ENGINEERING RESEARCH INSTITUTE THE UNIVERSITY OF MICHIGAN ANN ARBOR Progress Report No, 6 COMBINED USE OF HEAT AND RADIATION TREATMENT FOR STERILIZATION OF FOODS Period 7 April 1956 to 7 June 1956 Lloyd IL. Kempe Official- Investigator J.'T.- Graikoski Nancy J. Williams Peter F. Bonventre Collaborators Project 2391 QUARTERMASTER RESEARCH AND DEVELOPMENT COMMAND NATICK, MASSACHUSETTS CONTRACT NO. DA-19-129-qm-388, PROJECT NO. 7-84-01-002 August 1956

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 Collaborators: J. T. Graikoski Nancy J. Williams Peter F. Bonventre Project No. 7-84-01-002 Contract DA-19-129-qm-388 File No. S-510 Report No. 6 (Progress) Period 7 April 1956 to 7 June 1956 Initiation Date: 7 June 1955 Title of Contract: Combined Use of Heat and Radiation Treatment for Sterilization of Foods Studies for this project. which will be the have continued in the three areas of research required Complete data will be presented in the next report final one for the contract. I. EVALUATION OF CONSECUTIVE IRRADIATION AND HEAT PROCESSING FOR STERILIZING CANNED MEAT The combined irradiation and heat processing treatment required to sterilize canned ground beef has been extended to cover packs in No. 1 picnic tin cans inoculated with approximately 300 C. botulinum 2135B spores per can. As was found at the higher concentration of 5,000,000 C. botulinum 213B spores per can, an induction level of gamma radiation is required THIS IS NOT A FINAL REPORT. CONCLUSIONS STATED ARE SUBJECT TO "CHANGE ON THE BASIS OF ADDITIONAL EVIDENCE. THIS INFORMATION IS NOT TO BE PUBLISHED WITHOUT WRITTEN PERMISSION FROM HQ, QM R AND D COMMAND, NATICK, MASS. 1

before the combined process shows advantage. Thus it was found that the Fo required for sterilization at the 300 spore per can level was approximately 0.4 without preirradiation and was still 0.4 after irradiation with 0.5 megarep. However, following one megarep, the heat sterilization treatment required dropped to an Fo of 0.15. Irradiation alone required between 1.64 and 1.8 megarep of gamma radiation to produce sterility at the 300 C. botulinum 213B spores concentration level. Work is being initiated on inoculated packs containing PA 3679 spores. II. EFFECT OF CHEMICALS IN THE SUSPENDING MEDIUM ON THE LETHALITY OF GAMMA RADIATION FOR ANAEROBIC BACTERIAL SPORES This study has been extended to include a mixture of glutathione and sodium hydrosulfite, and different oxygen level concentrations in the gaseous environment above the suspending liquid. Tests with other chemicals are planned for June and July. For example, certain mercury compounds appeared to offer protection to anaerobic bacterial spores during irradiation. It has been found that: 1o Sodium hydrosulfite was as effective alone as was a mixture of glutathione and sodium hydrosulfite in protecting C.botulinum 213B spores against the lethal effects of gamma radiations. 2. Addition of these chemicals to previously irradiated spore suspensions did not offer ant protection. This indicates that these chemicals must be present during irradiation to be effective in protecting the spores against irradiation damage. 3. An oxygen atmosphere removed the protective effect of glutathione, but did not materially affect the protective activity of sodium hydrosulfite. 4. When irradiation was carried out in phosphate buffer, oxygen decreased the number of survivors while nitrogen increased them when the results were compared to irradiation in an air atmosphere, 2

III. EFFECT OF TEMPERATURE OF THE SUSPENDING MEDIUM ON THE LETHALITY OF GAMMA RADIATION FOR ANAEROBIC BACTERIAL SPORES Work on this phase of the project has largely been concerned with confirming data previously reported in order that the results can be published. Two papers are in preparation. The first deals with the effect of temperatures up to about 85~C during irradiation on the lethality of gamma irradiation for anaerobic bacterial spores. The second describes the critical temperature of approximately 85~ C which must be attained for either irradiated or unirradiated spores before appreciable heat kilTing occurs. However, once the critical temperature is attained irradiated spores die much more rapidly than do unirradiated spores. Also, the rate of death is a function of the degree of preirradiation. Data are being accumulated for temperatures above 85~C during irradiation. This work is difficult to carry on but the limited data so far obtained indicate that the combined heat and irradiation effect is obtained when these two energy forms are used simultaneously as well as when heat processing follows irradiation of the spores after a time interval of some hours. A final report covering the project will be prepared as of July 31. 3