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BEHIND THE SCENES

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SHEDDING TEARS IN THE TEST KITCHEN

We can’t tell you how many onions we’ve chopped over the years. Let’s just say a lot. As a result, we’ve shed more than a few tears. What causes cut onions to be so pesky? When an onion is cut, the cells that are damaged in the process release sulfuric compounds as well as various enzymes, notably one called sulfoxide lyase. Those compounds and enzymes, which are separated when the onion’s cell structure is intact, activate and mix to form the real culprit behind crying, a volatile new compound called thiopropanal sulfoxide. When thiopropanal sulfoxide evaporates in the air, it irritates the eyes, causing redness and tears.

Through the years we’ve collected dozens of ideas from readers, books, and conversations with colleagues, all aimed at reducing tears while cutting onions. We finally decided to put those ideas to the test. They ranged from common sense (work underneath an exhaust fan or freeze onions for 30 minutes before slicing) to the comical (wear ski goggles or hold a toothpick in your teeth). Overall, the methods that worked best were to protect our eyes by covering them with goggles or contact lenses or to introduce a flame near the cut onions. The flame, which can be produced by either a candle or a gas burner, changes the activity of the thiopropanal sulfoxide (the volatile compound that causes tearing) by completing its oxidization. Contact lenses and goggles form a physical barrier that the vapors cannot penetrate. So if you want to keep tears at bay when handling onions, light a candle or gas burner—or put on some ski goggles, even if it does look a bit silly.