Water Allows Bacteria to Grow – Always Use a Dry Knife in Your Peanut Butter!

How to Store Nut Butters to Prevent Food Poisoning

The hidden dangers of using a wet knife – water allows bacteria to grow!

Next time you’re artfully preparing your next gooey American delicacy known as the PB&J, stop and notice how you are making it? Do you use a clean, dry knife to scoop out the peanut butter, or instead, do you quickly rinse off a knife from the sink and fling droplets of water into the peanut butter jar? Hopefully, you use a clean, dry knife!

Food Safety Contributor and author Laila Carter
Laila Carter is a contributing editor and studies food safety at Kansas State

Because microorganisms need water to survive[1], getting droplets of water into your peanut butter could potentially create an environment for spores of bacteria to grow and proliferate.

Within the room temperature environment of a peanut butter jar, the droplets of water can activate spores of bacteria that would have otherwise remained inactivated. Over time, these spores can grow and proliferate to a large enough population to make you sick.

Peanut butter lasts a long time at room temperature. Naturally, peanut butter has a high fat content and low water activity. Most bacteria do not grow and proliferate in conditions of low water activity. When you see clear liquid on top of some natural peanut butter, it is from the separation of the different oils, not water.

Peanut butter is not a hospitable environment for most bacterial growth, but spores of bacteria and some strands of Salmonella can still reside in the inhospitable environment of peanut butter.

It is important to be aware that peanut butter can still be contaminated with Salmonella Typhimurium[2]. To minimize risk of a salmonella infection, be alert for news of a recall. The CDC is a credible administrator for recalls.

So next time you scoop out a heaping glob of peanut butter, make sure to use a clean dry knife. Also, if there is a recall on your brand of peanut butter, toss it out to avoid potentially contracting a foodborne illness.

To speak to the Editor, food safety attorney Tony Convey, Ph.D., email tony@rsaalaw.com.

[1] https://www.quora.com/Is-there-any-living-organism-that-doesnt-need-water-to-live

[2] https://www.cdc.gov/salmonella/2009/peanut-butter-2008-2009.html


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