Why Onions Make Us Cry and the Scientific Trick to Avoid It
The Tear Effect: A Biochemical Response
When we cut an onion, we trigger a chain reaction based on sulfur compounds and volatile enzymes. These elements, originally separated within the onion's cells, combine once the plant tissues are broken.
The 3 Key Compounds
- Alliinase: An enzyme stored in the cell vacuoles.
- Cysteine sulfoxides: Sulfur-containing amino acids in the cytoplasm.
- Lachrymatory factor synthase: Catalyzes the formation of the irritating gas.
The Molecular Process Explained
According to research from the
Journal of Agricultural and Food Chemistry, the sequence is:
- Cell rupture releases alliinase and sulfoxides
- Formation of sulfenic acid
- Conversion into syn-propanethial-S-oxide (the tear-inducing gas)
The Only Scientifically Validated Method
A study by
Zhejiang University showed that chilling onions to 4°C before cutting them reduces:
| Technique | Reduction in volatile compounds |
|---|
| Prior refrigeration | Up to 75% |
| Cutting under water | 40-50% |
How the Cold Works
Low temperatures slow down enzymatic activity, minimizing:
- The reaction speed of alliinase
- The volatilization of sulfur compounds
- The diffusion of the gas toward the eyes
Frequently Asked Questions
Do sharp knives reduce crying?
Yes, but only marginally (15-20% according to studies). A precise blade causes less cellular damage, but it does not inhibit the enzymes.
Do glasses or fans work?
Glasses physically block the gas, but they are uncomfortable. Fans disperse the compounds, with variable effectiveness (30-60%).
Are there onion varieties that don’t make you cry?
Sweet onions contain 25-30% fewer sulfoxides, according to the
HortScience Journal, but the effect depends on growing conditions.
