 Kombucha tea, including the culture of bacteria and yeast, which is not usually consumed | |
| Type | Flavored cold tea drink withfermentation byproducts |
|---|---|
| Country of origin | China |
| Alcohol by volume | <0.5% (commercial) |
| Proof (US) | <1 (commercial) |
| Color | Cloudy, commonly pale or dark brown and sometimes green |
| Flavor | Fermented, effervescent |
| Ingredients | Tea, sugar, bacteria,yeast |
| Variants | Fruit juices or spices added |
| Related products | Water kefir,kefir,kvass, beer,iced tea |
Kombucha (alsotea mushroom,tea fungus, orManchurian mushroom when referring to theculture; Latin nameMedusomyces gisevii)[1] is afermented, lightlyeffervescent,sweetenedblack tea drink. Sometimes the beverage is calledkombucha tea to distinguish it from the culture of bacteria andyeast.[2] Juice, spices, fruit, or other flavorings are often added.
Kombucha is thought to have originated in China, where the drink is traditional.[3][4] By the early 20th century it spread to Russia, then other parts of Eastern Europe and Germany.[5] Kombucha is nowhomebrewed globally, and also bottled and sold commercially.[1] The global kombucha market was worth approximatelyUS$1.7 billion as of 2019[update].[6]
Kombucha is produced bysymbiotic fermentation of sugared tea using asymbiotic culture of bacteria and yeast (SCOBY) commonly called a "mother" or "mushroom". Themicrobial populations in a SCOBY vary. The yeast component generally includesSaccharomyces cerevisiae, along with other species; the bacterial component almost always includesGluconacetobacter xylinus tooxidize yeast-producedalcohols toacetic acid (and other acids).[7] Although the SCOBY is commonly called "tea fungus" or "mushroom", it is actually "a symbiotic growth of acetic acid bacteria andosmophilic yeast species in a zoogleal mat [biofilm]".[1] The living bacteria are said to beprobiotic, one of the reasons for the popularity of the drink.[8][9]
Numerous health benefits have been claimed to correlate with drinking kombucha;[10] there is littleevidence to support any of these claims.[8][10][11] The beverage has caused rare seriousadverse effects, possibly arising fromcontamination duringhome preparation.[12][13] It is not recommended fortherapeutic purposes.[10][14]
Kombucha likely originated in theBohai Sea region of China.[4] It spread to Russia before reaching Europe and gained popularity in the United States in the early 21st century.[15][16][17] With an alcohol content under 0.5%, it is not federally regulated in the U.S.[18][19]
Prior to 2015, some commercially available kombucha brands were found to contain alcohol content exceeding this threshold, sparking the development of new testing methods.[20] With rising popularity indeveloped countries in the early 21st century, kombucha sales increased after it was marketed as an alternative to beer and other alcoholic drinks in restaurants andpubs.[21]
According to the market research firmGrand View Research,[clarification needed] kombucha had a global market size ofUS$1.67 billion as of 2019[update], and this is expected to grow toUS$9.7 billion by 2030.[6]
Theetymology ofkombucha is uncertain, but it is believed to be a misappliedloanword from Japanese.[22] English speakers may have confused the Japanese wordkonbucha withkōcha kinoko (紅茶キノコ, 'black tea mushroom'), popularized around 1975.[23][24]
In Japanese, the termkonbu-cha (昆布茶, 'kelp tea') refers to a kelp tea made withkonbu (an ediblekelp from the familyLaminariaceae) and is a completely different beverage from the fermented tea usually associated withkombucha elsewhere in the world.[25]
Merriam-Webster's Dictionary suggests kombucha in English arose from misapplication of Japanese words likekonbucha,kobucha 'tea made from kelp',konbu, fromkobu 'kelp', + cha 'tea'.[26]The American Heritage Dictionary notes the term might have originated from the belief that the gelatinous film of kombucha resembled seaweed.[27]
The first known use in the English language of the word to describe "a gelatinous mass of symbiotic bacteria (asAcetobacter xylinum) and yeasts (as of the generaBrettanomyces andSaccharomyces) grown to produce a fermented beverage held to confer health benefits" was in 1944.[26]
A kombucha culture is asymbiotic culture of bacteria and yeast (SCOBY), similar tomother of vinegar, containing one or more species each of bacteria and yeasts, which form azoogleal mat[28] known as a "mother".[1] There is a broad spectrum of yeast species spanning several genera reported to be present in kombucha cultures, including species ofZygosaccharomyces,Candida, Kloeckera/Hanseniaspora,Torulaspora,Pichia,Brettanomyces/Dekkera,Saccharomyces,Lachancea,Saccharomycoides,Schizosaccharomyces,Kluyveromyces, Starmera, Eremothecium, Merimbla, Sugiyamaella.[29][30][31]
The bacterial component of kombucha comprises several species, almost always including theacetic acid bacteriaKomagataeibacter xylinus (formerlyGluconacetobacter xylinus), which ferments alcohols produced by the yeasts intoacetic and other acids, increasing the acidity and limitingethanol content.[32][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.[33]K. xylinus producesbacterial 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.[34][non-primary source needed] 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.[31] The acetic acid bacteria in kombucha areaerobic, meaning that they require oxygen for their growth and activity.[29] Hence, the bacteria initially migrate and assemble at the air interface, followed by the excretion of bacterial cellulose after about 2 days.[35]
The mixed, presumablymutualistic culture has been further described as being lichenous, in accord with the reported presence of the known lichenous natural productusnic acid, though as of 2015, no report appears indicating the standard cyanobacterial species oflichens in association with kombucha fungal components.[36]
Kombucha is made by adding the kombucha culture into a broth of sugared tea.[1] The sugar serves as a nutrient for the SCOBY that allows for bacterial growth in the tea.[citation needed] Sucrose is converted, biochemically, into fructose and glucose, and these intogluconic acid and acetic acid.[15] In addition, kombucha containsenzymes andamino acids,polyphenols, and various otherorganic acids which vary between preparations.[citation needed]
Other specific components includeethanol (see below),glucuronic acid,glycerol,lactic acid, andusnic acid (a hepatotoxin, see above).[37][38][39]
The alcohol content of kombucha is usually less than 0.5%, but increases with extended fermentation times.[40] The concentration of alcohol specifically ethanol increases initially but then begins to decrease when acetic acid bacteria use it to produce acetic acid.[31] Over-fermentation generates high amounts of acids similar to vinegar.[1] The pH of the drink is typically about 3.5.[10]
Kombucha tea is 95% water and contains 4%carbohydrates and severalB vitamins, such asthiamin,riboflavin,niacin, andvitamin B6.[41]
Kombucha can be prepared at home or commercially.[1] 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 thepH. This technique is known as "backslopping".[42] 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.[1]
Commercially bottled kombucha became available in the late 1990s.[43] In 2010, elevated alcohol levels were found in many bottled kombucha products, leading retailers includingWhole Foods to pull the drinks from store shelves temporarily.[44] In response, kombucha suppliers reformulated their products to have lower alcohol levels.[45]
By 2014, US sales of bottled kombucha were $400 million, $350 million of which was by Millennium Products, Inc. which sellsGT's Kombucha.[46] In 2014, several companies that make and sell kombucha formed atrade organization, Kombucha Brewers International.[47] In 2016,PepsiCo purchased kombucha maker KeVita for approximately $200 million.[48] In the US, sales of kombucha and other fermented drinks rose by 37 percent in 2017.[21] Beer companies likeFull Sail Brewing Company andMolson Coors Beverage Company produce kombucha by themselves or via subsidiaries.[49]
As of 2021, the drink had some popularity in India'sNational Capital Region, partly due to its success in the west.[50]
Some commercial kombucha producers sell what they call "hard kombucha" with an alcohol content of over 5 percent.[49][51]
Kombucha is promoted with many claims for health benefits, from alleviatinghemorrhoids to combating cancer.[52] 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[53]: 15 ), there is noclinical proof that it provides any benefit.[1][8][54][55] In a 2003 review, physicianEdzard Ernst characterized kombucha as an "extreme example" of an unconventional remedy because of the disparity between implausible, wide-ranging health claims and the potential risks of the product.[10] It concluded that the proposed, unsubstantiated therapeutic claims did not outweigh known risks, and that kombucha should not be recommended fortherapeutic use, being in a class of "remedies that only seem to benefit those who sell them".[10]
Reports ofadverse effects related to kombucha consumption are rare, but may be underreported, according to a 2003 review.[10] TheAmerican Cancer Society said in 2009 that "serious side effects and occasional deaths have been associated with drinking Kombucha tea."[13] Because kombucha is a commonly homemade fermentation, caution should be taken because pathogenic microorganisms can contaminate the tea during preparation.[14][29]
Adverse effects associated with kombucha consumption may include severehepatic (liver) andrenal (kidney) toxicity as well asmetabolic acidosis.[56][57][58]
Some adverse health effects may arise from the acidity of the tea causingacidosis, and brewers are cautioned to avoid over-fermentation.[12][59][40] Other adverse effects may be a result of bacterial or fungal contamination during the brewing process.[40] Some studies have found thehepatotoxinusnic acid in kombucha, although it is not known whether the cases of liver damage are due tousnic acid or to some other toxin.[57][36]
Drinking kombucha can be harmful for people with preexisting ailments.[60] Due to its microbial sourcing and possible non-sterile packaging, kombucha is not recommended for people with poor immune function,[12] women who are pregnant or nursing, or children under 4 years old:[40] It may compromiseimmune responses or stomach acidity in these susceptible populations.[12] There are certain drugs that one should not take with kombucha because of the small percentage of alcohol content.[61]
A 2019 review enumerated numerous potential health risks (including hyponatremia, lactic acidosis, toxic hepatitis, etc.[55]: 68 ), 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 brewleachingheavy metals from containers, excessive consumption of highly acidic kombucha, or consumption by individuals with pre-existing health conditions."[55]
Kombucha contains a small amount ofcaffeine.[62][63]
Kombucha culture, when dried, becomes a leather-like textile known as amicrobial cellulose that can be molded onto forms to create seamless clothing.[64][65] 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.[66] Different growth media and dyes also change the textile's feel and texture.[66] Additionally, the SCOBY itself can be dried and eaten as a sweet or savory snack.[67]
Serious side effects and occasional deaths have been associated with drinking Kombucha tea
It originated in northeast China (Manchuria) and later spread to Russia and the rest of the world.
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