An onion makes you cry due to the following steps
1. When you cut the inner part of the onion it release an enzyme (lachrymatory-factor synthase)
2. That enzyme reacts in the rest of the onion to release a gas.
3. When that gas combines with water in the eye it creates an acid (Sulfuric acid) that makes you cry, as the eyes release more tears to wash out the irritant.
So, if you still want to cut some onions, there are some simple steps that keep you tear-free!
1. Use a sharp knife when cutting an onion-The enzymes are released when cells are broken or crushed; using a sharp knife slices through the onion rather than crushing and thus, fewer enzymes are released.
2. Chill your onions in the freezer for 10 – 15 minutes before cutting them. This reduces the amount of the acid enzyme released into the air.
3. Breathe through your mouth-The olfactory nerves, which are closely located to the tear duct nerves, will be by bypassed and there will be no tears generated. This is easily confirmed when you forget and breathe through your nose, instant tears!
4. Soak the onion in water. The enzyme is denatured by the water-air boundary.
5. Put vinegar on the chopping board. The acid also denatures the enzyme.
Further reading- The chemistry and health benefits of onions.
Anne Marie Helmenstine, PhD. (n.d.). Why Do Onions Make You Cry? Retrieved from About.com Chemistry.wikihow.http://chemistry.about.com/od/chemistryfaqs/f/onionscry.htm
Leann Hamre and Ben Rubenstein. (2012, 12 22). How To Chop Onions Without Tears. Retrieved from http://www.wikihow.com/Chop-Onions-Without-Tears
Lynn K. (2012, June 14). Why do onions make you cry? – The chemistry and health benefits of onions. Retrieved from Something About Science.http://somethingaboutscience.wordpress.com/2012/06/24/why-do-onions-make-you-cry-the-chemistry-and-health-benefits-of-onions/