There is No Crying in Cooking
Just like Tom Hanks said in the movie A League of Their Own, “There’s no crying in baseball” so it may go with prepping and cooking onions. I used to have a food service job in which I had to chop onions and fill a five gallon jug every Sunday. If you want to talk about tears, you should have seen me ten minutes into that process.
Onions belong to the genus Allium. Among the 500 or so species that belong to this genus, members also include garlic, shallots, leeks, and scallions.
Researchers originally thought that the reason onions create tears is due to sulfuric acid in the eyes. Huh? That is correct, I did say sulfuric acid. The process starts when an onion is first chopped or cut. As the onions are cut, enzymes called allinases are released. These enzymes convert amino acid sulfoxides into sulfenic acids. These acids, being unstable, re-arrange to form gaseous syn-propanethial-S-oxide. This gas was thought to stimulate the lachrymal glands in the eyes leading to the production of tears. The water in the tears combine with the gas to form sulfuric acid resulting in stinging eyes.
In actuality, the real tear jerker is called lachrymatory-factor synthase. This synthase is a second enzyme located in the onion which converts sulfoxides located in the onion into sulfenic acid. If the enzyme can be blocked then a new product called a tearless onion could be born. The problem is that the enzyme responsible for the tears is also the enzyme responsible for a good portion of an onions flavor.
Researchers have found that one way to tone down the tear factor is to have onions grown in sulfur deficient soil thus inhibiting the uptake of sulfur. This leads to less secondary sulfur compounds in the bulbs. In doing so, however, the health benefits could be reduced and the onion could lose flavor. Also, nature doesn’t really do things by accident so there must be some sort of grand design for an onion to have this tear inducing quality. Strip that away and perhaps the onions natural defenses against fungal and bacterial infections could be compromised.
In the meantime, perhaps home cooks and chefs should just grin and bear it because “there’s no crying in cooking!”