EVERY now and then a scientific finding flies in the face of conventional wisdom. And so it was with an accidental discovery by microbiologists at the University of Wisconsin's Food Research Institute that wooden cutting boards kill food-poisoning bacteria that survive very nicely on the plastic boards that have been widely promoted for years as safer than wood.

The scientists, Dean O. Cliver and Nese O. Ak, stumbled upon the finding while seeking ways to decontaminate wooden boards and make them as "safe" as plastic. Much to their surprise, they found that when boards were purposely contaminated with organisms like Salmonella, Listeria and Escherichia coli that are common causes of food poisoning, 99.9 percent of the bacteria died off within three minutes on the wooden boards, while none died on the plastic ones.

When contaminated boards were left unwashed overnight at room temperature, bacterial counts increased on the plastic, but none of the organisms could be recovered from the wooden boards the next morning.

It had long been believed that disease-causing bacteria from raw foods like chicken would soak into a wooden board and be difficult to remove, even when washed; then when other foods, like salad ingredients, that are eaten raw are cut on the same board, the dangerous bacteria could be picked up by them and transferred alive to the consumer. Plastic was assumed to be safer because it is nonporous and contaminating organisms could be readily washed off. A Word for Safety