How to Chop Onions Without Crying

April 11, 2011 at 2:00 am 14 comments

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.

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Source: Wikipedia – Onion, Wikipedia – Alliinase, e-How

Image: Wikipedia

Entry filed under: Food and Drink. Tags: , , , , , , , .

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14 Comments Add your own

  • 1. Nikola Malesevic  |  April 11, 2011 at 5:15 am

    I was surprised not to see a method that my girlfriend thought me once. If you pull your tongue out, all of these S-oxides (or whatever they’re called) stick to wet surface of the tongue and therefore cannot reach your eyes. Just remember to retract and pull it out frequently in order to keep it wet. Simple as that.

    • 2. Nikola Malesevic  |  April 11, 2011 at 5:17 am

      I forgot to mention that you should start doing this before making a first cut. Once the oxides reach your eyes, it’s already too late and you’re doomed to crying.

    • 3. Kyle  |  April 11, 2011 at 10:44 am

      I’m guessing this is similar to chewing gum, though I haven’t tried either method. Both probably help, but I would imagine that at least some LF molecules are still likely get by your mouth/tongue, so the effect is probably good, but imperfect. However, I like the fact that it’s simple to do. I’m going to try this one next time I chop an onion.

      • 4. Nikola Malesevic  |  April 11, 2011 at 12:42 pm

        Well, the method is not exactly the same – according to your article, by chewing you inhale and exhale a lot, dispersing the molecules around. When you stick your tongue out and then retract it – you’re basically eating all of these who attach to the wet surface. If only we could use these two methods simultaneously. :) Anyway, a great article!

      • 5. Kyle  |  April 11, 2011 at 12:50 pm

        I think the gum-chewing method suggests that you’re inhaling (“eating”) some of the molecules through your mouth, but yeah, it’s not completely the same. Someone should try an experiment: (1) chewing with your mouth open, (2) chewing with your mouth closed, and see if there’s a difference.

        Apparently my grandmother used to chew bread, so any chewing action may help.

        Thanks for the comments!

  • 6. Darlene  |  April 11, 2011 at 8:32 am

    Get someone who wears contact lenses to cut the onion!

    • 7. Kyle  |  April 11, 2011 at 10:54 am

      I was considering including contact lenses in the article, but figured it only applied to people who already wear them. Perhaps I should have lumped it into “protective eyewear.” From what I understand, contacts provide partial, but incomplete, protection from LF gas as they only cover part of the eye. However, partial protection is certainly better than no protection!

      • 8. Unintentional Housewife  |  April 12, 2011 at 11:56 am

        I wear contact lenses, and I can verify that they help a lot. However, it seems as if any LF gas that does get to your eye somehow gets trapped under the lens. At least, that’s how it seems. I can chop onions for a long time without tearing up, but if I do tear at all, I usually need to change my contacts before I can stop crying.

      • 9. Darlene  |  April 20, 2011 at 10:50 am

        I find my contacts offer almost full protection. I only have a problem if I cut more than 3 onions or so. And I put them in fridge usually. Guess I’ll have to stick out my tongue after 3!

  • 10. Debbie  |  April 11, 2011 at 9:09 am

    I was told to light candles – tried it – did minimize the eye tearing, but not totally.

  • 11. Jaclyn  |  April 12, 2011 at 11:05 am

    chilling them really does work. i read that tip a long time ago, tried it out – and no tears! i have kept my onions in the fridge (and my eyes free of onion-cutting tears) ever since.

  • 12. M. B. H  |  April 12, 2011 at 9:03 pm

    A foolproof method is to hold a piece of bread in your mouth partially sticking out to absorb the fumes. IIt really works.

  • 13. Elbyron  |  April 13, 2011 at 11:32 am

    I like to put the cutting board on the stove (if it’s not in use) and turn on the oven hood fan. It prevents the LF gas from building up. In the summer, chopping outdoors on the patio table also works well.
    Another suggestion is to hold the onion together as you slice through so that the gases stay trapped in the onion a bit longer.

  • 14. My Favorite Links – Volume 4  |  April 22, 2011 at 2:57 pm

    […] that will surely follow. But why do we cry and is there anything we can do about it? Find out at this post from Broken […]


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