Kombucha, a purported health drink known by names such as the “Elixir of Life,” “tea wine” and “mushroom tea,” can be purchased at health food stores or brewed at home using a kombucha culture, also known as a SCOBY (symbiotic colony of bacteria and yeast) or mother, and sweetened tea. Sometimes the home-brew method, if done incorrectly, can produce unwanted molds on the kombucha culture and in the tea. There are some things you can do to minimize the risk of mold and make sure your home-brew is as safe as possible.
Kombucha is a highly acidic drink with a normal pH of between 2.5 and 4. This acidity gives the drink and the SCOBY a natural resistance to most invaders like unwanted bacteria and mold. When brewing a new batch of kombucha, the tea is at its most vulnerable to molds at the beginning of the brew cycle because the pH level may be higher at that time, reducing the tea’s resistance to mold. To minimize the risk of mold contamination, at least 1/2 cup or more of previously brewed kombucha should be added to the container along with the mother culture and the fresh, sweetened tea. This keeps the acidity level up and makes the brew inhospitable to mold. Mold can get into the kombucha through the air, so keep your brew covered at all times. Washing your hands thoroughly before handling your tea and culture can also minimize risk of contamination. Also, avoid keeping your kombucha containers near plants or other things that might contain mold spores, such as fruits, bread and other kitchen food items.
Kombucha cultures are usually white and may have brown spots, or they may be slightly colored by the type of tea you are brewing. (Using a blueberry tea will produce a culture with a light pink color.) Mold, on the other hand, will usually be green or brown and fuzzy, similar to molds seen on any other food, and should be easily recognizable. If you notice brown tendrils handing from the underside of your SCOBY and into the tea, this is likely not mold and is probably formed from dead yeast cells. These are not harmful and can be strained out or not, depending on your preference.
What to Do
If you notice mold on your kombucha culture, it is safest to throw away the whole brew and begin anew. Some brewers will occasionally try to save the culture by trimming away the mold and putting it in a new tea solution, but this isn’t recommended because the mold cultures may have infected the entire mushroom, not just the visible part, as well as the tea. If you are concerned about molds, keep a second culture handy in case you have to discard one due to mold contamination.