The wooden cutting board and the bacteria that went missing

By Rafe Calder

Two microbiologists set out to find a safe way to clean a wooden cutting board. They found something else. The wood seemed to be doing the work.

What the Wisconsin study reported

The University of Alaska Fairbanks Geophysical Institute, in a piece in its Alaska Science Forum, describes a University of Wisconsin-Madison study by microbiologists Dean Cliver and Nese Ak. The aim, it says, was to find safe ways to clean wood after contact with contaminated food. The researchers used Salmonella, Listeria and E. coli, starting with about 10,000 cells per board, which the article says is roughly ten times what typically washes off a contaminated chicken carcass.

Its figures:

Wood, low dose: within 3 minutes, 99.9% of the bacteria could not be recovered. By the next morning, no live bacteria could be recovered.
Wood, high dose: with a million or more bacteria per board, 99.9% were gone within 2 hours.
Plastic: all of the bacteria survived. They lived through hot water and soap, and could still contaminate clean meat placed on the board later.

The article says the effect held for old and new wood and for every species tested so far, and it names none. The researchers did not know what makes wood hostile to bacteria, and were not sure the bacteria die, since they had not recovered dead ones. The article is a secondary account of the research, not the paper itself. It gives no year and we did not find the original.

What the extension service says now

A University of Wisconsin Extension office, in a 2020 article titled “How Safe is Your Cutting Board?”, reaches a more modest conclusion. It says there is no easy answer: wood, or a nonporous surface such as plastic, marble or glass, can work, and how you handle the board matters most.

Its practical advice:

Wash with hot, soapy water after each use, rinse with clear water, then air dry or pat dry with clean paper towels.
Nonporous acrylic, plastic or glass boards and solid wood boards can go in the dishwasher. Laminated boards may crack and split.
Sanitizing is optional: 1 tablespoon of unscented, regular liquid chlorine bleach (6% sodium hypochlorite) per gallon of water, flooded over the surface, then rinsed.
Replace any board, wood or plastic, that has cracks, crevices, chips or grooves where bacteria can hide.
Keep one board for raw meat, poultry and seafood and another for ready-to-eat foods.

On the standing time for the bleach solution, the same article says “several minutes” in one place and “at least one minute” in its numbered tips. We report both and settle neither.

Where the two sources disagree

On oil. The Alaska article says oiling wood enhances bacterial growth by sealing it, making it more like plastic. The extension article says to rub bamboo with mineral oil to help it retain moisture. The two are about different materials, so they do not necessarily clash, but a buyer reading both could be left unsure what to do with a hardwood board.

On the central question, the study reports wood beating plastic, and the extension article calls it even. The extension piece says bamboo is harder and less porous than hardwoods and resists knife scarring, a point the study article does not cover.

Our reading: the older study is about how bacteria behave in the first hours on a board, and the extension advice is about how a board lasts in a kitchen over years. The two sources do not claim to answer the same question, and neither says so.

Reading a board before you buy or give one

None of the sources we read ranks wood species, grain direction or brands, and we did not find a source that does. So we offer no ranking. What the sources do support is a short list of things a buyer can check by looking:

Is it solid, or laminated? The extension service warns that laminated boards may crack and split in a dishwasher.
Is the surface free of cracks, chips and deep grooves? That is the replacement rule.
Will you want two boards? The separate-board advice means a gift set of one is a start, not a system.

Dates in order

Wisconsin study: no year given in the article we read, and we found no original.
June 8, 2020: the extension article is published, according to its web address.

Side by side

Question	Alaska Science Forum on the Wisconsin study	Wisconsin Extension office
Wood vs plastic	Wood killed bacteria, plastic did not	Any of these materials can work
Oil	Oiling wood enhances growth	Mineral oil for bamboo
Cleaning	A good wipe is enough, says Cliver	Hot soapy water, optional bleach
Worn boards	Not discussed	Replace if grooved or cracked

What kind of sources these are

A university research institute’s science column describing a university study, and a university extension office’s consumer article. Neither is a board maker or seller. The first is secondhand and undated in the form we read; the second is a plain-language guide.

What we left out

Wood species rankings, brand and construction comparisons, claims about knife wear, and any health statement beyond what the two articles make. We also left out Discover Magazine and a USDA page we could not load.

Quick answers

Are wooden cutting boards more sanitary than plastic? A Wisconsin study, as reported by the University of Alaska’s science column, found 99.9% of bacteria gone from wood within hours while plastic kept them. Wisconsin Extension says either material can work.

How do you clean a wooden cutting board? According to Wisconsin Extension, wash with hot, soapy water after each use, rinse, and dry. It lists a bleach solution as optional.

When should you replace a cutting board? Wisconsin Extension says to replace any board with cracks, crevices, chips or grooves where bacteria can hide.

Roam first. Shop later.

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