If your eyes water while cutting onions, blame syn-propanethial-S-oxide. It's the irritating compound that's released in the form of droplets when a knife blade slices through the bulb. The reason your eyes tear up is to prevent the compound from destroying cells in your eyes. So, tricks like putting a spoon in your mouth to prevent tearing are a bad idea.
Scientists at Cornell University wanted to learn how to minimize the release of syn-propanethial-S-oxide and related irritants in onions. As reported in Phys.org, they cut onions using a variety of blades and cutting speeds. They learned that the sharper the blade and the slower the cut, the less irritants released. "This was because duller knives tended to push down on the onion, forcing its layers to bend inward—as the cut ensued, the layers sprang back, forcing juice out into the air," reports Phys.org. And fast cuts increased the amount of eye-stinging mist.
So now you know — sharp and slow is the way to go.
Previously:
• Japan's Awaji Island is famous for its sweet onions and onion-themed attractions
• Lattes with onions are a hit in China
• How Michelin star restaurants cut their onions
