1. After use, hand-wash the cutting board in warm soapy water, rinse it clean, and wipe it dry. NEVER put it in a dishwasher or let it soak in water.

2. At least every three months or whenever the wood looks dry, reapply a protective oil finish, such as mineral oil, to prevent water from penetrating and damaging the wood.

3. When the cutting surface becomes heavily scored, sand it with a random-orbit sander, starting with 100-grit and progressing to 180-grit, and 220 grit sandpaper. Then reapply the finish. 

Dean O. Cliver, Ph.D

We began our research comparing plastic and wooden cutting boards after the U.S. Department of Agriculture

told us they had no scientific evidence to support their recommendation that plastic, rather than wooden cutting

boards be used in home kitchens. Then and since, the U.S. Department of Agriculture’s Meat and Poultry

Inspection Manual (official regulations) and the U.S. Food and Drug Administration’s 1999 Food Code (recommended

regulations for restaurants and retail food sales in the various states of the U.S.) permit use of cutting

boards made of maple or similar close-grained hardwood. They do not specifically authorize acceptable plastic

materials, nor do they specify how plastic surfaces must be maintained.

Our research was first intended to develop means of disinfecting wooden cutting surfaces at home, so that they

would be almost as safe as plastics. Our safety concern was that bacteria such as Escherichia Coli O157:H7

and Salmonella, which might contaminate a work surface when raw meat was being prepared, ought not remain

on the surface to contaminate other foods that might be eaten without further cooking. We soon found that

disease bacteria such as these were not recoverable from wooden surfaces in a short time after they were applied,

unless very large numbers were used. New plastic surfaces allowed the bacteria to persist, but were easily

cleaned and disinfected. However, wooden boards that had been used and had many knife cuts acted almost

the same as new wood, where as plastic surfaces that were knife-scarred were impossible to clean and disinfect

manually, especially when food residues such as chicken fat were present. Scanning electron micrographs

revealed highly significant damage to plastic surfaces from knife cuts.

Although the bacteria that have disappeared from the wood surfaces are found alive inside the wood for some

time after application, they evidently do not multiply, and they gradually die. They can be detected only by splitting

or gouging the wood or by forcing water completely through from one surface to the other. If a sharp knife is

used to cut into the work surfaces after used plastic, or wood has been contaminated with bacteria and cleaned

manually, more bacteria are recovered from a used plastic surface than from a used wood surface.

“Manual cleaning” in our experiments has been done with a sponge, hot tap water, and liquid dish washing detergent.

Mechanical cleaning with a dish washing machine can be done successfully with plastic surfaces (even

if knife-scarred) and wooden boards especially made for this. Wooden boards , but not plastics, that are small

enough to fit into a microwave oven can be disinfected rapidly, but care must be used to prevent overheating.

Work surfaces that have been cleaned can be disinfected with bleach (sodium hypochlorite) solutions; this disinfection

is reliable only if cleaning has been done successfully.

The experiments described have been conducted with more than 10 species of hardwoods and with 4 plastic

polymers, as well as hard rubber. Because we found essentially no differences among the tested wood species,

not all combinations of bacteria and wood were tested, nor were all combinations of bacteria and plastics or

hard rubber. Bacteria tested, in addition to those named above, include Campylobacter jejuni, Listeria monocytogenes,

and Staphylococcus aureus. We believe that the experiments were designed to be properly representative

of conditions in a home kitchen. They may or may not be applicable to other plastic and wooden food

contact surfaces or to cutting boards in commercial food processing or foodservice operations, but we have

no reason to believe that they are not relevant, except that not all plastic surfaces are subject to knife-scarring.

Before our first studies had been published, they were criticized incorrectly for not having included used

(knife-scarred) cutting surfaces. We had been careful to include used surfaces, and so were surprised that

others who did later experiments and claimed to have refuted our findings often had used only new plastic and

wood. Although some established scientific laboratories say their results differ from ours, we have received

multiple communications form school children who have done science projects that have reached essentially the

same conclusions that we did.

We have no commercial relationship to any company making cutting boards or other food preparation utensils.

We have tested boards and cleaning and disinfection products, some of which were supplied to us gratis. We

have not tested all of the products that have been sent to us, simply because there is no time. We are aware

that there are other food preparation surfaces made of glass or of stainless steel; we have done very little with

these because they are quite destructive of the sharp cutting edges of knives, and therefore introduce another

class of hazard to the kitchen. We believe, on the basis of our published and to-be-published research,

that food can be prepared safely on wooden cutting surfaces and that plastic cutting surfaces present

some disadvantages that had been overlooked until we found them.

In addition to our laboratory research on this subject, we learned after arriving in California in June of 1995 that

a case-control study of sporadic salmonellosis had been done in this region and included cutting boards among

many risk factors assessed (Kass, P.H., et al., Disease determinates of sporadic salmonellosis in four northern

California counties: a case control study of older children and adults. Ann. Epidemiol. 2:683-696, 1992.). The

project had been conducted before our work began. It revealed that those using wooden cutting boards in their

home kitchens were less than half as likely as average to contract salmonellosis (odds ratio 0.42, 95% confidence

interval 0.22-0.81), those using synthetic (plastic or glass) cutting boards were about twice as likely as

average to contract salmonellosis (O.R. 1.99, C.I. 1.03-3.85); and the effect of cleaning the board regularly after

preparing meat on it was not statistically significant (O.R. 1.20, C.I. 0.54-2.68). We know of no similar research

that has been done anywhere, so we regard it as the best epidemiological evidence available to date that

wooden cutting boards are not a hazard to human health, but plastic cutting boards may be.

Publications to date from our work:

Ak, N.O., D. O. Cliver, and C.W. Kaspar; 1994. Cutting boards of plastic and wood contaminated experimentally

with bacteria. J. Food Protect. 57: 16-22.

Ak, N. O., D. O. Cliver, and C. W. Kaspar. 1994. Decontamination of plastic and wooden cutting boards for

kitchen use. J. Food Protect. 57: 23-30; 36.

Galluzzo, L., and D.O. Cliver. 1996. Cutting boards and bacteria--oak vs. Salmonella. Dairy, Food Environ. Sanit.

16: 290-293.

Park, P. K., and D. O. Cliver. 1996. Disinfection of household cutting boards with a microwave oven. J. Food.

Protect. 59: 1049-1054.

Park, P. K., and D. O. Cliver. 1997. Cutting boards up close. Food Quality 3 (Issue 22, June-July): 57-59.