Onions contain a chemical compound and an enzyme that mix to release an irritating gas when the onion is cut. This helps keep the bulb from getting eaten by animals as it grows in the ground.
Onions make your eyes burn for the same reason they make you cry: thanks to the combination of that chemical compound and the enzyme that synthesize when an onion is cut. This creates syn-propanethial-S-oxide, a volatile gas that makes your eyes burn and fill with tears.
Here’s how the process works:
The onion contains both the chemical precursor to the gas and an activating enzyme that floats in onion cells in little walled-off areas (vacuoles).
An onion gets sliced, diced or bitten into.
The precursor and enzyme mix, creating an unstable chemical irritant.
At room temperature, this irritant quickly becomes a gas that spreads through the air.
The gas triggers pain receptors in the eyes and nose designed to protect you from chemicals, smoke and other dangers.
The tear glands in the eyes then make tears to wash away the irritant.
So how do you cut onions without getting all teared up?
You can try:
1) Cutting onions under running water (awkward... but it works)
2) Wetting your knife intermittently while cutting into the onion (also works... but affects the taste)
3) Cutting onions under a stovetop exhaust (works quite well)
4) Make sure your knife is sharp... that'll damage the onion less and decrease release of the noxious fumes while cutting.
Comments