What causes tears when cutting onions? This common question has intrigued cooks and chefs for generations. The answer lies in a fascinating interplay between enzymes, amino acids, and the human eye. When onions are cut, a chemical reaction occurs that triggers a series of events leading to the production of tears. In this article, we will delve into the science behind this phenomenon and explore ways to minimize its effects.
Onions contain a chemical called syn-Propanethial-S-oxide, which is released when the cells of the onion are damaged during cutting. This chemical is a potent irritant to the human eye. When it comes into contact with the eye, it stimulates the trigeminal nerve, which is responsible for the sensation of pain and irritation. This stimulation leads to the production of tears, which help to wash away the irritant and protect the eye.
The release of syn-Propanethial-S-oxide is triggered by the action of enzymes called alliinase and myrosinase. These enzymes are stored in separate compartments within the onion cells. When the onion is cut, the cells are damaged, allowing these enzymes to mix and catalyze the reaction that produces syn-Propanethial-S-oxide.
Several factors can influence the severity of the tearing reaction when cutting onions. Some of these factors include:
1. Onion variety: Certain onion varieties, such as shallots and sweet onions, have lower levels of syn-Propanethial-S-oxide and may cause less tearing.
2. Cutting technique: Cutting onions quickly and efficiently can reduce the amount of syn-Propanethial-S-oxide released.
3. Chilling: Chilling onions before cutting can slow down the enzymatic reaction and minimize tearing.
4. Cooking: Cooking onions can destroy some of the syn-Propanethial-S-oxide, reducing the irritation to the eyes.
To minimize tears when cutting onions, consider the following tips:
1. Chill the onions before cutting them. This will slow down the enzymatic reaction and reduce the amount of syn-Propanethial-S-oxide released.
2. Cut onions quickly and efficiently to minimize cell damage and the subsequent release of the irritant.
3. Use a sharp knife to cut onions, as it will require less force and cause less cell damage.
4. Wear safety goggles to protect your eyes from the irritant while cutting onions.
5. Consider using onion varieties with lower levels of syn-Propanethial-S-oxide, such as sweet onions or shallots.
Understanding the science behind why onions cause tears can help you take steps to minimize the irritation. By employing the right techniques and tools, you can enjoy cooking with onions without the discomfort of watery eyes.
