You’ve probably been cooking before and noticed how you started tearing up while chopping your onion; but why do onions cause this reaction?
Unfortunately, the same chemicals that irritate your eyes are the chemicals that give the onion its unique flavor. Onions contain amino acid sulfoxides and sulfonic acids that they absorb from the soil they grow in. These alone are harmless to your eyes, but when you cut the onion, you break the cells and mix these enzymes. They then react with each other and create a vapor called propanethiol s-oxide. But this vapor still isn’t what causes the burning sensation.
The irritation is caused by another separate reaction. The vapor reacting with the moisture in your eyes forms sulphuric acid, and it’s the sulphuric acid that burns your eyes and prompts them to release tears that will wash the irritation away.
How to Chop Onions without the Tears
Now that we know what causes this reaction, how do we prevent it? Take a look at some of these onion chopping tips.
Put the onion in the fridge a few hours before chopping it up.
Refrigerating the onion slows the reactions down and changes the onion’s chemistry. You’ll get the same effect if you cut the onion in half and let the halves soak in water for an hour before cutting it up any further.
Stick your tongue out and breathe through your mouth.
While it’s not 100% effective, it works by drawing the gas over your wet tongue. The olfactory nerves, which are closely located to the tear duct nerves, will be by bypassed and there will be no tears.
Wear tight swimming goggles.
This method is simple. With the goggles on, the gas doesn’t reach your eyes. Just make sure they fit. Out of the methods in this list, this is the most fool-proof.
Do Your Chopping Next to A fan.
The fan should be blowing in a direction that directs the fumes away from your eyes.
Cut the Onions under Running Water
Although this method can be a bit tricky, the water neutralizes the vapor before it has a chance to reach your eyes.
Cut the root last
Most of the tear inducing chemicals are concentrated at the root so cutting it last (or leaving it out completely) minimizes the chemical reactions.
Also, make sure you use a sharp knife; fewer enzymes are going to mix with each other because instead of crushing the cells, a sharp knife cuts neatly through them. This should produce a significantly less amount of vapor.
Know what doesn’t work
There are a few old-wives-tales about how to cut onions without crying. A few of them are just myths. A few might work but there really isn’t any scientific proof whether they do or not. You might have heard about the following methods, but you can’t be sure 100% sure about their effectiveness. If you still want to try them regardless, feel free.
Chop the onion near a candle.
It’s said that the flame absorbs the vapor coming from the onion. Try to keep the candle as close to the chopping board as possible.
Rub some fresh lemon juice on the knife you’re using.
You should do this before you start chopping the onion and keep re-applying the lemon juice after a few cuts.
Put a piece of bread in your mouth.
The belief is that the bread will absorb the vapor before it reaches your eyes and will prevent you from breathing it in too.
Putting a spoon in your mouth
No one knows exactly why this works, but it’s been passed down numerous generations and many families believe it helps.
If all else fails
Most people withstand the discomfort of chopping onions because they would rather have all of the flavor it adds to the food you’re cooking. If you absolutely can’t stand the burning sensation and you don’t mind taking a little of the onions fragrance and flavor out of the food you’re cooking, there are two more ways to chop onions without tearing up.
Put the onion in the microwave before you chop it up.
Simply put the whole onion in the microwave on high for no more than two minutes. Partially cooking the onion deactivates the enzyme while keeping the strong aroma and not burning your eyes.
Use a blender or food processor.
An electronic food processer will most likely chop the onion a lot finer than you would by hand, causing almost all the enzymes to react. You’re going to be getting a lot less flavor out of onions chopped this way because food processors drain the liquid that comes from the chopped onion, but if you would rather have this than teary eyes, it’s an option that works every time.