John Myers
Rising gases, which irritate the mucous membranes of the eyes, are responsible for the tears when cutting onions. Water is an effective way to prevent this unwanted effect. It stops the chemical reaction that causes the irritant gas to form in the first place.
So when you peel onions under running water, you certainly don’t have to cry. It is just as effective if you briefly rinse all the utensils you need with water before cutting: knife, cutting board, and the onion itself. It is best to cut the vegetables under running water beforehand.
Place half the onion with the cut side on the wet board and keep moistening the knife from time to time. It is also important that the knife is as sharp as possible. With a blunt knife, larger amounts of the irritating substance would be released due to the higher pressure. The concentration is particularly high at the root of the onion. You should therefore only cut them at the end.
The irritating gas is produced when the onion’s cells are destroyed during cutting. The enzymes that are released react with sulphur-containing compounds, and the reaction product rises as a gas. The tears are a protective reaction of the eye and at the same time a model for the trick mentioned, with which one can cut onions without tears.
