Wok hei / 鑊氣
Wok hei (simplified Chinese: 镬气; traditional Chinese: 鑊氣; Jyutping: wok6 hei3; romanization based on Cantonese; and when literally translated into English, can be read as "Wok's air". The second character is qi in Mandarin, and thus wok hei is sometimes rendered as wok chi in Western cookbooks) is the flavour, tastes, and "essence" imparted by a hot wok on food during stir frying.[3][1] It is particularly important for Chinese dishes requiring high heat for fragrance such as char kuay teow and beef chow fun.
To impart wok hei, the food must be cooked in a wok over a high flame while being stirred and tossed quickly. For this reason it requires cooking over an open flame rather than an electric stove. In practical terms, the flavour imparted by chemical compounds results from caramelization, Maillard reactions, and the partial combustion of oil that come from charring and searing of the food at very high heat in excess of 200 °C (392 °F). Aside from flavour, there is also the texture of the cooked items and smell involved that describes wok qi.
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http://en.wikipedia.org/wiki/Wok