Wednesday, June 10, 2009

Plastic vs. wood

We spent almost the entire weekend in Williams-Sonoma, ending up with a new Shun citrus knife, three of these amazing Swiss non-stick knives by Kuhn Rikon, a lovely set of sunshine-yellow mixing bowls, a Microplane grater for hard and soft cheeses (which actually makes the cheese taste better!), and a slew of other items...

I spent most of the time oogling over the lovely wood salad bowls (and my new Kuhn Rikon knife, which is sunshine yellow too!). There is just something about wooden kitchenware items for me. Cody, who is completely obsessive about "germs," washes all of our dishes on the "sanitize" setting on our dishwasher. He complains about all of our wood cutting boards and spoons, whereas I just adore them and despise (depise!) silicon.

When I showed him another lovely wooden set, Cody said, "I like wood too, but it's too porous. You can never clean it well." His dad overheard and said, "You know, they actually found that wood retains less bacteria than plastic." I was a little blown away by this statement, because the FDA mandates all non-porous (aka plastic) cutting boards, utensils, etc. in restaurants, and the USDA suggests the use of plastic in the home, a decision which a spokesperson mentioned was simply "common sense." How could this be?, I wondered.

As it turns out, there were several studies in the mid-1990s to see if there was a difference between plastic and wood. Explains one of the researchers, "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" (Dean O. Cliver).

The USDA standards also lacked guidelines for home disinfection of cutting surfaces. So, explains Cliver, he and his fellow researcher Nese O. Ak set out to discover if there was a way to disinfect a wooden cutting surface so that it might be as sanitary as a plastic cutting surface. They thought, as most do, that plastic surfaces were less porous and so must be more sanitary.

They began inoculating a plastic board and a wooden board with the "cultures of common food-poisoning agents--up to 10,000 cells of Salmonella, Listeria, or Escherichia cali" (from here). What they found blew them away. 99.9 percent of the bacteria on the wooden board were unrecoverable and thought to be dead. Under the same conditions, none of the bacteria placed on the plastic died. They were excited and worried. How could the bacteria on the wooden cutting board simply disappear? And what if they resurfaced to infect food later?

They left both of the boards in a high-humidity and temperature room overnight, and found that in the morning, the microbe population on the plastic cutting board grew enormously, while the population on the wooden cutting board remained non-existant.

Furthermore, they tested exactly how long 1,000 Salmonella cells would survive on a wooden cutting board that bore knife scores (1,000 is the high-end estimation of how many of these cells get onto the board from a chicken). Their result was three minutes.

They also found no re-emergence of the harmful cells from the wooden boards.

In contrast, a plastic board with knife scores will not only absorb more of the bacteria, these bacteria will survive a soapy hot-water bath and were seen to re-emerge to contaminate foods. Furthermore, most home dishwashers only reach about 120-140 degrees F, but you need a temperature of at least 190 degrees F to sanitize plastic cutting boards (from here).

There were some discrepancies with wood, however. Wood that had been treated to be less porous ("more like plastic") was found to be much less effective at fighting off harmful bacteria, and this treated wood is commonly sold for household kitchens.

Both plastic and wooden cutting boards can be completely safe if properly sanitized, but plastic cutting boards must be discarded after heavy use, whereas good wooden cutting boards can be used for ages. I think it's an interesting thing to think about, and there's a lot about it to discuss, as well as much more research to be done. However, wood is not any more porous than plastic, and wood is also easier on your cutlery. Furthermore, it has been proven that there is something about wood (commonly thought to be an enzyme) that makes it more able to fight off bacteria. So, I think that's pretty cool research for those of us who couldn't give up wood, even in the face of criticism from our housemates and friends.

For another very interesting study about wood versus plastic, please read this PDF.

(Image found via Google Images/here)


A Lady's Life said...

I am not surprised.
Plastic when washed under extreme heat and then dried under heat leaves toxic fumes in the dishwasher.
I really dislike plastic.
Wood on the other hand, and also depending on which wood you use, can be anti inflammatory since it is used in teas as medicines to cure the ill.No wonder the germs die.
I prefer wood to plastic anytime.
Good Job!

Elyse said...

Wow! I had heard about the toxicness of plastic when it experiences slight temperature changes...I guess I had never thought about it in the washing machine, though. As plastic is only sanitize-able with either chemicals or extreme heat, I will definitely be sticking with my wooden cutting boards...thank you so much for sharing!

erin said...

cheers to wooden boards! thanks for visiting my site!

jen laceda said...

A very interesting essay on wooden vs plastic. Thanks for shedding some light into this matter. I am a cooking fanatic while my husband is the cleaning fanatic. We use both at home, however, I'm thinking of switching to solely wooden cutting boards.

Munted kowhai said...

Hey Elyse
This is a great post! I'm actually a microbiologist and we use wooden cutting boards. You are right, its not what you use, its how you sanitize it. If you get really thick and good wooden cutting blocks, you can actually sand down the top layer after some heavy use. Also, to sanitize wooden boards, I always use non chemical agents such as brine (salt water does great things for killing bacteria) or lime juice. I let the brine sit on the board for 10 minutes or so. Humans have lived a long time with wooden cutting boards and with better understanding of potential food borne microbes, we can safely use wooden cutting boards in our kitchens!

(also under high temp certain plastics leech)