The exposure of the tea leaves to humidity and oxygen during the process also causes endo-oxidation (derived from the tea-leaf enzymes themselves) and exo-oxidation (which is microbially catalysed).

Fermentation affects the smell of the tea and typically mellows its taste, reducing astringency and bitterness while improving mouthfeel and aftertaste.

The next year, nearby villages suffered from dysentery, and decided to drink the abandoned mildewed tea in desperation.

It may have been first traded by tea merchants much earlier than the legends state, across the historical borders of Han and Tibetan cultural areas.

[16] A third category, including the Japanese goishicha and Ishizuchi kurocha, is fermented with the piled and pickling methods successively.

[22][23][24] Pressed tea made into the shape of yeopjeon, the coins with holes, was called doncha (돈차; lit.

[25][26][27] Borim-cha (보림차; 寶林茶) or Borim-baengmo-cha (보림백모차; 寶林白茅茶), named after its birthplace, the Borim temple in Jangheung, South Jeolla Province, is a popular tteokcha variety.

Steamed tea leaves are kept pressed into sealed bamboo baskets until the anaerobic fermentation produces a compact cake with the desired flavor.

[13] A similar pickled tea is eaten by the Blang people of Xishuangbanna in Yunnan, China, on the border with Myanmar and Laos.

[32] The tea, known locally as miam and in Chinese as suancha (酸茶), is first packed into bamboo tubes, then buried and allowed to ferment before eating.

In commercially produced kombucha, the amount is very low, typically less than 0.5% alcohol by volume - which means it can be labelled as non-alcoholic.

[35] Alternatively, fermented teas can be created quickly through a ripening process spanning several months, as with Shu Pu'er.

This ripening is done through a controlled process similar to composting, where the moisture and temperature of the tea are carefully monitored.

Many varieties of dark tea are purposely aged in humid environments to promote the growth of certain fungi, often called "golden flowers" or jin hua (金花) because of the bright yellow color.