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GBlist: cutting boards again
Somebody wrote that this has been discounted - anyone have anything
current on the 'cutting board controversy'
John Salmen
TERRAIN E.D.S.
terrain@seaside.net
From Science News, February 6, 1993
By J. Raloff
Reprinted from the Central Coast Avicultural Society, April 1993
Reprinted from the San Diego Bird Breeders Journal
For several years We've been encouraged to use plastic or other
nonporous materials as cutting boards by leading
veterinarians. This article argues against that practice.
Chefs know that, any way you slice it, wooden surfaces are kinder to
knife blades than either plastic or glass. But in
recent years, everyone from kitchen suppliers to the Dept. of
Agriculture (USDA) has urged cooks to cut on non-porous
materials, typically plastic. Supposedly, plastic boards give bacteria,
such as Salmonella in chicken, less chance of
escaping rigorous cleaning, thus reducing the chance that such bugs will
survive to contaminate other foods.
If such arguments have frightened you away from slicing, dicing, or
boning on wood, you may be able to bring your
butcher block out of retirement. New research indicates that the safety
advocates were wrong: Pathogens prefer plastic.
No one was more surprised by this than Dean O. Cliver and Nese O. Ak,
two microbiologists at the University of
Wisconsin-Madison. They began studying cutting boards in hopes of
identifying decontamination techniques that might
render wood as safe as plastic. But the pair quickly found that within
three minutes of inoculating wooden boards with
cultures of common food-poisoning agents -- up to 10,000 cells of
Salmonella, Listeria, or Escherichia call - 99% of the
bacteria were unrecoverable and presumed dead. Under similar conditions,
none of the bugs on plastic died.
Indeed, when the researchers maintained plastic boards overnight at high
humidity and room temperature, microbe
populations grew; the researchers recovered no live bacteria from wood
the next morning.
The scientific literature suggests that the number of Salmonella cells
that might wash off a chicken carcass probably will
not exceed about 1,000, Cliver notes. "We can get less than 99.9 percent
kills [on the wooden boards in three minutes]
if we go to inordinately high levels of inoculation -- such as 1 million
or more bacterial cells," he says. In those instances,
he and Ak had to wait about two hours before achieving a 99.9 percent
reduction in the bugs they recovered.
"While the wooden boards appear to kill bacteria, we've not recovered
the little critters' dead bodies," Cliver
acknowledges. "So all we know is that by the best available means, we
can't get them back after they go onto a board.
The big concern is whether bacteria hiding deep within the wood might
subsequently surface to contaminate the foods on
the chopping block. As best as we can tell, that isn't going to happen,
" Cliver says.
The same is not true of knife-scored plastic cutting boards. The
scientists found that bacteria lodged in the plastic's cut
grooves not only survived a hot water-and-soap wash, but could later
surface to contaminate foods. By contrast, Cliver
says, with wood "a good wipe will do fine - and if you forget to wipe
the board, you probably won't be too bad off."
At one point, the Wisconsin researchers Inoculated wood and plastic on
three successive days, maintaining each board
without cleaning - at room temperatures and high humidity. By that time,
"the plastic boards were downright disgustingly"
Cliver says, "while the wood boards had about 99.9 percent fewer
bacteria than Ak had put on them."
"Wood is more forgiving - and perhaps user-friendly - than plastic is
once it's been cut some," Cliver says.
Boards sold to homeowners typically come from the factory treated with
mineral oil. "That treatment is intended to make
the wood more impermeable - like plastic," Cliver says. The bad news is
that It does make wood more like plastic....In
every one of our tests, if the wood had been treated to retard the
penetration of moisture, the bacteria survived longer."
Wood's presumed bactericidal activity does not depend on whether it is
new -- nor, apparently, on species. Cliver and
Ak have already tested boards from hard maple, birch, black cherry,
basswood, butternut and American black walnut.
Tests on oak and ash are pending.
The microbiologists hope to submit their findings for publication within
the next few months. One weakness. Cliver notes,
is their inability to nail down the mechanism or agent responsible for
wood's antibacterial properties.
Although no laws prohibit commercial establishments from using wooden
cutting boards, the Food and Drug
Administration's model codes for state agencies call for using only
"Non-absorbent" and easily cleaned materials for
surfaces that food contacts. The USDA also recommends acrylic or other
nonporous materials to consumers asking
about preferred cutting boards, according to Bessie Berry with its Meat
and Poultry Hotline in Washington, D.C.
Cooks should never cut on glass, she says because minute shards may chip
off and become embedded in food.
Microbiologist Pricilla Levine of USDA's Food Safety and Inspection
Service says she knows of no scientific studies
demonstrating the advantages of one cutting-board material over another
in inhibiting bacterial contamination. She told
Science News that her agency based its recommendations on "common
sense."
Like state and local inspectors, these federal agencies have bought the
myths that plastic is safer than wood, says food
scientist 0. Peter Snyder, a St. Paul, Minn. based consultant to the
retail food industry. For at least two decades, he
says, "sanitarians [Sanitation inspectors] out there have been telling
us to use plastic cutting boards, even though they had
no evidence that plastic was better."
Indeed, Snyder contends, the little research done on the subject has
failed to demonstrate plastic's superiority. He cited
one study conducted about 25 years ago that showed wooden cutting boards
were at least as good as plastic when it
comes to cleaning off microbial contamination.
If others confirm the Wisconsin data, Snyder says, sanitarians may have
to alter their advocacy in favor of wood. But, he
adds, considering how slowly practices change in the food business, 10
years aver such confirmatory data came in
"sanitarians would probably still be requiring [retail establishments]
to use plastic cutting boards."
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