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9 Tips to Chop an Onion Without Crying

We know how much of the cooking repertoire starts off with chopping or slicing onions as the base component for a meal. As a home cook, it’s hard to think of a meal prepare regularly that doesn’t involve onions right from the get go.

Onions are simply in just about everything savory and for good reason. They’re tried and trusted foundation vegetables that are easily, widely available and cost effective to boot.

Essentially, cutting your onions without crying is all about avoiding or tampering down the irritating compounds in the onions that are released as you cut.  That’s onion tears avoidance 101 but here at this guide we like to offer in depth advice and well researched material to the readers.

So let’s go a lot deeper with this and give you some interesting information AND our helpful hints, hacks, and tricks to avoid eye annihilation the next time you need to prep your onions! We’re going to get a bit scientific here, but it’s all in a good cause (no more onion tears) and we’re going to keep it relatively simple, so stay with us!

Why do onions make you cry?

Chopping an onion

In simple terms, onions make your eyes irritated and make your eyes produce tear fluid as a protective measure. Because when you cut into an onion, you are releasing its unstable chemicals into the atmosphere.

To be more explanatory, onions or allium cepa contain an irritating chemical called syn – Propanethial – S – Oxide. Syn – Propanethial – S – Oxide is an organosulfur compound and an unstable or volatile liquid that has a lachrymatory effect

It’s a substance that makes you cry. Today in English we use the word ‘lachrymose’ to describe somebody weepy or tearful (they’re probably chopping onions!) and both terms come from the Latin ‘lacrima’ which means ‘tear’.

As you slice into an onion you are breaking its cells and prompting it to release enzymes (proteins) that break down the amino acid sulfoxides, and this produces sulfenic acid.

The sulfenic acid is then acted on by a second enzyme and turned into syn – Propanethial – S – Oxide. Now, this nasty substance is a gas which diffuses through the air and straight into your eyes, face, and nose, stimulating your sensory receptors and creating a burning, irritant sensation.

Because your body always looks out for you, it responds protectively by creating and releasing tears to flush out the irritant.

And that, ladies, and gentlemen, is why an onion will make you cry! We shouldn’t hold it against our oniony friends, it’s simply how they’re made, and they offer us so much variety and yum in the kitchen that this small fault can be overlooked.

The irritation and the tears though, let’s look at getting rid of that, because nobody likes streaming eyes and burning skin in the kitchen if they can avoid it. Follow on for some handy guidelines that’ll have you slicing and dicing onions with ease and in comfort!

Cutting your onions without the tears – our top methods

Freeze your onion first

By putting your onions in the freezer for 15 minutes before you start slicing them, you’re effectively neutralizing the chemicals that make your eyes burn. This method is both simple and highly effective.

Also, if you have a very busy lifestyle, try freezing your onions in bulk for 15 minutes, then chop a lot of onions at one go to save time later. Divide your chopped onions into containers for future usage. The next time a recipe calls for onions you’ll be ready to go without all the hassle and fuss.

Only use super sharp knives for cutting your onions!

A sharp knife

When you use a dull knife blade to cut through your onion, you’re having to hack and saw through the onion flesh. This breaks open the cellular walls of the onion and releases those irritating substances we’ve discussed.

To avoid tears like a pro chef, only ever use a very sharp blade to chop your onions, and we recommend using a non – serrated chef’s or utility knife to do the job best.

A serrated knife may in some instances seem quicker, but those serrations are catching on the onion flesh and tearing it, thereby releasing sulfur compound gas, which is what you DON’T want.

Need some pointers for getting your knives wickedly sharp? Refer to our blog for a variety of knife sharpening and care articles.

Chop the onion with an ultra-sharp knife

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Holding a slice of bread in your mouth whilst chopping onions

A slice of bread

Now, none of us particularly wants to look like a mid – meal hamster in the kitchen, but sacrifices must be made! Some sources swear by the technique of holding a slice of bread in your mouth while you chop your onions.

Does it work? Oddly enough, yes it does.

To do it effectively, hold the bread in your mouth so that most of the slice is hanging out and downwards. Your yeasty shield will absorb any nasty gas offenders and the slice of bread itself will be a physical barrier stopping those same gases from hitting your delicate eyes.

Could you use other types of food for this? Following the logic of creating a physical barrier to the sulfur compound gas, other types of food would probably work just as well.

Bread is inexpensive and readily available, also it’s shaped quite comfortably to hold in the mouth, so it’s probably the easiest and least messy or complicated choice.

When you’re done chopping the onions, simply discard the slice of bread OR be frugal and munch away happily! Chopping onions is, after all, hungry making activity.

Prevent onion burn by using eye protection

Cutting an onion with eye goggle

One of the best methodologies for avoiding onion tears is to stop the sulfur compound gas from getting into your eyes in the first place. No gas = no irritation.

To this end, a lot of people use eye protection whilst they chop and dice their onion friends into oblivion. You could try swimming goggles (raid your kid’s swimming kit), safety goggles (check your garage) or just wear a ludicrously large and oh so chic pair of sunglasses, which has the unlooked benefit of allowing you to channel cinema greats like Audrey Hepburn!

Does it work? Yes, because you’re protecting your eyes and thereby not starting off the protective tear manufacturing process.

Harness the power of contact lenses

If you’re able to switch easily between glasses and contact lenses, many people report little to no eye irritation when wearing their contacts and chopping onions.

Contact lenses themselves provide a sort of shield and emollient effect on the eyeball which helps to offset the corrosive and burning action of the sulfur – based gas released by cut onions.

Cut your onions next to an open flame

Many cooks use this trick and apparently it works. If you’ve got a gas stove and burners ready to use, chopping your onions on a work surface near the open flames means that the gaseous sulfur compounds will be burnt off before they hit your eyes.

Use a food processor or automated slicing machine

Food processor

If chopping your onions manually is getting you down big time and you’re looking to save time, start using those handy kitchen aids that often sit on the counter gathering dust.

Most automated kitchen slicers and dicers can process large amounts of onion more quickly and more effectively than we can, so put them to work. Consider being extra clever and processing your onions in bulk for quick and handy freezing. Buying your onions in bulk also saves you money, so you’re saving time, effort, and money all in one go!

Blow your onion tears away by maximizing kitchen air flow

Another way to curb annoying onion gasses is to harness the power of your ventilation and air movement systems.

The next time you chop onions, consider using a table mounted fan that blows the air across the onions but away from you. Other air movement systems like above oven vent fans, ceiling fans and simply opening all the kitchen windows will also be quite effective.

Cut your onions very close to a running faucet

running faucet

This method is a bit fiddly and isn’t the best way to stop onion irritation but it’s something to try.

Cut your onions very close to the kitchen sink and run a stream of cold water slowly. Put the plug in to save that water, you can use it for rinsing dishes or for your plants! The sulfur gas as it’s released from the onion will naturally move towards the water stream, in theory bypassing your tender eyes in the process.

If you’re looking for detailed guides on different onion chopping techniques and our best hacks and tricks on getting those alliums sliced and diced, do refer to other sections of this blog – we have super articles dedicated to many types of onion preparation AND recipes for you to try!

Onion cutting FAQs

In conclusion

With this article, you’re prepped and ready to take on ANY onions any day of the week, and without tears too! Burning eyes and running noses simply have no place in the happy kitchen and the techniques we’ve given you here will sort out those streaming eyes in no time!

Until we see each other again, love your alliums and don’t forget to dive further into our blog posts – there’s something for everyone, from knife enthusiasts to dedicated foodies looking for a gorgeously munchable recipe fix.

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