Microwave Pasteurization of Starchy Foods

Abstract

The effect of microwave heating on pasteurization of rice cake, bread, rice ball and chinese noodle was studied. The internal temperature during microwave heating was determined with chromel-alumel thermocouple, and the surface temperature was measured with thermolabels. A polyvinylidene chloride wrap made the surface temperature uniform. Propagation of mold in rice cake, bread, rice ball and chinese noodle during storage at 30°C for 20 days could be inhibited by the microwave heating for 20-40s. The temperatures of samples reached 50-90°C after the heating. The rate of decrease in weight of samples during microwave heating was below 2.0%. A polyvinylidene chloride wrap repressed the decrease in weight, and prevented the contraction and deformation of the samples. Escherichia coli inoculated into bread, rice ball and chinese noodle could be completely destroyed by the microwave heating for 20-40s. E. coli was, however, recovered even after the microwave heating for 40s when inoculated into rice cake. A polyvinylidene chloride wrap slightly increased the effect of microwave heating on the destruction of E. coli inoculated into rice ball.