Mould on the Kombucha culture?
by Günther W. Frank

The Kombucha culture defends itself against alien microorganisms. The ph-value of the solution has a crucial influence on the growth of micro-organisms. The regulation of a particularly suitable pH value is therefore of great importance, and this is achieved from the start of the Kombucha fermentation process by a corresponding acidification.

In spite of this, mould may grow on the Kombucha culture (though it is extremely rare) just as it may grow on any foodstuff. Mould forms particularly where there is an open source of mould somewhere in the room, or where spores can somehow alight on the culture. The worse the conditions provided for the yeasts and bacteria in the Kombucha culture, the greater the chances of mould developing. If mould should appear this can have manifold reasons:

1. Perhaps there are mould spores in the tea leaves which you used. Best is the green tea. Green tea is from the same plant as the black tea except that green tea has not been fermented. Green tea contains less caffeine and a little more tannic acid. Many health benefits are attributed to the green tea. So try to get green tea in your tea shop.

2. The "feeding solution" (meaning the finished and sugared tea) must be made sufficiently sour The culture is thereby protected from damaging microorganisms before organic acids have been created through the fermentation process.

Important! If you start your first Kombucha batch, add the liquid that came with the culture. On all later batches, always keep back enough Kombucha drink to add at least (more is better) one tenth (10%) of the quantity to your new batch as a starter liquid. Should you by accident spill the supplied starter liquid, you can use approximately ½ to 1 regular spoon of vinegar per litre of tea. If you have problems with mould you also may add some spoons of vinegar.

3. The Kombucha loves warmth. Room temperature (21° Centigrade = 70° to 75° Fahrenheit) is generally sufficient to grow the Kombucha culture. The best growth however is in the range of about 80° to 85° Fahrenheit.

If you can't provide this warmth try to get a low heating plate. I discovered a device that helps to obtain the best results from your Kombucha beverage: The Electrim Heating Tray, produced in Great Britain. This is a low-wattage, electrically-operated heating tray that provides gentle warmth for successful fermentation. The heating tray is a quality product and is guaranteed for 1 year. It is completely safe for glass and plastic, for durable operation and economical to use. The size is 14.6 x 14.6 inches (= 37 x 37 cm), 35 Watts. It is made of two plastic halves with the heating element insulated from the bottom, so that only the top surface is heated. A power-on-light and an overheat safety cut-out are integrated. The heating tray is supplied in the USA with 120 Volt and a two pin U.S.A. plug, or in Europe with 220 Volt and the European plug. The heating tray is a really good help in the winter season. If can't get such a low heater tray in the USA, you may contact me.

      An ideal device for fermenting your Kombucha:
       Kombucha Heating Trays (click for more information)
4. Perhaps your Kombucha culture doesn't like the place where it stands. Try to give it another place.

The kitchen is not a good place. The steam and fat odors are detrimental to the growth of Kombucha. Any room in which cigarette or similar smoke can occur is an absolute no! Cigarette smoking causes mould to grow on top of the culture. Don't put the fermentation container close to potting plants. There may be damaging bacteria in the earth of the plants.

5. Perhaps the cloth you use to cover the fermentation container has to wide holes.The container has to be covered with a clean cloth, making the receptacle dustproof sealed. Perhaps the cloth you etc. is is large enough to allow mould spores (always floating in the air, omnipresent, ubiquitous) to fall through the holes of the cover. Cover the container with a cloth with fine hole sizes. It is advisable to use a tissue handkerchief or a dish towel (tea towel). Secure the tissue or the cloth with a rubber band.

If mould occurs

If mould should nevertheless occur, it should be treated the same way as mould on any other foodstuff. Prof. Henneberg mentions in connection with the preparation of Kombucha: "Washing the the culture skin carefully under running water and increasing the acidity with vinegar proved effective here. Hans Irion gives the following instructions regarding cases of mould forming on the Kombucha culture: "Small amounts of mould may be easily removed by dabbing the area with ordinary table vinegar."

If mould should form, I consider it best to be on the safe side and start again with a new culture.

May the Kombucha beverage provide you a lot of benefits. I am sure it will not disappoint you. Good luck!

Günther W. Frank
Genossensch.-Str. 10
75217 Birkenfeld im Schwarzwald

© Copyright Günther W. Frank 1996. Permission is granted to freely copy this document in electronic form, or in print if the publication is distributed without charge, provided it is copied in its entirety without modification and appropriate credits are included. On the WWW, however, you must link here rather than copy it. Any other use requires explicit permission by the author.

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