DISINFECTION OF HOUSEHOLD CUTTING BOARDS WITH A MICROWAVE-OVEN

Used cutting boards with numerous knife marks, particularly those made of polymers, are difficult to disinfect manually. Plastic cutting boa rds have been preferred to wood because they can be washed in dishwash ers and used in microwave ovens. Our study tested the microwave oven f or disinfection of cutting boards. Surfaces of plastic and wooden cutt ing boards were inoculated with up to 10(9) CFU of Escherichia coli or other bacteria in broth culture and later sampled by contact with aga r medium for CFU assay or by swabbing for ATP bioluminescence assay. O n wood, almost total elimination of vegetative cells occurred with exp osure times of the 3 to 4 min at a high setting on typical 450 to 600 g wooden boards, depending on board size, bacterial load, and moisture level. On plastic, microwave energy had almost no lethal effect on ba cteria: 12 min of exposure did not reduce the number of bacteria signi ficantly. Increased moisture (wetness) enhanced killing efficiency on wood, but was negligible on plastic. Temperatures near the wood surfac e reached 95 degrees C within the first 4 min, whereas plastic surface s reached no more than 40 degrees C. Our study indicates that brief '' cooking'' of wooden boards at a ''high'' setting in a microwave oven i s an effective way to kill bacteria, and thus a very simple and cheap method to protect food against cross-contaminating pathogens. Because plastic is relatively inert to microwaves, disinfection of plastic boa rds in a microwave oven is impractical.