The following is an excerpt from a general-composite conversation we’ve had with a number of people over the years. The names have been changed to protect the innocent. Perhaps the dialogue has not been transcribed verbatim…but whatever. You get the gist.
Q: Hey there, DearMartini, what’s up with the Onion-crying thing and the Garlic-stinking thing?
DM: Onions and garlic are the most aromatic tools in the culinary world. They offer flavor and aroma in so many different ways – without them, our lives (and tastebuds) would be terribly bland and boring.
Q: Why does chopping onions make us cry?
DM: That’s perhaps the most common cooking-related question in the Culinary Universe — the mystery of how and why onions make us cry… and how can we avoid crying.
Chefs Mia and Terri have taught home cooks like you the basic knife skill techniques for years. Each time, when we reach that point in class where we have to face the inevitable onion-dicing lesson, we are pelted with a barrage of questions from students. “How can we stop from crying?” “OMG, my eyes are burning! What’s happening to me??” “Does that method where we chop them under water actually work?” One of the best answers we have to the most common question, “How do we keep from crying when we chop onions?” is “Get someone else to do it for you.”
OK. All joking aside, if you wear eye protection in the form of goggles, contact lenses or scuba masks, then you’re pretty much out of the woods. The rest of us, however, have to suffer the intense burning and eye discomfort as we prep for dinner.
So, why do onions make us cry? The answer is both simple, and complex.
The simple answer is, onions have a natural defense mechanism to keep predators from eating them: there is a compound in them that releases gases and fumes into the air when their cell walls are broken, which react to the delicate membranes in our eyes and noses that cause the burning reaction.
For a more complex answer, we turn to our most honored and respected food scientist, Harold McGee, who wrote the definitive book on food science, On Food and Cooking, the Science and Lore of the Kitchen:
“The distinctive flavors of the onion family come from its defensive use of the element sulfur. The growing plants take up sulfur from the soil and incorporate it into four different kinds of chemical ammunition, which float in the cell fluids while their enzyme trigger is held separately in a storage vacuole. When the cell is damaged by chopping or chewing, the enzyme escapes and breaks the ammunition molecules in half to produce irritating, strong-smelling sulfurous molecules… One sulfur product is produced in significant quantities only in the onion, shallot, leek, chive and rakkyo: the “lacrimator,” which causes our eyes to water. This volatile chemical escapes from the damaged onion into the air, and lands in the onion cutter’s eyes and nose, where it apparently attacks nerve endings directly, then breaks down into hydrogen sulfide, sulfur dioxide, and sulfuric acid. A very effective molecular bomb!”
Q: WOW. TMI. All we wanted to know is how do we REALLY keep from crying when we chop onions.
DM: Well, if you really can’t handle wearing your swim goggles in the kitchen, we suggest a couple of things:
1) Keep your onions as cold as possible – the cold temperature slows down the enzyme, buying you a few more seconds of time before waterworks begin;
2) Keep your cuts to a minimum – be as efficient as you can with your chopping. No mincing or mashing, please. Remember, the more cell walls that are damaged, the more the enzymes have a chance to tango with the compounds;
3) Keeping your knife as razor-sharp as possible is related to #2 – a super-sharp knife can cut through just enough cell walls that it needs to without mashing, tearing or bruising more (which is what a dull knife would do).
4) If you have a lot of onions to chop at once, keep your kitchen well-ventilated or light a match over the fumes.
5) And if all else fails, get someone else to chop the onions for you!
Q: Ha. Ha. Very funny. Can’t we just buy them pre-chopped?
DM: Well, you could, but that won’t minimize the effects of crying. The compounds and volatile fumes only get stronger when they sit for longer periods of time.
Q: So is that why garlic stinks so badly on our hands after we chop it?
DM: You could say that…
Q: Do you have any tips on how to get the garlic smell off our hands?
DM: Try rubbing your hands with a stainless steel spoon under running water, then washing your hands with soap and water. The steel reacts to the garlic compounds on your fingers and neutralizes the odor. It’s always worked for us.
DM: Nice try, but no. Sorry.