Unless you never cook before, most of you might have experienced this. Everytime I cut an onion, my eyes will feel like burning and tearing. Why will this happened? After I search through the Internet, finally I found the solution~ And I am going to share with you guys!
Onion cells contain enzymes called allinases. When we're cutting, peeling or slicing an onion, the cells are broken, and allinases are released to break down amino acid sulfoxides, which will eventually form sulfenic acids. Sulfenic acids are very unstable and rearrange to form a gas called thiopropanal S-oxide or syn-propanethial-S-oxide (C3H6OS).
Next, let's see how syn-propanethial-S-oxide make our eyes so painful and tearing?
When syn-propanethial-S-oxide in the air reach the cornea of our eyes, it will react with the water in our tears, to form sulfuric acid. Free nerve endings of our eyes detect the sulfuric acids and through the ciliary nerve, central nervous system of our brain interprets as a burning sensation. These nerves activities activates the autonomic fibers, which then send a signal to the lachrymal glands of the eyes to stimulate more tears, to wash the irritant (sulphuric acid) away.
After reading the long explanation, you guys must be wondering. 'Do we have any solution?' Of course!
1) You can chill the onion in the refrigerator before cutting it. This will slows down the reactions inside the onion, thus, reducing the amount of syn-propanethial-S-oxide released.
2) Cutting the onion under water. This will cause the gas released into the water instead of the air.
3) Wipe some vinegar at the chopping board. The acid of vinegar will denatures the enzyme of the onion.
4) Soak the onion in salt water. The ionic property of salt water can helps to denature the enzyme of the onion.
5) Light a candle beside the chopping board. The gas released by the onion will be drawn into the flame of the candle.
Thanks for reading! No more tears! Only smile =D