{{Short description|Tea that has undergone microbial fermentation}} {{Redirect|Dark tea|the Brooklyn-based music project|Dark Tea (musical group)}} {{Distinguish|Black tea}} {{Use dmy dates|date=October 2023}} {{Infobox Chinese |title=Fermented tea |pic=Golden melon.jpg |piccap=Golden melon {{Transliteration|zh|pu'er}} tea |c={{linktext|黑|茶}} |p=hēichá |poj=hek-tê |l=Black/dark tea <!-- First alternative name --> |altname=Alternative Chinese name |t2=後發酵茶 |s2=后发酵茶 |p2=hòu fājiào chá |l2=post-fermented tea |hide=no }}
'''Fermented tea''' (also known as '''post-fermented tea''' or '''dark tea''') is a class of tea that has undergone microbial fermentation, from several months to many years. 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). The tea leaves and the liquor made from them become darker with oxidation. Thus, the various kinds of fermented teas produced across China are also referred to as dark tea, not be confused with black tea, which is actually referred to as "red tea" (''hong cha'', 红茶) in Chinese. The most famous fermented tea is {{Transliteration|zh|pu'er}} produced in Yunnan province.<ref name="Haizhen, Yang Zhu 2008">{{Cite journal |last1=Mo |first1=Haizhen |last2=Zhu |first2=Yang |last3=Chen |first3=Zongmao |title=Microbial fermented tea–a potential source of natural food preservatives |journal=Trends in Food Science & Technology |volume=19 |issue=3 |year=2008 |pages=124–130 |doi=10.1016/j.tifs.2007.10.001}}</ref><ref name="Hai-peng, 2013">{{Cite journal |last1=Lv |first1=Hai-peng |last2=Zhang |first2=Ying-jun |last3=Lin |first3=Zhi |last4=Liang |first4=Yue-rong |year=2013 |title=Processing and chemical constituents of Pu-erh tea: A review |journal=Food Research International |volume=53 |issue=2 |pages=608–618 |doi=10.1016/j.foodres.2013.02.043 |bibcode=2013FdRI...53..608L }}</ref>
The fermentation of tea leaves alters their chemistry, affecting the organoleptic qualities of the tea made from them. Fermentation affects the smell of the tea and typically mellows its taste, reducing astringency and bitterness while improving mouthfeel and aftertaste. The microbes may also produce metabolites with health benefits.<ref name="Haizhen, Yang Zhu 2008"/><ref>{{Cite journal |last1=Ling |first1=Tie-Jun |last2=Wan |first2=Xiao-Chun |last3=Ling |first3=Wei-Wei |last4=Zhang |first4=Zheng-Zhu |last5=Xia |first5=Tao |last6=Li |first6=Da-Xiang |last7=Hou |first7=Ru-Yan |year=2010 |title=New Triterpenoids and Other Constituents from a Special Microbial-Fermented Tea—Fuzhuan Brick Tea |journal=Journal of Agricultural and Food Chemistry |volume=58 |issue=8 |pages=4945–4950 |doi=10.1021/jf9043524 |pmid=20307093 |bibcode=2010JAFC...58.4945L |issn=0021-8561}}</ref> Additionally, substances like ethyl carbamate (urethane) may be produced.<ref>{{cite journal |pmid=24786007 |year=2011 |last1=Tang |first1=A. S. |last2=Chung |first2=S. W. |last3=Kwong | first3=K. | last4=Xiao | first4=Y. | last5=Chen |first5=M. Y. |last6=Ho |first6=Y. Y. |last7=Ma |first7=S. W. |title=Ethyl carbamate in fermented foods and beverages: Dietary exposure of the Hong Kong population in 2007–2008 |journal=Food Additives & Contaminants. Part B, Surveillance |volume=4 |issue=3 |pages=195–204 |doi=10.1080/19393210.2011.605524 |s2cid=1852027}}</ref>
The fermentation is carried out primarily by molds. ''Aspergillus niger'' was implicated as the main microbial organism in the {{Transliteration|zh|pu'er}} process,<ref name="Haizhen, Yang Zhu 2008"/><ref>{{Cite journal |last1=Gong |first1=Jia-shun |last2=Zhou |first2=H.J. |last3=Zhang |first3=X.F. |last4=Song |first4=Shan |last5=An |first5=W.J. |title=Changes of Chemical Components in Pu'er Tea Produced by Solid State Fermentation of Sundried Green Tea |journal=Journal of Tea Science |volume=25 |issue=3 |year=2005 |pages=126–132}}</ref><ref>{{Cite journal |last1=Abe |first1=M. |last2=Takaoka |first2=N. |last3=Idemoto |first3=Y. |last4=Takagi |first4=C. |last5=Imai |first5=T. |last6=Nakasaki |first6=K. |year=2008 |title=Characteristic fungi observed in the fermentation process for Puer tea |journal=International Journal of Food Microbiology |volume=124 |issue=2 |pages=199–203 |doi=10.1016/j.ijfoodmicro.2008.03.008 |pmid=18455823}}</ref> but that species identification has been challenged by comprehensive PCR-DGGE analysis, which points to ''Aspergillus luchuensis'' as the primary agent of fermentation.<ref>{{Cite journal |last1=Mogensen |first1=J.M. |last2=Varga |first2=J. |last3=Thrane |first3=U. |last4=Frisvad |first4=J.C. |last5=Imai |first5=T |last6=Nakasaki |first6=K |year=2009 |title=Aspergillus acidus from Puerh tea and black tea does not produce ochratoxin A and fumonisin B{{sub|2}} |journal=International Journal of Food Microbiology |volume=132 |issue=2–3 |pages=141–144 |doi=10.1016/j.ijfoodmicro.2009.04.011 |pmid=19439385}}</ref><ref>{{Cite journal |last1=Varga |first1=J. |last2=Frisvad |first2=J.C. |last3=Kocsubé |first3=S. |last4=Brankovics |first4=B. |last5=Tóth |first5=B. |last6=Szigeti |first6=G. |last7=Samson |first7=R.A. |year=2011 |title=New and revisited species in Aspergillus section Nigri |journal=Studies in Mycology |volume=69 |issue=1 |pages=1–17 |doi=10.3114/sim.2011.69.01 |pmc=3161757 |pmid=21892239 |bibcode=2011StMyc..69....1V }}</ref><ref>{{Cite journal |last1=Haas |first1=Doris |last2=Pfeifer |first2=Bettina |last3=Reiterich |first3=Christoph |last4=Partenheimer |first4=Regina |last5=Reck |first5=Bernhard |last6=Buzina |first6=Walter |last7=Samson |first7=R.A. |year=2013 |title=Identification and quantification of fungi and mycotoxins from Pu-erh tea |journal=International Journal of Food Microbiology |volume=166 |issue=2 |pages=316–322 |doi=10.1016/j.ijfoodmicro.2013.07.024 |pmid=23973844}}</ref><ref>{{Cite journal |last1=Hong |first1=Seung-Beom |last2=Lee |first2=Mina |last3=Kim |first3=Dae-Ho |last4=Varga |first4=Janos |last5=Frisvad |first5=Jens C. |last6=Perrone |first6=Giancarlo |last7=Gomi |first7=Katsuya |last8=Yamada |first8=Osamu |last9=Machida |first9=Masayuki |last10=Houbraken |first10=Jos |last11=Samson |first11=Robert A. |year=2013 |editor-last=McCluskey |editor-first=Kevin |title=Aspergillus luchuensis, an industrially important black Aspergillus in East Asia |journal=PLOS ONE |volume=8 |issue=5 |article-number=e63769 |doi=10.1371/journal.pone.0063769 |issn=1932-6203 |pmc=3665839 |pmid=23723998|bibcode=2013PLoSO...863769H |doi-access=free}}</ref>
Most varieties of fermented teas are produced in China, its country of origin, with several varieties also produced in Korea<ref>{{cite journal |last1=Moon |first1=Doo-Gyung |title=The Characteristics of Korean Traditional Post-Fermented Tea (Chungtaejeon) |journal=Bioactive Compounds in Nutraceutical and Functional Food for Good Human Health |date=2 April 2020 |doi=10.5772/intechopen.91855 |isbn=978-1-83880-887-7 |url=https://www.intechopen.com/chapters/71634|doi-access=free }}{{Predatory publisher}}</ref> and Japan.<ref name="bioactivity">{{cite book|author1=Hua-Fu Wang|author2=Xiao-Qing You|author3=Zong-Mao Chen|editor1-last=Zhen|editor1-first=Yong-su|title=Tea: Bioactivity and Therapeutic Potential|year=2002|publisher=Taylor & Francis|page=104|isbn=978-0-203-30127-2|url=https://books.google.com/books?id=tlEm6wjbAQUC&pg=PA104|access-date=11 August 2014}}</ref> 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.<ref name="Chemistry"/>
==History== 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 the Silk Road and Tea Road by tea caravans in the rainy season.<ref name="TG_PPT">{{cite web |first1=Vicony |last1=Teas |title= Dark Tea – Hei Cha |url=http://www.viconyteas.com/directory/tea-encyclopedia/dark-tea.html |access-date=4 November 2012}}</ref><ref name="Dark Tea Produce">{{cite web |last=Tea Net |title=Hei Cha |url=http://www.teanet.com.cn/z_interbusiness/interm/heicha.htm |publisher=Teanet.com |access-date=4 November 2012 |archive-url=https://web.archive.org/web/20120607124256/http://www.teanet.com.cn/Z_interBusiness/interm/heicha.htm |archive-date=7 June 2012}}</ref> When the tea was soaked in rain, the tea transporters abandoned it for fear of contamination. The next year, nearby villages suffered from dysentery, 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 the Ming 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.<ref name="Dark Tea Produce"/>
==Varieties== Fermented teas can be divided according to how they are produced. Piled teas, such as the Chinese post-fermented teas, and the Toyama {{Transliteration|ja|kurocha}} 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 include {{Transliteration|th|miang}} from Thailand and {{Transliteration|ja|awabancha}} from Japan.<ref>{{cite book|author1=Organizing Committee of ISTS|title=Proceedings of the International Symposium on Tea Science|date=1991|page=95}}</ref> A third category, including the Japanese {{Transliteration|ja|goishicha}} and Ishizuchi {{Transliteration|ja|kurocha}}, is fermented with the piled and pickling methods successively.<ref name="flavor">{{cite web|title=Effect Of The Flavor Component The Pu-er Tea In Aging Period|url=http://www.ocha-festival.jp/archive/english/conference/ICOS2004/files/PROC/Pr-P-19.pdf|access-date=11 August 2014}}</ref>
=== China === [[File:Puer tea, Chinese green tea, Rostov-on-Don, Russia.jpg|thumb|Pu'er tea from Yunnan, China]] {{see also|Chinese tea|list of Chinese teas}}
Fermented tea originated in China, where it is commonly known as {{Transliteration|zh|hei cha}} ({{lang|zh|黑茶}}) or dark tea. {{Transliteration|zh|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.<ref name="Haizhen, Yang Zhu 2008"/><ref name="Hai-peng, 2013"/>
The most famous and important producing areas and varieties include: * Anhui: {{Transliteration|zh|Liu an lan cha}} ({{lang|zh|安徽六安籃茶}}, Anhui Lu'an basket tea) * Guangxi: {{Transliteration|zh|Liu bao cha}} ({{lang|zh|廣西六堡茶}}, Guangxi Liubao tea, often sold as {{lang|zh|松黑茶}}, loose dark tea) * Hubei: {{Transliteration|zh|Qing zhuan cha}} ({{lang|zh|湖北青砖茶}}, Hubei green brick tea) * Hunan: {{Transliteration|zh|Fu zhuan cha}} ({{lang|zh|湖南茯磚茶}} ({{lang|zh|黑茶}}), the famous {{Transliteration|zh|fu zhuan}} {{lang|zh|茯磚茶}} "brick tea") * Jingyang, Shaanxi: {{Transliteration|zh|Fu zhuan cha}} ({{lang|zh|陕西泾阳茯茶}} ({{lang|zh|黑茶}}), the famous {{Transliteration|zh|fu zhuan}} {{lang|zh|茯磚茶}} "brick tea") * Sichuan: {{Transliteration|zh|Lu bian cha}} ({{lang|zh|四川路边茶}}, Sichuan border tea) * Tibet: {{Transliteration|zh|Zang cha}} ({{lang|zh|藏茶}}, Tibetan tea, often called Tibetan brick tea) * Yunnan: {{Transliteration|zh|Pu'er cha}} ({{lang|zh|雲南普洱茶}}, either "raw" {{Transliteration|zh|sheng pu'er}} {{lang|zh|生普洱}} or "ripened" {{Transliteration|zh|shu pu'er}} {{lang|zh|熟普洱}})
Shapes include: * Bamboo leaf logs * Cakes, or {{Transliteration|zh|bing cha}} ({{lang|zh|餅茶}}) * Bricks, or {{Transliteration|zh|zhuan cha}} ({{lang|zh|磚茶}}) * Loose, in baskets * Bird nests, or {{Transliteration|zh|tuo cha}} ({{lang|zh|沱茶}}), usually {{Transliteration|zh|pu'er tea}} * Squares, or {{Transliteration|zh|fang cha}} ({{lang|zh|方茶}})
=== Japan === Several distinct varieties of fermented tea are produced in Japan.<ref name=bioactivity /> Toyama prefecture's {{Transliteration|ja|kurocha}} is Japan's only piled tea, similar to the Chinese post-fermented teas. Toyama {{Transliteration|ja|kurocha}} is traditionally prepared by boiling in water, adding salt and stirring with a whisk as in a traditional tea ceremony. It is consumed on religious occasions or during meetings in the Asahi area of the prefecture.<ref name=toyamakurocha>{{cite web|last1=Kawakami|first1=Michiko|last2=Shibamoto|first2=Takayuki|title=Volatile Constituents of Piled Tea: Toyama Kurocha|url=https://www.jstage.jst.go.jp/article/bbb1961/55/7/55_7_1839/_pdf|access-date=11 August 2014|format=PDF|year=1991}}</ref> {{Transliteration|ja|Awabancha}} ({{lang|ja-Hani|阿波番茶}}), produced in Tokushima prefecture, and {{Transliteration|ja|batabatacha}}, like the Toyama {{Transliteration|ja|kurocha}} associated with Asahi, Toyama, are made from {{Transliteration|ja|bancha}}, or second flush tea leaves, with bacterial fermentation.<ref>{{cite web|title=Two Fermented Japanese Banchas|url=http://www.cantonteaco.com/blog/2014/05/two-fermented-japanese-banchas/|archive-url=https://web.archive.org/web/20140812204640/http://www.cantonteaco.com/blog/2014/05/two-fermented-japanese-banchas/|archive-date=12 August 2014|access-date=11 August 2014}}</ref> {{Transliteration|ja|Batabatacha}} has been found to contain vitamin B{{sub|12}}, but in insignificant amounts for human diets.<ref>{{cite web|last1=Raloff|first1=Janet|title=Bacteria Brew a B Vitamin Boost|url=https://www.sciencenews.org/blog/food-thought/bacteria-brew-b-vitamin-boost|access-date=11 August 2014|date=28 January 2004}}</ref> {{Transliteration|ja|Goishicha}} ({{lang|ja-Hani|碁石茶}}) from Ōtoyo, Kōchi and Ishizuchi {{Transliteration|ja|kurocha}} grown at the foot of Mount Ishizuchi in Ehime prefecture are made by fermenting the tea in a two step process, first with aerobic fungi, then with anaerobic bacteria.<ref name=flavor /><ref>{{cite web|title=Saijo City Sightseeing Information |url=http://www.city.saijo.ehime.jp/english/kankou/omiyage1.htm |access-date=11 August 2014 |archive-url=https://web.archive.org/web/20140812210629/http://www.city.saijo.ehime.jp/english/kankou/omiyage1.htm |archive-date=12 August 2014 }}</ref>
=== Korea === [[File:Tteokcha.png|thumb|''Tteokcha'']]
{{see also|Korean tea}}
{{Transliteration|ko|Tteokcha}} ({{Korean|hangul=떡차|labels=no|links=no|lit="cake tea"}}), also called {{Transliteration|ko|byeongcha}} ({{Korean|hangul=병차|hanja=餠茶|labels=no|links=no|lit="cake tea"}}), was the most commonly produced and consumed type of tea in pre-modern Korea.<ref name="Cheong_Cho">{{Cite journal|last1=Cheong|first1=Kyoung|last2=Cho|first2=Hee-sun|year=2006|title=The Customs of Ddeok-cha(lump tea) and Characteristics by Degrees of Fermentation|url=http://scholar.dkyobobook.co.kr/searchDetail.laf?barcode=4010022748264|journal=Journal of Korean Tea Society|volume=12|issue=3|page=71|archive-date=20 March 2017|access-date=21 March 2017|archive-url=https://web.archive.org/web/20170320161120/http://scholar.dkyobobook.co.kr/searchDetail.laf?barcode=4010022748264}}</ref><ref name="Jung">{{Cite journal|last=Jung|first=Seo-Kyeong|year=2015|title=Historycity about Coastal inflow of tteok-tea to Jeon-nam|journal=Journal of North-East Asian Cultures|language=ko|volume=1|issue=42|pages=105–126|doi=10.17949/jneac.1.42.201503.006|doi-access=free}}</ref><ref name="JoongAng">{{Cite news|url=http://koreajoongangdaily.joins.com/news/article/article.aspx?aid=2922237|title=Taste the slow life with these Korean food specialties|date=24 October 2010|work=Korea JungAng Daily|access-date=20 March 2017}}</ref> Pressed tea made into the shape of {{Transliteration|ko|yeopjeon}}, the coins with holes, was called {{Transliteration|ko|doncha}} ({{Korean|hangul=돈차|labels=no|links=no|lit="money tea"}}), {{Transliteration|ko|jeoncha}} ({{Korean|hangul=전차|hanja=錢茶|labels=no|links=no|lit="money tea"}}), or {{Transliteration|ko|cheongtaejeon}} ({{Korean|hangul=청태전|hanja=靑苔錢|labels=no|lit="green moss coin"}}).<ref name="SKLD_don">{{Cite web|url=http://stdweb2.korean.go.kr/search/View.jsp?idx=87179|title=doncha|website=Standard Korean Language Dictionary|publisher=National Institute of Korean Language|script-title=ko:돈차|access-date=20 March 2017|archive-date=20 March 2017|archive-url=https://web.archive.org/web/20170320144219/http://stdweb2.korean.go.kr/search/View.jsp?idx=87179}}</ref><ref name="SKLD_jeon">{{Cite web|url=http://stdweb2.korean.go.kr/search/View.jsp?idx=285158|title=jeoncha|website=Standard Korean Language Dictionary|publisher=National Institute of Korean Language|script-title=ko:전차|access-date=20 March 2017|archive-date=20 March 2017|archive-url=https://web.archive.org/web/20170320144417/http://stdweb2.korean.go.kr/search/View.jsp?idx=285158}}</ref><ref>{{Cite web|url=http://www.fondazioneslowfood.com/en/slow-food-presidia/don-tea/|title=Don Tea|website=Slow Food Foundation|access-date=21 March 2017}}</ref> ''Borim-cha'' ({{Korean|hangul=보림차|hanja=寶林茶|labels=no}}) or {{Transliteration|ko|Borim-baengmo-cha}} ({{Korean|hangul=보림백모차|hanja=寶林白茅茶|labels=no}}), named after its birthplace, the Borim temple in Jangheung, South Jeolla Province, is a popular {{Transliteration|ko|tteokcha}} variety.<ref>{{Cite web|url=http://www.fondazioneslowfood.com/en/ark-of-taste-slow-food/borim-backmocha/|title=Borim Backmocha|website=Slow Food Foundation|access-date=21 March 2017}}</ref>
=== Edible pickled tea === Though the early history of tea is unclear, it has been established that for centuries people have chewed tea leaves.<ref>{{cite book|last1=Mitscher|first1=Lester A.|last2=Dolby|first2=Victoria|title=The Green Tea Book: China's Fountain of Youth|date=1998|publisher=Avery Publishing Group|page=[https://archive.org/details/greenteabookchin00mits_0/page/24 24]|isbn=978-0-89529-807-2 |url=https://archive.org/details/greenteabookchin00mits_0|url-access=registration|access-date=11 August 2014}}</ref> Few peoples today continue to consume tea by chewing or eating.<ref name="Chemistry"/>
In Northern Thailand, a pickled tea product called miang ({{Linktext|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.<ref name="UN1989" /> Miang is related to the Thai and Lao street snack miang kham.<ref name="thompson">David Thompson. ''Thai Food''. Ten Speed Press (2002), p. 483. {{ISBN|978-1-58008-462-8}}.</ref>
Pickled tea known as lahpet is widely consumed in Burmese cuisine, and plays an important role in Burmese ritual culture. After fermentation, the tea is eaten as a vegetable.<ref name="Chemistry" />
A similar pickled tea is eaten by the Blang people of Xishuangbanna in Yunnan, China, on the border with Myanmar and Laos.<ref>{{cite web|title=Eating Tea and Masticating Betel|url=http://www1.kepu.net.cn/english/banna/folk/fol107.html|archive-url=https://web.archive.org/web/20040124073700/http://www.kepu.net.cn/english/banna/folk/fol107.html|archive-date=24 January 2004|publisher=Xishuangbanna Tropical Botanical Gardens|access-date=12 August 2014}}</ref> The tea, known locally as miam and in Chinese as {{Transliteration|zh|suancha}} ({{lang|zh|酸茶}}), is first packed into bamboo tubes, then buried and allowed to ferment before eating.<ref>{{cite web|last1=Fasi|first1=Jason|title=Lao Man'e: a Bulang Village in Transformation|url=http://the-leaf.org/Issue3/wp-content/uploads/2008/08/lao-mane.pdf|access-date=12 August 2014|page=3}}</ref>
==Production== Many fermented teas do not arrive on the market ready for consumption. Instead, they may start as green teas or partially oxidized oolong-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).<ref name=micro>{{citation|title=黑茶加工中微生物作用的研究 |last1=溫|first1=志杰|last2=張|first2=凌云|last3=吳|first3=平|last4=何|first4=勇強 |journal=茶葉通訊 "Tea Communication" |year=2010 |volume=37 |number=2}}</ref> 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. The product is "finished" fermented tea.{{citation needed|date=August 2014}}
Fermented teas are commonly sold as compressed tea of various shapes, including bricks, discs, bowls, or mushrooms.<ref>{{Cite web |title=Native Tastes Fermented Tea Production Methods and Processes |work=Native Tastes |url=http://nativetastes.at.hm/about-native-tastes/ |at=Methods and Processes |archive-url=https://web.archive.org/web/20140203062247/http://nativetastes.at.hm/about-native-tastes/ |archive-date=3 February 2014 }}</ref>{{better source needed|date=July 2022}} Ripened {{Transliteration|zh|pu'er}} teas are ripened while loose, then compressed. Fermented teas can be aged for many years to improve their flavor, again comparable to wines. Raw {{Transliteration|zh|pu'er}} tea can be aged up to 50 years in some cases without diminishing in quality, and ripened {{Transliteration|zh|pu'er}} can be aged up to 10 or 15 years. Experts and aficionados disagree about the optimal age.{{citation needed|date=August 2014}}
Many Tibetans and Central Asians use {{Transliteration|zh|pu'er}} or other fermented teas as a caloric and micronutrient food, boiled with yak butter, sugar and salt to make yak butter tea.
==Ageing and storage== [[File:JinHua "golden flower" from Liu Bao.jpg|thumb| {{Transliteration|zh|jin hua}} hei cha from Liu Bao with ''Aspergillus cristatus'', formerly ''Eurotium cristatum'']] 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" or {{Transliteration|zh|jin hua}} ({{lang|zh|金花}}) because of the bright yellow color.<ref name="Golden Flower Zhuan">{{cite web|title=Hei Cha|url=http://www.chawangshop.com|work=Dark Tea|publisher=Chawang Shop|access-date=4 November 2012}}</ref><ref name="TAN">{{cite journal |last1=TAN |first1=Yu-Mei |last2=WANG |first2=Ya-Ping |last3=GE |first3=Yong-Yi |last4=REN |first4=Xiu-Xiu |last5=WANG |first5=Yu-Chen |last6=LIU |first6=Zuo-Yi |title=贵州地区茯砖茶"金花菌"的分离和分子鉴定 |journal=菌物学报 Mycosystema |date=2017 |volume=36 |issue=2 |pages=154–163 |doi=10.13346/j.mycosystema.160125 |url=https://manu40.magtech.com.cn/Jwxb/article/2017/1672-6472/1672-6472-36-2-154.shtml |access-date=10 October 2023 |trans-title=Isolation and molecular identification of Aspergillus cristatus in fermented "fuzhuan" brick tea from Guizhou Province |language=zh |issn=1672-6472}}</ref>
==See also== * List of Chinese teas * Kombucha, a beverage produced by fermentation of brewed tea using a symbiotic culture of bacteria and yeast
==References== {{Reflist|30em|refs= <ref name="Chemistry"> {{cite book|editor1-last=Yamamoto|editor1-first=Takehiko|editor2-last=Juneja|editor2-first=Lekh Raj | editor3-last=Chu|editor3-first=Djoin-Chi|editor4-last=Kim|editor4-first=Mujo | title=Chemistry and Applications of Green Tea|date=1997|publisher=CRC Press|page=6 |isbn=978-0-8493-4006-2|url=https://books.google.com/books?id=2ZcnLaP6-eoC&pg=PA6 |access-date=11 August 2014}}</ref> <ref name=UN1989> {{cite book|title=Utilization of Tropical Foods: Sugars, Spices and Stimulants|date=1989|publisher=Food and Agriculture organization of the United Nations|isbn=92-5-102837-0|pages=[https://archive.org/details/utilizationoftro0000unse/page/55 55–56]|url=https://archive.org/details/utilizationoftro0000unse/page/55}}</ref> }}{{Alcohol and health}} {{Teas}} {{Portal bar|Drink|China}}
Category:Fermented tea Category:Chinese tea Category:Japanese tea Category:Korean tea