Why do onions make us cry?
[ 2006-04-04 08:52 ]
 It is not the strong odor of the onion that makes
us cry, but the gas that the onion releases when we cut this
member of the lily family.
The onion itself contains oil, which contains
sulfur, an irritant to both our noses and to our
eyes. Cutting an onion arouses a gas contained within the
onion, propanethiol S-oxide, which then couples with the
enzymes in the onion to emit a passive sulfur compound.
When this upwardly mobile gas encounters the water produced by
the tear-ducts in our eyelids, it produces sulfuric
acid.
 In response to the caustic acid, our eyes
automatically blink, and produce tears which irrigate the eye,
and which flush out the sulfuric acid.
Another reflex to rid the eyes of a foreign substance, that
of rubbing our eyes with our hands, often exacerbates
the situation, because our hands are coated with the caustic,
sulfuric acid producing oil from cutting the onion, which we
then rub directly into our eyes.
Much to our chagrin, the only remedy for ridding the onion
of its pungent, irritating oil is to boil it, not to slice it
or dice it. |
硫磺
刺激
酶
淚管
加劇，惡化
切成丁
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