Wood or Plastic for Cutting Boards?

Dean Cliver, a professor of food safety at the University of California, Davis, found that microwaving sponges — cellulose ones, not the natural kind — wipes out harmful bacteria. “We did soak sponges in some pretty bad things,” he said, “and one minute in the nuke and that pretty much did it.”

Dishcloths also become saturated with bacteria, although since they dry more quickly than sponges, bacteria are less likely to breed. They can be microwaved, too, or simply laundered regularly.

Professor Cliver’s other notable discovery involved cutting boards. “Somewhere along the line, wood got a bad name,” Professor Cliver said. Part of the blame, he said, must go to the rubber industry, which assailed wood cutting boards in order to promote hard rubber and plastic. In recent years, it has become conventional wisdom that plastic cutting boards are safer and easier to clean than wood cutting boards. Even the Food and Drug Administration says that plastic is less likely to harbor bacteria and easier to clean.

But in a study Professor Cliver conducted, he found that cellulose in wood absorbs bacteria but will not release it. “We’ve never been able to get the bacteria down in the wood back up on the knife to contaminate food later,” he said.

Plastic absorbs bacteria in a different way. “When a knife cuts into the plastic surface, little cracks radiate out from the cut,” Professor Cliver said. The bacteria, he said, “seem to get down in those knife cuts and they hang out. They go dormant. Drying will kill, say, 90 percent of them, but the rest could hang around for weeks.”

In one test he did, raw chicken juices were spread on samples of used wood and plastic cutting boards. Both boards were washed in hot soapy water and dried, then knives were used to simulate cutting vegetables for a salad. No bacteria appeared on the knives cut on wood, but there were plenty on the knives used on a plastic board.

Professor Cliver found that running plastic boards through the dishwasher only spread the bacteria around. The bacteria in the cracks remained. He said that the water in dishwashers must get hotter than 140 degrees or all sorts of bacteria can survive.

Wood cutting boards may be microwaved for five minutes, but Professor Cliver warned that some wood cutting boards contain metal pieces within. He added, “Some people who tried their boards in the microwave had some spectacular fireworks.” [NYTimes]