Influence of Microwave Radiation on Psychrotrophic Bacteria1

Abstract

Pure cultures of bacteria in nutrient broth at 107 or 108 organisms/ml and various raw meat products were exposed to either 915 or 2450 MHz microwaves. After various timed exposures, temperature increases were noted and samples were removed for plate-count determination of survivors. In nutrient broth, all psychrotrophic bacteria counts were dramatically reduced by short exposure (5 to 20 sec) to microwave radiation. In some instances, initial counts of 107 to 108/ml were reduced to zero after 15 sec of microwave exposure and a temperature of 60 C. Moraxella-acinetobacter (MA-3), Serratia marcescens, Pseudomonas synthaxa, and Alcaligenes viscolactis were extremely susceptible to the microwave treatments. When raw poultry parts, with initial total counts of 104/cm2 of surface area, were exposed to microwave radiation, organisms were reduced by 1 log cycle in 20 sec and by 2 log cycles in 40 sec. Total counts on microwave-treated chicken skin were reduced from 105/cm2 to 103/cm2 in 30 sec. Refrigerated storage of microwave-treated chicken parts indicated that such treatment could substantially increase shelf life.