Oxidation
定义
The enzymatic browning process in which tea leaf polyphenols react with oxygen, darkening the leaf and transforming its flavor from grassy-fresh to malty-rich. Oxidation level is the primary factor distinguishing the six major tea categories.
详情
When tea leaves are bruised or rolled, cellular enzymes — chiefly polyphenol oxidase — catalyze the reaction between catechins and atmospheric oxygen. This transforms colorless catechins into theaflavins (bright, brisk) and thearubigins (deep, smooth). Green tea is unoxidized (0%), white tea is minimally oxidized (5-12%), oolong spans a wide range (15-85%), and black tea is fully oxidized (90-100%). Processing controls oxidation through heat application (fixation), which denatures the enzymes and halts the reaction. The interplay between oxidation level and other processing steps — withering duration, rolling intensity, ambient humidity — creates the extraordinary diversity of tea flavor.