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Kombucha (Russian: chaynyy grib (чайный гриб), Chinese: chájūn (茶菌), Korean: hongchabeoseotcha (홍차버섯차), Japanese: kōcha-kinoko (紅茶キノコ)), is a lightly effervescent fermented drink of sweetened black and/or green tea that is used as a functional food. It is produced by fermenting the tea using a symbiotic colony of bacteria and yeast, or "SCOBY". Although kombucha is claimed to have several beneficial effects on health, the claims are not supported by scientific evidence. Drinking kombucha has been linked, in rare cases, to serious side effects and deaths, and improper preparation can lead to contamination.
Kombucha most likely originated in Northeast China or Manchuria, later spreading to east Russia sometime before 1910 and from there, to Germany and Europe. In Russian, the kombucha culture is called chainyy grib чайный гриб (literally "tea fungus/mushroom"), and the fermented drink is called chainyy grib, grib ("fungus; mushroom"), or chainyy kvas чайный квас ("tea kvass"). Kombucha was highly popular and seen as a health food in China in the 1950s and 1960s. Many families grew kombucha at home. No historical records show use in ancient China or Japan (see history of tea in China and history of tea in Japan).
A kombucha culture is a symbiotic culture of bacteria and yeast (SCOBY), containing Acetobacter (a genus of acetic acid bacteria) and one or more yeasts, which form a zoogleal mat. In Chinese, the microbial culture is called haomo in Cantonese, or jiaomu in Mandarin, (Chinese: 酵母; literally: "fermentation mother"). It is also known as Manchurian Mushroom.
Kombucha cultures may contain one or more of the yeasts Saccharomyces cerevisiae, Brettanomyces bruxellensis, Candida stellata, Schizosaccharomyces pombe, Torulaspora delbrueckii, and Zygosaccharomyces bailii. Alcohol production by the yeast(s) contributes to the production of acetic acid by the bacteria.
Although the bacterial component of a kombucha culture comprises several species, it almost always includes Gluconacetobacter xylinus (formerly Acetobacter xylinum), which ferments the alcohol(s) produced by the yeast(s) into acetic acid, increasing the acidity while limiting the kombucha's alcoholic content. The number of bacteria and yeasts that were found to produce acetic acid increased for the first four days of fermentation, decreasing thereafter. Sucrose gets broken down into fructose and glucose, and the bacteria and yeast convert the glucose and fructose into gluconic acid and acetic acid, respectively. G. xylinum is responsible for most or all of the physical structure of a kombucha mother, and has been shown to produce microbial cellulose, likely due to selection over time for firmer and more robust cultures by brewers.
The acidity and mild alcoholic element of kombucha resists contamination by most airborne molds or bacterial spores. A study showed that kombucha inhibits growth of harmful microorganisms such as E. coli, Sal. enteritidis, Sal. typhimurium, and Sh. Sonnei. As a result, kombucha is relatively easy to maintain as a culture outside of sterile conditions. The bacteria and yeasts in kombucha promoted microbial growth for the first six days of fermentation; after that, they steadily declined. Kombucha retained its antimicrobial capability even after being heated, and at a pH of 7. While the beverage inhibited growth of certain bacteria, it had no effect on the yeasts. The study also found that large proteins and catechins such as Epigallocatechin gallate also contributed to the antimicrobial properties of kombucha.
Kombucha contains multiple species of yeast and bacteria along with the organic acids, active enzymes, amino acids, and polyphenols they produce. The exact quantities vary between samples, but may contain: acetic acid, ethanol, gluconic acid, glucuronic acid, glycerol, lactic acid, usnic acid and B-vitamins. It was also found that kombucha contains about 1.51 mg/mL of vitamin C.
Reports of adverse reactions may be related to unsanitary fermentation conditions, leaching of compounds from the fermentation vessels, or "sickly" kombucha cultures that cannot acidify the brew.
According to the American Cancer Society, "Kombucha tea has been promoted as a cure-all for a wide range of conditions including baldness, insomnia, intestinal disorders, arthritis, chronic fatigue syndrome, multiple sclerosis, AIDS, and cancer. Supporters say that Kombucha tea can boost the immune system and reverse the aging process." However, "Available scientific evidence does not support claims that Kombucha tea promotes good health, prevents any ailments, or works to treat cancer or any other disease. Serious side effects and occasional deaths have been linked with drinking Kombucha tea."
No clinical study supports claims that Kombucha can cure disease. Case reports "raise doubts about the safety of kombucha," including incidents of central nervous system impairment, suspected liver damage, metabolic acidosis, and toxicity in general. Acute conditions caused by drinking of kombucha, such as lactic acidosis, are more likely to occur in persons with pre-existing medical conditions. Other reports suggest exercising caution if regularly drinking kombucha while taking medical drugs or hormone replacement therapy. Kombucha may also cause allergic reactions.
Some adverse health effects may be due to the acidity of the tea, cautioning preparers to avoid over-fermentation.
In Japan, Konbucha (昆布茶?, "kelp tea") refers to a different beverage made from dried and powdered kombu (an edible kelp from the Laminariaceae family). For the origin of the English word kombucha, first recorded in 1995 and of uncertain etymology, the American Heritage Dictionary suggests: "Probably from Japanese kombucha, tea made from kombu (the Japanese word for kelp perhaps being 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)."
The Japanese name for what English speakers know as kombucha is kōcha kinoko 紅茶キノコ (literally, 'red tea mushroom'), compounding kōcha "black tea" and kinoko 茸 "mushroom; toadstool". The Chinese names for kombucha are hóngchájùn 红茶菌 ('red tea fungus'), cháméijūn 茶黴菌 ('tea mold'), or hóngchágū 红茶菇 ('red tea mushroom'), with jūn 菌 'fungus, bacterium or germ' (or jùn 'mushroom'), méijūn 黴菌 'mold or fungus', and gū 菇 'mushroom'. ("Red tea", 紅茶, in Chinese languages corresponds to English "black tea".)
A 1965 mycological study called kombucha "tea fungus" and listed other names: "teeschwamm, Japanese or Indonesian tea fungus, kombucha, wunderpilz, hongo, cajnij, fungus japonicus, and teekwass." Some further spellings and synonyms include combucha and tschambucco, and haipao, kargasok tea, kwassan, Manchurian fungus or mushroom, spumonto, as well as the misnomers champagne of life, and chai from the sea.[clarification needed]
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