By Terry and Ben of Kombuchahome.com Apr 19th, 2015
You already know about the many health benefits of drinking kombucha tea, but did you know that second ferment kombucha has even more healthy nutrients? That’s because the yeasts and the bacteria that make up the SCOBY (Symbiotic Colony Of Bacteria and Yeast) are still present in the kombucha tea, even after you have taken the SCOBY out when you’re done making a basic kombucha recipe. Most of the colony remains in the SCOBYs (the “mother” you used to start the batch of brew and the “baby” it produces) but there are millions of free-floating yeasts and bacteria in the liquid tea itself. That’s why you sometimes find a tiny baby SCOBY in a bottle of unpasteurized store-bought kombucha – the yeasts and bacteria in the bottle have gotten together in their own colony.
During the first (primary) fermentation, the yeasts in the SCOBY use the nutrients in the sweetened tea mixture to grow and multiply. During this process, they produce byproducts like ethanol. The bacteria take the ethanol and use it to nourish themselves, breaking it down into organic acids. The longer the bacteria have to work, the more of these organic acids they produce, changing the kombucha from sweet to sour. There are several important acids that have health benefits:
Gluconic acid helps fight yeast infections like candidiasis.
Lactic acid helps regulate digestion.
Malic acid is a natural detoxifier.
However, the main acid produced is acetic acid, which is another name for vinegar. The longer the bacteria work, the more acidic and sour the kombucha tea becomes, especially during primary fermentation. One advantage of secondary fermentation is that it slows the production of acetic acid, which means that the nutrient value of the kombucha will continue to increase without getting sour too quickly.
With longer fermentation periods, the antimicrobial compounds also accumulate, making second ferment kombucha a more effective antioxidant. At the same time, the sugar decreases, making the kombucha a healthier drink, especially for people who are concerned about diabetes. This makes second ferment kombucha a good method for making sugar-free kombucha.
The yeasts also produce carbon dioxide, giving fresh kombucha tea a slight bubbly or fizzy quality. But since this first brewing is done in an aerobic environment, much of the CO2 escapes. It’s important to cover the brewing jar with a piece of thin but finely-woven material in order to protect the SCOBY from airborne molds and contaminants while also letting in enough oxygen for the yeasts in the SCOBY to breathe as they “eat” the tea and reproduce. Of course, that same material allows the carbon dioxide produced by the yeast to escape at the same time.
During second fermentation, the SCOBY is removed, and the fermentation container is tightly sealed. The yeasts and bacteria switch over to anaerobic reproduction, which does not require oxygen. All of the carbon dioxide now stays dissolved in the kombucha liquid – at least until the container is unsealed! That’s why you need to make sure you have the right bottles for kombucha when you’re doing second fermentation.
More Alcohol Potential
Freshly-brewed kombucha has very little alcohol. The bacteria convert most of the ethanol produced by the yeast into organic acids, so kombucha tea is generally safe for anyone to drink, even children. With only an average of 0.5%ABV (alcohol by volume) fresh kombucha tea is even less alcoholic than “lite” beer. However, because kombucha continues to ferment even after being bottled, the longer it’s in the bottle the more alcohol accumulates – though rarely above 2-3%ABV – and because of this, the Food and Drug Administration passed a law in 2010 regulating the sale and labeling of bottled kombucha. That’s why most bottled kombucha is pasteurized these days; pasteurization kills off the yeast and stops the transformation of sugars into ethanol. And that’s why if you want to grow a SCOBY using store-bought kombucha you need to look for unpasteurized, raw kombucha that has its full quota of live yeasts and bacteria.
When you do a second ferment kombucha by bottling your kombucha tea and storing it at room temperature for a few days, you’ll increase the alcohol content a little bit. However, if you add more food for the yeast to work on (extra sugar, fresh fruit, dried fruit, etc.) into those bottles, you’ll end up with kombucha tea that can reach 2-5%ABV, depending on how long you store it and what ingredients you’ve added.
More Flavor Possibilities
Even if you’re not concerned with getting a buzz from your “booch,” you can use second fermentation to add flavor to your kombucha. This is the best way to add flavor to kombucha without putting your SCOBY at risk. Some ingredients, like raw honey, fresh fruit, and whole spices, have the potential for introducing mold or contamination that will harm the native yeasts and bacteria in the SCOBY during the first fermentation period. During second fermentation, the SCOBY is out of the way, and any possible contaminants on the added ingredients will find it hard to grow in the oxygen-free and high-acid environment of the bottled kombucha tea.