What is it?
The term Kombucha identifies a whole category of functional beverages based on fermented teas (green or black quality), slightly effervescent and sweetened, typically oriental.
The composition of the microbial populations in the various scoby cultures is variable. More often, we observe the prevalence of yeasts belonging to the genus Saccharomyces, which carry out alcoholic fermentation, and the presence of bacteria belonging to the species Gluconacetobacter xylinus, which oxidize alcohols into acids.
The origin of the kombucha, as well as the etymology of the term, is unknown; in fact, the word was translated into the Western alphabet only in 1991, but it is conceivable that the drink has been present in Eastern Russia since the early 1900s.
Kombuchas are traditionally produced at home or local level; only at the end of 1990 did they appear in America as a bottled drink.
The kombucha are known in Chinese as chájūn, in Japanese as kocha-kinoko, in Korean as hongchabeoseotcha and in Russian as chaynyy grib ; all these nouns have the same meaning, or "tea mushroom".
Some believe that kombuchas are capable of contributing to the treatment of many diseases and disorders, even if there is no concrete evidence to prove it.
On the other hand, many cases of adverse effects related to the consumption of kombucha have been documented and, in the home preparation, there is a certain risk of adverse contamination.
A systematic review revealed that the various, mostly vague, benefits of kombucha consumption do not justify the risks. Therefore, beverages should not be recommended as therapeutic foods; this does not mean that they still fall within the set of functional drinks.
Health Implications
As anticipated, the consumption of kombucha was advertised on the belief that these can boast certain therapeutic effects, including:
- Improve various pathological conditions including AIDS, cancer and type 2 diabetes mellitus
- Stimulate the immune system
- Increase libido
- Reverse the formation of gray hair.
However, the scientific evidence on humans is considered rather unsatisfactory. Although animal and in vitro tests suggest that kombucha consumption may prove, if not therapeutic, to be useful, in 2014 a human experimentation project was launched (in vain) to confirm or refute these theories.
In a 2003 systematic review, researcher Edzard Ernst defined kombucha as an "extreme example" of unconventional remedy, due to the large disparity between the improbable therapeutic effects and the harmful potential of kombuchas. It was then concluded that the list of real therapeutic benefits is rather insignificant and in any case lower than the risks that derive from it; furthermore, it is possible to state with certainty that kombucha should never be recommended for medicinal use in certain diseases.
Side effects
Reports on adverse effects related to the consumption of kombucha are fortunately rather rare, but still relevant. The lack of complaints is due in part to the rarity of the circumstances and partly to the underestimation of the perceived symptoms.
Adverse effects associated with kombucha consumption include: liver toxicity, renal toxicity and metabolic acidosis. A woman died following the consumption of kombucha, although it was not possible to correlate cause and effect unequivocally.
Some possible negative effects of kombucha on health are: acid pH (tendency to blood acidosis), excess micro-organisms and unwanted bacterial or fungal contamination. With regard to this latter occurrence, some studies have revealed the presence of usnic acid in kombucha, which is a hepatotoxin typically secreted by the cyanobacteria of lichens .
Topical use of kombucha has also been associated with anthrax infections on the skin, but it is not clear whether the contamination occurred during storage or production.
Thanks to its microbial contribution and to the frequent dirt of the containers, the kombucha is strictly forbidden to immunodepressed subjects, to pregnant women, to nurses and to children under 4 years.
As far as commercial preparations are concerned, it is instead likely to assume greater safety in use.
Chemical composition
The sucrose of kombucha is biochemically converted first into fructose and glucose, and subsequently into gluconic acid and acetic acid (well present in the drink).
Kombuchas also contain enzymes, amino acids, polyphenols and various organic acids ; the exact quantities of these elements vary depending on the case.
Other specific components of kombucha include ethanol, glucuronic acid, glycerol, lactic acid, usnic acid (see above) and water-soluble vitamins ( group B and ascorbic acid ).
The alcohol content of kombucha is generally less than 1%, but increases with fermentation time.
Biology of Kombucha
Those of the kombucha are mixed symbiotic cultures of bacteria and yeasts, similar in composition and appearance (lattice in suspension) to the "mother of the vinegar".
The cultures may contain one or more yeasts, such as Saccharomyces cerevisiae, Brettanomyces bruxellensis, Candida stellata, Schizosaccharomyces pombe and Zygosaccharomyces bailii .
Also the bacterial component of kombucha includes several Species, almost always including Gluconacetobacter xylinus (which ferments the alcohols produced by yeasts in acetic acid and other acids); its function in the beverage is to increase the acidity and limit the ethanol content.
The population of bacteria and yeasts that produce acetic acid increases especially in the first 4 days of fermentation and then decreases.
G. xylinum produces microbial cellulose and is responsible for most of the physical structure of the suspended lattice (mother).
Given the presence of usnic acid, the mixed (presumably symbiotic) culture of kombucha has also been described as lichen ; however, since 2015, no report has identified cyanobacteria species (typical of this living combination) in association with the fungal components of the drink.
Other Uses
The dried Kombucha "mother" takes on the consistency of a leather-like fabric. Known as microbial cellulose, it can be shaped into various shapes to create seamless dresses.
Using various liquids for the culture (such as coffee, black tea and green tea) it is possible to obtain microbial cellulose of different colors, without having the need to dye them artificially (an eventuality that is possible).
The various growth media and dyes also change the texture of the fabric and the perception to the touch.
Microbial cellulose is similar to vegetable cellulose and is characterized by sustainability and biodegradability.
In 2011, London-based designer Suzanne Lee presented the kombucha textile fiber for footwear and clothing. In 2014, designer Sacha Laurin debuted with a clothing collection made entirely of kombucha fabric.
