Why Do Onions Make Us Cry?
By Ashton Yoon | June 6, 2017 10:00 am
We all know that feeling: the burning sensation as we slice into a fresh onion, eyes watering and wincing to relieve the stinging. There are claims that home remedies can solve this problem, including burning a candle, putting the onion in the freezer before chopping, or cutting the onion underwater. In this article we will investigate the culprit behind our onion tears and a possible scientific resolution that has emerged in the 21st century.
The teary-eyed response to cutting an onion is due to the chemical syn-propanethial-S-oxide, which the onion has evolved as a defense mechanism against predators. Each cell inside the onion contains a vacuole filled with enzymes [1] called allinases that convert amino acid sulfoxides that are present in the onion cell to sulfenic acids [2] (namely 1-propenyl-L-cysteine sulphoxide, or PRENSCO)[3]; these are then transformed by another enzyme into syn-propanethial-S-oxide [4] (Fig 1).When the onion cell structure is broken during chopping, the enzymes are released and are then able to interact with other chemicals inside the onion cell, thus catalyzing the chemical reactions that produce syn-propanethial-S-oxide [1] (Fig 1).
http://blogs.discovermagazine.com/scienceandfood/2017/06/06/why-do-onions-make-us-cry/#.WWDGpumQywV
