Why do onions make you cry?
(Najamuddin Ghanghro, Karachi (original from Larkana))
Onions, like other plants, are
made of cells. The cells are divided into two sections separated by a membrane.
One side of the membrane contains an enzyme which helps chemical processes occur
in your body. The other side of the membrane contains molecules that contain
sulfur. When you cut an onion, the contents on each side of the membrane mix and
cause a chemical reaction. This reaction produces molecules such as ethylsufine
which make your eyes water.
To prevent crying when you cut an onion, cut it under a running tap of cold
water. The sulfur compounds dissolve in water and are rinsed down the sink
before they reach your eyes. You can also put the onion in the freezer for ten
minutes before you cut it. Cold temperatures slow down the reaction between the
enzyme and the sulfur compounds so fewer of the burning molecules will reach
your eyes.