When cutting up an onion, you’re likely to start crying. We learned about the three different kinds of tears a few weeks ago; lubricating, reflex, and emotional. Assuming that onion hasn’t done anything terrible to you, your tears are most likely of the reflex variety. They are produced in order to flush an irritant out of your eye. But how did that pesky onion get all the way up there? Why it’s a chemical chain reaction, my dear!
Onions, like garlic, chives, and such, absorb sulfur from the soil. When you cut through an onion, you crush or open up certain cells that release an enzyme which then react with the sulfur bits to produce sulfenic acids. That stuff is rather unstable, and rearranges itself into… wait for it… syn-propanethial-S-oxide! (dun, dun, dunnnn) That’s a deadly combo of hydrogen sulfide (toxic, flammable, and smelly), sulfur dioxide (comes out of volcanoes, causes acid rain), and sulfuric acid (aka: battery acid).
So that nasty cocktail wafts it’s way up to your eyeball, and your body turns on the waterworks to flush it out. I was thinking about this enlightening fact last night when making my dinner, which involved sauteed onions. I had a thought; I can’t cry if the acid never reaches my eyes. So while I was cutting, I was gently blowing down towards the onion. It worked! However, I don’t recommend you letting your dinner guests watch you do this. Probably a social faux pas.
