Why the onion makes us cry is one of the great questions of gastronomy, and the culprits are sulfur compounds that are released and transformed by cutting the onion

The gastronomic possibilities offered by the omnipresent onion are unlimited: raw, cooked, as the protagonist of a dish, forming part of a dressing or as a faithful companion of the potato in the tortilla.

The onion, belongs to the Allium genus as well as other species of gastronomic interest such as leeks, garlic or chives, among others. The onion is a very interesting food from the nutritional and even medicinal point of view since it can boast a wide list of properties and positive attributions for health. However, among all the qualities of this edible bulb, there is one that is somewhat uncomfortable and is precisely the eye irritation that causes us when we cut it.

One of the characteristics of the onion is the presence of sulphoxide amino acids in its cellular liquids. When cutting the onion, the cells of this are broken releasing these sulfur compounds. Another substance released when cutting the onion, is an enzyme called alinasa, which converts the sulphoxide amino acids into sulfenic acids, one of which, after another reaction, finally gives rise to the thiopropanal sulfoxide, which is the gaseous substance that triggers the itch, irritation and tearing when it reaches our eyes.

How to prevent the onion from making us cry?

Any of the methods that reduce tearing when cutting onions are based on inactivating or reducing some of the substances involved in the production of thiopanal sulphoxide. For example: heating the onion before cutting would inactivate the enzyme alinasa, which would not form the substance that causes ocular irritation. Likewise, cooling the onion before cutting it would slow down the reactions responsible for the formation of the lachrymatory compound. Finally, wet the onion or cut it in a ventilated place would save us a few tears by diluting or reducing the concentration of the substance that triggers eye irritation