Wood vs Plastic

There are two basic types of cutting boards in use today, wood and plastic. Plastic boards are a good deal harder on the cutting edges of knives than are wooden boards, but plastic has been growing in popularity because it seems to be more sanitary. The crucial word in the preceding sentence is "seems."

Scientists at the Food Research Institute, Department of Food Microbiology and Toxicology, University of Wisconsin at
Madison, began research to try to find a way to make wooden cutting boards just as sanitary as plastic cutting boards "seem" to be. Later, a distributor of both wooden and plastic boards, concerned about the safety of his products, raised funds in his industry, to help underwrite the research.

The scientists in charge of the investigation were Dr. Dean Cliver and Dr. Nese Ak, both microbiologists. Their findings were so startling that they made national headlines, through an Associated Press story written by Mary MacVean, and distributed on March 10, 1993.

THE SAMPLES

The first step was to make standardized test samples for comparing wood and plastic. The scientists cut 2 inch by 2 inch pieces from cutting boards made of the following listed materials. For some of these materials they also included pieces of cutting boards that had long been in use, either in homes, in grocery stores, or in biology laboratories.

WOOD: hard maple (both face grain and end grain), American black walnut, ash, basswood, beech, birch, black cherry, butternut, oak.

POLYMER: polyacrylic, polyethylene, polypropylene, polystyrene, hard rubber.

Within the wood group there were no significant differences in performance among tree species, nor were there differences between bare wood boards and those treated with "mineral" oil, nor between rough boards and sanded boards. However, in one important set of tests, the previously used wooden boards were measurably superior to the brand new ones.

Similarly, within the polymer group, there were no significant differences between types of plastic. However, in
most of the tests, new plastic boards were significantly superior to used ones. The startling and dramatic differences in performance in all the experiments were between the wood group, generally, and the plastic group, generally. Those differences were both profound and unambiguous, but they were not the differences that anyone had anticipated.

THE EXPERIMENTS

In the first series of experiments, each sample board was washed down with culture medium infected with a known quantity of "Escherichia coli" (human intestinal bacteria). Then the boards were allowed to sit under a variety of controlled conditions, and for a variety of controlled times, after which they were rinsed down with sterile culture medium. Then this medium was examined for surviving bacteria.

Three minutes after initial contamination, at room temperature, all the bacteria on the plastic boards were still
alive and active. In that same brief time, more than 99.9% of the bacteria on the wooden boards had died. Twelve hours later, still at room temperature, the bacteria count on the plastic boards had increased. After the same twelve hours, no bacteria at all could be found on the wooden boards.

The same experiments were also carried out under refrigeration (39 degrees Fahrenheit), and under both high and
normal humidity. The results were all virtually identical.

Next, "To measure the bacteria-absorbing and holding capacity of wood under extreme conditions, high levels of inoculum (more than a million per milliliter) were applied three days in a row, with overnight incubation under high humidity conditions, and with no attempt to clean the contaminated surfaces. Although some bacteria were recovered in this set of experiments, the percent recovery was extremely low; but when the same experiment was repeated with plastic blocks, growth of the test microorganisms was observed under these conditions."

RAISING THE STAKES
After this, the scientists' next tactic was to try more virulent types of food poisoning bacteria. First they repeated
the experiments with a hardier strain of "E. Coli." Then they tried "Listeria monocytogenes", and finally "Salmonella
typhimurium". The "Listeria" had a slightly higher survival rate than the other organisms, but essentially the results were
unchanged.

Next they repeated the trials using a "natural" contaminant, the liquid from packages of fresh chicken purchased at a
supermarket. In this test, the bacteria naturally present in fresh chicken juices multiplied on the "new" wooden cutting
boards about 16-fold (four generations) after twelve hours. On the plastic boards (both new and used) the bacteria multiplied between 1,000-fold and 1,000,000-fold in the same overnight period. Meanwhile, on the "used" wooden cutting boards, all of the bacteria died.

As a control to this part of the trial, chicken juice was filter sterilized, which removes all the microorganisms without
altering the chemistry of the medium. This sterile juice was then contaminated with the known strains of bacteria. The results of these tests were essentially the same as those in the first series, which used laboratory culture medium.

GREASE

Next, to add further realism, all sample boards were rubbed down with fresh chicken fat. Then they were ultraviolet
sterilized, to kill any bacteria present in the fat. Then the boards were contaminated as before.
On those wooden blocks which absorbed all of the contaminant overnight, despite the fat coating, the bacteria count declined by more than 99.9%. By contrast, on all the plastic blocks, and on those wooden blocks where the contaminant remained pooled on the surface overnight, the bacteria count increased.

THEORY

This last result has an interesting implication. It suggests that the naturally absorbent quality of wood is a key factor in
the inability of bacteria to survive on it. The result also suggests the importance of cleaning grease off of wooden cutting
boards thoroughly and promptly.

Drs. Cliver and Ak theorize that the pores in wood may trap and immobilize bacteria, and then the microorganisms would die rapidly as the wood dries. According to this theory, used wooden cutting boards outperform new ones perhaps because the numerous cuts on their surfaces would increase their natural ability to absorb juices, and thereby to speed evaporation. By contrast, grease on the surface of a wooden board would make that surface repel liquid, causing the greased wooden boards to perform similarly to plastic, which always repels liquids. Further research would be needed to test this theory, and to discover exactly how wooden cutting boards are so deadly to bacteria.

Although all plastic materials naturally repel liquids, the cuts on the surfaces of "used" plastic cutting boards tend to
trap liquids, and thereby to slow down their evaporation. This seems to be why plastic cutting boards, especially used ones, provide an ideal environment for bacteria to multiply.

Indeed, the researchers found that it is very difficult to sterilize the cut surfaces of used plastic cutting boards. A strong penetrating bleach solution is necessary, or a full cycle in a commercial dishwasher, for complete sterilization of a plastic board. Hand washing in hot soapy water is not enough to sterilize a used plastic board, but it is more than enough for a wooden board.

Anti-bacterial Cutting Boards

Anti-bacterial Cutting Boards are plastic Cutting Boards treated with active agents such as "triclosan", Microban and Bacteron, the same active agents as are used in anti-bacterial handsoaps.

Sadly, though, the United States Department of Agriculture (USDA) has found that this treatment has little or no effect whatsoever when used in Cutting Boards.

Prior to 1997, two companies advertised self-sanitizing plastic Cutting Boards that they claimed would stop the growth of bacteria, particularly salmonella and E.coli. The agent called Bacteron (aka bicyclomycin , Bicozamycin, Bacfeed) was mixed into the surfacing of the boards. On 27 June 1997, the American Environmental Protection Agency (EPA) ordered them to stop this claim of "anti-bacterial" Cutting Boards, as the claims were not proven. Dr D. Carl Batt of Cornell University, at a National Sanitation Foundation conference, said that he had concluded that
there was no significant advantage to plastic Cutting Boards advertised as "anti-bacterial" (using Bacteron or Microban) over untreated plastic Cutting Boards. ​
Don't let Wooden Cutting Boards sit with wet undersides. You could get mould growing underneath and this will surely cause your board to warp.
Many people buy a beautiful Wooden Cutting Board and then worry about cut marks. This is one of your most important kitchen tools. USE IT as a tool! Don't be the least bit concerned about knife cuts. Once a year when the board is perfectly dry give it a sanding with 120 then 240 grit sandpaper and it will be just like new. In my own experience I do not oil our cutting boards. A quality hard maple board with proper care should last a life time and when you do sand it annually it's like new in a couple minutes. An oiled board will take several pieces of sandpaper as the oiled wood will keep filling the sand paper and you will have to replace with a new piece every half minute.