Onions are a staple in so many dishes, but why do they have to make us cry? And, more importantly, can you prevent it?
Given the way onions can traverse the range from a spicy bite to downright sweet, it’s no wonder we find them crucial to so many dishes. Cutting an onion, though, is often a dreaded kitchen task. We’ve all experienced the weepy redness that results from breaking an onion’s skin, and none of us like it.
What’s worse are the many myths that claim to prevent onion tears. Wives’ tales abound on how to stop this layered allium from making us cry, but very few of them work. So, let’s look at what really causes onion tears and what can versus what won’t stop them.
What Causes Onion Tears?
Let’s start with what makes onions such tear-jerkers. When we hold them or even peel them, everything seems just fine. But take a knife to them and, oh my, let the floodgates open! So, what gives?
When you cut through an onion’s cell walls, syn-Propanethial-S-oxide (or S-oxide for short) is released into the air. S-oxide is a lachrymatory gas, which is a fancy way of saying it makes you cry. In fact, it’s similar to tear gas, which is sort of terrifying.
Of course, we can’t be too mad about it. Onions don’t exactly want to be eaten, and it’s not like they can learn jujitsu for self-defense. We shouldn’t be surprised evolution gave them such a sneaky weapon. That doesn’t mean we have to sit there and take it though. Let’s see what we can (and what we shouldn’t) do to prevent the waterworks going forward.
Onion Tear-Prevention Myths
A lot of rumors percolate around how to prevent onion tears. We’ll get to what really works in a second, but let me save you from looking like a total fool in the kitchen, and go over what doesn’t work first.
Myth 1: Press Your Tongue to the Roof of Your Mouth
Then, without moving it, repeat after me: “This doesn’t work.”
Really, it doesn’t.
The practice will keep a naive cook quiet while they’re chopping, though, so use this one as you will. Just know that pressing your tongue to the roof of your mouth does not block the S-oxide from reaching your tear ducts.
Myth 2: Light a Candle Near a Cutting Board
This method does make things smell less onion-y, which for many is a plus, but it doesn’t burn off the tear-inducing gas as one might predict. The flame is simply too small for the amount of gas the onion releases. Now maybe, if you cut the onion directly next to a bonfire, on the beach, with the wind blowing away from you, you might be able to avoid onion gas in the eye. But even then, I doubt it.
Myth 3: Chew Bread while You Slice
The idea seems to be that bread, when mixed with saliva, will somehow act as a filter for the gas. Of course, the S-oxide isn’t in your mouth, it’s going from the onion to your eyes (maybe a bit through your nose, too)—so you shouldn’t be surprised this one doesn’t work. It is an excuse to eat bread, though, so do as you will.
How To (Really) Prevent Onion Tears
All right, now let’s look at what really works. These three tried-and-true methods actually prevent onion tears.
Refrigerate Onions Before Chopping
We want to stop a gas from reaching our eyes. Science tells us that gases move more slowly at lower temperatures. So, yes, refrigerating your onions will leave you with fewer tears. It’s not a perfect method. The s-oxide is still there; it’s just moving a bit slower. However, it’s better than pulling a warm onion out of your pantry. So, before you slice and dice, give your onions a ten- to twenty-minute cooldown.
That being said, never store your onions in the fridge or freezer. Onions will turn mushy and develop a less than pleasant odor if stored in refrigeration too long.
Wear Protective Gear
This is what we recommend when a massive amount of onion dicing is necessary. It’s the only surefire way to ensure no tears. That’s because we’re literally placing a barrier between the S-oxide and our precious eyes. Regular glasses do all right, and contact lenses seem to help, too. But if you want to make sure you don’t shed a single tear, you’ll want to go full-blown snorkel mask. The downside, of course, is that now you’re wearing a snorkel mask in your kitchen. That’s fine if you’re on your own. In a house full of guests, well, at least it’s a conversation starter.
Soak the Onions
This last option definitely works, but it comes at a price. It’s simple.
Cut the roots off the onion, peel it, and then throw it in an ice bath for about 10 minutes. The ice bath is guaranteed to get rid of the s-oxide, however, this method also reduces the onion’s bite. See, the water washes away some of the flavor molecules as well, which really mellows things out. Now, in some applications, like a salad or sandwich, that might work out perfectly. Other times, though, say in a salsa, you won’t be doing yourself any favors.
No matter what tear prevention method you choose, we ask that you don’t give up on these magical alliums. Onions are a staple throughout many different regions and cultures. To give them up would be a shame. So yes, they may force us to let loose the waterworks now and again, but we have to point out, and we think you’ll agree, all the best things in life are worth shedding a tear for. Onions are no exception.