| Fermented tea | |
|---|---|
 Golden melonpu'er tea | |
| Chinese | 黑茶 |
| Literal meaning | Black/dark tea |
| Hanyu Pinyin | hēichá |
| HokkienPOJ | hek-tê |
| Alternative Chinese name | |
| Traditional Chinese | 後發酵茶 |
| Simplified Chinese | 后发酵茶 |
| Literal meaning | post-fermented tea |
| Hanyu Pinyin | hòu fājiào chá |
Fermented tea (also known aspost-fermented tea ordark tea) is a class oftea that has undergone microbialfermentation, from several months to many years. The exposure of the tea leaves tohumidity andoxygen during the process also causes endo-oxidation (derived from the tea-leafenzymes themselves) and exo-oxidation (which ismicrobiallycatalysed). The tea leaves and the liquor made from them become darker with oxidation. Thus, the various kinds of fermented teas produced acrossChina are also referred to as dark tea, not be confused withblack tea, which is actually referred to as "red tea" (hong cha,红茶) in Chinese. The most famous fermented tea ispu'er produced inYunnan province.[1][2]
The fermentation of tea leaves alters their chemistry, affecting theorganoleptic qualities of the tea made from them. Fermentation affects thesmell of the tea and typically mellows its taste, reducing astringency and bitterness while improvingmouthfeel and aftertaste. The microbes may also produce metabolites with health benefits.[1][3] Additionally, substances likeethyl carbamate (urethane) may be produced.[4]
The fermentation is carried out primarily by molds.Aspergillus niger was implicated as the main microbial organism in thepu'er process,[1][5][6] but that species identification has been challenged by comprehensivePCR-DGGE analysis, which points toAspergillus luchuensis as the primary agent of fermentation.[7][8][9][10]
Most varieties of fermented teas are produced in China, its country of origin, with several varieties also produced inKorea[11] andJapan.[12] In Myanmar,lahpet is a form of fermented tea that is eaten as a vegetable, and similar pickled teas are also eaten or chewed in northern Thailand and southern Yunnan.[13]
The early history of dark tea is unclear, but there are several legends and some credible theories.
For example, one legend holds that dark tea was first produced accidentally, on theSilk Road andTea Road by tea caravans in the rainy season.[14][15] When the tea was soaked in rain, the tea transporters abandoned it for fear of contamination. The next year, nearby villages suffered fromdysentery, and decided to drink the abandoned mildewed tea in desperation. The legend concludes that the tea cured those suffering, and quickly became popular.
Other historical accounts attribute the first production of dark tea to theMing dynasty in the 15th and 16th centuries. 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.[15]
Fermented teas can be divided according to how they are produced. Piled teas, such as the Chinese post-fermented teas, and theToyamakurocha produced in Japan, are fermented with naturally occurring fungus under relatively dry conditions. Other fermented teas, called pickled teas, are fermented in a wet process with lactic acid bacteria. Pickled teas includemiang from Thailand andawabancha from Japan.[16] A third category, including the Japanesegoishicha and Ishizuchikurocha, is fermented with the piled and pickling methods successively.[17]
Fermented tea originated in China, where it is commonly known ashei cha (黑茶) or dark tea.Hei cha is produced in many areas of China, mostly in the warmer southern provinces. It is commonly pressed into bricks or cakes for ageing.[1][2]
The most famous and important producing areas and varieties include:
Shapes include:
Several distinct varieties of fermented tea are produced in Japan.[12] Toyama prefecture'skurocha is Japan's only piled tea, similar to the Chinese post-fermented teas. Toyamakurocha is traditionally prepared by boiling in water, adding salt and stirring with a whisk as in a traditionaltea ceremony. It is consumed on religious occasions or during meetings in theAsahi area of the prefecture.[18]Awabancha (阿波番茶), produced inTokushima prefecture, andbatabatacha, like the Toyamakurocha associated withAsahi, Toyama, are made frombancha, or second flush tea leaves, with bacterial fermentation.[19]Batabatacha has been found to contain vitamin B12, but in insignificant amounts for human diets.[20]Goishicha (碁石茶) fromŌtoyo, Kōchi and Ishizuchikurocha grown at the foot ofMount Ishizuchi inEhime prefecture are made by fermenting the tea in a two step process, first with aerobic fungi, then with anaerobic bacteria.[17][21]
Tteokcha (떡차;lit. "cake tea"), also calledbyeongcha (병차;餠茶;lit. "cake tea"), was the most commonly produced and consumed type of tea in pre-modern Korea.[22][23][24] Pressed tea made into the shape ofyeopjeon, the coins with holes, was calleddoncha (돈차;lit. "money tea"),jeoncha (전차;錢茶;lit. "money tea"), orcheongtaejeon (청태전;靑苔錢;lit. "green moss coin").[25][26][27]Borim-cha (보림차;寶林茶) orBorim-baengmo-cha (보림백모차;寶林白茅茶), named after its birthplace, theBorim temple inJangheung,South Jeolla Province, is a populartteokcha variety.[28]
Though the early history of tea is unclear, it has been established that for centuries people have chewed tea leaves.[29] Few peoples today continue to consume tea by chewing or eating.[13]
InNorthern Thailand, a pickled tea product called miang (เมี่ยง) is chewed as a stimulant. Steamed tea leaves are kept pressed into sealed bamboo baskets until the anaerobic fermentation produces a compact cake with the desired flavor. The fermentation takes four to seven days for young leaves and about a year for mature leaves.[30] Miang is related to the Thai and Lao street snackmiang kham.[31]
Pickled tea known aslahpet is widely consumed inBurmese cuisine, and plays an important role in Burmese ritual culture. After fermentation, the tea is eaten as a vegetable.[13]
A similar pickled tea is eaten by theBlang people ofXishuangbanna inYunnan, China, on the border with Myanmar and Laos.[32] The tea, known locally as miam and in Chinese assuancha (酸茶), is first packed into bamboo tubes, then buried and allowed to ferment before eating.[33]
Many fermented teas do not arrive on the market ready for consumption. Instead, they may start asgreen teas or partially oxidizedoolong-like teas, which are then allowed to slowly oxidize and undergo microbial fermentation over many years (comparable to wines that are sold to be aged in a cellar).[34] Alternatively, fermented teas can be created quickly through a ripening process spanning several months, as withShu Pu'er. This ripening is done through a controlled process similar tocomposting, where the moisture and temperature of the tea are carefully monitored. The product is "finished" fermented tea.[citation needed]
Fermented teas are commonly sold ascompressed tea of various shapes, including bricks, discs, bowls, or mushrooms.[35][better source needed] Ripenedpu'er teas are ripened while loose, then compressed. Fermented teas can be aged for many years to improve their flavor, again comparable to wines. Rawpu'er tea can be aged up to 50 years in some cases without diminishing in quality, and ripenedpu'er can be aged up to 10 or 15 years. Experts and aficionados disagree about the optimal age.[citation needed]
ManyTibetans andCentral Asians usepu'er or other fermented teas as a caloric and micronutrient food, boiled withyak butter, sugar and salt to makeyak butter tea.
Post-fermented tea usually gets more valuable with age. Dark tea is often aged in bamboo baskets, bamboo-leaf coverings, or in its original packaging.
Many varieties of dark tea are purposely aged in humid environments to promote the growth of certain fungi, often called "golden flowers" orjin hua (金花) because of the bright yellow color.[36][37]
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