Fermentation process

Fermentation is actually a process of enzymatic oxidation and the extent of fermentation determines the type of tea produced.

The most important reaction in tea fermentation is the oxidative chemical reaction induces the polyphenol oxidase on the polyphenols in tea leaves.

This subsequently causes the formation of different colors, aromas, and tastes in tea with various degree of fermentation. It also determines the tea shelf life. The longer the fermentation, the longer the tea can last. 

Fermentation process creates a whole set of powerful antioxidants that are present in black tea. Black tea actually contains more complex polyphenols than green tea.

During fermentation also, amino acids also get converted into aldehydes, unsaturated liquids form aldehydes and lower acids. Oxidation of carotenoid to terpenoids, aldehydes and ketones and degradation of chlorophyll to brown and black pigments occurs.

The changes are reflected in the read amber color, reduced astringency and more complex flavor found in black tea beverages.

Some unique antioxidants called biflavonols, thearubigens, and theaflavins.

There are four main theaflavins common to black teas and a second group of minor theaflavins, including the isotheaflavins and neotheaflavins.
Fermentation process