EFFECT OF MICROWAVE-RADIATION ON INACTIVATION OF CLOSTRIDIUM-SPOROGENES (PA-3679) SPORES

Three techniques for studying effects of microwave radiation on microo rganisms were introduced. Spores of Clostridium sporogenes (PA 3679) w ere chosen as a test organism because the kinetic parameters for therm al inactivation are well known and because of the importance of the ge nus Clostridium to the food industry. For the first technique, a speci ally designed kinetics vessel was used to compare inactivation rates o f microwave-heated and conventionally heated spores at steady-state te mperatures of 90, 100, and 110 degrees C. Rates were found to be simil ar at the 95% confidence level. The second and third techniques were d esigned to study the effect of relatively high power microwave exposur e at sublethal temperatures. In the second approach, the suspension wa s continuously cooled via direct contact with a copper cooling coil in a well-mixed vessel, outside the microwave oven. The suspension was p umped through a Teflon loop in the oven, where it continuously absorbe d approximately 400 W of microwave power. Inactivation occurred in bot h irradiated and unirradiated samples. It was suspected that copper io ns entered the suspension from the copper coil and were toxic to the s pores. The fact that the results were similar, however, implied the ab sence of nonthermal microwave effects. In the third approach, the copp er coil was replaced with a silicone tubing loop in a microwave transp arent vessel. The suspension was continuously irradiated at 150 W of m icrowave power. No detectable inactivation occurred. Results indicated that the effect of microwave energy on viability of spores was indist inguishable from the effect of conventional heating.