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From Wikipedia, the free encyclopedia

Kombucha is the Western name for sweetened tea or tisane that has been fermented using a macroscopic solid mass of microorganisms called a "kombucha colony".

Contents 1 Biology of kombucha 2 History 2.1 Russian "tea mushroom" 3 Components 4 Health Claims 5 Scientific Claims 6 Safety and contamination 7 See also 8 References 9 External links

[edit] Biology of kombucha

The culture contains a symbiosis of Acetobacter (acetic acid bacteria) and yeast, mostly Brettanomyces bruxellensis, Candida stellata, Schizosaccharomyces pombe, Torulaspora delbrueckii and Zygosaccharomyces bailii. The culture itself looks somewhat like a large pancake, and though often called a mushroom, a Mother of vinegar or by the acronym SCOBY (for "Symbiotic Colony of Bacteria and Yeast"), it is clinically known as a zoogleal mat.

[edit] History

The recorded history of this drink dates back to the Qin Dynasty in China (around 250 BC). The Chinese called it the "Immortal Health Elixir," because they believed Kombucha balanced the Middle Qi (Spleen and Stomach) and aided in digestion, allowing the body to focus on healing. Knowledge of kombucha eventually reached Russia and then Eastern Europe around the Early Modern Age, when tea first became affordable to the populace. The name "kombucha" is said to have originated in Japan in 415 AD. Reportedly, a Korean physician called Kombu or Kambu treated the Emperor Inyko with the tea. It became known by a combination of the name, "Kombu" and the word, "cha," meaning tea.^[1] However, in Japan, kombucha tea is known as "kocha kinoko" which translates as "tea mushroom". Kombu literally means "kelp" in Japanese^[2] and the name "Kombucha" is used to refer to a hot drink made from powdered kelp.

[edit] Russian "tea mushroom"

The process of brewing kombucha was introduced in Russia and Ukraine at the end of the 1800s, and became popular in the early 1900s. The kombucha culture is known locally as chayniy grib, (чайный гриб - 'tea mushroom'), and the drink itself is referred to as grib (гриб - 'mushroom'), "tea kvass" (квас) or simply kvass, although it differs from regular kvass which is traditionally made from water and stale rye bread.

[edit] Components

Kombucha contains many different cultures along with several organic acids, active enzymes, amino acids, and polyphenols.^[3]For the home brewer, there is no way to know the amounts of the components unless a sample is sent to a laboratory. The US Food and Drug Administration has no findings on the effects of kombucha.^[4] Final kombucha may contain some of the following components depending on the source of the culture: Acetic acid, which provides much anti-microbial activity; butyric acid, gluconic acid, glucuronic acid, lactic acid, malic acid, oxalic acid, usnic acid, as well as some B-vitamins.^[5]

Due to the acidic fermentation process used in its brewing, Kombucha contains ethyl alcohol in amounts that vary from 0.5% to 1.5%^[6], depending on anaerobic brewing time and proportions of microbe. Commercial preparations are typically 0.5% for distribution and safety reasons.

[edit] Health Claims

A review of the published literature on the safety of kombucha suggests no specific oral toxicity in rats,^[7] although it has also been shown to increase the size of both the liver and spleen in mice.^[8] While no randomized case-controlled studies have been published in humans, several case reports have suspected liver damage, metabolic acidosis and cutaneous anthrax infections. ^[9] Other reports suggest that care should be taken when taking medical drugs or hormone replacement therapy while regularly drinking kombucha.^[10] It may also cause allergic reactions. ^[11]

Other health claims may be due to the simple acidity of the drink, possibly influencing the production of stomach acids or modifying the communities of microorganisms in the GI tract. For example, anecdotal reports suggest better experience with foods that 'stick' going down such as rice or pasta. This is mostly due to relief of stomach gas responsible for preventing proper digestion.^{[citation needed]}

[edit] Scientific Claims

Health claims for kombucha focus on a chemical called glucuronic acid, a compound that is used by the liver for detoxification. The idea that glucuronic acid is present in kombucha is based on the observation that glucuronic acid conjugates (glucuronic acid + waste chemicals) are increased in the urine after consumption of kombucha.

Early chemical analysis of kombucha brew suggested that glucuronic acid was the key component, and researchers hypothesized that the extra glucuronic acid would assist the liver by supplying more of the substance during detoxification. These analyses were done using gas chromatography to identify the different chemical constituents, but this method relies on having proper chemical standards to match to the unknown chemicals. A more recent and thorough analysis, outlined in the book in Analysis of Kombucha Ferments by Michael Roussin.^[12] suggests a different explanation. Roussin reports on an extensive chemical analysis of a variety of commercial and homebrew versions of kombucha, and finds no evidence of glucuronic acid at all. These scientific measurements contradict the earlier studies and conflict with the original hypothesis.

Instead, Roussin discovered that the active component in kombucha is most likely glucaric acid. This compound, also known as D - glucaro -1,4 lactone, helps in the elimination of glucuronic acid conjugates that are produced by the liver. When glucuronic acid conjugates are disposed in the bowel during the elimination process, normal gut bacteria can break up these conjugates using an enzyme called beta-glucuronidase. Glucaric acid is an inhibitor of this bacterial enzyme, so the end result is that the glucuronic acid + waste is properly eliminated the first time, rather than being reabsorbed and detoxified over and over. Thus, glucaric acid probably makes the liver more efficient.

Interestingly, glucaric acid is commonly found in fruits and vegetables, and is being explored independently as a cancer preventive agent.^[13] It has also been discovered that the bacterial beta-glucuronidase enzyme can interfere with proper disposal of a chemotherapeutic agent, and that antibiotics against the gut microbiota can prevent toxicity of some chemotherapy drugs (http://cancerres.aacrjournals.org/cgi/content/abstract/56/16/3752.)

Reports of adverse reactions may be related to unsanitary fermentation conditions, leaching of compounds from the fermentation vessels,^[14] or "sickly" kombucha cultures that cannot acidify the brew. Cleanliness is important during preparation, and in most cases, the acidity of the fermented drink prevents growth of unwanted contaminants. If a culture becomes contaminated, it will most likely be seen as common mold, green or brown in color.

[edit] Safety and contamination

As with all foods, care must be taken during preparation and storage to prevent contamination. Keeping the kombucha brew safe and contamination-free is a concern to many home brewers. Key components of food safety when brewing kombucha include clean environment, proper temperature, and low pH.

There is a low rate of homebrew contamination which might be explained by protective mechanisms, such as formation of organic acids and antibiotic substances. Thus, subjects with a healthy metabolism do not need to be advised against cultivating Kombucha. However, those suffering from immunosuppression should preferably consume controlled commercial Kombucha beverages.^[15]

In every step of the preparation process, it is important that hands and utensils (anything that is going to come into contact with the culture) are dish soap clean so as not to contaminate the kombucha. Kombucha becomes very acidic (in the neighborhood of pH 3.0 when finished) and so can leach unwanted and potentially toxic material from the container in which it is fermenting. Food-grade glass is very safe. Gunther Frank says on his website ^[16] that besides glass, acceptable containers include china, glazed (without lead) earthenware, stainless steel and food-grade high density polyethylene (HDPE) and polypropylene (PP). Keeping cultures covered and in a clean environment also reduces the risk of introducing contaminants and bacteria.

Maintaining a correct pH is an important factor in a home-brew. Acidic conditions are favorable for the growth of the kombucha culture, and inhibit the growth of molds and bacteria. The pH of the kombucha batch should be between 2.5 and ^[3] 4.5. A pH of less than 2.5 makes the drink too acidic for human consumption, while a pH greater than 4.5 increases the risk of contamination. Use of fresh "starter tea" and/or vinegar can be used to control pH. Some brewers test the pH at the beginning and the end of the brewing cycle to ensure that the correct pH is achieved.

If mold does grow on the surface of the kombucha pellicle, or "mushroom," it is best to throw out the batch and start afresh.

[edit] See also

• Tibicos

[edit] References

• Tietze, Harald W.: Kombucha - The Miracle Fungus. Gateway Books. ISBN 1-85860-029-4.
• Dipti, et al. Lead induced oxidative stress: beneficial effects of Kombucha tea. Biomed Environ Sci. 2003 Sep;16(3):276-82.
• Ernst, et al. Kombucha: a systematic review of the clinical evidence. Forsch Komplementarmed Klass Naturheilkd / Research in Complementary and Classical Natural Medicine 2003;10:85-87.
• Pauline, et al. Studies on toxicity, anti-stress and hepato-protective properties of Kombucha tea. Biomed Environ Sci. 2001 Sep;14(3):207-13.
• Teoh, et al. Yeast ecology of Kombucha fermentation. Int J Food Microbiol. 2004 Sep 1;95(2):119-26.
• Frank, Günther W.: Kombucha - Healthy beverage and natural remedy from the Far East. Its correct preparation and use, Ennsthaler Gesellschaft GmbH & Co KG: 1995, ISBN 978-3850683371

[edit] External links

Wikimedia Commons has media related to: Kombucha

• Preparing the infusion for Kombucha
• Kombucha - Healthy Elixer Or Not?
• The Wiki-how on making Kombucha
• The Kombucha Journal in 30 languages
• Old-style forum about mycology.
• Original Kombucha Mailing List