The onion is that member of the vegetable family which has a bittersweet relationship with its consumers. As much as we savor its rich flavors, most of us dread the chopping business, and the reason is obvious — an unwanted stream of tears.
According to chemist and author Eric Block,
See, the onion is a perennial bulb that lives in the ground with lots of critters who are looking for a snack…so it has evolved a chemical defense system.
Fair enough, onion, but don’t forget that humans are above in the food chain.
A number of chemical reactions evoke our lacrimal glands to produce tears, which are also a part of a defense mechanism. So, onions are not the only ones with an A-level strategy. The chemical reactions can be understood in three simple steps:
Each onion cell has a lump filled with a synthase enzyme called vacuole. When we make a cut, the onion cells tear apart and release enzymes from vacuole, which react with the onion’s amino acid sulfoxides.
Although the enzymes and amino acid sulfoxides are chemically neutral, fused together, they make sulfenic acid. Now, sulfenic acid is inherently unstable, so after a series of chemical reactions, it changes to syn-propanethial S-oxide.
Being lighter than air, syn-propanethial S-oxide rises up and comes in contact with our eyes which in turn activates the lacrimal gland. One final reaction results in the formation of sulfuric acid. Now, sulfuric acid is devil’s nectar which poses a threat to our cornea.
Therefore, the brain, our knight in shining armor, signals for the production of more and more tears to combat the attack on our eyes. Sadly, sensitive eyes tend to produce more tears which make us fear the tedious task of chopping onions.
Now, that wasn’t tough to understand. In order to minimize the effects of these chemicals, you can refrigerate the onions since the molecules tend to move slowly when cold. Hopefully, this hack will change your tears of pain to tears of joy.