Type | Flavored cold tea drink with fermentation 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 (also tea mushroom, tea fungus, or Manchurian mushroom when referring to the culture; Latin name Medusomyces gisevii) [1] is a fermented, lightly effervescent, sweetened black tea drink. Sometimes the beverage is called kombucha tea to distinguish it from the culture of bacteria and yeast. [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 now homebrewed globally, and also bottled and sold commercially. [1] The global kombucha market was worth approximately US$1.7 billion as of 2019 [update] . [6]
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). [7] 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 [ biofilm ]". [1] The living bacteria are said to be probiotic, 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 little evidence to support any of these claims. [8] [10] [11] The beverage has caused rare serious adverse effects, possibly arising from contamination during home preparation. [12] [13] It is not recommended for therapeutic purposes. [10] [14]
Kombucha most likely originated in the Bohai Sea district in China. [4] The drink was consumed in Russia and from there entered the rest of Europe. [17] Its consumption increased in the United States during the early 21st century. [18] [19] Having an alcohol content of less than 0.5%, kombucha is not a federally regulated beverage in the United States. [20] [21]
Prior to 2015, some commercially available kombucha brands were found to contain alcohol content exceeding this threshold, sparking the development of new testing methods. [22] 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. [23]
According to the market research firm Grand View Research,[ clarification needed ] kombucha had a global market size of US$1.67 billion, as of 2019 [update] and this is expected to grow to US$9.7 billion by 2030. [6]
In Japanese, the term konbu-cha (昆布茶, 'kelp tea') refers to a kelp tea made with powdered 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.[ citation needed ]
The etymology of kombucha is uncertain; however, it is speculated that it is a misapplied loanword from Japanese. [24] It has been hypothesized that English speakers mistook the Japanese word kombucha to mean fermented tea, when in fact, this type of fermented tea in Japanese is called kōcha kinoko ( 紅茶キノコ , 'black tea mushroom') which became popular around 1975. [25] [26] Webster's Dictionary says the use of kombucha in English likely stems from the misapplication of Japanese words: kombucha, kobucha 'tea made from kelp', kobu, konbu 'kelp', and cha 'tea'. [27] The American Heritage Dictionary states that it was "perhaps ... used by English speakers to designate fermented tea due to confusion or because the thick gelatinous film produced by the kombucha culture was thought to resemble seaweed." [28]
The first known use in the English language of the word to describe "a gelatinous mass of symbiotic bacteria (as Acetobacter xylinum) and yeasts (as of the genera Brettanomyces and Saccharomyces) grown to produce a fermented beverage held to confer health benefits" was in 1944. [27]
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 [29] known as a "mother". [1] There is a broad spectrum of yeast species spanning several genera reported to be present in kombucha culture including species of Zygosaccharomyces, Candida, Kloeckera/Hanseniaspora, Torulaspora, Pichia, Brettanomyces/Dekkera, Saccharomyces, Lachancea, Saccharomycoides, Schizosaccharomyces, Kluyveromyces, Starmera, Eremothecium, Merimbla, Sugiyamaella. [30] [31] [32]
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. [33] [ 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. [34] 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. [35] [ 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. [32] The acetic acid bacteria in kombucha are aerobic, meaning that they require oxygen for their growth and activity. [30] Hence, the bacteria initially migrate and assemble at the air interface, followed by the excretion of bacterial cellulose after about 2 days. [36]
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. [37]
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 into gluconic acid and acetic acid. [17] In addition, kombucha contains enzymes and amino acids, polyphenols, and various other organic acids which vary between preparations.[ citation needed ]
Other specific components include ethanol (see below), glucuronic acid, glycerol, lactic acid, and usnic acid (a hepatotoxin, see above). [38] [39] [40]
The alcohol content of kombucha is usually less than 0.5%, but increases with extended fermentation times. [41] The concentration of alcohol specifically ethanol increases initially but then begins to decrease when acetic acid bacteria utilize it to produce acetic acid. [32] 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, contains 4% carbohydrates and several B vitamins, such as Thiamin, Riboflavin, Niacin and Vitamin B-6 [42]
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 the pH. This technique is known as "backslopping". [43] 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. [44] 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. [45] In response, kombucha suppliers reformulated their products to have lower alcohol levels. [46]
By 2014, US sales of bottled kombucha were $400 million, $350 million of which was by Millennium Products, Inc. which sells GT's Kombucha. [47] In 2014, several companies that make and sell kombucha formed a trade organization, Kombucha Brewers International. [48] In 2016, PepsiCo purchased kombucha maker KeVita for approximately $200 million. [49] In the US, sales of kombucha and other fermented drinks rose by 37 percent in 2017. [23] Beer companies like Full Sail Brewing Company and Molson Coors Beverage Company produce kombucha by themselves or via subsidiaries. [50]
As of 2021, the drink had some popularity in India's National Capital Region, partly due to its success in the west. [51]
Some commercial kombucha producers sell what they call "hard kombucha" with an alcohol content of over 5 percent. [50] [52]
Kombucha is promoted with many claims for health benefits, from alleviating hemorrhoids to combatting cancer. [53] Although people may drink kombucha for such supposed health effects[ which? ], there is no clinical proof that it provides any benefit. [1] [8] [54] [55] In a 2003 review, physician Edzard 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 for therapeutic use, being in a class of "remedies that only seem to benefit those who sell them". [10]
Reports of adverse effects related to kombucha consumption are rare, but may be underreported, according to a 2003 review. [10] The American 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] [30]
Adverse effects associated with kombucha consumption may include severe hepatic (liver) and renal (kidney) toxicity as well as metabolic acidosis. [56] [57] [58]
Some adverse health effects may arise from the acidity of the tea causing acidosis, and brewers are cautioned to avoid over-fermentation. [12] [59] [41] Other adverse effects may be a result of bacterial or fungal contamination during the brewing process. [41] 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. [57] [37]
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: [41] It may compromise immune 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[ which? ], 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." [55]
Kombucha culture, when dried, becomes a leather-like textile known as a microbial cellulose that can be molded onto forms to create seamless clothing. [62] [63] 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. [64] Different growth media and dyes also change the textile's feel and texture. [64] Additionally the SCOBY itself can be dried and eaten as a sweet or savory snack. [65]
Vinegar is an aqueous solution of acetic acid and trace compounds that may include flavorings. Vinegar typically contains from 5% to 18% acetic acid by volume. Usually, the acetic acid is produced by a double fermentation, converting simple sugars to ethanol using yeast and ethanol to acetic acid using acetic acid bacteria. Many types of vinegar are made, depending on source materials. The product is now mainly used in the culinary arts as a flavorful, acidic cooking ingredient or in pickling. Various types are used as condiments or garnishes, including balsamic vinegar and malt vinegar.
Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitute 1% of all described fungal species.
Mother of vinegar is a biofilm composed of a form of cellulose, yeast, and bacteria that sometimes develops on fermenting alcoholic liquids during the process that turns alcohol into acetic acid with the help of oxygen from the air and acetic acid bacteria (AAB). It is similar to the symbiotic culture of bacteria and yeast (SCOBY) mostly known from production of kombucha, but develops to a much lesser extent due to lesser availability of yeast, which is often no longer present in wine/cider at this stage, and a different population of bacteria. Mother of vinegar is often added to wine, cider, or other alcoholic liquids to produce vinegar at home, although only the bacteria is required, but historically has also been used in large scale production.
Ginger ale is a carbonated soft drink flavoured with ginger. It is consumed on its own or used as a mixer, often with spirit-based drinks. There are two main types of ginger ale. The golden style is credited to the Irish doctor Thomas Joseph Cantrell. The dry style, a paler drink with a much milder ginger flavour, was created by Canadian John McLaughlin.
Traditional ginger beer is a sweetened and carbonated, usually non-alcoholic beverage. Historically it was produced by the natural fermentation of prepared ginger spice, yeast and sugar.
Makgeolli, sometimes anglicized to makkoli, is a Korean alcoholic drink. It is a milky, off-white, and lightly sparkling rice wine that has a slight viscosity, and tastes slightly sweet, tangy, bitter, and astringent. Chalky sediment gives it a cloudy appearance. As a low proof drink of six to nine percent alcohol by volume, it is often considered a "communal beverage" rather than hard liquor.
Tej is a honey wine, like mead, that is brewed and consumed in Ethiopia and Eritrea. It has an alcohol content generally ranging from 7 to 11%. It is often home processed and consists of three main ingredients; honey, water and a medicinal shrub called "gesho". Tej is also available commercially to buy in many different types. It is generally consumed during social events such as festivals or weddings, and religious events like Ethiopian New Year (Enkutatash). Consequently, tej forms an important part of Ethiopian society and culture and is considered the national drink of Ethiopia.
Lactobacillales are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped (bacilli) or spherical (cocci) bacteria that share common metabolic and physiological characteristics. These bacteria, usually found in decomposing plants and milk products, produce lactic acid as the major metabolic end product of carbohydrate fermentation, giving them the common name lactic acid bacteria (LAB).
Tibicos, or water kefir, is a traditional fermented drink made with water and a water kefir grains held in a polysaccharide biofilm matrix created by the bacteria. It is sometimes consumed as an alternative to milk-based probiotic drinks or tea-cultured products such as kombucha. Water kefir is typically made as a probiotic homebrew beverage. The finished product, if bottled, will produce a carbonated beverage.
Tepache is a fermented beverage made from the peel and the rind of pineapples, and is sweetened either with piloncillo or brown sugar. It is sometimes seasoned with chili powder and served cold. Tepache is usually sold as a chilled drink by street vendors in Mexico, stored in barrels to expedite the fermentation process. It is served either in a clay mug or in a clear plastic bag with a straw inserted for easier travel. In the U.S., it is sold in juice bars or traditional Mexican restaurants within Mexican American communities of the Southwestern United States.
Fermentation is a type of redox metabolism carried out in the absence of oxygen. During fermentation, organic molecules are catabolized and donate electrons to other organic molecules. In the process, ATP and organic end products are formed.
In food processing, fermentation is the conversion of carbohydrates to alcohol or organic acids using microorganisms—yeasts or bacteria—without an oxidizing agent being used in the reaction. Fermentation usually implies that the action of microorganisms is desired. The science of fermentation is known as zymology or zymurgy.
Fermented 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 and exo-oxidation. 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" in Chinese. The most famous fermented tea is pu'er produced in Yunnan province.
Symbiotic culture of bacteria and yeast (SCOBY) is a culinary symbiotic fermentation culture (starter) consisting of lactic acid bacteria (LAB), acetic acid bacteria (AAB), and yeast which arises in the preparation of sour foods and beverages such as kombucha. Beer and wine also undergo fermentation with yeast, but the lactic acid bacteria and acetic acid bacteria components unique to SCOBY are usually viewed as a source of spoilage rather than a desired addition. Both LAB and AAB enter on the surface of barley and malt in beer fermentation and grapes in wine fermentation; LAB lowers the pH of the beer/wine while AAB takes the ethanol produced from the yeast and oxidizes it further into vinegar, resulting in a sour taste and smell. AAB are also responsible for the formation of the cellulose SCOBY.
An alcoholic beverage is a beverage containing alcohol (ethanol). Alcoholic drinks are typically divided into three classes—beers, wines, and spirits—and typically their alcohol content is between 3% and 50%.
Cider is an alcoholic beverage made from the fermented juice of apples. Cider is widely available in the United Kingdom and Ireland. The UK has the world's highest per capita consumption, as well as the largest cider-producing companies. Ciders from the South West of England are generally higher in alcoholic content. Cider is also popular in many Commonwealth countries, such as India, South Africa, Canada, Australia, New Zealand, and New England. As well as the UK and its former colonies, cider is popular in Portugal, France, Friuli, and northern Spain. Germany also has its own types of cider with Rhineland-Palatinate and Hesse producing a particularly tart version known as Apfelwein. In the U.S. and Canada, varieties of alcoholic cider are often called hard cider to distinguish it from non-alcoholic apple cider or "sweet cider", also made from apples. In Canada, cider cannot contain less than 2.5% or over 13% absolute alcohol by volume.
Microbial food cultures are live bacteria, yeasts or moulds used in food production. Microbial food cultures carry out the fermentation process in foodstuffs. Used by humans since the Neolithic period fermentation helps to preserve perishable foods and to improve their nutritional and organoleptic qualities. As of 1995, fermented food represented between one quarter and one third of food consumed in Central Europe. More than 260 different species of microbial food culture are identified and described for their beneficial use in fermented food products globally, showing the importance of their use.
Symbiotic fermentation is a form of fermentation in which multiple organisms interact in symbiosis in order to produce the desired product. For example, a yeast may produce ethanol, which is then consumed by an acetic acid bacterium. Described early on as the fermentation of sugars following saccharification in a mixed fermentation process.
Jun, or Xun, is a fermented drink similar to kombucha, differing only in that its base ingredients are green tea and honey instead of black tea and cane sugar. Jun is brewed by fermenting green tea with a symbiotic culture of bacteria and yeast (SCOBY). Fruits, sweeteners, spices, and other flavor enhancers are also commonly added to make the taste of the beverage more appealing. Though Jun bears similarities to other fermented drinks like kombucha, water kefir, and kvass, it has enough differences to be considered a distinct drink.
Wine preservatives are used to preserve the quality and shelf life of bottled wine without affecting its taste. Specifically, they are used to prevent oxidation and bacterial spoilage by inhibiting microbial activity.
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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