Onion

:For the parody newspaper, see The Onion.

Why do onions make you cry?

As onions are sliced, cells are broken open. Onion cells have two sections, one with enzymes called allinases, the other with sulfides (amino acid sulfoxides). The enzymes break down the sulfides and generate sulfenic acids. Sulfenic acid is unstable and decomposes into a volatile gas called syn-ropanethial-S-oxide. The gas then dissipates through the air and eventually reaches one's eye, where it will react with the water to form a mild solution of sulfuric acid. The sulfuric acid irritates the nerve endings in the eyes, making them sting. The tear glands then produce tears in response to this irritation, to dilute and flush out the irritant.

Related Topics:
Cells - Enzymes - Sulfides - Amino acid - Gas - Sulfuric acid - Nerve - Eye

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The release of gas can thus best be prevented by cutting the onions under running tap water or completely under water, though this may not be very practical. Wetting the onions and your hands before slicing will lessen the effect, as some of the gas will react with the moisture on the onions and on your skin (instead of the moisture on your eyes). This reaction may result as an odour which may be removed with Lemon. It also helps to breathe exclusively through the mouth during the preparation. Using a sharp knife will rupture fewer cells and cause less eye irritation. For more tips and information, please check links in External links section. Chilled onions (onions kept in the fridge for a while) will make you 'cry' less than onions kept at room temprature because lower temperature inhibits the enzymes and gas diffusion. Also, some people 'freeze' the knife (leave it in the freezer for around 2 minutes) before cutting the onions to prevent the tears.

Related Topics:
Lemon - External links - Diffusion

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Different species of onions will release different amounts of sulfenic acids, thus some will cause more tear formation and irritation than others.

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