Fermentation Guides: Kombucha

1. What is kombucha?

Kombucha is a fermented drink dating back to as early as 220 B.C. This drink is made with tea, sugar, and various strains of bacteria and yeast. The resulting liquid contains vinegar, B vitamins, and a number of other chemical compounds. It is a fizzy, low-calorie beverage that comes in a variety of flavors. It’s like a soda but also has a slight vinegar taste due to the acetic acid bacteria present in the fermentation process.

2. Ingredients

• Tea: most kombuchas are made with black, green or white tea, as several microbes involved in the kombucha fermentation thrive on caffeine and tannins.
• Sugar: the microbes require sugar as their energy source in the fermentation process. Depending on the fermentation duration, more or less sugar has been digested and isn’t present anymore.
• SCOBY: the sugary tea is being fermented by dozens of different strains of bacteria and yeast, and all these microbes together are called SCOBY (symbiotic culture of bacteria and yeasts). These are added to the sugary tea in the form of mature kombucha and the rubbery cellulose layer that forms during the kombucha fermentation.
• Additional tastes: additional ingredients can be added for taste, from fruit and vegetables to herbs and spices.

3. Health benefits

There are numerous health claims regarding kombucha and I have had many participants in my courses who confirmed these claims for themselves. Also, scientific studies are indeed starting to show health benefits. However, as always in nutrition science, only a trend based on many studies confirm actual health benefits. Until the health claims are supported by clinical studies, it is best to give it a go and listen to your own body to decide whether there is a health benefit for yourself.

4. What happens during fermentation?

During Kombucha fermentation, sucrose is hydrolysed by yeast cells into fructose and glucose, which are then metabolised to ethanol. The ethanol is then oxidised by acetic acid bacteria (AAB) to produce acetic acid which is responsible for the reduction of the pH and also contributes to the sour taste of Kombucha.

5. How to consume

Kombucha can be drunk either like a soft drink, or it can be mixed with other ingredients to create cocktails. Kombucha is also great for creating tasty sauces like sweet and sour sauces or barbeque sauces.

6. Shop bought: what to buy

If you want to drink kombucha for their possible health benefits, try to find an artisanal kombucha that wasn’t pasteurized or filtered. This means that the beneficial microbes are still present. However, these unfiltered and unpasteurized drinks have a much shorter shelf-life, which is why they’re mostly only sold in specialty stores or organic shops, not in large supermarket chains. The next best thing to this raw, unfiltered kombucha is a filtered, unpasteurized kombucha (the filtering removes the microbes with mecanical tools in order to stop the fermentation and thus extend the shelf life). A pasteurized kombucha isn’t very close to a proper, raw kombucha anymore, but it’s still a pleasant drink!

7. Make at home

Kombucha is an easy ferment to make at home. No special equipment is needed. For safety reasons, we recommend to do the second fermentation in PET bottles made for fizzy drinks, instead of glass bottles. These PET bottles can’t explode and also, in those you can feel the pressure and stop fermentation once they’re fully pressurized. You also need a kombucha recipe, sugar, tea, and a SCOBY. You can find a SCOBY in relevant Facebook groups, on Ebay, you can ask friends or you can by more expensive ones in online shops. Important: if you use a SCOBY for commercial purposes, buy a lab tested one or send it to a lab yourself to get tested for unwanted microbes.