Wednesday, November 14, 2012

Why do onions make us cry when chopping them?

                               Why do onions make us cry when chopping them?

When we cut an onion, we have experienced the burning and tearing of eyes, we get from the vapors when cutting. When we cut an onion, we break its cells., releasing their contents. The contents are amino acid sulfoxides which then form sulfenic acids.
The enzymes present in our body are now free to mix with these sulfenic acids to produce propethenoil S-oxide, a volatile sulphur compound. This gas reacts with the water in the tears to form sulphuric acid. The sulphuric acid burns, stimulating eyes to produce more tears to wash the irritant away.
The sulphur containing compounds just like onions, also leave a characteristic odour on fingers.

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