How to Chop an Onion

Ever wonder why your eyes burn when you cut into an onion?  With a strong onion, it can be the most unbearable sensation.

When an onion is whole, it encapsulates certain enzymes.  These enzymes are amino acid sulfoxides from sulfuric acids.  Once the onion is split open with a knife, cells are dividing amino acid sulfoxides from sulfuric acids.  Anne Marie Helmenstine, Ph.D. explains why this affects our eyes. "Enzymes that were kept separate now are free to mix with the sulfuric acids to produce propethiol S-oxide, a volatile sulfur compound that wafts upward towards our eyes.  This gas reacts with the water in your tears to form sulfuric acid.  The sulfuric acid burns, stimulating your eyes to release more tears to wash the irritant away" ("Why Do Onions Make You Cry?").  This chemistry explains why people cry when they are cutting onions.  Now that we know the why; how do we prevent this from happening when we chop onions?

Helpful hints about chopping onions...

• Refrigerate the onions before you cut into them.  (Some kitchens peel them and put them in the freezer for 30 minutes before they chop onions)
• Use a SHARP knife!  Dull knives release more of the vapors because it is smashing the cells apart as opposed to cleanly cutting them.
• Cut the onion with as few knife cuts as possible. It is not parsley, do not go over the onion back and forth with the knife. 
• My personal secret... I wear my contacts.  I don't know the "why" behind it, but when ever I use my contacts instead of my glasses, I never tear up.  When I wear my glasses, it is almost as if the glasses trap in the onions gasses even more.