5. Fermentation: Where the Magic Happens

When it comes to brewing kombucha, fermentation is where the magic unfolds. This is the stage that transforms sweet tea into kombucha. During fermentation, the SCOBY (Symbiotic Culture of Bacteria and Yeast) does the heavy lifting, feeding on sugar and producing the acids, gases, and beneficial bacteria that define kombucha’s unique profile. Today, we’re taking you behind the scenes to explore how we ferment our kombucha.

Step 1: Setting the Stage for Fermentation

Once our tea has been brewed and sweetened, it’s ready for the SCOBY—a living culture that’s central to the fermentation process. Once it’s introduced to a sweet tea around 25 degrees celsius, the yeast in the SCOBY starts to consume the sugar, caffeine and everything else in the brew. Yeast in the SCOBY initially breaks down the sugar into ethanol and CO₂, while bacteria convert both some sugars and ethanol into acetic and other organic acids that add tang and lower the pH. Yeast fermentation can also impart fruity/floral ester flavours. Meanwhile, the tea provides caffeine, nitrogen, and polyphenols, essential nutrients that sustain the SCOBY. Polyphenols (like tannins) in tea also support bacterial growth whilst providing astringency/flavour previously mentioned in the tannin section. In essence, the tea nurtures the SCOBY (and provides flavour), while the SCOBY works on the sugar and fermentation byproducts. This balance of acids and gases is where kombucha’s signature complexity comes from.

Step 2: Timing the Fermentation Process

Fermentation is a dance of time and temperature. At Left Field Kombucha, we typically let our batches ferment for up to 14 days, although this can vary depending on factors like ambient temperature and tea strength. Shorter fermentation periods produce a sweeter kombucha, while longer fermentations result in a tarter, more acidic profile. We carefully monitor each batch to determine the exact moment when it’s ready. Checking morning and afternoon the PH, BRIX (sugar level), ABV, and of course its flavour, colour, and carbonation so we know exactly when it’s at its best.

Step 3: Monitoring and Fine-Tuning the Process

Fermentation is an active process that requires constant attention. Our Head Brewer checks each batch twice daily to assess the balance of acids and flavours is progressing as it should. This careful monitoring is essential because even an hour or two can make a difference in the final taste and quality.

We ferment each batch in a controlled setting, controlling temperature, humidity, and the carbon dioxide level in our fermentation room, which allows the SCOBY to do its work at an ideal rate. By giving our SCOBY the best possible conditions, we ensure a kombucha that’s balanced and true to our standards time after time.

Fermentation is the heart of the kombucha making process.