Onions are a staple in kitchens around the world, but they’re also notorious for causing tears. Have you ever wondered why chopping an onion leads to such an emotional reaction? It’s not just a quirky kitchen nuisance; there’s actual science behind this phenomenon.
The Chemical Process Behind the Tears
Sulphuric Compounds in Onions
Onions contain sulfur-based compounds. When you cut an onion, you break its cells, releasing a series of chemical reactions. An enzyme called alliinase converts the amino acids in the onion into sulfenic acid. This acid is unstable and quickly rearranges itself into a volatile compound known as syn-propanethial-S-oxide.
The Role of Syn-Propanethial-S-Oxide
Syn-propanethial-S-oxide is the real tear-jerker here. This gas diffuses into the air and eventually reaches your eyes. Your eyes have sensory nerves that detect irritants. When this gas comes into contact with the moist surface of your eyes, it reacts with the water to form a mild sulfuric acid.
Why Your Eyes React With Tears
This mild sulfuric acid irritates the sensory nerves in your eyes. In response, your nervous system triggers a reflex to flush out the irritant. This reflex activates the lacrimal glands in your eyes to produce tears. The tears help to wash away the sulfuric compounds, protecting your eyes from irritation.
Preventive Measures to Avoid Crying
Chilling the Onions
One way to minimize tears is to chill the onions before cutting them. Cold temperatures slow down the chemical reactions and reduce the amount of gas released.
Sharp Knives and Proper Cutting Technique
Using a sharp knife can also help. A dull knife crushes the cells of the onion, releasing more irritants. A sharp knife, however, makes a cleaner cut and damages fewer cells. Additionally, learning proper cutting techniques to minimize the disruption of the onion’s cells can be beneficial.
Using Goggles or Fans
Some people use goggles to shield their eyes from the gas. Alternatively, cutting onions near a fan can help to blow the irritants away from your eyes.
In conclusion, the tears caused by onions are a result of a complex chemical reaction. Understanding this process can help you take measures to reduce the tearful experience.
So next time you’re prepping onions, remember it’s just chemistry at work and perhaps try a few of these tips to keep the tears at bay.