Kombucha

Kombucha (also tea mushroom, tea fungus, or Manchurian mushroom when referring to the culture; Latin name Medusomyces gisevii)<ref name=Jayabalan/> is a fermented, effervescent and sweetened black tea drink. Sometimes the beverage is called kombucha tea to distinguish it from the culture of bacteria and yeast.<ref>Template:Cite news</ref> Juice, spices, fruit, or other flavorings are often added. Commercial kombucha contains small amounts of alcohol.

Kombucha is believed to have originated in China, where the drink is traditional.<ref>Template:Cite news</ref><ref>Template:Cite web</ref><ref name=":1">Template:Cite book</ref> While it is named after the Japanese term for kelp tea in English, the two drinks have no relation. By the early 20th century kombucha spread to Russia, then other parts of Eastern Europe and Germany.<ref name="Troitino2017">Template:Cite news</ref><ref>Template:Cite book</ref> Kombucha is now homebrewed globally, and also bottled and sold commercially.<ref name="Jayabalan" /> The global kombucha market was worth approximately Template:US$Template:Thinspbillion Template:As of.<ref name=big-kombu/>

Kombucha is produced by symbiotic fermentation of sugared tea using a symbiotic culture of bacteria and yeast (SCOBY) commonly called a "mother" or "mushroom". The microbial populations in a SCOBY vary. The yeast component generally includes Saccharomyces cerevisiae, along with other species; the bacterial component almost always includes Gluconacetobacter xylinus to oxidize yeast-produced alcohols to acetic acid (and other acids).<ref>Template:Cite journal</ref> Although the SCOBY is commonly called "tea fungus" or "mushroom", it is actually "a symbiotic growth of acetic acid bacteria and osmophilic yeast species in a zoogleal mat Template:Bracket".<ref name=Jayabalan/> The living bacteria are said to be probiotic, one of the reasons for the popularity of the drink.<ref name="bauer">Template:Cite news</ref><ref>Template:Cite news</ref>

Numerous health benefits have been claimed to correlate with drinking kombucha;<ref name="Ernst2003" /> there is little evidence to support any of these claims.<ref>Template:Cite journal</ref> The beverage has caused rare serious adverse effects, possibly arising from contamination during home preparation.<ref name=mskcc/><ref name="acs" /> It is not recommended for therapeutic purposes.<ref name="Ernst2003" /><ref name=mayo>Template:Cite web</ref>

History

Kombucha likely originated in the Bohai Sea region of China.<ref name=":1" /> In 20th century China, some traditional Chinese medicine practitioners used it as a remedy for lung and stomach ailments, but the drink was not widely known across the country.<ref name=":4">Template:Cite journal</ref> It spread to Russia before reaching Europe and gained popularity in the United States in the early 21st century.<ref name="Sreermalu2000">Template:Cite journal</ref><ref name="hamblin">Template:Cite web</ref><ref name="Katz2012">Template:Cite book</ref> In the intervening years, its popularity in the West eclipsed its popularity in China, where it remains less known,<ref name="x015">Template:Cite web</ref> though consumption is increasing in many East Asian countries.<ref name="m313">Template:Cite web</ref> With an alcohol content under 0.5%, it is not federally regulated in the U.S.<ref>Template:Cite web</ref><ref>Template:Cite web</ref>

There are numerous myths surrounding the history of kombucha, likely invented in the West as a marketing gimmick. There is no evidence that kombucha originated in Qin dynasty China and that it was served to Emperor Qin Shi Huang. Furthermore, there is no evidence that kombucha was ever present in Korea or Japan before the late 20th century, making claims that a Korean doctor named Kombu served the drink to Japanese Emperor Ingyo entirely apocryphal.<ref name=":1" /><ref name=":4" /><ref>Template:Cite web</ref>

Kombucha was first introduced to Japan from Russia and became a health fad in the country following the publication of Sumako Nakamitsu's 1974 bestseller, Kōcha Kinoko Health Methods.<ref>Template:Cite thesis</ref> Although kombucha had already been consumed in China before it became known in Japan, overseas interest in the beverage for its purported wellness benefits contributed to increased attention and consumption in China during the 1980s.<ref name=":4" />

Prior to 2015, some commercially available kombucha brands were found to contain alcohol content exceeding this threshold, sparking the development of new testing methods.<ref>Template:Cite news</ref> With rising popularity in developed countries in the early 21st century, kombucha sales increased after it was marketed as an alternative to beer and other alcoholic drinks in restaurants and pubs.<ref name=":0">Template:Cite news</ref>

According to the market research firm Grand View Research,Template:Clarify kombucha had a global market size of Template:US$Template:Thinspbillion Template:As of, and this is expected to grow to Template:US$Template:Thinspbillion by 2030.<ref name=big-kombu>Template:Cite web</ref>

Etymology and terminology

The etymology of kombucha is uncertain, but it is believed to be a misapplied loanword from Japanese.<ref name="Algeo97">Template:Cite journal</ref> English speakers may have confused the Japanese word konbucha with Template:Nihongo3, popularized around 1975.<ref>Template:Cite news.(Internet Archive)</ref><ref>Template:Cite web</ref> In Japanese, the term Template:Nihongo3 refers to a kelp tea made with konbu (an edible kelp from the family Laminariaceae) and is a completely different beverage from the fermented tea usually associated with kombucha elsewhere in the world.<ref name=":3">How kombucha went from seaweed tea in Japan to a hit in North America</ref>

Merriam-Webster's Dictionary suggests kombucha in English arose from misapplication of Japanese words like Template:Transliteration, Template:Transliteration 'tea made from kelp', Template:Transliteration, from Template:Transliteration 'kelp', + Template:Transliteration 'tea'.<ref name="Definition of KOMBUCHA">Template:Cite web</ref> The American Heritage Dictionary notes the term might have originated from the observation that the gelatinous film of kombucha resembled seaweed.<ref>Template:Cite encyclopedia</ref> The first known use in the English language of the word appeared in the British Chemical Abstracts in 1928.<ref>Template:Cite journal</ref>

In Chinese, kombucha was historically known as hǎibǎo (Template:Zh), derived from the SCOBY's resemblance to a jellyfish, and wèibǎo (Template:Zh), referring to its perceived medicinal benefits. Today, it is commonly called hóngchá jūn (Template:Zh), a term based on the Japanese kōcha kinoko.<ref name=":4" />

Composition and properties

Yeast and bacteria in kombucha magnified 400 times

A SCOBY used for brewing kombucha

Biological

A kombucha culture is a symbiotic culture of bacteria and yeast (SCOBY), similar to mother of vinegar, containing one or more species each of bacteria and yeasts, which form a zoogleal mat<ref name=Blanc>Template:Cite journal</ref> known as a "mother".<ref name=Jayabalan>Template:Cite journal</ref> There is a broad spectrum of yeast species spanning several genera reported to be present in kombucha cultures, including species of Zygosaccharomyces, Candida, Kloeckera/Hanseniaspora, Torulaspora, Pichia, Brettanomyces/Dekkera, Saccharomyces, Lachancea, Saccharomycoides, Schizosaccharomyces, Kluyveromyces, Starmera, Eremothecium, Merimbla, Sugiyamaella.<ref name="Villarreal-Soto 2018 580–588">Template:Cite journal</ref><ref>Template:Cite web</ref><ref name=":2">Template:Cite journal</ref>

The bacterial component of kombucha comprises several species, almost always including the acetic acid bacteria Komagataeibacter xylinus (formerly Gluconacetobacter xylinus), which ferments alcohols produced by the yeasts into acetic and other acids, increasing the acidity and limiting ethanol content.<ref>Template:Cite journal</ref>Template:Citation needed The population of bacteria and yeasts found to produce acetic acid has been reported to increase for the first 4 days of fermentation, decreasing thereafter.<ref>Kombucha Fermentation and Its Antimicrobial Activity Guttapadu Sreeramulu, Yang Zhu,* and Wieger Knol Journal of Agricultural and Food Chemistry 2000 48 (6), 2589–2594 Template:Doi</ref> K. xylinus produces bacterial cellulose, and is reportedly responsible for most or all of the physical structure of the "mother", which may have been selectively encouraged over time for firmer (denser) and more robust cultures by brewers.<ref name="Nguyen2008">Template:Cite journal</ref>Template:Primary source inline The highest diversity of kombucha bacteria was found to be on the 7th day of fermentation with the diversity being less in the SCOBY. Acetobacteraceae dominate 88 percent of the bacterial community of the SCOBY.<ref name=":2" /> The acetic acid bacteria in kombucha are aerobic, meaning that they require oxygen for their growth and activity.<ref name="Villarreal-Soto 2018 580–588"/> Hence, the bacteria initially migrate and assemble at the air interface, followed by the excretion of bacterial cellulose after about 2 days.<ref>Template:Cite journal</ref>

The mixed, presumably mutualistic culture has been further described as being lichenous, in accord with the reported presence of the known lichenous natural product usnic acid, though as of 2015, no report appears indicating the standard cyanobacterial species of lichens in association with kombucha fungal components.<ref name=LiverToxUsnic/>

Chemical composition

Kombucha is made by adding the kombucha culture into a broth of sugared tea.<ref name=Jayabalan/> The sugar serves as a nutrient for the SCOBY that allows for bacterial growth in the tea.Template:Citation needed Sucrose is converted, biochemically, into fructose and glucose, and these into gluconic acid and acetic acid.<ref name= "Sreermalu2000"/> In addition, kombucha contains enzymes and amino acids, polyphenols, and various other organic acids which vary between preparations.Template:Citation needed

Other specific components include ethanol (see below), glucuronic acid, glycerol, lactic acid, and usnic acid (a hepatotoxin, see below).<ref name=Teoh>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>

The alcohol content of kombucha is usually less than 0.5%, but increases with extended fermentation times.<ref name=bccdc/> Some tests have found commercial kombuchas with a range of alcohol contents ranging from undetectable to 4%.<ref name="d507">Template:Cite web</ref> The concentration of alcohol, specifically ethanol, increases initially but then begins to decrease when acetic acid bacteria use it to produce acetic acid.<ref name=":2" /> Over-fermentation generates high amounts of acids similar to vinegar.<ref name=Jayabalan/> The pH of the drink is typically about 3.5.<ref name=Ernst2003/>

Nutritional content

Kombucha tea is 95% water and contains 4% carbohydrates and several B vitamins, such as thiamin, riboflavin, niacin, and vitamin B₆.<ref name="fdc">Template:Cite webTemplate:Dead link</ref>

Production

Several brands of commercial kombucha on store shelves, Eastern Pennsylvania, 2019

Kombucha can be prepared at home or commercially.<ref name=Jayabalan/> It is made by dissolving sugar in non-chlorinated boiling water. Tea leaves are then steeped in the hot sugar water and discarded. The sweetened tea is cooled and the SCOBY culture is added. The mixture is then poured into a sterilized beaker along with previously fermented kombucha tea to lower the pH. This technique is known as "backslopping".<ref>Template:Cite book</ref> The container is covered with a paper towel or breathable fabric to prevent insects, such as fruit flies, from contaminating the kombucha.

The tea is left to ferment for a period of up to 10 to 14 days at room temperature (18 °C to 26 °C). A new "daughter" SCOBY will form on the surface of the tea to the diameter of the container. After fermentation is completed, the SCOBY is removed and stored along with a small amount of the newly fermented tea. The remaining kombucha is strained and bottled for a secondary ferment for a few days or stored at a temperature of 4 °C.<ref name=Jayabalan/>

Kombucha culture fermenting in a jar, 2006

Commercially bottled kombucha became available in the late 1990s.<ref name="Wollan2010">Template:Cite news</ref> In 2010, elevated alcohol levels were found in many bottled kombucha products, leading retailers including Whole Foods to pull the drinks from store shelves temporarily.<ref>Template:Cite news</ref> In response, kombucha suppliers reformulated their products to have lower alcohol levels.<ref>Template:Cite news</ref>

By 2014, US sales of bottled kombucha were $400 million, $350 million of which was by Millennium Products, Inc. which sells GT's Kombucha.<ref>Template:Cite web</ref> In 2014, several companies that make and sell kombucha formed a trade organization, Kombucha Brewers International.<ref>Template:Cite news</ref> In 2016, PepsiCo purchased kombucha maker KeVita for approximately $200 million.<ref>Template:Cite news</ref> In the US, sales of kombucha and other fermented drinks rose by 37 percent in 2017.<ref name=":0" /> Beer companies like Full Sail Brewing Company and Molson Coors Beverage Company produce kombucha by themselves or via subsidiaries.<ref name="boozy" />

As of 2021, the drink had some popularity in India's National Capital Region, partly due to its success in the west.<ref name="TNIE 2021">Template:Cite web</ref>

Hard kombucha

Some commercial kombucha producers sell what they call "hard kombucha" with an alcohol content of over 5 percent.<ref name=boozy>Template:Cite news</ref><ref>Template:Cite news</ref>

Health claims

Kombucha tea with ice cubes

Kombucha is promoted with many claims for health benefits, from alleviating hemorrhoids to combating cancer.<ref name=piles>Template:Cite news</ref> Although people may drink kombucha for such supposed health effects (attributed first to the protective impact of tea itself, and to fermentation products including glucuronic acid, acetic acid, polyphenols, phenols, and B-complex vitamins such as folic acid <ref name= Baschali >Template:Cite journal</ref>Template:Rp), there is no clinical proof that it provides any benefit.<ref name=Jayabalan/><ref name="Villarreal-SotoBeaufort2018">Template:Cite journal</ref><ref name=kapp>Template:Cite journal</ref> A review found only one human study on kombucha.<ref name="kapp" /> Kombucha is an "extreme example" of an unconventional remedy because of the disparity between implausible, wide-ranging health claims and the potential risks of the product.<ref name=Ernst2003/> It concluded that the proposed, unsubstantiated therapeutic claims did not outweigh known risks, and that kombucha should not be recommended for therapeutic use, being in a class of "remedies that only seem to benefit those who sell them".<ref name=Ernst2003>Template:Cite journalTemplate:Dead linkTemplate:Cbignore</ref>

Adverse effects

Reports of adverse effects related to kombucha consumption are rare, but may be underreported, according to a 2003 review.<ref name=Ernst2003/> The American Cancer Society said in 2009 that "serious side effects and occasional deaths have been associated with drinking Kombucha tea."<ref name=acs>Template:Cite book</ref> Because kombucha is a commonly homemade fermentation, caution should be taken because pathogenic microorganisms can contaminate the tea during preparation.<ref name=mayo/><ref name="Villarreal-Soto 2018 580–588"/> The risk of proliferation of bacteria associated with botulinum toxin is one reason that the pH of kombucha must be low, as Clostridium botulinum struggles to proliferate below pH 4.6.<ref name=maricopa>Template:Citation</ref><ref name="t025">Template:Cite web</ref>

Adverse effects associated with kombucha consumption may include severe hepatic (liver) and renal (kidney) toxicity as well as metabolic acidosis.<ref name=Dasgupta11>Template:Cite book</ref><ref name=Dasgupta13/><ref name=AbdualmjidSergi13>Template:Cite journal</ref>

Some adverse health effects may arise from the acidity of the tea causing acidosis, and brewers are cautioned to avoid over-fermentation.<ref name="mskcc">Template:Cite web</ref><ref>Template:Cite journal</ref><ref name=bccdc/> Other adverse effects may be a result of bacterial or fungal contamination during the brewing process.<ref name=bccdc/> Some studies have found the hepatotoxin usnic acid in kombucha, although it is not known whether the cases of liver damage are due to usnic acid or to some other toxin.<ref name=Dasgupta13>Template:Cite book</ref><ref name=LiverToxUsnic>Template:Cite encyclopedia</ref>

The acidity of kombucha may be threatening to the demineralization of teeth, leading towards later tooth decay.<ref name=":5">Template:Cite journal</ref> Kombucha surpasses the critical pH of teeth, which is approximately 5.5, which disrupts the chemical stability of the enamel, leading to enamel erosion.<ref>Template:Cite journal</ref><ref name=":6">Template:Cite journal</ref> Acids react with the bases within calcium hydroxyapatite, the primary component of tooth enamel, neutralizing them and increasing the dissolution of the enamel, causing degradation of the teeth.<ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref name=":6" />

Drinking kombucha can be harmful for people with preexisting ailments.<ref name=GreenwaltSteinkraus2000>Template:Cite journal</ref> Due to its microbial sourcing and possible non-sterile packaging, kombucha is not recommended for people with poor immune function,<ref name=mskcc/> women who are pregnant or nursing, or children under 4 years old:<ref name=bccdc>Template:Cite report</ref> It may compromise immune responses or stomach acidity in these susceptible populations.<ref name=mskcc/> There are certain drugs that one should not take with kombucha because of the small percentage of alcohol content.<ref>Template:Cite journal</ref>

A 2019 review enumerated numerous potential health risks (including hyponatremia, lactic acidosis, toxic hepatitis, etc.<ref name=kapp/>Template:Rp), but said "kombucha is not considered harmful if about 4 oz [120 mL] per day is consumed by healthy individuals; potential risks are associated with a low pH brew leaching heavy metals from containers, excessive consumption of highly acidic kombucha, or consumption by individuals with pre-existing health conditions."<ref name=kapp/>

Caffeine

Kombucha contains a small amount of caffeine.<ref name="auto">Template:Cite web</ref><ref name="auto1">Template:Cite web</ref>

Other uses

Kombucha culture, when dried, becomes a leather-like textile known as a microbial cellulose that can be molded onto forms to create seamless clothing.<ref>Template:Cite web</ref><ref>Template:Cite web</ref> Using different broth media such as coffee, black tea, and green tea to grow the kombucha culture results in different textile colors, although the textile can also be dyed using other plant-based dyes. Different growth media and dyes also change the textile's feel and texture.<ref name="Hinchliffe">Template:Cite web</ref> Dried and processed SCOBY has been investigated as a leather substitute.<ref name="t748">Template:Cite journal</ref> Additionally, the SCOBY itself can be dried and eaten as a sweet or savory snack.<ref>Template:Cite web</ref>

See also

• Cannabis tea, a cannabis-infused drink prepared by steeping various parts of the cannabis plant in hot or cold water
• Enviga, a carbonated green tea drink promoted with bogus health claims
• Jun, a fermented drink made from green tea and honey
• Kefir, a fermented dairy product
• Kvass, a traditional fermented drink made from bread
• List of unproven or disproven cancer treatments
• Mushroom tea, an infusion of mushrooms in water, made by using edible/medicinal mushrooms (such as lingzhi mushroom) or psychedelic mushrooms (such as Psilocybe cubensis)
• Tibicos, or "water kefir"

External links

• Template:Commons category-inline