ENGINEERING RESEARCH INSTITUTE THE UNIVERSITY OF MICHIGAN ANN ARBOR Progress Report No. 1 DETERMINATION OF RADIATION STERILIZATION DOSE FOR CANNED MEAN Lo Lo Kemp.e Jo To Graikoski Project 2681 QUARTERMASTER RESEARCH AND DEVELOPMENT COMMAND NATICK, MASSACHUSETTS CONTRACT NO. DA-19-129-qm-964 October 1957

CONTRACT RESEARCH PROJECT REPORT QUARTERMASTER FOOD AND CONTAINER INSTITUTE FOR THE ARMED FORCES, CHICAGO Hq, QM Research and Development Command, QM Research and Development Center, Natick, Mass. The University of Michigan Engineering Research Institute Ann Arbor, Michigan Official Investigator: Lloyd L. Kempe Collaborator: Jo To Graikoski Project No. 7-84-01-002 Contract No. DA-19-129-qm-964 File No, S-510 Report Noo 1 (Progress) Period 1 August 1957 to 1 October 1957 Initiation Date: 1 August 1957 Title of Contract: Determination of Radiation Sterilization Dose for Canned Meat SUMMARY Combined irradiation-heat sterilization dosages have been determined for canned green peas inoculated- with 300 PA-5679 spores per can. A marked reduction of the Fo value required for sterilizing canned green peas followed even very light dosages of gamma radiation, For example, following 0.6 megarad, an Fo of less than 1 was sufficient, but without irradiation, an Fo between 4,1 and 4,9 was necessary under these conditions. Since these results appear encouraging, additional studies are being carried out using C, botulinum 213B inoculao Preparations are being made to determine the true radiationsterilization dose for canned meats and the combined irradiation-heat processing treatments needed for canned pork luncheon meat. THIS IS NOT A FINAL REPORT, CONCLUSIONS STATED ARE SUBJECT TO CHANGE ON THE BASIS OF ADDITIONAL EVIDENCEo THIS INFORMATION IS NOT TO BE PUBLISHED WITHOUT WRITTEN PERMISSION FROM HQ, QM R AND D COMMAND, NATICK, MASS. 1

PHASE Io EFFECT OF PREIRRADIATION OF CANNED GREEN PEAS ON THE Fo SUBSEQUENTLY REQUIRED FOR STERILIZATION Combined irradiation-heat processing may be conceivably applied to other foods than meat. The logically expected benefits would follow from possible lessened texture damage, etc., that could result from the reduced heating involved. With this in mind, canned peas were selected for study. MATERIALS AND METHODS Frozen green peas were obtained in 2-1/2-lb boxes from the stock supply of The University of Michigan Food Service. These peas carried the label of the Frost Queen Packing Co. of Tacoma, Washington. The packages indicated that the peas contained a "slight amount" of added salt. In preparation for a run, 15 lb of the frozen peas were placed in a stock pot and then were covered with a brine containing 1.8% sodium chloride and 2o2% sucrose, This brine has previously been described for peas by Reed et al.1 The stock pot was then placed in a boiling water bath for about 1-1/2 hr during which time the frozen peas melted and were brought to a temperature of 205~F. No. 1 Picnic tin cans were filled with these peas; care was taken to cover the peas with brine. Covers were then placed loosely on the cans and these were set in an autoclave whiclh was kept filled with flowing steam. After the cans had been exhausted for a few minutes in the flowing steam, individual cans were removed from the autoclave, inoculated with one ml of a spore suspension, sealed in a commercial-type closing machine, dumped into cold, running water for 20 minutes, and then refrigerated until they were either irradiated, heat-processed, or incubated as required. Irradiation was carried out in the center well of the large Cobalt-60 souce at The University of Michigano Since these cans were irradiated during the summer, they were covered with dry ice to deep them cold during irradiation. Irradiation, dosimetry, heat processing, and incubation were carried out in the same way as previously described for canned meat.2 However, the data are reported in megarad rather than megarep as directed.3 2

RESULTS Data from runs CP-1 through CP-6 are shown in the table belowo An inoculum of 300 PA-3679 spores per can was used. These data are summarized in the figure. Fo Values Required to Sterilize Canned Green Peas Packed in No. 1 Picnic Tin Cans, Inoculated with 300 PA-3679 Spores Per Can, and Irradiated with Gamma Rays from Cobalt-60 Before Heat Processing at 230~F and Incubated at 85P'F- Run No. CP-1 Can Size Product Inoculum Irradiation Processing Temperature Incubation Temperature -No. 1 Picnic (211 x 400) -Green Peas -300 PA-3679 spores per can -None -230~F -85~F Fo Can No. Days to Gas Formation Inoculated Control s 1 3 2 3 Noninoctilated.'Controls 3 4 4 4 Can 1, 3.25 5 Can 2, 3525 6 Can 3, 3.25 7 8 7 Can 1, 4.11 9 Can 2, 4.11 10 6 Can 3, 4.11 11 12 Can 1, 4.91 13 Can 2, 4.91 14 - 15 16 3

Run No. CP-1 (Concluded) Fo Can No. Days to Gas Formation Can 1, 5-97 Can 2, 5.97 Can 1, 6.95 Can 2, 6.95 Can 1, 8.50 Can 2, 8.50 *Can 1, 2.20 Can 2, 2,20 17 18 19 20 21 22 253 24 25 26 27 28 29 350 31 352 5 4 5 4 5 5 Can Can Can 1, 2.95 2, 2.95 3i 2. 95 33 34 35 36 Conclusion: Under these conditions canned green peas were sterilized by an Fo between 4.1 and 4.9. * Cans 29 through 56 were packed and processed as part of run CP-6. 4

Run CP-2 -- Can Size Product Inoculum Irradiation Processing Temperature Incubation Temperature -No. 1 Picnic (211 > -Green Peas -300 PA-3679 spores -As Indicated -Not Heat- Processed -85~F! 400) s per can Megarad Can No. Days to Gas Formation Inoculated Controls Noninoculated Controls 1.502 1.770 2.05 2.42 1 2 3 4 5 6 7 8 5 6 7 4 3 3 4 8 9 10 11 12 15 14 15 16 17 18 19 20 Conclusion.: Under these conditions, canned green peas were sterilized by between 1.77 and 2.05 megarad of Cobalt-60 gamma radiation. 5

Run CP-3 - Can Size Product Inoculum Irradiation Processing Temperature Incubation Temperature -No. 1 Picnic (211 x 400) -Green Peas -300 PA-5679 spores per can -0o465 Megarad -230~F -85~F Fo Can No. Days to Gas Formation Inoculated Controls 1 2 2 2 Noninoculated Controls 3 4 2 9 Can Can Can Can Can Can 1, 6.00 2, 6.00 3, 6.oo 1, 4.6o 2,' 4.6o 3, 4.60 5 6 7 8 9 10 11 12 Can 1, 3.40 Can 2, 35.40 13 14 15 16 Can Can Can 1,. 2.25 2, 2.25 35, 2.25 17 18 19 20 Can 1, Can 2, Can 31 Can 1, Can 2, Can 35, 1.39 1.539 1.39 0.74 0.74 0.74 25 26 27 28 8 20 m *29 *30 *51 *32 Conclusion: Following 0.465'megarad of gamma radiation, from Cobalt-60o canned green peas were sterilized by an F0 between 1.39 and 2.25. * Processing temperature reached 23540F 6

Run CP-4 -- Can Size Product Inoculum Irradiation Processing Temperature Incubation Temperature -No. 1 Picnic (211x 400) -Green Peas -300 PA-3679 spores per can -0.930 megarad -230~F -85~F F0 Can No. Days to Gas Formation 0.... Noninoculated Controls Inoculated Controls 1 2 3 4 5 6 7 3 3 3 4 2 2 2 Can 1, Can 2, Can 3, 0.69 0.69 0o69 8 9 10 11 Can Can Can Can Can Can 1, 1.44 2, 1.44 3, 1.44 1, 0.25 2, 0.25 3, 0.25 12 13 14 15 16 17 18 19 4 I0 Can 1, Can 2, Can 3, 0.49 0,49 0.49 20 21 22 23 Can Can Can 1,. 014 2. 0.14 3, O.14 24 25 26 27 Conclusion: Following Oo930megarad of gamma radiation from Cobalt-60, canned green peas were sterilized by an Fo between 0.25 and 0.49 7

Run CP-5 -- Can Size Product Inoculum Irradiation Processing Temperature Incubation Temperature -No. 1 Picnic (211 x 400) -Green Peas -300 PA-3679 spores per can -Oo697 megarad -230~F -85~F Fo Can No. Days to Gas Formation..,, Noninoculated Controls Inoculated Controls 1 2 3 4 5 6 7 6 6 4 3 3 3 5 Can Can Can 1, 1.10 2, 1.10 35, 1.10 8 9 10 11 Can 1, Can 2, Can 53 0.69 0.69 0.69 12 15 14 15 Can Can Can 1, 0.33 2, 03355 3, 0533 16 17 18 19 4 6 6 6 6 Can 1, 0.18 Can 2, 0.18 20 21 22 25 Conclusiono Following 0.697 megarad of gamma radiation from Cobalt-60, canned green peas were sterilized by an Fo between 0.33 and 0.69..... _..... -............. r. ~,.0 8

Run CP-6 - Can Size Product Inoculum Irradiation Processing Temperature Incubation Temperature -No. 1 Picnic (211 x 400) -Green Peas -300 PA-3679 spores per can -0.279 megarad -230oF -85 ~F Fo Can No. Days to Gas Formation Noninoculated Controls Inoculated Controls 1 2 3 4 5 6 7 8 3 23 6 3 3 6 7 Can 1, Can 2, 3.16 3.16 9 10 11 12 Can Can Can 1, 0.77 2, 0.77 3, 0.77 13 14 15 16 Can 1, 1.47 Can 2, 1.47 17 18 19 20 4 4 4 4 5 4 4 5 5 Can Can Can 1, 2.19 2, 219 3, 2.19 21 22 23 24 Conclusion: Following 00279 megarad of gamma radiation from Cobalt-60, canned peas were sterilized by an Fo between 2.2 and 3.2. 9

6r C C C C C C C) w z i? C oj 4 - - 300 Spores PA-3679 3 1 _ Green Peas 2 I.I ).9 ).8 ).7 ).6 ).5 ).4 ).2 )8 37 )6 35 )4 32 Radiation 3~01 _ ~only 0 - C 0.( O.C 0.( O.C 0.( O.C O.(.O.C 0.( 0.( 0 1.0 MEGARAD 2.0 3.0 Fo required to sterilize green peas packed in No. 1 Picnic tin cans, inoculated with 300 PA-3679 spores per can, and irradiated with gamma rays from Cobalt-60 before heat processing at 230~F and incubation at 85~F. 10

A marked reduction in the F value required for sterilizing canned green peas followed even light dosages of gamma radiation. Thus, following 0.6 megarad, the Fo.value required was reduced to less than 1. Furthermore, no radiation "induction" dosage was noted in canned peas as had been.previously found in canned meat,2 The heat resistance of the spores of PA-3679 was less in this canned pea medium than we have previously reported for canned meat 2 However, the radiation resistance was apparantly unaffected since approximately 1.9 megarad was required in both instances for a 300 PA-3679spores-per-can inoculum DISCUSSION The fact that no "induction" radiation dosage was necessary before the effect on reduction of the Fo value subsequently required for sterilization of canned peas began, has both practical and theoretical significance. From a possible utilization standpoint, the fact that less than 0.6 megarad is sufficient to reduce the Fo required to less than 1 is significant since Morgan has reported that peas withstand much higher dosages than 0.6 megarad without noticeable radiation damage. Furthermore, it is generally recognized that reduced heat processing produces better canned products. PHASE II DETERMINATION OF RADIATION STERILIZATION DOSE FOR CANNED MEAT Preparations are being made to conduct this work. Since, in our source, the radiation times must necessarily be extended to about 2 days for these experiments, it is considered best to carry them out next winter when the cave in which our Cobalt-60 is housed will be at a temperature of about 10~F. Specificially, we are doing the following at present 1) Accumulating Clostridium botulinum 213B spores. 2:) Designing, fabricating, and studying dosimetry patterns ina carrier for mushroom-type cans containing meat. 11

3) Arranging with the American Can Coo to provide a seaming chuck for the vacuum-type-can closing machine which they have loaned The University of Michigan for these purposes PHASE III DETERMINATION OF THE COMBINED IRRADIATIONHEAT PROCESSING TREATMENTS REQUIRED TO STERILIZE CURED MEAT PRODUCTS Arrangements have been made through Dro W. M. Urbain of Swift and Coo to furnish us "Savortite" Pure Pork Luncheon Meats for these studies. When the meat arrives, which should be relatively soon, we plan to carry out these studies immediatelyo 12

BIBLIOGRAPHY lo Reed, Jo M0, Bohrer, Co Wo, and Cameron, E. Jo, "Spore destruction rate studies on organisms of significance in the processing of canned foods," Food Research, 16 (1951), 383408o 2o Kempe, LoLo, et al., "Final Report, Combined Use of Radiation Treatment for Sterilization of Foods, June 7, 1955 to July 31, 1957," QMC, R and D Command, Contract DA-19-129-qm-388, Project 7-48-01-002. 35 Donald, George Eo, Lto Colo, Cm Ic; Letter QGCAL-SDRP, Adoption of Rad by Radiation Preservation of Foods Project, May, 1957. 4. Morgan, Bo Lo, Letter, Approximate Levels of Radiation Before Foods are Negatively Affected, 24 June 1957. 5o "A New Principle for Agitating in Processing of Canned Foods," Bulletin No. 20, The Research Department of Continental Can CoO,Inc., 1950.