Here’s Why You Shouldn’t Use a Metal Knife to Cut an Avocado
Turns out your metal knives could be shortening the life of our favorite green fruit.
Most of us don’t consume a whole avocado at once (okay, sometimes), and we are always looking for hacks to keep the rest as fresh as possible until we use it.
Reader’s Digest recently shared a sneaky inhibitor to keeping our avocados nice and green—metal knives. According to the site, simply swapping a metal knife for a ceramic or plastic version when cutting an avocado can make a huge difference in preventing the dreaded brown spots.
We all know that when exposed to air for too long, avocados start to brown. The scientific term here is enzymatic browning—that's when an enzyme called polyphenol oxidase and a chemical called polyphenols undergo a reaction upon being exposed to air, causing discoloration.
Unfortunately, there’s no way to completely avoid it, as avocados have to be exposed to air at some point, but celebrity chef Nick Stellino told RD that metal knives, especially those containing copper and iron (which is any stainless steel knives), initiate enzymatic browning more quickly. And this may be the same for other produce varieties as well.
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So is Stellino right? Possibly! Several people have tested out the effects of metal knives on food, with varying success.
The most reputable, Cook’s Illustrated conducted an experiment with plastic and stainless steel knives to see if switching up your knife really did make an impact on lettuce. They found the plastic knife was able to keep the lettuce fresher up to 24 hours longer. Another site with maybe a little bit of bias, called My Ceramic Knives conducted a similar experiment on apples and avocados. Unsurprisingly, they found the ceramic knife helped prevent enzymatic browning a little longer.
There was one blogger who had a different experience. Christopher Eppig, PhD, did a similar experiment—not with avocados, but with apples, potatoes and onions. Eppig found no variance in the way plastic, ceramic, and metal knives impacted enzymatic browning.
If you're struggling with keeping your avocados green, you may want to switch to a plastic device for cutting them—it certainly can't hurt. Of course there are other ways to slow down browning, including saving the pit, properly storing your avocados, and knowing the best way to cut them.