 5 5  A B C  10 11 12  6 6 6  D E F  13 14 15  8 8 8  A B C  16 17 18  10 10 10  transducers may therefore  D E F  be used for numerous trials while providing  consistent  and repeatable measurements.  The Plastics, geometric  rectangular teflon  Montreal,  PQ)  center.  Working  allows  thermocouples  bricks  is  described  to by  bricks were  sandwiching with be  a solid  more  Weintraub  constructed  a  from two teflon slabs (Cadillac  copper/constantan material provides  accurately (1986).  The  placed. bricks,  mm thick, 150 mm long and 111 mm wide, were  thermocouple  consistent  Detailed averaging  at  dimensions  construction  of  approximately  the and the 21.7  designed to model the size and  31  TABLE 4 Some thermophysical properties  of teflon.  Properties of t e f l o n (Mantell, 1958) Specific Gravity (p) Specific Volume Thermal Conductivity Specific Heat (Cp) Thermal Expansion Heat Resistance Heat Distortion Water Absorption  Calculation  2.1 - 2.3 g/cm 476.2 - 434.8 c m / k g 6 x 1 0 " " cal/s cm C ° 0.25 cal/g C ° 10 x 1 0 " / C ° 500 °F (continuous) 270 °F (66 psi) 0.0 % 3  3  (k)  5  of t h e r m a l diffusivity (Leniger and Beverloo,  k  6 x 1 0 " "cal/s cm  a =  shape  of  a filled  pilot-scale vertical  The on  the  Cp  2.2 g c m "  1.09 x 1 0 "  retort  Each  brick  of thermal behavior  construction.  heating were  used to  adjust  a  thickness  19  (0.75  and  j  are  heating  f^  conduction  j,  brick  Since  and  Since  C°  2  dimensions  standard  x 0.25 cal/g  m /s  7  pouch.  3  was  calibrated  using  pure  steam  in  a  retort.  reproduction  brick  C°  = p  =  1975)  of  and  approximates  mm  dependent  upon  the in) the  between  each teflon  f  values  are  an  infinite  slab,  f values (Ball  of  and  position  dependent correction  each brick  Olson, in  brick is  the  to  dependent upon factors  for  f values  for  1957; Stumbo, brick,  brick  correction  1973). factors  32 were  used to  from the  c.  adjust  The  With Steam  thermal  studied  using  Two  responses  of  the  FMC  meshed  transducers  same  placed  racks  on  An  rack  and by  ballast. It was  transducer  no  responses  The  main  steam  of  consisted  a 5 minute  (opened  distance  125°C  water.  the  1957).  transducers  Laboratory  processed  Sterilizer  as  in  pure  modified  steam by  Britt  1987)  were  that  centered  their  in  surfaces expose  the  were  retort openly  with  nine  exposed  the transducers  to  hoped  that this would  reduce  to  uniform  placing them on the racks for each experimental  was  pressure  selected.  venting with  2.5 turns) so that the using  500W  such  supply  retort was flooded  circulated cold  a standard  any variability  run  in the  resulting from retort influences.  temperature of  teflon  attempt was made to  by randomly  using  the  (Britt,  each  retort environment.  the  for  steam or steam/air mixtures.  heating conditions  off,  to j values  Processing  (1987) to operate with pure  the  each brick  brick surface of 9.5 mm (Olson and lackson, 1942; Ball and Olson,  Comparison  were  the j values of  period  was The  365.42 total  and  re-circulation  pump  were while  heating  a 6 minute  cooling water transducers  kPa (53  from the  psig)  period  of  come-up low flow  submerged.  The  simultaneously  and  a  50  target minutes  time. At cold  steam  water  cooling water  adding  and  valve was  draining  33 3. Process  Lethality  Using formula (F ).  Calculation  microcomputer  method  (Stumbo,  Calculations were  0  specifically  located  software  1973)  was  based on  teflon  (Pro  Calc  used  to  Associates, calculate  Surrey,  centerpoint  of  accounts  transducers.  variable  j  for the  values.  Smith  lethality contributed  Come-up  Stumbo's  lethality  heating and cooling parameters determined and  Tung  (1982)  compared formula methods available for calculating thermal process method  BC),  times  by  were  the  not  cooling  taken  into  for  the  discussed  lethality.  cycle  values  and  Stumbo's  through  consideration  the for  use these  lethality calculations.  4. Retort  Pressure  An was each  electronic  mounted  in the  experimental  calibrator  by  pressure  histories  retort  an  Kaye  pressure  experimentation. pressure  top  run.  (Chandler  supplied  using the  pressure  The  HP of  overpressure  the  shell to  the  control This  was  supply  recorded  needle  was  the  was  water  under for  were  set  the  chosen  25  to  recirculation  psig  provide  at  pump  for  had to  example,  steam pure  conditions  steam  at  pressure  voltage  Palo  Alto,  one  minute  further  CA).  The  during  work  to  115 and  The  intervals  retort  do  was  analyses.  kPa)  and  OH) during  consistent  be appropriate for retort pouch  pure  deadweight  (172.37 a  pressure  excitation  Packard,  magnetic tape at  a  an  logged  Columbus,  retort  using  and  (Hewlett  on  Sensotec,  record  OK)  runs  and  A-5/1148,  calibrated  Tulsa,  experimental  that would  condition,  Co.,  power  setting  pressures  retort  transducer  6214A  datalogger  typical overpressure  (Model  Engineering  against which  Retort  of  transducer  all head  supply  a  processing.  not 125°C  produce create  an retort  34 pressures  of  approximately air to  70.58 and 132.67 kPa gauge,  101.33 kPa. A high pressure  create a steam/air mixture  pressure. kPa  only  The  (14.76  target psig)  retort  while  processing at 125°C.  in the  pressure  processing  Atmospheric pressure is  air line was used to supply the retort  provided at  respectively.  115°C  headspace which a  theoretical and  39.70  produced the  overpressure kPa  necessary  (5.76  of psig)  target 101.79 while  IV. RESULTS A N D D I S C U S S I O N  A.  RETORT  TEMPERATURE  The  efficacy  temperature  A during  retort  cook  the  bracketed  of  period  of  the  location.  The  locations  during  Figure  is  4  retort  deviations of  recorded  the  time.  traditionally  temperature  a  an  cook  column  cook  plot cook  thermocouple  time  standard during  of  period  is  temperatures  period.  This  mean temperature  deviations the  cook  of  one  at the  be  at  plot  for can  is  at the  by the Figure all be  come-up  recorded and  in  standard  Temperature  bottom  of  the  each  individual  for  the  combined  bottom  to  the  of  different  used  (represented  the  interval.  deviation  particular time.  35  temperature  showing  temperature  deviation  monitored  This  locations  thermocouples  car during  minute  recorded  can  with output  is recorded  temperature  period.  the  distribution  mean  standard  plot  locations at any  retort  standard  and  the  conditions.  different  describes  computer  of  each  and  at  monitored  in the  minutes,  temperature  entire  was  form  determining  time.  Temperature  at  1 8 - 5 0  temperature  from the overall  and  the  mean  sample the  in  run.  locations  mean  uniformity  sample  locations  by  specific operating  stability  of  retort  a  experimental  period,  of  the  is  26 selected  combined  grand  5  the  assessed  retort under  Temperature  within  Table  hand  form  during  the  mean  for  the  in  of  locations  right  stability over the  any  at a specific  histories of  and  the  describes  experimentation.  temperature  table  is  of a specific location over a period  series  deviation  system  and stability of the  distribution  the  uniformity  a retort  distribution  Temperature within  of  of  the  table.  locations  inside  observe  temperature  horizontal  line)  5 is a sample  thermocouples used  to  at  observe  for plot each the  36 TABLE 5 Sample computer output of temperature  TEMPERATURE  D I S T R I B U T I O N WATER P R O C E S S  Thermocouple  r 1me  0.  19 34 0 4 0 0  16 1 15 6 1 . 46 1 82 9 64 3 95 7 83 7 3. 100 3 4. 88 6 107 3 94 8 5. 1 12 9 6 . 101 4 1 18 3 7 . 106 5 120 4 8 . 1 10 0 121 7 9 . 117 5 122 8 1 0 . 120 3 123 6 11 . 124 . 1 124 7 1 2 . 126 1 125 5 1 3 . 125 7 125 2 14 . 126 2 124 9 1 5 . 126 3 125 7 1 6 . 126 2 125 8 1 7 . 126 3 125 9 1 8 . 126 . 1 125 9 1 9 . 126 1 126 1 2 0 . 126 2 126 2 21 . 126 1 126 1 2 2 . 126 2 126 . 1 2 3 . 126 . 1  a.  20 35 0 3 0 2  16 15 62 107 74 1 14 74 108 81 113 90 1 18 97 123 99 122 100 123 106 124 1 13 125 1 17 126 121 126 124 125 124 126 124 126 125 126 125 126 125 126 125 126 125 126 125 126 125 126 125  1 8 1 3 8 1 5 1 8 1 6 5 4 0 4 9 9 9 7 7 3 0 6 3 3 1 4  5 5 1 9 3 2 2 2 2 4 1 5 3 6 1 6 1 7 2 6  21 36 0 4 0 2  16 15 52 69 61 90 61 102 76 109 92 1 14 106 120 1 16 121 118 122 121 123 122 123 125 124 125 125 125 125 125 124 126 125 126 125 126 125 126 126 126 126 126 126 126 126 126 126 126  0 8 0 7 6 2 1 8 3 5 3 9 5 2 6 8 7 6 7 4 2 9 1 9 7 5 5 4 8 9 2 9 1 9 2 9 1 0 2 2 2 1 2 1 2 3 2  22 37 0 2 0 1  15 8 15 7 56 0 10B 7 57 2 112 9 66 9 1 10 3 69 1 1 14 1 76 1 1 19 5 81 3 124 1 78 1 123 5 91 1 124 2 104 1 125 0 1 1 10 125 5 1 16 2 126 7 1 19 3 126 3 122 4 125 7 123 2 126 5 124 0 126 4 124 7 126 4 124 8 126 5 125 1 126 4 125 2 126 6 125 4 126 3 125 4 126 4 125 6 126 4 125 6  RUN  number a n d c o r r e c t i o n 23 38 0 2 -0 1  15 15 83 88 67 106 99 103 108 1 10 1 14 1 15 120 120 120 121 122 122 123 123 125 123 126 124 126 125 125 125 126 125 126 125 126 125 126 125 126 125 126 126 126 126 126 126 126 126 125  8 7 6 0 0 8 0 3 6 0 4 0 0 0 6 6 9 3 9 1 0 8 3 7 0 4 5 2 1 0 1 6 0 8 0 8 1 9 2 0 1 1 1 0 1 1 9  24 39 0 3 0 2  15 16 57  8 3 1 112 3 72 0 1 1 18 56 2 110 3 68 3 1 14 6 8 6 .2 119 0 100 1 123 9 108 5 123 3 1 14 4 124 0 1 18 0 124 6 120 2 125 .2 121 .6 126 .4 123 . 1 126 .0 123 7 125 5 124 2 126 2 125 2 126 1 125 3 126 1 125 5 126 . 1 125 7 126 0 125 9 126 1 126 0 126 1 126 .0 126 . 1 126 .0 126 .3 126 . 1  25 40 0 2 -0 6  15 9 16 1 95 1 97 1 80 9 1 13 6 102 3 106 1 109 7 1 1 18 1 16 6 1 16 6 121 0 121 2 121 6 122 1 123 5 122 9 124 3 123 7 125 1 124 2 126 4 125 2 126 1 125 7 125 6 125 3 126 2 125 1 126 3 125 8 126 2 126 0 126 3 126 0 126 4 126 0 126 3 126 2 126 3 126 2 126 3 126 1 126 3 126 3 126 1  C00K10  MEAN  factor  26 41 0 2 -0 1  16 17 60 1 16 74 112 74 111 88 1 16 98 120 107 124 115 123 1 18 124 121 125 122 125 123 126 124 126 124 125 124 126 125 126 125 126 125 126 125 126 126 126 126 126 126 126 126 126 126  histories.  0 7 9 8 9 S 2 8 2 1 9 7 5 9 4 7 7 6 0 0 3 6 6 9 5 4 8 9 6 6 2 5 5 6 7 5 9 6 0 6 0 5 0 5 1 6 1  27 42 -0 1 0 2  15 17 100 107 106 116 106 107 1 12 1 14 1 17 1 18 122 122 122 123 123 123 124 124 125 124 126 126 126 126 125 125 126 125 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126  9 3 1 6 3 5 5 7 1 2 6 4 1 8 7 1 3 7 3 3 2 9 5 0 2 4 7 9 2 8 4 4 2 4 2 4 3 5 5 5 2 5 2 5  5 5 5  28 43 -0 1 0 2  15 18 62 119 69 109 93 1 13 103 1 16 109 121 1 15 125 1 18 123 120 124 121 125 123 125 124 126 124 126 124 125 124 126 125 126 125 126 125 125 125 126 125 126 126 126 126 126 126 126 126  7 8 0 3 4 7 0 4 7 4 8 2 3 4 6 8 6 5 8 0 0 3 0 6  9 1 9 6 6 4 4 1 7 1 7 9 8 1 9 1 0 1 0 3 1 3 1  29 44 -0 1 0 2  31  30  32  33  0 2  -0  1  -0  1  0  2  15 7 18 1  15  7  15  8  15  7  15  9  95  e  61  7  98 6  72  3  106  1  81 109 95 106 98 1 12 106 1 18 113 122 118 122 120 123 120 124 121 125 121 126 123 126 124 125 124 126 124 126 125 126 125 126 125 126 125 126 126 126 126 126 126 126 126 126  3 0 5 0 4 8 6 0 3 6 0 6 7 7 8 4 6 0 6 3 1 1 4 61 1 1 6 3 3 2 6 1 7 1 8 3 0 2 0 1 0 3 0 3  73  3  8  82  4  109  2  108  84  9  107  8  98  3  107  94  6  112 7  106  2  1 12 6  107  6  1 18 5  112 4 4  123  3  122  9 120 2 122 9  S D. )  (  16 1 8 .  0  (  84 6 3 ,  22  40)  (  91 9 4 .  20  03)  (  95 95,  16  60)  ( 103 0 4 ,  14  83)  ( 110 0 5 .  12 2 5 )  0  124  0  121  3  124  0  124  3  122 8  124  6  123  125  1 123  125  3  ( 115 9 8 .  10  ( 117 7 0 .  10 0 3 )  124  1 126  3  124  2 3  126  7 85)  ( 121 7 2 .  5 20)  ( 122 9 9 ,  3 56)  (124  2 64)  4  124  8  126  0  125  1 126  1  124  9  125  5  125  1 125  6  124  7  126  0  124  9  126  3  125  4  126  1 125  5  126  1  125  6  126  2  125  8  126  7  126  2  125  9  126  3  125  7  126  3  125  9  126  3  9  126  2  125  9  126  1 126  125  9  126  2  126  125  126  0  126  2  126  126  0  126  1 126  126  4  1 126  3  0  9  126  ( 125 2 0 .  1 65)  ( 125 1 6 ,  0  78)  ( 125 4 5 ,  0  89)  ( 125 8 3 ,  0  59)  ( 125 9 3 .  0  42)  ( 125 9 6 .  0  39)  ( 126 0 2 .  0  33)  ( 126 1 3 ,  0  3D  ( 126 1 1 . 0  23)  ( 126 1 0 ,  0  24)  ( 126 1 8 .  0  22)  3  1 126  3  126  1  0  63,  3  125  125  71)  70,  (119  0  83)  1  122 0  120  Mean.  6  7  123  (  9  1 14 6 116  117  117  S.D.  37  Table 5  Continued  126 126 126 2 5 . 126 126 2 6 . 126 126 2 7 . 126 126 2 8 . 126 126 2 9 . 126 126 3 0 . 126 126 31 . 126 126 3 2 . 126 126 3 3 . 126 126 3 4 . 126 126 3 5 . 126 126 3 6 . 126 126 3 7 . 126 126 3 8 . 126 126 3 9 . 126 126 4 0 . 126 126 41 . 126 126 4 2 . 126 126 4 3 . 126 126 4 4 . 126 126 4 5 . 126 126 4 6 . 126 126 4 7 . 126 126 4 B . 126 126 4 9 . 126 126 5 0 . 126 126 24.  Mean S.O.  2 .2 .2 . 1 .2 .2 .3 1 3 2 3 1 3 2 3 1 3 2 3 1 3 2 3 2 3 1 3 2 4 2 3 2 3 2 3 3 3 1 3 1 3 2 4 2 3 1 3 2 3 1 3 2 3 2 3  126 125 126 125 126 125 126 125 126 125 126 125 126 125 126 125 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126  3 .7 .3 .8 .2 .8 .3 8 3 8 3 .9 3 9 3 9 2 0 .2 .0 3 O 3 0 3 0 3 . 1 3 1 2 1 3 0 3 1 3 0 3 0 3 2 3 .2 .3 1 3 2 2 1 2 1 3 1 3  126 2 126 3 0.06  125 9 126 3 0.21  0 . 10  0 . 07  126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126  3 2 3 2 3 2 3 3 3 3 4 1 4 2 4 2 3 3 3 2 4 1 4 3 4 1 4 3 4 2 3 2 4 2 4 3 4 2 4 2 4 3 5 2 4 2 4 3 4 2 4 2 3 2 4  126 2 126 3 0.06  126 125 126 125 126 125 126 125 126 125 126 125 126 125 126 125 126 125 126 126 126 126 126 126 126 126 126 126 126 126 126 125 126 126 126 126 126 126 126 125 126 126 126 126 126 126 126 126 126 125 126 125 126 126 126  .4 126 .7 126 .3 126 .7 126 .3 126 .8 126 .3 126 .8 126 5 126 .9 126 .5 126 .9 126 .4 126 .9 126 3 126 9 126 3 126 9 126 .3 126 .0 126 .3 .126 .0 126 .4 126 0 126 4 126 0 126 .5 126 . 1 126 4 126 0 126 4 126 9 126 4 126 0 126 3 126 0 126 4 126 .0 126 4 126 9 126 3 126 0 126 4 126 .0 126 4 126 0 126 3 126 0 126 4 126 9 126 3 126 9 126 4 126 0 126 4 126  125 8 126 4 0.25 0 . 07  0. 1 1  G r a n d mean t e m p e r a t u r e > Standard devlatIon Stabl 1 I z a t l o n or time come - u p Retort  • •  126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126  . 1 .2 .3 .2 .3 . 1 . 1 .2 . 1 .3 .4 .4 .2 .3 . 1 .4 . 1 3 .3 .4 . 1 .4 .2 4 .2 4 .2 .4 . 1 .4 . 1 .4 3 4 1 .4 .3 .4 1 4 1 4 3 .4 . 1 4 0 4 1 4 0 4 0 4 2  126 1 126 3 126 2 126 2 0.08 0 . 18 0 . 08  126 24 0 20 18  .0 . 1 . 1 .2 . 1 1 . 1 2 2 2 2 . 1 2 1 2 1 2 1 2 1 2 3 2 3 2 1 2 0 2 1 2 1 2 0 2 1 2 0 2 1 2 1 2 1 2 1 2 1 2 1 2 1 1 0 2  rain  C  c  0. 1 1  126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126  2 3 4 4 3 3 4 5 5 4 5 3 5 4 5 3 5 5 5 3 5 4 5 3 5 5 6 4 6 4 5 4 4 1 5 4 5 3 5 4 5 4 6 3 5 4 5 4 5 3 5 3 4 3 5  126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126  5 . 1 .6 . 1 .6 2 5 2 6 3 .7 .3 6 .3 6 3 6 3 .6 3 6 .3 7 3 7 4 7 4 5 3 6 3 7 3 6 4 7 4 6 4 6 4 6 4 7 4 6 4 7 3 6 3 6 4 7  126 5 126 .3 126 .5 126 3 126 .5 126 3 126 6 126 2 126 6 126 3 126 6 126 4 126 7 126 3 126 7 126 2 126 6 126 3 126 6 126 2 126 6 126 3 126 6 126 2 126 7 126 5 126 7 126 4 126 7 126 1 126 6 126 3 126 6 126 3 126 6 126 3 126 7 126 3 126 6 126 4 126 6 126 4 126 7 126 3 126 6 126 3 126 6 126 3 126 6 126 3 126 6 126 2 126 6 126 2 126 6  126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126  126 2 126 2 126 3 126 2 0 . 1 1 0.06  126 3 126 4 0.09  126 3 126 6 0 . 14  126 3 126 6 0 . 10  0 . 14  0 . 06  0 . 07  . 1 . 1 .4 . 1 .3 .2 .5 . 2 .3 .2 .7 .2 .4 .2 .6 .2 .0 .2 .2 .2 .7 .2 .6 .2 .3 .2 . 1 .2 .4 .2 .2 .2 .3 2 5 .2 .5 .2 . 1 2 4 3 7 .3 .0 2 .5 .2 4 2 1 .2 1 .3 . 1  O. 21  126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126 126  1 3 0 2 1 2 2 2 2 2 2 2 3 2 3 1 2 2 2 2 2 2 3 2 3 2 3 2 3 1 3 2 2 2 3 2 4 2 3 3 3 3 3 1 4 2 3 1 3 2 2 1 3 2 4  O. 14  126 .0  126  1 126  1 126  2  126 .0  126  2  1 126  3  126 . 1 126  126  1 126  1 126  2  126  1 126  4  126  2  126  3  126  3  1 126  3  126  1  126 .2 126 .2  126 126  126 . 1 126  3 2  126 126  3 2  126 126  126  2  126  3  126  4  126  2  126  3  126  3  126 .2  126  3  126  3  126  3  126 .2  126  3  126  3  126  5  126 .2  126  3  126  3  126  3  1 126  3  126  126  2  126  3  126  3  126 .2  126  2  126  3  126  4  126  0  126  3  126  0  (126  0 . 18)  126  3  126  3  126  3  126 .2  126  2  126  2  126  3  ( 126 2 5 ,  0. 20)  (126  30,  0  20)  ( 126 2 7 .  0  19)  ( 126 2 9 .  0  19)  ( 126 2 2 .  0  18)  ( 126 2 7 ,  0  16)  ( 126 2 8 ,  0  18)  ( 126 31 .  0  17)  ( 126 31 ,  0  16)  ( 126 3 0 ,  0  19)  ( 126 3 0 .  0  16)  ( 126 2 6 .  0  15)  ( 126 2 9 .  0  )6)  ( 126 2 S ,  0 . 17)  (126  126 .2  126  1 126  3  126  2  126 .2  126  2  126  3  126  4  126 .3  126  3  126  3  126  3  2  126  1 126  3  126  2  126  2  126  3  126  3  126  2  126  1 126  3  126  1  2  126  2  126  3  126  1  126 .2  126  2  126  3  126  1  126  1 126  0 . 13  2  0.08  126  2  O. 13  126  33,  0  16)  ( 126 2 6 ,  0 . 17)  ( 126 2 8 ,  0 . 17)  ( 126 3 5 ,  0 . 17)  ( 126 2 9 ,  0 . 16)  ( 126 2 7 ,  0 . 17)  1  126  126  19)  1  126 .2  126  21 .  3  126 .2  126 .2  0. 20)  ( 126 2 0 .  3  126 .2  126  ( 126 1 9 .  4  126 .2  126 .2  0. 22)  1  126 . 1 126 1 126  ( 126 1 3 .  3  0 . 11  ( 126 3 0 ,  0 . 16)  ( 126 2 4 ,  0 . 17)  ( 126 2 4 ,  0 . 16)  ( 126 2 8 ,  0 . 17)  38 performance sample  of  plot  of  thermocouple identify  the  the  maintaining  mean  location  over  detrimental deviation  to  temperature the  of  cook  can result  of  121.1 °C. the  C°  above  National minute,  Food  In  be within  this  piping,  water  process  temperatures temperatures  fell was  be  sufficiently  used  to  be  Association  readings should  guidelines  (Milleville  and  for  the  during  the  to  the  the The  below  the  above  system,  the  retort  car.  reference table  minute that  target the  reference Table  that  temperatures, target  in  the  of  range  temperatures.  is  the  temperatures  while  the  of  the The  for  be must  all  food  retort  must  cook  begins. the  first  1.67 C ° . ( 3  F°)  device.  located  overall  of  average  in  the  mean  retort  two  target  the  reference  range  not  after  temperature  6 compares  the  ensure  addition,  thermometer  U.S.  temperature  after  in  The  To  all points  14%  temperature  should  lowest  have a maximum range  thermometer  indicates  cook  to  Badenhop,  uniform  temperature.  one  up  temperature.  the  where  stated  a  process  processed,  (1985)  temperature  of  process  within  that  lethalities  variation  specified  reported  0.83 C ° (1.5 F°) of the reference  and  temperatures.  of  as a range  temperature  retort  external  temperatures  are  target  all thermocouple  and should  can  process  adopted  — 0 . 5 C°  but  in  British  tolerance  than the  Processors  differences  temperature  a retort load the  in  and  as a mean deviation,  be  plot  each  locations.  Berry  Annotated  expressed  at or  of  greater  foods.  general  +1  tolerance  in  This  at  a  of  felt  containers  period.  deviation  (1979)  is within  or  standard  6 is a  sterilization  that  equal to  its  Figure  retort can  reviewers  car  and  temperature.  of cold areas in the  0.56 C °  stated  distribution  drain  entire  cook  fluctuations and the presence  the  a temperature  1980)  be  a stable  cold spots among the thermocouple  Temperature  at  retort in  thermometer  the  retort  car  thermometer  TEMPERATURE DISTRIBUTION WRTER PROCESS RUN COOK10 ° 19 A "  348  20+ 35y  21* 36 6  22 * 37 '  23 * 381  24* 39"  252 40 9  26Y 41 1  27 * 42 "  28 " 43v  29x 44  30 1  31 '  32-  33  TEMPERATURE DISTRIBUTION WATER PROCESS RUN COOK10 MEAN AND S.D FOR RLL CHANNELS AT EACH TIME  ft  18.0  22.0  26.0  30.0  | T  34.0  38.0  TIME (MIN)  |  42.0  14-| | | { t I  46.0  FIGURE 5 Sample plot of mean and standard deviations of temperature at each recorded time during the cook period.  50.0  54.0  f o r all thermocouples  58.0  o  TEMPERATURE DISTRIBUTION WATER PROCESS RUN COOKIO MEAN TEMP I S.D FOR DIFFERENT CHANNELS  00  19  23 20  22 21  <->°.  27 24  26 25  31 28  30 29  4—4-  + * I  35 32  34  39 36  33  •-I t *  38  43 40  37  42 41  4)  _4  UJ  or ZD  I— d o LUt\l.  CNJ .  FIGURE 6 Sample plot of the mean temperature and its thermocouple location over the entire cook period.  standard  deviation  at  each  1)1  44  42 temperatures were target,  and  setpoint  2.0  of the  1.5 C ° C°  below  that  the  retort  car.  This  the  specific  retort,  are  125°C  ensured  is  a  that  positive  setpoint  target  feature  temperature  however,  is  temperature,  it is c o m m o n practice to  temperatures that the  should  1.67 C° (3  than  variations  the  were  be  noted  F°) above  115°C  that  both  necessary to  the  target  minimum temperature  lower  retort  reference and  between  the target  ensure  that  thermometer. The  fact  the  The  large  controller are  retort will  in  the  for  this  adjustment.  To  and  setpoint  car  discrepancy  observed  some  minimum  retort  exceeded  thermometer  the  actual  were  design.  temperature  in the  than  warrants  adjust the  retort  reference  temperatures  the  advisable  for  ensures  It  the  process of  and  not  temperature  using  temperatures  compensate  higher  target.  controller was  monitored  thermometer  safely  between  the  retort car temperatures for the  reached in the retort car.  temperatures  reference  temperatures  average  6 indicates these higher setpoints were  temperatures were  Retort  for  retort temperature  temperatures. Table target  below the  average so  produced.  that  retort slightly  This  practice  the  process  remain above  temperature.  The each  overall  standard  experimental  temperature  run  in the  deviations  were  retort  of  temperature  calculated as an  car with  respect  during  indication of  to  the  the  indicate  retort  weir  temperature  uniformity a  and  of the  height  was  conditions.  significant  retort car. Overall  temperature  of  115°C  Analysis  (p<0.05)  in  of  C°)  than  influencing  at  observed  variance  uniformity was observed  (±0.21  overall  time and location. Table  the range and mean overall standard deviations of temperature temperature  cook  125°C  the to  results overall  period  for  variability  of  7 compares for in  C°)  Table  8  temperature  be slightly  (±0.26  different  better at  during  the  43  Comparison of overall temperatures.  Target  TABLE 6 mean retort car temperatures with reference  Average  Reference Thermometer Temperature (°C)  115.6 - 116.4  114.0 - 115.0  115.9  114.4  125.5 - 126.5  123.5 - 124.4  126.0  124.0  125°C  Range Average  cook  Overall Mean Car Temperature (°C)  115°C  Range  Target  thermometer  period. The  effect  of weir height was  not significant  (p>0.05).  44 TABLE 7 Range and mean of overall temperature uniformity entire cook period.  'Weir  (26 thermocouples)  Temperature (°C)  WeiiHeight  115  1  0.18 -• 0.22  0.20  115  2  0.21 •• 0.23  0.22  115  3  0.18 •• 0.25  0.21  125  1  0.25 •• 0.30  0.27  125  2  0.21 •• 0.38  0.28  125  3  0.21 •• 0.26  0.22  Height 1=29.2 cm, 2 = 31.1  Analysis of  1  Overall Standard Range (C°)  Deviation Mean (C°)  cm, 3 = 34.6 cm TABLE 8 overall standard deviations  variance for  during  of temperature.  df  M e a n Square  Temperature  1  0.10272E-01  5.50 *  Weir  2  0.18500E-02  0.99  ns  2  0.13389E-02  0.71  ns  280  0.18667E-02  Source of Variation  height  Temp x Weir Error ns - not significant (p>0.05) * significant (p<0.05)  F-Ratio  the  45 1. T e m p e r a t u r e  Distribution  The  standard  minute  interval  distribution.  Analysis  one  height  and  each  during  their  temperature  deviations  of  the  interaction  interval,  temperature  cook  variance  distribution.  minute  of  results  were  Table  the  period  9  were  not  reach  the  greater  experimental  the  uniformity  target  than  deviation  99.5%  of  0.30  thermocouples. distribution  were  will  observed  this. Although  distribution  regions  (Table  5).  come-up  period,  where  it  occurred.  In  uniformity  more  although  general,  to  final  temperature temperature  range  times  most locations  in the  cases, several  stabilize.  During  rapidly in upper  This  is  appears  experimental  an  runs  115°C  uniformity and  of  of  for  the  minutes.  1.8 retort  a  to  a  appeared  were  a  between achieve the  a  target for  temperatures  and in the patterns  faster to  For  required  period,  to  standard  C°  retort car reached  and  range  location  with  minutes  the  at  0.30 C ° .  22  distribution  circulation  circulation  at  -  come-up  of  the  period  water channels  indication  better  18  more  the  influencing  thermocouple  range  of  weir  channel  during  the  temperature  rise  achieve  temperature  quickly than at 125°C.  range  the  the  the  temperature  temperature,  temperature  cook  approximately  a a  in some  to increase more  entrance  The  have  of  the  in  a standard deviation  for  was  of  (p>0.05)  the  locations at each  compare  effects  range  during  time  level,  9 indicates  in 18 minutes,  temperature  the  temperature  confidence C°  Table  below  temperature the  retort  runs,  the  significant  of times for the retort car to stabilize below  During  used to  indicated  compares  average  for all thermocouple  of  poorest  there was significant  standard  deviations  uniformity  occurred  improvement  through  (Table during the  9)  in  the  the initial  raw  data  minutes  remainder of this  indicated of  the  period. The  that cook,  average  46 TABLE 9 Range of temperature uniformity at each minute interval, the average uniformity during the cook period, and the range of times for the retort to stabilize.  WeiiHeight  Temperature (°C)  'Weir  Mean Std. Dev. (C°)  Range of Std. Dev. (C°)  1  Time to Stabilize Below 0.30 C ° (min)  115  1  0.13 - 0.42  0.19  16 - 20  115  2  0.13 - 0.32  0.21  18 - 19  115  3  0.12 - 0.31  0.20  18 - 19  125  1  0.13 - 0.47  0.22  20 - 22  125  2  0.16 - 0.33  0.21  20 - 20  125  3  0.14 - 0.28  0.20  19 - 21  Height  1 = 2 9 . 2 cm, 2 = 31 .1  standard  deviations  indicated  c m 3 = 34.6 cm  satisfactory  overall  temperature  distribution  during  the  cook.  Although between  study  thermocouple  maximum  and  individual  thermocouple  presented  Table  locations,  deviations it  locations 10  locations  significant factor and  standard  minimum extremes  in  thermocouple  of  was  from  does  not  identify  in  temperature.  is  therefore  based all  indicates the  on  two  specific  the  target  The  pooled  cook  temperatures  temperature  exhibiting  of  temperatures  analysis  mean  periods.  of  areas  comparison  necessary.  experimental  (p<0.05), since the  A  uniformity  of  temperatures  well  at  variance  Temperature  were  the  was  of a  spaced (115  125°C).  The  effects  of  weir  height  were  significant  (p<0.05,  Table  11)  where  all  47 TABLE 10 Analysis of variance for pooled mean thermocouple  Source of Variation  df  Mean  Square  temperatures.  F-Ratio  Temperature  1  Weir  2  8.5286  152.53 *  13  7.9527  142.23 *  Position  1  0.77002  13.77 *  Interactions Temp x Weir  2  1.1512  20.59 *  Channel  13  0.21156  3.78 *  Temp x Position  1  0.51607E-01  0.92 ns  Channel  26  0.57904E-01  1.04  ns  Weir x Position  2  0.26389E-02  0.05  ns  0.25241  4.51  *  height  Water  Channel  Temp x  Weir x  Channel x Position Error ns - not significant (p>0.05) * - significant (p<0.05)  13 429  127.84E + 02  0.55914E-01  228.63E + 03 *  48 three  weir  overall  heights  mean  were  significantly  temperature.  Weir  temperature, whereas weir height  Water indicating  there  top water The  channels  some  the  retort  mean temperatures than the  Thermocouple regions, higher  was mean  slight difference  lowest  within  (p<0.05).  temperatures  lowest  overall  mean.  temperatures  within  at  water  the  the  to  mean  with  Table  12  retort  car.  The  mean temperatures.  reference  channels  respect  overall  (p<0.05),  significantly higher  lower  with  thermometer.  exhibited  slightly  In  lower  higher channels.  position  significant  of  other  the  temperature  car had  the  each  the highest  significantly  car  from exhibited  influenced  retort  were  1  3 showed  stratification  in the  temperatures  within  height  significantly  channel (11)  mean  general,  was  different  than  the  In  the  water  general, exit  channels,  the  region.  the  entrance Figure  entrance  region  and  showed  exit  slightly  6  illustrates  graphically  the  between temperatures at the entrance (odd  numbers)  and exit (even  numbers).  The  temperature  x weir  height  for both experimental temperatures, weir  height  (p<0.05).  was  used.  was  mean temperatures were  Temperature  In general, the  discussed,  interaction was significant (p<0.05).  observed  x  same pattern for  both  water  in water  test  regions locations 11  of  indicated water  the  channel  coldest 1  (120.6°C)  (121.2°C) appeared to  and the exit region  of  locations  be  the  and  interaction  temperatures.  Within  the  retort  on  average  2  (120.6°C).  entrance  the tallest  was  significant  channel mean temperatures,  experimental  position interaction was significant (p<0.05). range  channel  largest when  Generally,  Water  car,  and exit  channel 10. Physically, these two  In  were  general,  regions  channel  Duncan's  (p<0.05),  of  already x  multiple the  exit  the  hottest  water  channel  exit regions  are closest  49 TABLE 11 Duncan's multiple range test comparing pooled mean thermocouple temperatures different weir heights.  Weir Height  Pooled Mean Temperature (s.d.) (°C)  2  of  Duncan's Test 1  1  120.6 (5.0)  a  2  120.8 (5.1)  b  3  121.0 (5.1)  c  'Values with the same letter are not significantly different W e i r height 1 = 2 9 . 2 c m , 2=31.1 c m , 3 = 34.6 cm  (p>0.05).  2  to  where  coldest  the  hot  locations  water  first  the  retort  in  contacts car  the  averaged  retort  car.  During  approximately  0.6  experimentation,  the  C°  than  the  and  the  of  the  lower  hottest locations.  Although bottom  water  there  channels,  was  a slight  as well  as  temperature between  the  gradient entrance  between and  water channels, the overall temperature distribution appeared to  the  exit  top  regions  be satisfactory.  50 TABLE 12 Duncan's multiple range test comparing pooled mean thermocouple different water channels and the reference thermometer.  Water Channel  Thermometer  'Values  Pooled M e a n Temperature (s.d.) (°C)  temperatures  Duncan's Test 1  119.2  (4.9)  a  2  120.7  (5.1)  b  1  120.8  (5.1)  b,c  3  120.8  (5.1)  b,c,d  6ab  120.9  (5.1)  c,d,e  6cd  120.9  (5.1)  c,d,e  5  120.9  (5.1)  c,d,e  9  120.9  (5.2)  d,e,f  7  120.9  (5.2)  d,e,f  8  120.9  (5.1)  e,f  4  121.0  (5.1)  e,f  10  121.1  (5.1)  f  11  121.2  (5.1)  g  with the same letter are not significantly  different (p>0.05).  of  51 2. T e m p e r a t u r e  The  Stability  standard  deviations  location  during  stability.  Table  for  thermocouple  the  cook  period  the  entire  temperature  cook  13 compares  for  of  the  locations  unknown  period range  reasons.  were and  during  with  the  Table  respect  used  means cook.  to  of  to  each  compare  standard  the  the  temperature  deviations  Temperatures  14 summarizes  thermocouple  increased results  of  observed during  the  the  analysis  of variance for the temperature stability comparison.  The  effect  temperature  stability.  115°C (±0.11  The  temperature  Mean  stability  was was  of  stability  weir was  height  was  significantly  significant slightly  C°) than at 125°C ( ± 0 . 1 6  effect  temperature  of  (p<0.05)  better  at  a  with  retort  respect  to  temperature  of  C°).  significant  better  at  (p<0.05,  each  Table  temperature  15),  where  when  mean  using  weir  height 3.  The Table  effect  of water  channel on temperature  16 indicates mean temperature  reference  thermometer  were  Water channel 11, however,  During order slightly plate  to  the  cook  maintain the  during where  the hot  Since  likely influenced to a greater water  channels.  significantly  steam  temperature.  first  stabilities in water different  channels  1 -  (p>0.05)  As  water  enters  was  injected  mentioned, channel  into  the  11 was  the  car,  the  extent by  this  temperature  located  temperatures  one  another.  others.  the  retort  (p<0.05).  10 and at the  from  was significantly less stable than the  period,  cook. water  not  stability was significant  circulating temperature just  below  at that  increase  than  water  in  increased the  top  channel  were  at the  other  52 TABLE 13 Range and mean of standard deviations of temperature during the entire cook period.  Weir Height'  Temperature (°Q  Weir  factor  0.12  115  2  0.04 - 0.42  0.11  115  3  0.05 - 0.23  0.10  125  1  0.06 - 0.70  0.16  125  2  0.05 - 0.39  0.20  125  3  0.05 - 0.25  0.12  1 = 2 9 . 2 cm, 2 = 31.1  the  general,  cm, 3 = 34.6 cm  water  the  1  stabilities  worst (±0.16 was  were  125°C.  x  weir  mean C°)  observed  Weir  temperature  significant  height  x  the water  was  stabilities  height  (p<0.05). in  region  interaction  weir  was  indicated (±0.12  The  entrance channel  2  were  (±0.20  two  significantly  (±0.14  C°)  interaction  height  Water  1 (±0.32  of  significant  the  at  worst  channels  C°).  (p<0.05).  The  two  for  weir  125°C  Temperature  and exit was  a  (±0.14  observed C°).  be  C°)  significant  significantly worst mean temperature stability was observed weir  to  stability than the exit region  height  and  channel  entrance  a better mean temperature  interaction  at  within  In  Temperature  height  (C°)  0.05 - 0.62  position  significantly  Deviation Mean  Standard Rang e (C°)  1  (p<0.05).  exhibited  thermocouple  115  Height  The  for each  mean (±0.18  significant  x  position  temperature C°)  regions  (p<0.05).  for water channel  The  11 with  C°).  channel x position  interaction  was  significant (p<0.05).  In  general,  the  53 TABLE 14 Analysis of variance for temperature stability.  Source of Variation  df  Mean  Square  F-Ratio  Temperature  1  0.33842  74.18 *  Weir  2  0.99829E-01  21.88 *  13  0.37946E-01  8.32 *  height  Water  Channel  Position  1  0.10573  23.18 *  Interactions Temp x Weir  2  0.50485E-01  11.07 *  Channel  13  0.10245E-02  0.22  Temp x Position  1  0.38763E-01  8.50 *  Channel  26  0.16929E-01  3.71  *  Weir x Position  2  0.69109E-02  1.51  ns  13  0.33888E-01  7.43 *  429  0.45620E-02  Temp x  Weir x  Channel x Position Error ns - not significant (p>0.05) * - significant (p<0.05)  ns  54 TABLE 15 multiple range test comparing mean temperature  Duncan's heights.  Weir Height  1  2  Mean Std. Dev. (C°)  2  stabilities of different  weir  Duncan's Test 1  3  0.12  a  1  0.14  b  2  0.15  b  Values with the same letter are not significant (p>0.05). W e i r height 1 = 2 9 . 2 cm, 2 = 31.1 cm, 3 = 34.6 cm  mean temperature stability was not regions  of all channels, except  observed  in the exit region  The the cook  results period.  indicated  different  (p>0.05) between  the entrance  for water channels 9 and 11. The  worst  and  exit  stability was  of channel 11. satisfactory  temperature  stability  in the  retort  car  during  55  TABLE 16 Duncan's multiple range test comparing mean temperature water channels and the reference thermometer.  Water Channel  Mean Std. Dev. (C°)  stabilities of  Duncan's Test 1  1  0.11  a  6cd  0.11  a  5  0.11  a  9  0.12  a  7  0.12  a  6ab  0.12  a  4  0.12  a  10  0.13  a  2  0.13  a  0.13  a  0.19  b  Thermometer 11  'Values with the same letter are not significant  (p>0.05).  different  56 B.  HEAT  TRANSFER  The heating were  influence of temperature, weir height, tray level and tray position on  and  cooling  parameters,  Rate Index  Heating  and j  were  studied.  These  parameters  rate  (f^)  indices  of  heat transfer efficiency within minutes,  traverse curve  required  one as  log  a  undergoing  cycle.  rate of  and  the  teflon  transducers  were  calculated  retort car. Stumbo (1973) defined f^  straight  line  Ball and O l s o n curve  the  the  the  transfer  coefficient, by (a)  surface  temperature  out  determined  temperature  on  pointed  diffusivity  the  time-temperature  dependent  teflon  for  the  portion  of  a heat  to  determine  as the  penetration  (1957) essentially defined a heat  for  a  specific  point  in  an  time,  curve  to  penetration  object,  which  is  changes in heat energy.  The is  i^,  used to evaluate the heat transfer distribution in the water processing system.  1. H e a t i n g  in  f^,  the  change at the center of a transducer during heat  transfer  gradients  which  mathematical dependence where  the and  f^  heat  by  cause of  determined  transfer  heating  geometry was reported  is  coefficient,  rate Olson  by  coefficient. index  (f^)  the  heat  thermal diffusivity  transfer.  heating  the  Biot  The for  the  rate  index  number,  relationship  conduction  on  which  • h  (1/a  2  +  1/b  2  +  1/c ) 2  heat  in turn  between  heating  the  (1983)  the  of  0.933 f  of  Ramaswamy  and Jackson (1942):  a =  heating  (1)  is  thermal a  brick  57 where  a, b and c are one-half the brick thickness, length and width,  Analysis  of  variance  results  in Table  17 indicate  position and several interactions significantly (p<0.05) The  influence of weir height was not  A (16.58  smaller  +1.07  mean  f^  value  values  were  temperature  observed  min) than at 115°C (16.73  conditions occurred at the  at  of  extremely  the  coefficient  coefficients McCinnis  at  will  the  (1986),  high  affect  higher  using  retort  heat  temperature  transfer  fj  values.  better  a similar retort,  may  be  were  initial  present.  reported  larger  heat  for  A  heat  the  transfer  fj  product limiting  in the  surface  responsible  125°C  (1940) reported the  increased  of  heat transfer  below which, changes  Therefore,  temperature  rate indices.  temperature  and  coefficients  heat transfer coefficient exists for the transducers, transfer  a  tray  (p>0.05).  +1.17 min), suggesting  retort  tray level,  influenced heating  higher temperature. Jackson and Olson  independent when  temperature,  a significant main effect  was  respectively.  heat  transfer  difference.  coefficients  ac  water temperatures increased during heating.  Heat  transfer  experimental transfer 1  conditions  exhibited  indicating the flow  rate  uppermost significant  heights  in  between  between  Tables  poor  heat  that,  might water  with be  weir  in  trays,  very  while  levels and  to  in weir  Table  for weir  observation  lowest  sustain  an  weir  for  18b  the  three  suggests  height  2. Weir  heat height  region. x  tray  level  evidence  water  flow  through  the  did  not  identify  any  height  3  interaction  overall  for  the  data  Weir  provides  trays,  height),  adequate  distribution  height  shown  value for tray 10 than the other  1 (the  this  are  18c.  uniform  comparison. This  Temperature  deviations  18b  larger f^  height  insufficient  channels.  temperature between  transfer  tray  18a,  trays were  a significantly (p<0.05)  concern  variability  weir  conditions  had  the  indicated  water  most the  58  TABLE 17 Analysis of variance for heating rate indices  Source of Variation  df  Mean  Square  VF-Ratio  Temperature  1  1.7956  5.75 *  Weir  2  0.33532  1.07  Level  5  2.8608  9.16 *  Position  2  Interactions Temp x Weir  2  0.28676  0.92  Temp x  5  0.81050  2.60 *  2  0.84373  2.70 ns  10  1.1803  3.78 *  Weir x Position  4  0.8922  2.86 *  Level x Position  10  height  Level  Temp x Position Weir x  Level  Error ns - not significant (p>0.05) * - significant (p<0.05)  280  47.841  18.497 0.31229  ns  153.19 *  ns  59.23 *  59 widest  range  mean  fj  of f|  values  values between  may  channels caused by slower  water  be  explained  non-uniform  flow  trays occurred  rates  by  with weir  differences  in  circulation patterns  result  in smaller heat  flow  height rates  1. Differences  through  in the retort  the  in  water  car. As mentioned,  transfer coefficients  and  consequently  slower heat transfer rates.  Table studied. rate  The  indices  19  indicates  entrance  results exit  of  end  at the  most  (1986),  who  each tray during  entrance.  pipes  the  exhibited  of  f^  values  significantly  efficient  heat  among  (p<0.05)  transfer  the  tray  McGinnis  and channels  laminar sub-layer  smaller mean  was  at  the  having  in the  found  heating to  (1986)  cited  an abrupt  entrance  heat be  transfer  significantly lower  Deissler's  entrance,  region  of  coefficients  exit  region  of  to  the  middle  retort  car  compared of  the  the  entrance  most levels,  the  may  region.  In  trays, region.  create  which The  the  (1955)  and 10.  tray  entrance  flow  than values  study  in which  the  of  flow  general,  tray  least efficient  occurred  would  explain  its  conditions  level x  tray  occurred in the  producing position  in the exit  plate  better  interaction  the to  the  be less  f^  in  value  entrance  heat  in  local  may occur  mean  at the  at  measured  thickness of  smaller  the  behavior  channel was found  baffled distribution  turbulent  efficient heat transfer conditions and the  heating  measured  than in the remaining length of channel. Similar less severe conditions the  positions  by the tray exit and tray middle regions. This corresponds with  McCinnis of  variability  position  indicating  region, followed  the  transfer  suggested  end at the  entrance  positions  of all tray  and middle  positions  of  trays 1  60  Duncan's multiple range weir height 1.  Tray  TABLE 18a test comparing values associated with  Mean f  (s.d.)  h  (min)  1  (0.49)  a  5  16.42  (0.45)  a  1  16.59  (0.67)  a  3  16.60  (2.06)  a  6  16.63  (0.56)  a  10  17.51  (1.51)  b  1  (p>0.05).  TABLE 18b range test comparing fj values associated with  Tray  'Values with  Test  16.39  Duncan's multiple weir height 2.  Mean f  h <*.d.) (min)  different trays for  Duncan's Test  8  16.52  (0.58)  a  5  16.54  (0.41)  a  6  16.66  (0.80)  a  1  16.76  (1.24)  a  3  16.79  (2.09)  a  10  16.80  (0.74)  a  the same letter are not significantly different  trays for  Duncan's  8  Values with the same letter are not significantly different  different  1  (p>0.05).  61 TABLE 18c Duncan's multiple range test comparing f^ values associated with different trays weir height 3.  Tray  M e a n f|  (s.d.)  (min)  Duncan's Test  8  16.12  (0.63)  a  5  16.53  (0.37)  b  6  16.56  (0.85)  b  1  16.59  (0.58)  b  10  16.64  (0.77)  b  3  17.12  (2.20)  c  Values with the same letter are not significantly different  1  (p>0.05).  TABLE 19 Duncan's multiple range test comparing f^ values associated with different positions.  Position  Mean fj  (s.d.)  (min)  1  Duncan's Test  Entrance  16.02 (0.60)  a  Exit  16.59 (1.02)  b  Middle  17.35 (1.22)  c  Values with the same letter are not significantly different  1  (p>0.05).  tray  for  62 2. C o o l i n g  Rate Index (f )  °  c  Cooling the  cooling  rate  indices  of  efficiency within  the  the  teflon  transducers  retort car.  Stumbo  in minutes, required for the straight line portion log  cycle.  except  The  heat  concepts  energy  is  temperatures  more  temperatures.  Conversely,  are  essentially  removed.  quickly,  more  of  cooling  rates  foods  cooling  calculated to defined  f  determine  as the  time,  a cooling curve to traverse  to  exposing efficient  (1973)  identical  Faster  thus  were  those  to  of  heating  (smaller  less  time  f ) at  periods  contribute  to  be  greater  water  flow  rate  indices,  reduce  product  quality less  one  damaging  to  product  lethality.  Cooling heating  rates  rates  are  during  generally  thermal  considered  processing.  Increased  for this water system possibly could have produced Pooling  all  collected  + 0.83) values were  Analysis  of  data,  the  grand  mean  f^  smaller f  (16.65  than rates  or  equal  during  cooling  values than f^  +1.12  to  values.  min)  and  f  (16.57  20 indicate temperature,  tray  level, tray  nearly identical.  variance  results  in Table  position and several interactions significantly (p<0.05) influenced cooling rate indices. Weir height did not significantly (p>0.05) affect overall cooling rate indices.  Transducer temperature observed ±0.90  before  temperatures were the  cooling  allowed to stabilize near the experimental retort  period  was  started.  A  smaller  mean  f  value  was  at a retort temperature of 125°C (16.46 ±0.73 min) than at 115°C (16.67  min), suggesting  better  heat removal conditions occurred  at the higher temperature. C o o l i n g water temperatures were experimental  runs,  however,  the  higher  retort  temperature  when  cooling  fairly consistent may  influence  began  between cooling  63  TABLE 20 Analysis of variance for cooling rate indices (f ). c  Source of Variation  df  Mean  Square  F-Ratio  Temperature  1  3.6354  Weir  2  0.65595E-01  Level  5  4.2638  Position  2  Interactions Temp x Weir  2  0.56723E-01  Temp x Level  5  2.2977  Temp x Position  2  0.96011E-01  0.61  10  0.45089  2.88 *  Weir x Position  4  0.60125  3.85 *  Level x Position  10  9.1098  58.28 *  height  Weir x Level  Error ns - not significant (p>0.05) * - significant (p<0.05)  280  21.461  0.15632  23.26 * 0.42 ns 27.28 * 137.29 *  0.36  ns  14.70 * ns  64 water temperatures enough  Tung be  et  dependent  different possible  al. (1984a) found on  initial that  observed  to create differences in surface heat transfer coefficients.  temperature.  differences  before  diffusivity in f  thermal diffusivity  Changes  temperatures  thermal  the  in transducer  cooling  changes  values;  however,  certain  be  materials to  considered.  contributed  this  test  thermal diffusivities  should  have  of  to  possible  some  effect  caused It  may  extent  was  not  by be  t o . the  studied  in  detail.  Tables  21a, 21b and 21c show  tray levels for the three weir values  between  general, trays.  the  tray  three  Excluding  levels, weir  tray  heights. Weir  although  heights  1,  the variability of f  the  not  show  most  height  2 exhibited  as uniform  very  values  efficient  cooling  of  seems  most uniform f  the  cook  f  tray  (3).  The  increased  water  flow  rate  during  to  have  cooling  increased circulation in the middle and upper/middle trays top  and  bottom  experienced which was  interaction of  further  was the  regions.  Tray  heat removal  in contact with  same for  being on by  water  the retort  all three  suggested  most trays  1,  cooling  weir  the flow  car. The  heights.  conditions  and least efficient in the  In  were  In  between  been  in  the  tray  (10)  and  the  may  have  created  in comparison to the very  bottom in the  period.  variability  middle trays (5, 6, 8), with less efficient cooling in the very top lower  between  the  as during  similar patterns  observed  of  the  retort  shell,  range of f • values among tray  levels  most  the  tray  efficient  middle positions of  of  the  probably  retort  general,  bottom  car,  level x  in the trays  tray  entrance  position region  1 and 3 and  the  middle and exit regions of tray 10.  Table of  trays,  22 indicates  followed  by  the  cooling exit  was  most  efficient  and middle regions.  overall These  in  the  entrance  are similar to  the  region results  TABLE 21a Duncan's multiple range test comparing f values associated with different trays for weir height 1.  Mean f Tray  1  (s.d.)  c (min)  Duncan's Test  1  5  16.14  (0.62)  a  8  16.40  (0.23)  a,b  1  16.58  (0.70)  b  6  16.60  (0.51)  b  3  16.89  (1.01)  c  10  16.98  (0.89)  c  Values with the same letter are not significantly different  (p>0.05).  TABLE 21b Duncan's multiple range test comparinjg f values associated with different trays for c weir height 2.  Mean f  (s.d.)  Duncan's  Tray (min)  Test  8  16.29  (0.29)  a  5  16.33  (0.56)  a  1  16.36  (0.79)  a  6  16.43  (0.68)  a  10  16.85  (0.77)  b  3  17.08  (1.41)  b  Values with the same letter are not significantly different  1  (p>0.05).  66 TABLE 21c Duncan's multiple range test comparing f values associated with different trays weir height 3.  Mean f Tray  (s.d.)  c (min)  Duncan's Test  1  16.12  (0.84)  a  8  16.42  (0.42)  b  5  16.47  (0.50)  b  6  16.64  (0.85)  b  10  16.68  (0.77)  b  3  16.99  (1.42)  c  Values with the same letter are not significantly different  1  (p>0.05).  TABLE 22 Duncan's multiple range test comparing f values associated with different positions.  Position  Mean f  c (min)  (s.d.)  Duncan's Test  Entrance  16.11  (0.50)  a  Exit  16.60  (0.64)  b  Middle  17.00  (1.01)  c  Values with the same letter are not significantly different  1  (p>0.05).  tray  for  67 observed flow  rate of  create  heating the  uniform  position weir  for  cooling  cooling  interaction  height.  rate indices, but water,  rates  suggested  represent  compared  across that  the  the  to  heat the  length  effect  of  removal  instead. The  heating water of  the  position  trays. is  not  flow Weir the  increased  rate,  did  not  height  x  tray  same  at  each  68 3.  Heating  Lag Factor  Heating  lag  (j^)  factors  were  calculated  as  an  indication  of  effectiveness  in establishing a constant heat transfer rate and for  calculations.  These  temperature  and  extension of  the straight line portion  representing  factors, the  when  initial  beginning  of  multiplied  product  process  by  the  temperature,  the  system's  subsequent  difference locate  retort  between  the  lethality  the  intersection  retort of  the  of a heat penetration curve and a vertical line  or zero  time  (Stumbo,  1973).  Heating  lag factors  are mathematically defined as:  r  where  T  is  is the  retort temperature, T.^  is the  pseudo-initial temperature  r  and T  generally  Calculation that  the  of  the  is  point,  distribution temperatures experimental largest  The  the  within  the  between runs.  of  object  heating. The  the  of  the  pseudo-initial  effectiveness  criteria  of  Ball  Ball  and  Olson  (1957),  influenced  by  the  initial  temperature  factor  object  (Ball  and  varied  centerpoint is  being  average come-up times were  function  from  for  the of  1957). 0.7  ranged an  approximately  -  the  from  experimental  (1923). indicated  difference object;  position initial  The 5.1  who  heated  heated, and the  Olson,  temperatures  transducers  a  of  transducers temperature  by  lag  transducer  between  initial temperature  for  medium and the  transducers  Initial  difference  covered  heating  shape  is the  4 2 % come-up  strongly  heating  time.  the  extensively be  retort  come-up  Although  jj  using  could  measured  the  calculated  the  between  ih  11.6 run  for -  the  temperature  range C°  of  and  of  individual  20.8°C, being  initial  with  5.1 C ° .  18 minutes, there was variability  69 in c o m e - u p times with  respect  values  with  were  associated  specific retort  tray  faster  establishment  of  the retort car. Smaller  a constant  heating  rate  for  a  temperature.  Analysis of variance level,  to specific locations within  position  and  results in Table  several  23 indicate temperature, weir height,  interactions  significantly  (p<0.05)  influenced  tray  heating  lag factors.  A (0.625 of  larger  mean  heating  rate,  larger  the  effectiveness  since  Equation  value. The  retort  lower  would  retort  period,  24  heat the  circulation  at  a  retort  temperature  retort  shows  a  temperatures  higher  values observed  be able to establish constant  indicates  transfer  time  occurred  for  for not  heights,  weir have  thus weir  weir  rate water  x  and  produced  as to  different height been  creating  Temperature 115°C  2  the  retort  of  is deceiving  125°C  in terms  in establishing a constant  temperature  for the two  calculation. It is conceivable, even with  system was  water would weir  observed  will  generate  a  temperatures will  have  pre-heated water,  that  heat transfer conditions  sooner for a  temperature.  Table constant  of  different fj  also influenced the  time  was  ±0.107) than at 115°C (0.584 ±0.093). This difference  comparing  the  value  height the  produced the largest values.  height  was  not  the  two  shorter  fill  the  retort  for  3. As  slightly  interaction smallest  the  of  indicated j^  and  values,  begin  the  delay,  time  for  through amount  steam  of  height  weir  3  the of  injected shorter  height  weir  a  come-up  as for the  combination weir  the  longest  car as soon  while  establishing  flowing  longer  come-up  in  During  used. The  this  retort  longer  effective  heights.  height  a result to  as  weir car  each weir  returned a  3  3.  height 1  and  125°C  70  Analysis of  Source of Variation  TABLE 23 variance for heating lag factors <i >. n  df  Mean  Square  F-Ratio  Temperature  1  0.13290  Weir  2  0.37876E-01  Level  5  0.38103  392.44 *  Position  2  0.16978  174.87 *  Interactions Temp x Weir  2  0.17512E-01  18.04 *  Temp x Level  5  0.56048E-02  5.77 *  Temp x Position  2  0.67311E-02  6.93 *  Weir x  10  0.11343E-01  11.68 *  Weir x Position  4  0.15360E-02  Level x Position  10  0.25211E-01  280  0.97093E-03  height  Level  Error ns - not significant (p>0.05) * - significant (p<0.05)  136.88 * 39.01 *  1.58 ns 25.97 *  71 Tables tray  levels  25a, 25b and  for  the  three  small  values  associated  trays.  During  temperature  the  upper  interaction  tray  whereas weir  Table than of  the the  exit  26  data  regions  occurred results  which  exit  recorded  of  variability  A  gradient  of  values  is  and  tests,  retort  in the  exit  regions.  occurred  for  both the  all of  entrance  car,  the  first  to  which  Temperature experimental  10 and  the  Weir  more  height  uniform  with  values  with lower  quickly  x  in  tray  level  between  trays,  range of values.  had  the  a  significantly  come-up  changing  temperature  rose  between  apparent,  associated  temperatures  most  During  values  reflects.  position  middle and exit  tray  larger  gradient  had  definite  retort  values.  1  exposed  the  the largest j,  pattern  trays  this  positions.  of  values, whereas  upper  distribution  the  was  interaction suggested  general  2 and 3 had the widest  and  car  the  heights.  height  shows  middle  distribution  with  weir  heights  retort  weir  regions,  showed  25c show  heating  gradients  showed  period,  that  the  mean  entrance  conditions.  between slower  smaller  side  Temperature  the  entrance  temperature  and  increases  x tray position interaction indicated similar temperatures.  Tray  level  x  regions  of tray  1 produced  entrance  regions  of  trays  tray the  3 -  8  position largest exhibited  72  Duncan's heights.  TABLE 24 range test comparing values associated with  multiple  Weir  Mean  Height  (s.d.)  different weir  Duncan's Test  2  1  0.594 (0.078)  a  2  0.594 (0.093)  a  3  0.626 (0.119)  b  1  'Values with the same letter are not significantly different (p>0.05). W e i r Height 1 = 2 9 . 2 c m , 2-= 31.1 cm, 3 = 34.6 cm  2  TABLE 25a values associated with range test comparing  Duncan's multiple weir height 1.  Tray  Mean  (s.d.)  Duncan's Test  (0.037)  a  8  0.558 (0.043)  a  5  0.559 (0.045)  a  6  0.572 (0.052)  a  3  0.612 (0.076)  b  1  0.710 (0.069)  c  10  0.551  'Values with the same letter are not significantly different  different trays for  1  (p>0.05).  73 TABLE 25b range test comparing values associated with  Duncan's multiple weir height 2.  Tray  Mean  (s.d.)  Duncan's Test  10  0.513  1  (0.019)  a  8  0.543 (0.027)  b  6  0.565 (0.043)  b,c  5  0.569 (0.047)  c  3  0.630  (0.089)  d  1  0.743  (0.075)  e  Values with the same letter are not significantly different  different  (p>0.05).  trays for  74 TABLE 25c range test comparing values associated with  Duncan's multiple weir height 3.  Tray  Mean jj  (s.d.)  10  0.536 (0.018)  a  8  0.566 (0.041)  b  5  0.577 (0.043)  b  6  0.583 (0.056)  b  3  0.665 (0.098)  c  1  0.830 (0.098)  d  with the same letter are not significantly  Duncan's multiple range positions.  Position  TABLE 26 test comparing values  Mean  trays  Duncan's Test  Values  different  different  1  (p>0.05).  associated with  (s.d.)  Duncan's Test  Entrance  0.559 (0.073)  a  Middle  0.627 (0.115)  b  Exit  0.628 (0.089)  b  Values with the same letter are not significantly different  different  1  (p>0.05)  tray  for  75 4. C o o l i n g  Lag Factor  Cooling effectiveness  lag  in  (j^)  factors  establishing  calculations.  These  factors,  temperature  when  cooling  intersection the  of  the  vertical  were a  constant  when  as  and  of  the  representing  an  indication  cooling  multiplied  starts  extension  line  calculated  by  the  rate the  the  water  portion  beginning  of  the  for  difference  cooling  straight-line  and  of  retort  system's  subsequent  lethality  between  the  temperature,  of  the  locate  the  curve  and  cooling  cooling  product  (Stumbo,  1973).  Mathematically, cooling lag factors are defined as:  T =  T  where  T  is  w  transducers cooling.  the  when  The  w  cooling  -  T . p|c T. ic  values  can be  constant  rate of  cooling.  water  results  and  several  interactions  Cooling  lag  factors  were  ±0.077)  than  that a higher transducer smaller j ' value. The c  and  T . j  is  c  values  T.  is  the  pseudo-initial  are  an indication of extended  variance  125°C  temperature,  started  position  of  ( 3 )  associated with  Larger j  of  -  cooling  principles  Analysis  w  in Table  slightly  (1.428  also influenced the i calculation. 'c  for  ±0.088). This  temperature  different f  larger  at the  periods  (p<0.05) retort is  temperature  similar to  27 indicate  significantly  the  those  for  for  values.  of time in establishing a  tray level,  influenced  cooling  temperatures  of  since  for the two  tray  lag  factors.  115°C  (1.441  Equation  start of the cool will generate  values observed  the  temperature  temperature,  deceiving,  of  3  shows  a slightly  temperatures will  have  76 TABLE 27 Analysis of variance for cooling lag factors (i >. c  Source of Variation  df  Mean Square  F-Ratio  Temperature  1 •  0.14029E-01  3.99 *  Weir  2  0.10045E-01  2.86 ns  Level  5  0.72355E-01  20.59 *  Position  2  0.18146  51.64 *  Interactions Temp x Weir  2  0.54530E-01  15.52 *  Temp  x Level  5  0.32927E-01  9.37 *  Temp  x Position  2  0.46876E-02  1.33  10  0.18489E-01  5.26 *  Weir x Position  4  0.43835E-02  1.25 ns  Level x Position  10  0.29544E-01  8.41 *  280  0.35138E-02  height  Weir x  Level  Error ns - not significant (p>0.05) * - significant (p<0.05)  ns  77 Tables  28a,  28b  and  28c  indicate  between tray levels observed  for each weir  did  any  not  occur  between 3  the  upper  exhibited  initial  with  use  and lower  a mixed  part  of  of  weir  trays for weir  temperatures  general  patterns  A  slight  heights  gradient  decreased  slightly  faster  than  hot  the  x  level  interaction  values to 2 were  height  of  values  values  appeared height  tray  water,  3, whereas the  in  the  and tends showed  the  bottom to  the  sink  tray when  range  of  range for weir heights  j  1 and  equal.  entrance region  values. The positions  as  temperature channels, x  height  be greatest for weir  The  level  mixed. Weir  variability  distribution data indicated that during  density  are  j  1 and 2, whereas weir  regions. C o l d water has a greater two  of  height. Complete uniformity of j  height.  pattern. Temperature  cooling,  the  a  result  of  gradients  the  existed during  position  exhibited the largest j the smallest.  in Table  29 as having the smallest j  entrance regions will be exposed to cooling conditions before the  particularly tray  of trays is shown  the  interaction  retort  design.  between early  the part  showed  Temperature entrance  of  the  the exit  and  cooling and  distribution exit  regions  period.  middle  data  In  positions  values, while the entrance positions of trays  other  showed of  water  general, of  tray  tray 10  3 - 8 exhibited  78 TABLE 28a range test comparing j values associated with different trays for  Duncan's multiple weir height 1.  Tray  Mean j  X  (s.d.)  Duncan's Test  1  1  1.375  (0.017)  a  3  1.392  (0.048)  a;b  6  1.417  (0.056)  a,b,c  8  1.430  (0.058)  b,c,d  10  1.460  (0.038)  c,d  5  1.474  (0.094)  d  'Values with the same letter are not significantly different  (p>0.05).  TABLE 28b range test comparing j values associated with different trays for  Duncan's multiple weir height 2.  Tray  Mean j  X  (s.d.)  Duncan's Test  1  3  1.387  (0.061)  a  1  1.400  (0.037)  a,b  8  1.441  (0.063)  b,c  6  1.448  (0.044)  c  5  1.462  (0.092)  c  10  1.473  (0.053)  c  Values with the same letter are not significantly different  (p>0.05).  79 TABLE 28c range test comparing j values associated with  Duncan's multiple weir height 3.  Tray  Mean j 'c  (s.d.)  Duncan's Test  1  Values with  1  6  1.383  (0.170)  a  8  1.398  (0.144)  a,b  3  1.432  (0.061)  b,c  1  1.443  (0.029)  c  5  1.460  (0.122)  c  10  1.548  (0.067)  d  the same letter are not significantly different  Duncan's multiple positions.  (p>0.05).  TABLE 29 range test comparing j values associated with  Position  Mean i 'c  (s.d.)  Entrance  1.391  (0.056)  a  Middle  1.441  (0.094)  b  Exit  1.472  (0.091)  c  Values with the same letter are not significantly different  different tray  Duncan's Test  1  different trays for  1  (p>0.05).  80 5. C o m p a r i s o n  Pure with  With  steam  the water  temperature  of  Steam  Processing  experiments  system.  Heating  125°C. Table  calculated from the  were  pure  performed  and cooling  to  compare  heat  parameters were  transfer  efficiency  calculated for  30 compares the overall means and standard  steam experiments with  a retort deviations  the parameters calculated from  the  water experiments.  The than  for  mean heating water,  environment. transfer, Pflug steam. with  suggesting  When  changes  (1964)  higher  in  heat  this  value  water  water  flow  mean  transfer will  to  rates.  The  cooling  rate  cases, however,  the  flow rates were  The  that  because  heat  observed  mean  is  the and  heat  transfer  pure  steam  the  steam  factor  consequently  for  in f^  coefficient  heat transfer  calculated  using  limiting  water  heat values.  than  coefficients  the  approximately  pure  increased  system  7.2% smaller for  the steam experiments.  may  water cooling  the results suggest that cooling was more  efficient  water the  did not  removal  flow  past the  retort shell contained  had  system's f been  more  Water was  the the  than the retort car. At 125°C, the water signifying  efficient  transfer  surface  values  was  used for  system. C o o l i n g  steam experiments  value,  more  a smaller  fj  index  medium  the water  heat  5 . 5 % smaller for  if an increased water flow rate could be used.  procedure  with  was  coefficient  affect  have  system than the in both  transfer  and Adams (1983) found  possibly be improved  The  was approximately  heat  the  reported  Peterson  rate index  transducers  as fast  a larger volume  of  value was smaller than efficient  than  heat  input.  in  water the Water  to be more than double during the cooling period.  heating  lag  factor  was  smaller  for  water  than  for  steam  81 TABLE 30 Comparison of heating and cooling parameters calculated water immersion processes at 125°C.  Steam  Heating  Rate  Std. Rate  (min)  (min) Dev.  16.58  0.71  1.07  17.65  16.46  1.47  0.73  0.691  0.623  (min)  0.102  0.107  1.276  1.428  0.081  0.098  Factor  Mean Std.  15.71  Factor  Std. Lag  (min)  (min) Dev.  Mean  Cooling  Water  Index  Std. Lag  (min) Dev.  Mean  Heating  pure steam  Index  Mean  Cooling  using  (min) Dev.  (min)  and  82 experiments.  This  difference  is  a  reflection  of  the  difference  (water - 18 min, steam - 6 min) and the heating rates  The  mean  cooling  lag  factor  method  than  the water  cooling  rates  observed  and  cooling  rate.  Assuming  constant  smaller  values  time  frames,  j  retort  was  cooling the  method.  time cooling  indicate  smaller for  for  The  each  less  efficient  cooling when using the water immersion heating.  come-up  times  observed.  the results  method  conditions  in  were  steam  experiment  reflect to  the  turnaround  difference  establish  established from  cooling  a  within  in  constant similar  heating  into  83  C. LETHALITY DISTRIBUTION The conditions  effectiveness throughout  centerpoint  lethality  of the  were  characteristics, non-uniform uniformity retort,  throughout  in  times  by  uniform  at  transducers.  prevent  are developed  to  geometry,  various  retort  from  retort  theoretical  Normally, However, size  process since the  and  thermal  will  identify  locations  performance.  over-processing to  sterilizing  calculating  and retort variabilities.  resulting  will  providing  determined  respect  values  0  retort  was  in  food-simulating  with F  system  product  conditions a  process  car  the  standardized  sterilizing  since  for  of food  differences  water  retort  values  lethalities are a function transducers  the  in  compensate  some  Sterilizing  areas  for the worst  of the sterilizing  conditions.  Stumbo's formula method was chosen for the F for  the sterilizing  time  were  not  experimental j that  minutes, of  heating  considered  Both  c  The  of  values were  j = 1.41.  appreciable  effect  in  and cooling.  the  0  a retort  It  is  effects  of the  interesting  to  accounts come-up  note  that  very similar to the assumption of Ball's formula method,  methods  values  Sterilizing  calculations.  assume  f^  is  differences in results were found  F  calculations, which  0  calculated  temperature  of  were  equal  to  f .  For  these  reasons,  no  using Ball's method.  based  on  121.1 °C (250°F),  an arbitrary  process  an initial transducer  time  of 30  temperature  15°C (59°F) and z = 1 0 C ° (18 F°).  Analysis level,  tray  of variance  position  sterilizing conditions  and  results in Table several  in the retort.  31 indicate temperature,  interactions  significantly  (p<0.05)  weir height,  tray  influenced  the  84 TABLE 31 Analysis of variance for lethality values ( F ) calculated using Stumbo's formula method. 0  Source of Variation  df  Mean Square  F-Ratio  Temperature  1  5.4886  22.08 *  Weir  2  1.2868  5.18 *  height  Level  5  35.049  141.01  Position  2  98.043  394.43 *  Interactions Temp x Weir  2  0.09897  0.40  Temp x Level  5  0.80635  3.24 *  Temp x Position  2  0.84518  3.40 *  Weir x Level  *'  ns  10  2.5780  10.37 *  Weir x Position  4  0.71653  2.88 *  Level x Position  10  Error ns - not significant (p>0.05) * - significant (p<0.05)  280  20.951 0.24857  84.29 *  85 TABLE 32 Duncan's multiple range test comparing Stumbo's lethality values ( F ) different weir heights.  associated with  0  Weir Height  1  2  Mean F (min)  (s.d.)  0  2  Duncan's Test 1  1  9.68 (1.32)  a  3  9.71 (1.55)  a  2  9.88 (1.51)  b  Values with the same letter are not significantly different W e i r Height 1=29.2 cm, 2 = 31.1 cm, 3 = 34.6 cm  Overall  sterilizing conditions  of  115°C  F  values. This is interesting, since f^  0  better  (9.88  were  during  removal  processing  was  contribution heating  ± 1 . 4 2 min) than  better was  and  cooling  apparently  better  during  125°C (9.62  ±1.51  min) as evidenced by  at 125°C. O n  during  made  of  cooling  than  for  parameters  at  temperatures  heat transfer was  the other  calculations showed  125°C  F  retort  calculations showed  cooling to  (p>0.05).  at  hand, f  and  consequently  115°C.  calculations  0  The  a  total  seems  the  slightly heat  smaller sterilizing  contribution  of  have  slightly  to  been  the  greater using parameters obtained at the lower temperature.  Weir sterilizing between have  had  values  height  conditions weir no  influenced were  heights  the  best  1 and  using  significantly  weir  3 as Table  significant (p>0.05)  were  overall  sterilizing height  indication of the overall ability of the  2, while  affected.  mean f^, In  this  of  there  32 indicates. Weir  influence on  (p<0.05)  conditions  the was  height and j  case,  the  retort. no  was values,  Mean  difference shown  to  however,  value  is  an  retort to establish constant heating conditions.  86 Table  24 showed  condition.  that weir  Considering  heights  all parameters, weir  sterilizing conditions than weir  Non-uniform 33a,  the  particular  value  with  values  for  when 1  height  efficient at establishing this  2 provided  more  effective  overall  height 1.  sterilizing conditions  upper  weir  two  exhibited  is  height  each weir  weir  top  trays  interest  using weir  with  the  most  between  tray  levels  are  indicated  by  Tables  33b and 33c. Sterilization patterns differed somewhat between weir heights,  generally Of  1 and 2 were  tray  height trays  height,  with  the  showed  the  overall  conditions a  significantly  taller weirs. uniformity  than  lower  (p<0.05)  Considering  between  the  trays  trays.  lower  the  range  of  was  equally  F  0  F  0  good  1 and 2. Weir height x tray level interaction indicated tray  3 resulted (8  lethality  10, which  1 than  heights  higher  but  and  in  10)  the  with  poorest weir  sterilizing  heights  2  conditions  and  3  (p<0.05),  equally  while  exhibited  the  highest lethality conditions.  Table of  trays,  followed  surprising, heating. both  34 indicates sterilizing conditions  since  by  the  exit  similar patterns  Temperature  x  tray  were  observed  were  position  experimental temperatures  conditions  regions  for  and  the  observed  for  interaction  provided the  were  greatest  in  middle heat  indicated  the  regions.  transfer the  position  at  125°C.  position interaction indicated all three weir heights had the same pattern.  In general, locations with  the highest  F  0  conditions  region is  during  position  the  lowest  Weir  height  not  for  lethality x  tray  entrance/exit/middle  values appeared to have been the  entrance regions of the upper trays, with the lowest of the bottom trays.  This  entrance  similar conditions, while  middle  entrance  in the middle and exit  regions  87 TABLE 33a Duncan's multiple range test comparing Stumbo's lethality values ( F ) different trays for weir height 1. 0  Tray  Mean F (min) 0  (s.d.)  Duncan's Test 1  1  8.54  (1.07)  a  10  9.44  (0.91)  b  3  9.62  (2.38)  b,c  6  9.88  (0.68)  c  8  10.29  (0.43)  d  5  10.32  (0.65)  d  'Values with the same letter are not significantly different  (p>0.05).  TABLE 33b Duncan's multiple range test comparing Stumbo's lethality values ( F ) different trays for weir height 2. 0  Tray  Mean F (min) 0  (s.d.)  Duncan's Test 1  1  8.42  (1.46)  a  3  9.35  (2.54)  b  . 5  10.22  (0.63)  c  6  10.22  (0.98)  c  8  10.48  (0.46)  c  10.59 (0.69)  c  10  associated with  Values with the same letter are not significantly different  (p>0.05).  associated wit!  88  TABLE 33c Duncan's multiple range test comparing Stumbo's lethality values ( F ) different trays for weir height 3. 0  Tray  Mean F (min) 0  (s.d.)  Duncan's Test 1  1  8.04 (0.96)  a  3  8.85  (2.56)  b  5  9.99 (0.67)  c  6  10.11  (0.79)  c  8  10.55  (0.52)  d  10  10.70  (0.76)  d  'Values with the same letter are not  associated with  significantly different  (p>0.05).  TABLE 34 Duncan's multiple range test comparing Stumbo's lethality values ( F ) different tray positions. 0  Position  Mean F (min) 0  (s.d.)  Duncan's Test 1  Middle  8.88 (1.66)  a  Exit  9.61 (1.08)  b  Entrance  10.77 (0.84)  c  Values with the same letter are not significantly different  (p>0.05).  associated with  89 D.  RETORT  PRESSURE  The target  efficacy  retort  process.  of  pressure  This  is  pouches, where  critical  protect  the package  described  to  were  and  stability were  the  cool  period,  maintain  during  earlier, of  the  recorded difference or  were  target  evaluated 50 -  75  temperature  those  during  the  the retort  The  stability flexible  its  ability  throughout  containers,  attain  the  such  a  thermal as  retort  improve  heat  transfer  and  176.09  and  in retort height  pressure and  of  172.37  39.70  in the  kPa at  literature.  period,  1 8 - 5 0  35 summarizes  the  The  produced  125°C. retort  minutes, retort  These  pressure  and  during  pressure  data  periods.  during the cook  period was  The  minimum  kPa.  pressure  Statistical  resulted  interactions.  and  The  maximum  analysis  174.0 kPa (25.2  from  retort  results  pressure  during the  cool  mean  indicated  no  temperature,  indicate  the  system in attaining the target pressure during the cook  mean retort  kPa  1.29 kPa and coefficient of variation of 0.74% for  171.50  weir  cited cook  pressure  runs.  grand  to  is necessary to maintain compression  115°C  minutes. Table  experimental  x  retort  kPa at  consistent with  (p>0.05)  with  overpressure  101.79  grand mean retort  combined  pressure  upon  gases within the package and to  psig) with a standard deviation of the  dependent  processing  collected during the cook and c o o l  The  is  integrity.  overpressures  overpressures  system  a consistent target  non-condensible  theoretical  retort  and  on the  As  a  pressures significant  weir  height  effectiveness  of  period.  period was  171.6 kPa (24.9  psig) with a standard deviation of 1.14 kPa and coefficient of variation of 0.66% for the  combined  experimental  runs.  The  minimum  and  maximum  mean  pressures  90 recorded  were  difference or  169.36  (p>0.05)  temperature  x  and  in  173.06  retort  weir  kPa.  pressure  height  resulted  interactions.  the retort system in attaining the target  The evaluated range  using  of  the  run,  the  during  (p>0.05)  x  weir  stability  height  was  170.7  of  mean  standard  (p>0.05)  significant  A during spike  differences  weir  pressure the  cook  stability  the  weir  height  effectiveness  period.  cool  these  periods  periods  The  grand  a range  of  The  kPa.  retort  results  No  good  the  standard  0.79 -  temperature,  were  and  mean  1.07 kPa  significant  indicate  of  for  any  differences  weir  height  pressure  or  stability  or  run,  the  the  combined  during in  temperature  during  during  cool  experimental  this period pressure  x  cool  period  were  stability  weir  height  period  was  was  2.59  runs. The  kPa  minimum  150.9 and 177.2 kPa. resulted  from  retort  interactions.  These  results  acceptable  but  lower  than  period.  pressure  initial minutes  in Figure  occupying  height  significant  the  from  0.93 - 4.61 kPa for the  No  during  and  during  178.7  deviation  any  indicate  cook  significant  minimum and maximum pressures,  resulted  and maximum pressures, for  temperature,  the  during the cool  kPa with  no  temperature,  indicate  pressures.  and  interactions.  results  pressures  0.95  The  retort  the  observed  runs.  were  of  indicated  period.  grand  with a range  period  period  the cook  The  cook  pressure  temperature  maximum  experimental  this  in  and  The  during  deviation  analysis  from  pressure  stabilities  standard  the  combined  during  during  pressure  minimum  deviation for  retort  Statistical  of  drop  all cool  7. This pressure retort  of  headspace  drop  as much periods occurred  collapsed  as  as 20 kPa was and  is  when cooling  illustrated  consistently in  steam in the water  entered  the  observed  form  of  a  steam/air mixture the  retort  and  91 TABLE 35 Summary of retort pressure data duringI cook  Grand Mean Pressure (kPa) Standard Deviation  174.0  171.6  1.29  1.14  0.74  0.66  Minimum Observed  Mean (kPa)  171.50  169.36  Maximum Observed  Mean (kPa)  176.09  173.06  0.95  2.59  0.79 - 1.07  0.93 - 4.61  (kPa)  Range (kPa) Minimum Observed  Pressure (kPa)  170.7  150.9  Maximum Observed  Pressure (kPa)  178.7  177.2  water  unable  Cool  (%)  Grand Mean Standard Deviation  hot  periods.  Cook  (kPa)  Coefficient of Variation  and cool  was  to  being  shunted  compensate  and water  back  quickly  to  enough  the for  the  transfer, thus resulting in a brief  retort  system  good  through  had  totally  the  compensated for  remainder  of  the  cool  reservoir. void  but this  The  air  created  make-up  by  the  significant pressure pressure  period  drop,  as evidenced  supply  steam drop.  pressure by  the  was  collapse  Once  the  stability  was  small  range  of standard deviations.  This result With  if  pressure  the  reference  slightly  pressure to  drop  is  was  the target  potentially  to  fall  troublesome,  substantially  overpressure  below  since the  package internal  of the thermal process,  increase the retort pressure just prior to  initiating the c o o l  the pressure will not fall below the internal pouch  pressure.  damage pouch  would  pressure.  it is advisable period to  to  ensure  Cook period  92  180 175  o- o. o- o. o o- ,  S. D W  o.0o<>oo'  ° o.0.0  o-o  o °  170  165-  V)  Q_  160  155 150  15  20  25  30  35  40  45  50  55  Time (minutes)  Cool period 180-i  175O.  S. 07 Z3 V)  0)  . .o- -o-  170  165160155150  50  55  60  65  70  Time (minutes) FIGURE 7 Example pressure histories of an experimental run.  75  V. Temperature distribution  and  throughout  the  115°C  than  studies  stability cook  at  temperature  not  during  the  slight  temperature indicated  regions averaged  period  was  slightly  Variation  cook  immersion  satisfactory.  of  more  retort  indicated  Overall  favorable  weir  height  on  standard  the  the  retort  period  gradient the  based  by  readings  during  between in  quite  influenced  thermocouple  indicated  be  distributions  mean  was  water  temperature  temperature  uniformity  at a retort temperature  did  not  affect  the  of  overall  uniformity.  were  deviations  the  to  125°C.  Temperature readings  in  CONCLUSIONS  between cook  0.6  entrance and exit regions  C°  from  weir  0.19 to  regions  warmer  or  top  0.22 C ° . A  displaying and  and as  exit the  lower  regions exit  than  of  regions the  of  height.  variable  cooler  bottom  period. Very small temperature  identified  approximately  ranged  identified  entrance  retort,  temperature  deviations  water of  hottest  thermocouple Mean  standard  comparison  of  temperatures.  A  water  channels  differences were channels.  water  The  channels  regions,  of water channel 11 and the exit region  coldest  1 and  identified  also  as  2, the  of water channel  10.  Temperature during  the  cook  stability  standard  thermocouple  stability  using  during  the  retort,  except  cook  0.20  period.  C°  indicating  Temperature  the  stability  magnitude was  relatively  of  a  readings  temperature  to  better  of  of 115°C and using the tallest weir height. Mean standard deviations of 0.10  slightly  deviations  temperature  from  indicated  on  retort  ranged  period  based  temperature uniform  throughout  for water channel 11, which displayed less stable conditions.  93  increased the  94 Heat transfer studies indicated that the of  heat transfer  during  both  the  cook  and  retort  cool  temperature  periods.  influenced the  Smaller f^  and  f  rate  values,  indicating  more efficient heat transfer, were found for a retort  temperature of 125°C  than  115°C.  by  of  The  f, h  and  f  values  were  not  affected  c  variations  of  weir  7  height.  Heat depending between for  transfer on  the  uniformity weir  between  height  all trays.  Weir  height  a significantly  larger  value  used.  During indicated  the  than  which  and 8. The  during  tray  during  both  the  entrance  period,  the  slightly  height  2  uniform  occurred trays, weir  cook  more  period.  Weir  values between  uniformity within  cook  and  cool  trays varied  periods.  exit  During  were  the  uniform  between  10. Although  period  f^  values  trays,  except  weir  height  1 displayed the widest  heat  transfer  2 gave  cool  exit  and  periods. middle  positions  period, the least efficient locations were the middle and exit regions of tray 10.  depending  Smaller f^  for  locations  in  height  occurred  and  tray  cook  3  range  between  trays  was  most  uniform  f  the  in trays  trays was similar for all three weir  position of trays than at the  cook  values  height  variability  most efficient heat transfer conditions both  the  produced  fj  in  during  Generally, the most efficient cooling occurred  range of f  Heat transfer  varied  trays.  cool  values between trays.  Weir  1 showed  created the most variability between of f^ values between  trays  the  and  and  on f  the  values  middle positions.  1, 5, 6 heights.  position were  in  the  found  Generally,  at the  in the entrance positions of all trays the of  cook trays  period, 1 and  the  least  10. During  middle positions of trays  efficient the  cool  1 and 3 and  95 Heating constant  heat  values was f  r.nd  cooling  transfer  lag factors  conditions.  indicated, however,  values on  the  the  influence  unknown  lag factor calculations did  values resulted using weir establishment  An  indicated differences  of  a  heights  constant  heat  of  retort  degree  of  not  establishment  temperature  on  and  influence of variable f^  of j and  make a conclusion possible. Smaller  1 and 2 than weir  transfer  in the  rate.  Weir  height  height  3, indicating quicker did  not  influence  j  values.  A  gradient  associated with between ]'  c  trays  j|  upper were  values between  region than the  A  of  trays  not  process.  between  and  clear,  trays.  however,  there  Within trays,  of  the  was  lower  trays.  appeared  and j  to  with  smaller  values  Patterns of j  be  values were  immersion processes  indicated larger f^  values were  indicated,  better  values  uniformity  smaller in the  of  entrance  regions.  water  temperatures  Larger f  trays  larger values with  middle and exit  comparison  at similar retort  values  produced  with  values were  a pure produced  steam by  process  the  water  by the cooling method used for the steam  process.  Distribution of F conditions range with  of  F  trays,  larger  middle  tray  entrance in  trays  values  0  upper  trays,  found  between  F  0  the  occurred  resulted  while values  positions.  positions  values within the retort was variable. Non-uniform sterilizing  0  using  using weir  the were  all  height  smallest values found  Generally,  of  the  middle  middle  and  exit  at the the to  weir  2. Larger  occurred entrance  largest upper  positions  of  heights,  F  while  bottom  the  values were  0  the  position values  0  trays, the  in  F  however,  bottom than  were the trays.  at  smallest associated  trays. the  Within  exit  and  in  the  exhibited  smallest values Areas  in  the  were retort  96 showing  the  lowest  F  values  0  penetration studies on food  Retort  pressure  will  require  products for future  studies  demonstrated or weir  during  a significant  initial  cook  minutes  period,  of  the  however,  cool  period.  Once  stable  height.  the  when  performing  heat  process determinations.  that  regardless of the retort temperature the  attention  pressures  were  maintained  Stable pressures were maintained  pressure  drop  occurred  target  pressure  was  during  the  re-established,  stability was maintained for the remainder of the c o o l period.  It should thus  the  They  give  variability to  results an which  evaluate  be  noted  may not indication, might  retort  be  that these studies were apply  directly  however,  of  encountered.  performance  could  to the The be  performed in a pilot-scale  a commercial retort potential  temperature  methodologies applied  of  to  the  and  developed  assess  efficacy of a wide variety of batch-type food sterilizing systems.  retort,  same heat  transfer  in this  processing  type.  study  condition  VI. LITERATURE  Adams,  CITED  J.P. and Peterson, W.R. 1982. Recent studies in processing institutional-sized retort pouches. 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