master-cooks | The Scientific Reason Onions Make You Cry

When you cut an onion, you break its cells, releasing a series of chemical reactions. The process begins with an enzyme called alliinase, which converts amino acid sulfoxides into sulfenic acid. This unstable compound then rearranges itself into a volatile gas known as syn-propanethial-S-oxide. As this gas wafts upward, it comes into contact with the cornea of your eyes. The eyes detect the irritant and send signals to the brain through the sensory neurons. In response, the brain triggers the lachrymal glands to produce tears in an attempt to wash away the irritant. The lachrymatory factor in onions is a defense mechanism evolved to deter herbivores from eating them. Different onion varieties have varying levels of this compound, which is why some onions make you cry more than others. Cooking or soaking onions in water before cutting can denature the enzymes responsible for this reaction, reducing the likelihood of tears. Using a sharp knife can also minimize cell damage, limiting the release of the irritant. Understanding these processes provides insight into the complex interactions between plants and their environment, as well as simple culinary practices that can enhance our cooking experience.

It's time to stop crying over your onions

Many people employ various techniques to lessen the discomfort of cutting onions, and some methods can complement each other effectively. For example, chilling onions before slicing can be beneficial, as the compounds responsible for irritation are less volatile at lower temperatures. Additionally, cutting onions in a well-ventilated space or near a fan can help disperse these irritating chemicals. Combining these two strategies can significantly reduce the discomfort.

Another option is Martha Stewart's burner trick, which involves chopping onions close to an open flame, like a gas stove. While this may seem unusual, the concept is that the flame will attract and eliminate the irritating compounds before they reach your eyes. However, since some individuals have more sensitive tear glands, not every method will work for everyone, and it may require some experimentation to discover what suits you best.

If you find that none of these methods are effective, don’t lose hope! A "no tears" onion known as the Sunion was introduced in 2017 after 30 years of hybridization. Unlike traditional onions, Sunions are reported to become sweeter over time. Dietitian Heather Martin tested them on the show Today and noted that she experienced no burning or stinging, even when holding the sliced onion close to her face. Sunions can be found at select retailers, including Aldi, Kroger, Costco, Publix, Meijer, and Whole Foods.

The Scientific Reason Onions Make You Cry

It's time to stop crying over your onions

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