How to Chop Onions Without Crying
By Kyle Kurpinski
Plants, like all other living organisms, are composed of cells. When you eat a vegetable, or chop it with a knife, some of these cells are ruptured and their contents are released. Certain plants, like the onion, have developed defense mechanisms against this type of destructive action. When onion cells are destroyed, enzymes called alliinases initiate a series of chemical reactions resulting in the release of synpropanethial-S-oxide (also known as onion lachrymatory factor, or LF), a volatile gas that stings the eyes. To combat the stinging effect of the gas, the lachrymal gland at the corner of each eye produces tears to help wash the irritant away. For the plant, LF is an excellent natural deterrent against roaming herbivores, but for humans, it makes us look quite silly and emotional when preparing salad.
There are many ways to reduce or eliminate the “onion effect” during chopping, all of which involve minimizing your exposure to the noxious LF gas:
1) Chop under water. Copious amounts of water can help prevent LF gas from reaching the eyes. Try peeling the onion under running water and/or chopping the onion in a large water-filled bowl.
2) Chill or freeze the onion. The enzymes required to produce LF work well at room temperature, but are inhibited under colder conditions. By chilling the onion before cutting, you greatly reduce the activation of the chemical reactions.
3) Use a sharp blade. A sharper blade causes less damage to the onion cells, thereby releasing less chemicals.
4) Use a fan. Disperse the LF gas by aiming a small fan towards your cutting area and away from you.
5) Wear goggles. Protective eyewear can help prevent LF gas from reaching your eyes. You’ll need something that forms a seal around your eyes, however; standard glasses won’t do.
6) Do not chop the root. The root of the onion contains a greater concentration of the alliinases than the rest of the plant. By avoiding the root (or at least saving it for the end) you can reduce the amount of LF produced during chopping.
7) Chew gum. This one is a little weirder, and doesn’t seem to work as well for many people, but it’s still an option if you can’t do any of the above. Supposedly, vigorous chewing causes you to breathe more through your mouth, which disperses the LF gas and directs it away from your eyes and lachrymal glands.
8) Use a “better” onion. If you’re desperate for a truly tear-free onion, genetic engineering provides an alternative to freezing and gum chewing. In 2008, researchers at the New Zealand Institute for Crop & Food Research utilized gene-silencing technology to suppress a gene required for LF production. No more LF, no more sobbing over your chopping board.