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Problem of Mold on Kombucha
When one refers to a ferment that has gone moldy or befouled, they are almost always describing a specific kind of contamination: the appearance of common molds on the surface of the mother. The mother forms atop a kombucha ferment, and is the only portion of the ferment that is exposured to air. Mold needs to breath oxygen in order to survive, and so it will not grow in the drink itself. This does not mean that a contaminated kombucha brew is safe to drink: a moldy mother may indicate a toxified drink, and thus both the mother and tea should be discarded.
The vast majority of kombucha contaminant are common molds of the genera Aspergillus and Penicillium. (Roussin) (Srinivasan, et al) These are molds that you are already familiar with; they usually
- are the sort that sprout up on old bread and rotten biomass,
- appear "fuzzy" with conidia spores, and
- are colored white, brown, black, and many brilliant shades of blue, cyan, and green. (Vargas & Jones)
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| agar cultures of Aspergillus and Penicillium; photo courtesy of Dr. David Midgley |
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| photo courtesy of Happy Herbalist |
If you're able to spot mold on bread or cheese, then you can rest easy and know that it's easy to identify kombucha contaminants The surrounding photos show smooth, healthy mothers; it closely resembles mother resembling a the petri dishes above. It is easy to distinguish mold which is growing atop a even mother such as these - take note of the raised and degraded surfaces which characterize the suspiciously colorful patches of mold.
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| photos courtesy of Organic-Kombucha.com |
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When it's not mold.
An uneven mother does not guarentee contamination; irregular mother surfaces are very common. The virgin brewer will spend some time learning the dynamically changing nature of her kombucha culture. It is, after all, a living thing which adapts to environmental conditions and nutrient availability. As she learns the art of kombucha cultivation, the virgin brewer will incidentally grow lumpy, bubbly, or discolored mothers. But with some training, she will quickly learn to distinguish a mother that is contaminated from one that is merely strangely composed.
When I started a continuous brew preparation a few weeks ago, the first mother that was not only revolting, but a source of contamination anxiety, a sort of brewer's hypochondria:
In this brew, note the dark patch at the upper edge of the mother. This portion is contained in it's own "bubble" beneath the surface of the mushroom. These sorts of discolorations are not rare occurences. Brown spots have many causes, such as rogue kombucha strain in the brew, or unhealthy or imbalanced culture. In the above case, I had mixed together several different strains of kombucha, which had all been developing independently for several months. This is the reason for the mother's deformed appearance, and also, the discolored patch.
Identifying a contaminated kombucha batch is not difficult - the tell-tale signs are always spotted on the very top of the brow, and are usually very visible. If you have doubts about the patheogenic integrity of a brew, I suggest that you on the side of caution and start over.
For the most part, kombuchaphobia is unwarranted. However, there have been several studies on the potential toxicity of contaminated kombucha ferments. These will be addressed in a future posting.