洋蔥//////////////////

為什麼剝洋蔥會流眼淚?
剝洋蔥時，洋蔥組織會釋放出一種「蒜胺酸」這種酵素，這酵素會將胺基酸亞轉換成次磺酸。次磺酸再重組成（SPSO），就是這個化學物質引起流眼淚的。

當角膜偵測到角膜上有SPSO後，便會引發刺痛感覺，讓淚腺分泌淚液洗掉刺激物。

解決洋蔥淚的問題，可以在切洋蔥前先加熱，破壞掉蒜胺酸這類酵素。




"What is the irritant that causes eyes to water when slicing onions ?" (Answer in English)

為甚麼切洋蔥時會令眼流眼水及睜開眼睛?"

Onions (and garlic) contain derivatives of sulphur-containing amino acids. When slicing onions, one of these compounds, such as S-1-propenyl-cysteine-sulphoxide, is decomposed by an enzyme to form the volatile propanthial-S-oxide, which is the irritant or lacrimator.
Upon contact with water , in this case your eyes, the irritant hydrolyses to propanol, sulphuric acid and hydrogen sulphide. Tearfully, the eyes try to dilute the acid. However, it is these sulphur compounds that form the nice aroma when onions are being cooked.


English and Chinese Answer

我有個朋友講過可以先用水洗一洗,
佢話冇流得咁厲害喎....