Factors Influencing Radiation Resistance of Vegetative Bacteria and Spores Associated with Radappertization of Meat

The influence of some factors involved in radappertization of meats on the radiation resistance of two isolates of Moraxella‐Acinetobacter (M‐A), Microcodes radiodurans, Escherichia coli , and Bacillus cereus spores was determined. Combinaton of subfreezing temperature and lyophilization increased the resistance of vegetative cells and showed M‐A isolates to be most resistant. Cells lyophilized in ground beef were less resistant than cells lyophilized in a commercial culture medium. A preirradiation heat treatment prior to lyophilization sensitized the cells to radiation. No appreciable difference in resistance was found with the presence of up to 8% sodium chloride during irradiation of M‐A and M. radiodurans. The radiation resistance of B. cereus spores was not affected by changes in temperature, drying, or suspending medium to the same extent as were the vegetative cells. B. cereus spores were more resistant at ambient temperature than at ‐30 ± 10°C. All these factors must be considered in assessing the magnitude of radiation resistance of various organisms, be cause there is no predictable pattern of radiation resistance.