Kill-Green

Kill-green (sha qing, literally "killing the green") uses high heat to denature polyphenol oxidase and peroxidase, the enzymes responsible for oxidation. Without this step, plucked tea leaves would naturally oxidize and eventually become black tea. The method of kill-green profoundly shapes the finished tea's character: pan-firing (chao qing) in a large wok produces the toasty, nutty flavors of Chinese green teas like Longjing and Bi Luo Chun; steaming (zheng qing) produces the vegetal, marine qualities of Japanese sencha and gyokuro; baking (hong qing) in an oven produces a subtler, more uniform result used for some green and yellow teas. The timing and intensity of kill-green require great skill — too little heat allows residual oxidation, turning the tea yellowish and bitter; too much heat scorches the leaves, creating harsh, burnt flavors. The temperature typically reaches 200-300 C at the wok surface, and the leaves must be constantly moved to prevent burning. Kill-green is applied immediately after withering for green tea, after partial oxidation for oolong, and is not applied at all for black tea and most white tea.