stories : Nagging Question
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Why Do Onions Make You Cry?It’s because they’re so irritating |
When an onion is ruptured—such as by a knife—its cells break open and release irritating compounds that form a substance called propanethial sulfoxide, which is similar to sulfuric acid, says Dr. Irwin Goldman, associate professor of horticulture at the University of Wisconsin-Madison.
As the nerve endings of your eyes’ corneas detect the irritant, your brain tells your eyes to produce tears to wash it away. In other words, all that crying is your body’s way of protecting your eyes. (It also seems to help if you block the cornea by wearing goggles—or even contact lenses. Or you could try CHOW contributor Daniel Duane’s method.)
Using “gene silencing” technology, Dr. Colin Eady of Crop & Food Research in New Zealand recently developed a tearless onion by shutting down the gene in the vegetable that produces the irksome substance. It’s still in the development stage, however, and there’s no word yet on whether the new onion tastes better or worse than its weepy relative.
CHOW’s Nagging Question column appears every Friday.
Regardless of the nature of the compound (others have referred to it as "tear gas" in the past), the best way to cope until they get the genetics of the non-weepy onion sorted out is to do what good chemical warfare experts have known to do for many years. To make a tear gas manageable, you just keep it liquid or reduce its vapor pressure as low as you can... and the easiest way to do this with onions is to stick them in the freezer for 15 minutes or so before chopping. The chilled liquid/gas thus vaporizes into the room-temperature air much more slowly, and gives you a chance to get the job done before your eyes start to get irritated.
(Depending on how cold your freezer is, you might need to leave the onions in there a little longer. Ours routinely runs at -20C, and fifteen minutes usually does the job.)
--DD
I had heard that the irritating compounds worked on the receptors in the nose, not the eyes, to cause the tearing, and that mouth-breathing cut back on the tear production.
Chilling the onions looks like it would work well in either case. Great suggestion, DD
How about lighting a candle next to where you are cutting the onions? Somebody told me that works.
samhopkins, that might well work, but I haven't tried it. The approach with putting onions in the freezer, though, definitely works, as I've been doing it for about twenty years now with all kinds of onions. Give it a try..
The only REAL way to avoid crying while cutting onions to use a VERY sharp knife while cutting very FRESH (certaintly not refrigerated) onion.
I've found it very helpful to chop my onions last on the cutting board. If I chop anything after them, that's when I start to cry. Better to do a chop and run.
I agree with plowthor and would add slice the onion rather than chop the onion. When I've stored onions in the fridge they seem to want to sprout more quickly than when I store them in the pantry.
The trick given to me by a friend was to run the knife under cold water periodically while chopping. It consistently works, and I have no idea why.
I am always wondering why people react different to onions. While I hardly can chop an onion without getting a running nose and streaming eyes, my husband can chop onions for hours without problems. Anyone knows why?
Sharp knife and correct technique = no tears. The correct technique, as many here already know, is to peel the onion keeping the root end intact, slice in half through the root, make horizontal and vertical slices parallel to the board without cutting through the root, then vertical slices at 90 degrees to separate into dice. It works because the juice doesn't get sprayed around into the air - the old rocking, chopping method sprays a lot of juice around and is guaranteed to lead to teary eyes.
With regard to the Dr. Goldman's description, I wonder if the tear response really passes through the brain or if it's more local and doesn't include actual brain involvement, i.e., like the reflex response to touching a hot object, which can happen so quickly because it doesn't need to go all the way to the brain but rather is processed in the spinal cord.
i understand that its really annoying and irritating when you start tearing when cutting into the onions. don't you think its more of a hassle to do all these tricks just to avoid crying and a runny nose? the tearing occurs as a defense mechanism by the onion, releasing its gas, which when inhaled triggers the tearing and a runny nose. in my opinion, a fresh onion will have more moisture and stronger "tear gas" and to avoid that, i have tried holding water in my mouth before i start peeling and cutting the onion. second method is a chewing gum. i believe the gum absorbs the smell, "contains it" and the water is cool therefore settles the smell down. when the atmosphere is cold, the air is more condensed, and when its warm, it spreads. does it make any sense in a way?
The irritating compounds in onions are volatile. This means when they are released (by chopping, crushing, blending, etc.) they become airborne - think of fumes. When these fumes reach the eyes, the reaction with the film of tears on your eyes makes a dilute acid which then causes the crying reaction to help rinse out the acid.
Now, the irritating compounds are also water-soluble (if they weren't the fumes wouldn't react with the tears on our eyes to produce the acid in the first place), so rinsing knife, cutting board and the onions themselves every so often will eliminate the tears. (It helps if you have quick knife skills too so you can cut everything and get them under water before the fumes get a chance to reach your eyes.
I have found that when I have my contact lenses in cutting onions doesn't make me cry but if I don't have them in I will cry. I wonder if anyone else has noticed this.
strange, its all about the fumes, i guess the fumes of the onions irritated the eyes as well.... not just the smell of the onions.