Why do onions make us cry when we cut them and how can we slice them without tearing up? These are two simple questions that anyone who cooks eventually asks. This vegetable is among the most widely used in the kitchen and is a star ingredient in countless recipes, available all year round.
In home gardens, they are extensively cultivated, so having large quantities on hand is common. But when it comes time to cut them, onions have the ability to irritate the eyes. Let’s explore why this happens and how to avoid tearing up during the process.
Why Do Onions Make Us Cry?
Onions make us cry for a very simple reason: they contain tear-inducing substances. For the plant, these substances serve as a defense mechanism. They have antifungal and antibacterial properties, deterring parasites and pathogens from attacking the underground bulbs. This defense also extends to potential herbivorous predators grazing in the fields. Chemically and molecularly, here’s what happens. In essence, when we cut the onion in the kitchen, we activate an enzyme called alliinase, which is released during the cut. When this encounters molecules of 1-PRENSCO, the most important sulfoxide in onions derived from the amino acid cysteine, a chemical reaction catalyzes the production of ammonia, pyruvic acid, and sulfenic acids like 1-propenylsulfenic acid. At this point, the molecules of 1-propenylsulfenic acid are captured by a second enzyme (called Lachrymatory-Factor Synthase), which produces the tear-inducing factor syn-propanethial-S-oxide.
Action of Onions on the Eyes
These chemicals combine and naturally release when we cut the onion. They are highly volatile and water-soluble, meaning they circulate in the air and dissolve in water. When they reach our corneas, they cause tearing. A vicious cycle ensues. Since tears are mostly composed of water, the substances released by the onion will tend to dissolve even more. For this reason, once the tearing starts while cutting the onion, it’s hard to stop, and the situation worsens. The solution is to leave the vegetable and knife on the cutting board and step away. This way, the substances dispersed by the onion in the environment no longer reach the eyes, the burning sensation alleviates, and the eyes stop tearing up. But what are the methods to prevent onions from making us cry?
How to Cut Onions Without Shedding Tears
The simplest and safest method to cut onions without shedding tears is to cut them under running water. As explained earlier, the molecules released by the onion are highly water-soluble. By placing the vegetable under running water, they are immediately washed away and do not have time to reach our eyes.
But cutting onions under a continuous stream of water is not the most convenient operation. Let’s see some other suggestions.
Tricks to Cut Onions Without Crying
If you have many onions to cut, aside from the inconvenience, cutting them with constantly flowing water is frankly wasteful. The alternative is to occasionally wet the knife you’re using because a wet blade can retain most of the volatile molecules. The discomfort won’t be eliminated 100%, but it will be reduced significantly.
Another trick is to freeze the onions for 5/10 minutes before cutting them or place them in a bowl of water and ice. The tear-inducing molecules are much more active at higher temperatures, so chilling them will partly solve the problem.
Finally, there’s a simple mechanical remedy to protect your eyes from onions. Although it might seem ridiculous to some, its effectiveness is guaranteed 100%! To cut onions without crying, just wear ordinary and practical swimming goggles.
