Wood vs. Plastic
Reprinted with permission from the September/October 2004 issue of Cook's Illustrated magazine.
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Kitchen Science: The Truth about Cutting Boards and Bacteria
The Bac StoryIn 1994, a research report was published that proved to be the opening salvo in a long battle over which material was more sanitary for cutting boards, wood or plastic. The researchers found that fewer bacteria could be recovered from wooden boards infected with live cultures than from plastic boards treated the same way. These results caused the researchers to question the prevailing view that plastic was more sanitary than wood; some have further interpreted the data to mean that wood is, in fact, a safer material for cutting boards. In a report that followed, researchers at a U.S. Department of Agriculture (USDA) lab have concluded that beef bacteria on polyethylene and wooden cutting boards had statistically similar patterns of attachment and removal. Even so, the idea that wood is more sanitary than plastic persists and was recently reaffirmed in the food section of the New York Times.
So What's on Your Cutting Board?We wanted to get our own perspective on the problem, so we asked four staff members to donate their used boards, two wooden and two-plastic. We found very little bacteria growing on these boards when we sampled them, so we took the boards to a local lab to have them artificially inoculated with bacteria. The procedure worked as follows: A drop of the medium containing millions of bacteria was placed on the boards, the boards were left to sit for 40 minutes to allow for absorption of the bacteria, and an attempt was then made to remove the bacteria. In repeated tests, between 6.0 percent and 8.1 percent of the bacteria were recovered from the plastic and between 1.3 percent and 6.2 percent from the wood. Given that the number of bacteria recovered from each type of board was well into the hundreds of thousands, there was little to assure us that one material was much safer that the other.
Soap and Water to the RescueScrubbing the boards with hot soapy water was a different story, Once the contaminated boards had been cleaned, we recovered an average of 0.00015 percent from the plastic and 0.00037 percent from the wood - or fewer than 100 bacteria from each board. In a related test, we were able to transfer bacteria from contaminated, unwashed boards made from both wood and plastic to petri dishes using potatoes and onions. But our most surprising discovery by far was that the bacteria could persist on unwashed boards of both types for up to 60 hours!
What then, is the truth about cutting boards? Both plastic and wooden boards can hold on to bacteria for long periods of time. Both plastic and wooden boards allow for transference of bacteria to other foods. Luckily: we found that scrubbing with hot soapy water was an effective (though not perfect) way of cleaning both kinds of bonds: the USDA also recommends the regular application of a solution of 1 teaspoon bleach per quart of water. Simply put, maintenance, not material, provides the greatest margin of safety.
-John Olson. Science Editor