Rice Microbial Community Responses to 915 MHz Microwave Heating

ABSTRACT. The objective of this study was to investigate the impact of microwaves set at the 915 MHz frequency on inactivation of harmful microbes across rice beds of different thicknesses, during microwave (MW) drying. Medium-grain rough rice at initial moisture content of 23% wet basis was dried using a MW dryer set to transmit energy at power levels 5, 10, and 15 kW for 4, 6, and 8 minutes and for rice bed thicknesses at 5, 10 and 15 cm. Increasing MW specific energy from zero (control) to 900 kJ/kg-grain resulted in statistically significant decreases in rice microbial loads. At the highest specific energy the reduction of the aerobic bacterial and aflatoxigenic fungal loads was 4.56 and 2.93 Log colony forming units, respectively; virtually no statistically significant disparity of A. flavus mold count was observed across the entire rice bed of up to 15 cm thickness.