What’s in finished Kombucha
Probiotics: Bacteria & Yeast
The specific bacteria and yeast strains in the kombucha are what make it act the way it does, and what produce the fizz and flavor of kombucha. Not all kombucha cultures will contain the exact same strains, but these are some that have been recorded in studies:
- Acetobacter [2] is an aerobic (requiring oxygen) bacteria strain that produces acetic acid and gluconic acid. It is always found in kombucha. Acetobacter strains also build the scoby mushroom. Acetobacter xylinoides and acetobacter ketogenum are two strains that you might find in kombucha.
- Saccharomyces [2] includes a number of yeast strains that produce alcohol and are the most common types of yeast found in kombucha. They can be aerobic or anaerobic (requires an oxygen-free environment). They include Saccharomycodes ludwigii, Saccharomycodes apiculatus, Schizosaccharomyces pombe, Zygosaccharomyes, and Saccharomyces cerevisiae.
- Brettanomyces [2] is another type of yeast strain, either aerobic or anaerobic, that are commonly found in kombucha and produce alcohol or acetic acid.
- Lactobacillus [2]: A type of aerobic bacteria that is sometimes, but not always, found in kombucha. It produces lactic acid and slime.
- Pediococcus [2]: These anaerobic bacteria produce lactic acid and slime. They are sometimes, but not always, found in kombucha.
- Gluconacetobacter kombuchae [2] is an anaerobic bacteria that is unique to kombucha. It feeds on nitrogen that is found in tea and produces acetic acid and gluconic acid, as well as building the scoby.
- Zygosaccharomyces kombuchaensis [3] is a yeast strain that is unique to kombucha. It produces alcohol and carbonation as well as contributing to the mushroom body.
Kombucha also contains a variety of other nutrients, particularly various acids and esters that give the drink its characteristic tang and fizz. Included in these components is gluconic acid, which is the primary difference between the makeup of kombucha and the makeup of apple cider vinegar.
The actual bacteria, sugar, and acid content of kombucha depend on many factors, including the initial culture, the type of tea used, the type of sugar used, the strength of the tea, the type of water, the brewing time, the culturing temperature, and more. Due to the nature of kombucha, it is not possible to state an exact microbial composition for Kombucha. [1]
While different SCOBYs may vary in their exact makeup, what is common to all kombuchas is gluconic acid, acetic acid, and fructose. [2]
Caffeine Content
One question often asked is “How much caffeine is in kombucha?”. Given that kombucha is made with black tea which contains a fair amount of caffeine, this is an important question if you generally avoid caffeinated beverages.
There are a lot of different findings in this area that run the gamut from the caffeine is greatly reduced during the fermentation process to it isn’t reduced at all. One source, Dr. David Chappuis in his work The Green Tea Book, found that caffeine content of kombucha reduced by approximately 25% over a two-week brewing time. This could be extrapolated upon to assume that it would continue to decrease through longer brewing.
With many different findings from many different sources, it seems safe to say that there is some caffeine in the final brew, though most sources consider it to be a relatively small amount.
Alcohol Content
Like other fermented foods, kombucha does contain some alcohol as a by-product of the fermentation process. The alcohol content of kombucha is generally considered very low by most standards, especially when traditional brewing practices are kept.
Sugar Content
Kombucha starts as a very sweet tea and, over time through the brewing process, becomes more tart and less sweet. The sugar content can therefore be controlled by the amount of time it is allowed to brew. A longer brew of at least several weeks will contain much less sugar and much more organic acids.
Remember, too, that kombucha brewing is dependent on the temperature at which it cultures. Sugar content will vary with the seasons as well as the length of time it is allowed to culture for. For that reason, tasting the kombucha at various stages of the brew is the most reliable way to discern the sugar content and the length of brew time.
SOURCES
1. Ai Leng Teoha,, Gillian Heard, Julian Cox.(2044). Yeast ecology of Kombucha fermentation. International Journal of Food Microbiology, 95(2), 119-126. doi:10.1016/j.ijfoodmicro.2003.12.020
2. Jayabalan, R., Malini, K., Sathishkumar, M., Swaminathan, K., & Yun, S. E. (2010). Biochemical characteristics of tea fungus produced during kombucha fermentation. Food Science and Biotechnology, 19(3), 843-847.
3. Kurtzman, C. P., Robnett, C. J. and Basehoar-Powers, E. (2001), Zygosaccharomyces kombuchaensis, a new ascosporogenous yeast from ‘Kombucha tea’. FEMS Yeast Research, 1: 133–138. doi: 10.1111/j.1567-1364.2001.tb00024.x