September 19, 2007 - Microwave sponges to kill bacteria, mold

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If you want a clean kitchen sponge, ditch the bleach and nuke it.

The federal government says testing has found that the best bets for killing the harmful bacteria, yeast and molds that can inhabit kitchen sponges are to use the microwave and dishwater. 

Government food safety experts tested common suggestions for cleaning sponges, including microwaving them, running them through the dishwasher, soaking them in a 10 percent bleach solution and soaking them in lemon juice.

To test the effectiveness of each method, sponges were soaked for 48 hours at room temperature in a mixture of raw ground beef and laboratory compounds that encourage the growth of pathogens.

Both microwaving the sponges for 1 minute on high and running them through a full dishwasher cycle (including drying) killed nearly
100 percent of the bacteria, mold and yeast.

Soaking in a bleach solution killed just 90 percent, and lemon juice only knocked out 70 percent, both well below what's considered effective.

One safety caveat -- only wet sponges should be microwaved; dry sponges can catch fire.