ONIONS & TEARS
There are many methods recommended for cutting onions to avoid tears. Each method has its supporters. Try each of them, if one works for you, use it.
• cut the root off last;
• refrigerate before cutting;
• peel them under cold water;
• have a fan behind you or alongside to blow the vapors away;
• place a piece of bread on the knife tip to absorb the fumes;
• chew gum while peeling and slicing onions.
• hold you breath and cut them as quick as you can
• have someone else cut them for you!
Why we cry when cutting onions.
Onions produce the chemical irritant known as syn-propanethial-S-oxide. It stimulates the eyes' lachrymal glands so they release tears. Scientists used to blame the enzyme allinase for the instability of substances in a cut onion. Recent studies from Japan, however, proved that lachrymatory-factor synthase, (a previously undiscovered enzyme) is the culprit (Imani et al, 2002).
The process goes as follows:
• Lachrymatory-factor synthase is released into the air when we cut an onion.
• The synthase enzyme converts the sulfoxides (amino acids) of the onion into sulfenic acid.
• The unstable sulfenic acid rearranges itself into syn-ropanethial-S-oxide.
• Syn-propanethial-S-oxide gets into the air and comes in contact with our eyes. The lachrymal glands become irritated and produces the tears!
Library of Congress, Science Reference Services, Everyday Mysteries