If you’ve ever chopped onions, you know that doing it without crying isn’t easy. As soon as you start cutting through the layers, a certain irritating smell alerts you, and immediately your eyes fill with tears.
Today we’re going to learn how to cut or chop onions without crying and analyze the most common tricks, discovering which ones work and which ones don’t.
The substance responsible for the eye irritation that causes tearing is alliinase, a substance that is released when cutting onions and that produces the emission of an irritating molecule called syn‑propanethial‑S‑oxide or propanethial.
This molecule, which is a sulfur‑containing essential oil, is highly volatile and is absorbed through the nose when inhaled. Therefore, and this is how we start debunking absurd methods, wearing diving goggles that don’t cover your nose is not a useful way to chop onions.
Why Does Cutting Onions Cause Tears?
As I mentioned before, the reason for the tearing is the irritation of the nasal mucous membranes when inhaling the molecule released when cutting the onion layers. This emission usually has a small range, approximately 50‑90 cm.
When you breathe in propanethial, its irritating effect causes your eyes to water or even makes you feel unwell, forcing you to leave the kitchen. The methods we’ll discuss are based on avoiding or reducing the emission of this volatile substance and, at the same time, minimizing its effects.
To prevent or reduce the emission of alliinase, it’s best to cut onions that are very cold. This makes the gas less volatile, and it’s usually either not released at all or released in much smaller quantities.
Therefore, one of the tricks used in many homes is to put the onion in the freezer for a few minutes or in the refrigerator for an hour or more before cutting it.
Another way to avoid being affected by the fumes would be to chop the onion while submerged in a basin of water, so that no irritating gases are released. Obviously, this method will work, but it’s not practical, especially if we need to make a fine brunoise.
How to Cut an Onion Properly?
Step 1:
Cut the onion in half to obtain two parts. Our professional tip is that, once cut, you place one of the two halves cut‑side down to minimize tears caused by the onion.
Step 2:
Remove the brown outer layer from the first half and place it face down on the cutting board. Repeat this step for the other half. Then, cut off just the end of each half to expose the white bulb of the onion, ready for chopping.
Step 3:
Carefully hold the end of the onion and begin making vertical, crosswise cuts (always keeping the knife away from your hand). The more cuts you make, the smaller the pieces of onion will be; wider cuts will result in larger pieces. Be careful not to cut all the way through, as it’s important to keep the back part you’re holding the onion with intact.
Step 4:
Next, slice the onion horizontally across the grain. Again, the more slices you make, the thinner the pieces will be.
Step 5:
Place your fingers in a claw shape and rest them on the onion, making sure your fingernails are well away from the blade. It’s your knuckles that are in contact with the knife, not your fingers. Then, slice the onion crosswise with a quick, downward motion.
Step 6:
Continue chopping the entire onion, including the other half, until it is perfectly chopped and ready to cook.