Tea oxidation

Tea oxidation is a set of enzyme-driven reactions in damaged tea leaves that transform polyphenols into pigments and flavor compounds. Its extent helps distinguish major tea styles.

Polyphenol oxidase: An enzyme that uses oxygen to oxidize phenolic compounds into reactive quinones. It catalyzes a principal route by which damaged tea leaves develop oxidized pigments.
Camellia sinensis: An evergreen shrub whose leaves and buds are used to make tea. The source plant supplies the enzymes and compounds involved in tea oxidation.
Black tea: Tea made from leaves that undergo substantial enzymatic oxidation before drying. Its color and flavor arise largely from extensive oxidation during manufacture.
Non-enzymatic browning: Browning reactions that occur without enzymes, including Maillard reactions and caramelization. It distinguishes enzyme-driven leaf oxidation from browning during heating or storage.
Peroxidase: An enzyme that uses hydrogen peroxide to oxidize a range of substrates. It can contribute alongside polyphenol oxidase to oxidation in processed tea leaves.
Tea catechins: Polyphenolic compounds in tea leaves, including epicatechin and epigallocatechin gallate. Their abundance and variety shape which oxidation products can form.
Oolong: A tea style made from leaves that undergo partial oxidation before drying. Its varied oxidation levels produce a broad range of floral, fruity, and roasted profiles.
Fermentation: Microbial or biochemical processes that convert substances into other products, often without oxygen. Tea oxidation is often called fermentation, but black tea manufacture is not microbial fermentation.
Catechin: A flavan-3-ol, a type of polyphenol found in tea and other plants. Tea catechins are key substrates whose transformation changes flavor and color.
Oxygen: A reactive chemical element that supports many oxidation reactions. Exposure to oxygen enables key enzyme-driven reactions in processed leaves.

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