Onions are perennial plants in the Allium family. This means, in the first year of their
life cycle, they form a tasty bulb that serves as the store of their energy. The following
year, the plant produces a flower and seeds, allowing it to reproduce.
Onions
contain amino acid sulfoxides, which
produce sulfenic acids inside the cells.
When we begin
cutting an onion, the cells are
disrupted and the normal cell enzymes mix with the sulfenic acids, thereby producing propanethial S-oxide.
Propanethial S-oxide is a gaseous
sulfur chemical that through the air and into our eyes. When this gas
interacts with the water in our tear film, sulfuric acid is produced. This acid
is not compatible with our tears and our eyes begin to burn. Our brain says, “Something
is in my eye!”
The synthase
enzyme and the
aminoacid sulfoxides are
stored in the onions separately. When they are exposed
to each other the following processes occur.
1.Lachrymatory-factor synthase enzyme is released into the air when we an onion is cut.
2.This
synthase enzyme converts aminoacid sulfoxides of the onion into sulfenic acids.
3.The sulfenic acid, which is unstable, rearranges itself into syn-ropanethial-S-oxide.
4.This syn-propanethial-S-oxide
is released into the air and
comes in contact with our eyes. Our
lachrymal glands become irritated, thereby producing
tears.
For chemistry lovers:-
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