The Kitchen Vent Trick To Cutting Onions Without The Tears
If you want to build on the flavor of a dish, onions are an easy way to do so, and that's why they're a staple ingredient in many recipes. But whether your recipe calls for slicing them or chopping them, it's hard to cut onions without your eyes tearing up in the process. There are many hacks that claim to prevent this, such as shoving bread in your mouth as you cut or using a wet knife. While some people have had success with these uncomfortable and potentially dangerous methods, all you actually need to do is make sure your kitchen is well-ventilated. That's where a kitchen vent comes in.
A kitchen vent, the exhaust hood located above your stove, is technically designed to remove airborne grease, smoke, heat, and odors generated during cooking. However, the ventilation it creates also works when cutting onions. The more ventilated your kitchen is, the less likely your eyes will water.
How it works
Simply turning on your kitchen vent while you cut onions might seem too good to be true, but the reason it works is backed by science. The whole reason onions make people cry is due to a chemical reaction that occurs when they're cut raw. During this chemical reaction, onions release enzymes and sulfenic acid which turn into a gas called propanethial S-oxide. When this gas comes in contact with your eyes, it turns into sulfuric acid, triggering the formation of tears.
You can't stop an onion from releasing enzymes or sulfenic acid because it's part of the plant's natural defense mechanism. However, you can control how much propanethial S-oxide gets in your eyes. This is the reason ventilation is so important when cutting onions, and why a kitchen vent is so effective. It works by clearing the air, and whisking away the gas along with it, ultimately reducing the watering of your eyes. For best results, place your chopping board directly under the vent.
What you can do to increase the effectiveness of this hack
Though a kitchen vent can significantly reduce the amount of eye-irritating gas in the air, it won't completely prevent your eyes from watering, especially if you're cutting a lot of onions, or working with yellow ones, which have a higher sulfur content compared to other varieties. Fortunately, you can increase the effectiveness of the kitchen vent hack by refrigerating your onions for roughly 30 minutes before cutting them.
It seems simple enough, but lowering the temperature of an onion actually slows the release of the sulfur compounds and the chemical reaction that results. That means if you refrigerate your onion prior to cutting, and also turn on your kitchen vent, you'll be less likely to tear up. Keep in mind that refrigeration isn't a good idea for storing your onions because it makes onions go soft over time, so reserve refrigeration for when you're just about to cut them to ensure your onions (and your eyes) will be in good shape.