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Kombucha is the Western name for sweetened tea or tisane that has been fermented by a macroscopic solid mass of microorganisms called a "kombucha colony," usually consisting principally of Acetobacter-species and yeast cultures. It has gained much popular support within many communities, mentioned by talk show hosts and celebrities. The increase in popularity can be seen by the many commercial brands coming onto the retail market and thousands of web pages about this fermented beverage.
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, or by the acronym SCOBY (for "Symbiotic Colony of Bacteria and Yeast"), it is clinically known as a zoogleal mat.
History and etymology
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 by the populace.
The word kombucha, while sounding Japanese to foreign ears, is a misnomer when applied to this beverage. In fact, Kombucha (昆布茶) in Japanese refers to a tea-like infusion (cha) (actually, more of a thin soup) made from kelp (kombu), usually served to patients in convalescence. The Japanese refer to 'kombucha' as kōcha-kinoko (紅茶キノコ), which literally means black tea mushroom.
Russian "tea mushroom"
The process of brewing kombucha was introduced in Russia and the 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" or simply "kvass", although it differs from regular "kvass" which is not made from tea and is generally fermented only with yeast and not the other bacteria which ferment tea to form kombucha.
Kombucha contains many different cultures along with several organic acids, active enzymes, amino acids, anti-oxidants, and polyphenols. 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. Final kombucha may contain some of the following components depending on the source of the culture:
No clinical studies have been performed that demonstrate any health effects of kombucha. A review of the published literature on the safety of kombucha suggests no specific oral toxicity in rats, although other reports suggest that care should be taken when taking medical drugs or hormone replacement therapy while regularly drinking kombucha It may also cause allergic reactions or other complications, and one should discontinue use or consult a medical professional if complications arise.
Advocates believe kombucha works by assisting in the phase II liver detoxification pathway, leading to efficient elimination of endogenous and exogenous bodily wastes. This hypothesis is due to the observation of increased glucuronic acid conjugates in the urine after kombucha consumption.
Early chemical analysis of kombucha brew suggested that glucuronic acid was a key component of it, perhaps assisting the liver by supplying more of the substance during detoxification. But more recent analysis of kombucha offer a different explanation, as outlined in the book in Analysis of Kombucha Ferments by Michael Roussin. 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 any concentration.
But Roussin suggests that another component may have health benefits: D - glucaro -1,4 lactone, also known as glucaric acid. It serves as an inhibitor of the beta- glucuronidase enzyme, a bacterial product from the gut microbiota that can cleave the glucuronic acid conjugates and send bodily wastes back into circulation, thus increasing the exposure time before the waste is ultimately excreted. Therefore, the active component of kombucha likely exerts its effect by preventing bacterial disruption of glucuronic acid conjugates and increasing the detoxification efficiency of the liver. Glucaric acid is being explored independently as a cancer preventive agent.
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. 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.
There are many ways to prepare kombucha. Though kombucha is almost always prepared with sugar and tea, almost any beverage containing sugar and caffeine (such as cola or sweetened coffee) will allow the culture to grow, though the resultant beverage may be quite unpalatable. Many brewers also recommend using organic ingredients wherever possible to prevent the addition of unwanted chemicals and preservatives.
In one method, the beverage is made by placing some existing kombucha culture in a jar, usually a 3 liter glass container, then pouring in cold black tea with sugar. In about 8-12 days, the first portion of the beverage is ready; part of it is removed for consumption, and more tea with sugar is added to fill the jar. A mature kombucha is several centimeters thick and produces a portion of beverage every day. As the kombucha slowly grows, from time to time slices are taken off it, which can be used to start new cultures in separate containers.
Another method allows for the bottling and saving of kombucha for later consumption. As in the previous method, the culture is placed into a large glass jar and the tea is added. The jar is covered with a coffee filter or paper towel secured with string or rubber bands, and left for seven or eight days. Part of the kombucha is poured off into glass jars and refrigerated for a few days, while part is kept back to start a new batch. The refrigeration allows the flavor to deepen, and the natural carbonation to build up.
Each time the kombucha culture goes through the fermentation process, it creates one new "mushroom" layer, or zoogleal mat, which will form atop of the original. After three or four layers have built up, the tea will become sour and taste somewhat like sour cider. When the new batch is ready, one may either use the second layer to start another batch, along with the original one for its own batch or it may be thrown away. Each culture can be used over and over again but most people discard an older one and use the newer to make their next batch of tea.
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 and the FDA. Key components of food safety when brewing kombucha include clean environment, proper temperature, and low pH.
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. For safety reasons, Kombucha should be brewed in food-grade glass containers only. Kombucha should not be brewed in lead crystal, ceramic, plastic, painted, or metallic containers including stainless steel, as the acidic solution can leach by-products into the finished product. Keeping cultures covered and in a clean environment also reduces the risk of introducing contaminants and bacteria.
Kombucha grows best in a warm place (about 80°F / 27°C) and out of direct sunlight. Optimum conditions ensure speedy maturation, reducing risk for contamination.
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 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 over.
Additional subjective effects
Aside from any possible health benefits, many users report a subtle but definite perceptual shift after consuming kombucha. It is generally characterized by mild euphoria, relaxation, and an overall sense of physical and mental well-being. Kombucha contains trace amounts of alcohol and caffeine, unless made with decaffeinated tea. Alcohol amounts vary from 0.5% to 1.7% depending on brewing time and amounts of sugar used in the fermentation of the tea which may account for the experiencing of these effects by some consumers. The pH/acetate may increase blood flow to the brain. Another possible cause of these effects is the psychoactive amino acid L-theanine, which is naturally present in tea. Stimulation of the circulatory and immune systems, and associated glandular releases, may also account for some of these effects. However, these reports are most likely a result of toxins produced by contaminated cultures.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Kombucha". A list of authors is available in Wikipedia.|