chemical reaction
Onions contain amino acid sulfoxides, which produce sulfenic acid within onion cells. When you start chopping an onion, it destroys the cells and normal cellular enzymes mix with the sulfenic acid to produce propylthioal S-oxide. Propylthialdehyde S-oxide is a sulfur-containing chemical that is a gas that floats in the air and gets into the eyes. When this gas interacts with moisture in the tear film, sulfuric acid is produced. This acid is incompatible with your tears and your eyes begin to burn.
basic tear production
Two types of tears are produced inside the eye. Basal tears provide essential lubrication to the eye, while reflex tears are the type of tears we usually think of when we cry. Reflex tears are produced in response to emotions and some external stimuli. External irritants, such as dust or smoke, trigger nerve endings in the cornea to communicate with the brain, opening the tear ducts. The lacrimal gland is located under the upper eyelid on the side of the temple and produces tears reflexively. Your tear glands begin to produce tears to dilute or flush out harmful substances.
How to avoid tearing when chopping onions
There are some tips that are known to reduce onion chopping tears. Here are some of the most effective methods:
- Store onions in the refrigerator and consider placing them in the refrigerator 10-15 minutes before cutting them. This freezes the enzymes and prevents them from mixing with the sulfenic acid, thereby reducing the production of propylthial S-oxide. Therefore, sulfuric acid is reduced when cutting onions.
- Soak onions in water before cutting them. The gas will be absorbed into the water. Just place the onions in a small bowl of water for about half an hour and then start chopping them.
- Damage the onions as little as possible. Use a very sharp knife to cut the onions. Crushing onions, rather than chopping them hard, tends to release more gas. A sharp knife allows for quick, clean slicing with less damage to the onion flesh.
- Cut off the stems, keeping the root end. The roots have the highest sulfur content, which can cause more tears.
- Use sweeter onions, such as red, green, or Vidalia onions, rather than the more pungent white or yellow onions.
- Use an electric food processor instead of a knife.
- Cut onions in a well-ventilated area. Turn on the range hood, chop vegetables near an open window, or turn on a fan. Point the fan at your work surface to draw the smoke away from you.
- Wear safety goggles when chopping onions. You may get some funny looks, but it will definitely prevent acid from getting into your eyes.
- Remember not to touch your eyes when chopping onions. Be sure to wash your hands thoroughly when finished.
