There’s a reason so many recipes start with chopped onion; onions are a great way to build flavor in a dish. Onions get their distinctive flavor from sulfur, which they absorb from the soil they’re grown in. When they’re eaten raw, sulfur-rich onions are sharp and pungent, but when they’re cooked, the various sulfur compounds react with one another and produce new flavors ranging from nutty to sweet. However, there’s a downside to all of that delicious, flavor-producing sulfur — it seems virtually impossible to chop an onion without crying.
We all know that chopping onions is guaranteed to produce a few tears, but why? Blame it on synthase. This tear-inducing enzyme converts the sulfoxide molecules that are released when an onion is cut, into sulfenic acid. The sulfenic acid, in turn, rearranges itself into a chemical that floats in the air, comes into contact with our eyes, and causes irritation — enough irritation to make us cry.
If you use a lot of onions in cooking, then the odds are good you’ve looked for a way to avoid this irritating problem. And the internet is full of advice ranging from the seemingly normal (like using a very sharp knife) to the slightly bizarre (have you ever held a match in your mouth while you cut onions?).
I decided that it was time to put some of these claims to the test. Armed with little more than a sharp chef’s knife and wooden cutting boards, The Daily Meal’s Recipe Editor, Julie Ruggirello, and I braved four bags of yellow onions. In an attempt to control the accuracy of the experiment as much as possible, we used two equally sharp knives; tried each claim at the same time, in the same kitchen, and under the same conditions; and took note of our observations immediately following each experiment. We also allowed a five-minute break between experiments, leaving the room so that our eyes could recover.
During the course of this two-day, 12-test experiment certain trends emerged. For example, cutting onions while leaving the root intact produced fewer tears (which is consistent with claims that the root end of the onion has a higher concentration of sulfuric compounds than its other parts). Claims that you can build up a tolerance to the lachrymatory effects of cutting onions seem plausible as well, based on this experiment; Julie cut the onions wearing glasses (though she regularly wears contact lenses, which we hypothesize can act as a protective barrier against irritating sulfuric compounds) and she experienced slightly higher levels of irritation than I did — probably because I cut onions almost daily without anything to protect my eyes.
Though there is still much to be considered (and tested) when it comes to cutting onions tear-free, we have 10 proven methods that will reduce or eliminate your urge to cry next time you’re chopping these tasty alliums.
Cut the Onion Underwater
Kristie Collado is The Daily Meal’s Cook Editor. Follow her on Twitter @KColladoCook.