Why You Should Never Use A Dull Knife To Cut Onions

Is it just us, or are onions in almost every single delicious dish we whip up at home? Onions bring their earthy allium flavor to so many staple recipes, from pasta sauce to stew to French onion soup. Of course, they also make for wonderful condiments in the form of onion jam, pickled onions, and Indian raw onion relish.

A kitchen without onions is a sad kitchen indeed, but with so many widely available varieties, it's easy to avoid this fate. Whether you prefer to cook with white, yellow, green, or red onions, it's a good idea to have at least one type on hand at all times. It's also a good idea to learn how to cut the vegetable correctly. As we all know, onions are prone to making us cry when we slice them, which is why you never want to use a dull knife when you're tackling this kitchen task.

As you've probably experienced more than a few times in your life, onions can bring tears to your eyes when you cut them. According to Britannica, that process all starts underground. As onions grow, they pull in the sulfur from the surrounding soil, which then turns to amino acids inside the vegetable. Later, when the onion is sliced, these amino acids are released and able to mix with other enzymes in the onion, ultimately sending a chemical called syn-propanethial S-oxide into the air. That substance wafts up to your eyes, creating a stinging sensation and, thus, tears.

There are lots of tricks and hacks that are supposed to ward off these onion tears, including chilling the onions before chopping (via Yummly) or wearing goggles (via Epicurious) or glasses. But, according to Bon Appétit, there's another method that is a bit simpler — and that's ensuring you draw your sharpest kitchen knife for the task. The outlet states that a dull knife does extra damage to the onion's cells, causing the vegetable to leak more of that pesky syn-propanethial S-oxide. But a sharp knife slices through those cells cleanly, mitigating the damage and the amount of the tear-provoking chemical that is released. So the next time you're dicing your way through a mess of onions, grab a sharp chef's knife and enjoy their flavor with fewer tears.