Onions make you cry but also pull the flavours of most dishes together, whether it’s raw, caramelised or baked. Actually, there are very few dishes that we wouldn’t add a bit of onion to!
Imagine the situation: You are happily chopping onions for your lunch and… what happens next? Exactly, your eyes sting and tears start running down your face.
Why does chopping an onion make you cry?
For plants and animals alike, life is all about survival and reproduction. With time, the lachrymatory factor evolved as a defense mechanism, protecting onions against microbes and predators like us from eating the bulbs.
The real answer comes down to some pretty fascinating biochemistry. However, pinpointing the precise unstable chemical responsible for making your eyes cry has been a long process. Here you can find the science behind why humans tear up when chopping up onions.
Originally, it was described that the alliinase, an enzyme also found in garlic, was responsible for turning your tear ducts into water slides. However, we all know that garlic does not make us cry the same way onions do.
So… why do onions make you cry but garlic does not?
Most recent studies have recently identified that onions carry different chemicals responsible for making you cry and how these enzymes work. Scientist found that Onions produce two chemical known as: syn-propanethial-S-oxide and lachrymatory-factor synthase.
According to the Library of Congress, the chemical process is as follows:
- Lachrymatory-factor synthase is released into the air when we cut an onion.
- The lachrymatory-factosynthase enzyme converts the amino acid sulfoxides of the onion into sulfenic acid.
- The unstable sulfenic acid rearranges itself into syn-Propanethial-S-oxide, an irritant that stimulates the eyes’ lacrimal glands.
- syn-Propanethial-S-oxide gets into the air and comes in contact with our eyes. The lacrimal glands become irritated and produce the tears!
what can we do to reduce all this onion-crying drama?
All of these chemicals are released in greater volume if you choose to use a less-sharp knives because using a dull knife he onion’s cell wall becomes damaged and the onion releases more chemicals.
To stop crying when chopping onions, you should use a freshly sharpened knife and cut the onions quickly and cleanly, minimising the cell damage to the onion and reducing the chemicals release.
In summary, when you chop onions, they release chemical compounds that irritates your eyes and triggers your tear glands.