Which Chemical in Onion Causes Tears?
Onions have been a staple in kitchens around the world for centuries, known for their versatility and distinct flavor. However, one aspect of onions that many find quite intriguing—and sometimes quite irritating—is their ability to cause tears while chopping. The question that often arises is: which chemical in onion causes tears? In this article, we will delve into the science behind this phenomenon and explore the role of a specific compound that makes onions so tear-inducing.
The chemical responsible for the tear-inducing effect in onions is called syn-Propanethial-S-oxide (S-oxide). This compound is released when the cells of the onion are damaged, such as when they are cut or chopped. The S-oxide then reacts with the moisture in the air, leading to the formation of sulfuric acid and sulfenic acid. These acids then react with the enzymes in the tears, causing irritation and the sensation of burning, which prompts the eyes to produce more tears as a protective mechanism.
The presence of S-oxide in onions is not a new discovery. In fact, researchers have been studying this compound for over a century. In the early 20th century, scientists began to investigate the causes of onion-induced tears and identified S-oxide as the primary culprit. Since then, numerous studies have been conducted to understand the mechanisms behind this phenomenon and to find ways to mitigate its effects.
One interesting aspect of S-oxide is that it is heat-sensitive. This means that cooking onions can reduce the amount of S-oxide released, thereby minimizing the tear-inducing effect. For example, when onions are sautéed or roasted, the heat breaks down the S-oxide, resulting in fewer tears during preparation. Additionally, some people have found that peeling onions under running water or using a sharp knife can also help reduce the tear-inducing effect.
In conclusion, the chemical responsible for the tear-inducing effect in onions is syn-Propanethial-S-oxide (S-oxide). This compound is released when the cells of the onion are damaged, leading to the formation of sulfuric acid and sulfenic acid, which irritate the eyes and prompt tear production. While there is no foolproof way to eliminate the tear-inducing effect of onions, understanding the science behind it can help us find ways to minimize its impact during cooking and preparation.
