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HOW TO: Make Kombucha at Home

HOW TO: Make Kombucha at Home

You’d be forgiven for thinking the name kombucha, a sweet/tart sparkling fermented beverage made from sweetened tea and fermented with both yeast and bacteria, came from the Japanese terms kombu (kelp) and cha (tea). However, most sources agree it originated in Manchuria, what is now northeast China, around 220 BCE, and was brought to Japan by a Korean doctor named Kombu to cure the digestive ailments of Emperor Ingyo in 414 CE. Since then, the so-called “mushroom tea” has enjoyed various surges in popularity around the world and has been touted for its health benefits. It’s currently one of the most popular “health tonics” in North America, though evidence for some of the wilder claims—curing cancer, for example—is somewhat lacking.

While store-bought kombucha tends to be fairly expensive, it’s easy to brew at home with a little patience. The base recipe is simply 5 g tea leaves steeped in a liter of boiling water; then you stir in 50 g sucrose until it dissolves, cool to room temperature, and add the fermenting culture, which is a slimy, blob-like thing called a SCOBY—a symbiotic culture of bacteria and yeast. It isn’t too different from the rubbery SCOBY used to make water kefir, but composition varies. You can purchase a kombucha SCOBY at your homebrew shop, or you can find a regular brewer of kombucha and get a piece of theirs. It tends to grow a little from batch to batch, and as long as you keep it hydrated in a low-pH solution (a few hundred milliliters of your last successful fermented kombucha acts as a perfect preservative), you can use it indefinitely and give it out to friends and family for their next batch.

What’s in a SCOBY?

Back to composition. Within the rubbery cellulose structure of the SCOBY is embedded a host of microflora. The bacteria are most commonly vinegar-producing species: Acetobacter xylinum, A. pasteurianus, A. aceti, A. intermedius, and the cellulose-producing Gloconacetobacter kombuchae are often present. Common yeasts include species of our well-mannered friend Saccharomyces: Saccharomycodes, Schizosaccharomyces, and Zygosaccharomyces; but also a few wilder cousins, which may include Brettanomyces/Dekkera, Candida, Torulospora, Koleckera, Pichia, Mycotorula, and Mycoderma.1

What this means is that your SCOBY’s yeasts will first hydrolyze some of the sucrose you add into glucose and fructose to produce ethanol via glycolysis, which the acetic bacteria will then process into various organic acids, mainly gluconic and acetic. All the microflora work in tandem, but the beverage is constantly evolving during fermentation, and pH steadily drops as organic acids increase.

However, it can be a lengthy process—after seven days, only about 65 percent of the sucrose present has become ethanol, CO₂, and other compounds. After 21 days, about 80 percent will have been metabolized. The rest remains unfermented, so depending upon when you determine the kombucha to be ready for consumption, it could be sweet, balanced between sweet and tart, or mostly tart. While there is evidence to suggest that the kombucha SCOBY is capable of producing L-lactic, citric, and even ascorbic acid, the most common acids by far are acetic, gluconic, and glucuronic. So, you may want to be cautious letting your ferment go for a full three weeks—you may get a bit of a vinegar burn at the back of the throat.


This parallel fermentation process also means your kombucha will have varying amounts of ethanol as it ferments, usually peaking around the sixth day. Alcohol content will then begin decreasing as bacteria convert it to acetic and other organic acids. This also depends, of course, on which yeasts are present in your SCOBY—fermentation time and composition can be tailored to produce a more alcoholic kombucha, but without a really complex lab setup, it’s difficult to determine just how much alcohol is present at any given time. (And as we learned from a breathalyzer incident involving Lindsay Lohan, it’s probably not wise to assume that your finished kombucha is alcohol-free, so exercise caution when letting your kids drink it!)

Teas & Sugars

Pretty much any variety of tea can be used to brew kombucha, but black and green teas are the most popular. Sugar is pretty much sugar, but you can use other fermentable sweeteners as well, including fruit juice and honey. There are even companies selling kombucha SCOBYs that are tailored to specific ingredients.

For example, Jun kombucha SCOBYs are fine-tuned for green tea sweetened with raw honey. Most sources say black tea produces an end product that carries the most health benefits, from antioxidants to trace minerals and amino acids, many of which are produced during fermentation and are not present in the unfermented tea. (In that respect, kombucha can be more than the sum of its component parts, which may explain some of the health benefit claims.)

The variety of teas and sugars available means the sky’s the limit as far as the range of flavors you can impart to your kombucha, but it also means that you may get a sluggish or stuck ferment if your SCOBY is not cut out to effectively process the tea and sugar you feed it. I tried a batch with cascara tea, which is made from the rind of the coffee fruit and makes a naturally low-pH, dark red beverage that only slightly resembles coffee. My SCOBY was less than impressed. I did get some fermentation, but it was never as rapid or thorough as it was with the control black- and green-tea batches.


As with any ferment involving Acetobacter, you’ll need to take a few precautions. First, isolate your kombucha operations and equipment from your homebrewing. Cross-contamination is a real concern. Second, remember that acetic bacteria like free access to oxygen, but fruit flies like free access to anything that contains vinegar. What’s commonly recommended for kombucha fermentation is a wide-mouth jar or bucket with a tea towel, piece of cheesecloth, or a large coffee filter secured over the top with a rubber band. This will let the air in and keep the bugs out.

Your SCOBY’s microflora are also sensitive to temperature fluctuations. The suggested range is 70–80°F (21–27°C) for healthy fermentation. Cooler than 68°F (20°C) and fermentation will slow or even halt. Warmer than about 85°F (29°C) and you risk mold or harmful bacteria growing in your ferment. If you find mold in your kombucha, the best and safest course of action is to throw out the whole thing (SCOBY included), sterilize your equipment, and start over. Unlike miso, you can’t just scrape the mold off and continue because kombucha doesn’t have that extra layer of protection afforded by salt. Once mold spores are present, they are nearly impossible to get rid of without also killing the microflora in your SCOBY.

One precaution you can and should take to prevent unwanted microflora from growing, as with so many fermented foods, is controlling pH. A good pH meter is almost a necessity with kombucha making; at the very least, get some reliable test strips. A good baseline pH for beginning your ferment is 4.5. If the pH is any higher, add an acid, preferably distilled white vinegar, to get it below that mark. A good target pH for finished kombucha is 3.6. That’s definitely acidic, but as mentioned earlier, there will still be some unfermented sucrose in the kombucha to balance.

Choosing the Right SCOBY

When choosing a SCOBY from a local homebrew shop, there are a couple of things to keep in mind. One company, Fermentaholics, offers a live kombucha pellicle immersed in a 12-fluid-ounce (355-milliliter) starter solution of finished tea. This is enough to start a one-gallon (3.79-liter) batch of your own. They suggest brewing the tea, adding the sugar (or honey—they also offer a Jun SCOBY), cooling to a maximum temperature of 85°F (29°C), and then adding the pellicle and all the starter liquid.

Stir, take a small sample, measure its pH, and then if it’s below 4.5, secure the fermenter with a cloth or coffee filter and rubber band, and allow it to ferment in the proper temperature range. After a week, taste the tea (and don’t be too grossed out by the pellicle that should have formed on the surface). If things smell and taste good, you can bottle all of the batch except for a cup or two and then use that plus the pellicle for the next batch.

That said, my liquid pellicle was actually quite sluggish for the first couple of weeks; while refermentation in the bottle is supposed to take only a matter of days, I had some bottles that required a couple of weeks before they were fully carbonated. This, of course, varies with temperature and ingredients, but try and get the freshest SCOBY you can—otherwise you may need to be patient.

Speaking of patience, other companies offer a dried pellicle for sale. The good thing is it keeps in its mummified state nearly indefinitely and requires no refrigeration. What it does require, though, is a period of rehydration in a low-pH tea solution, and that period is at least 30 days. Yes, bringing your leathery little pellicle back from the dead takes a full month at least before it’s ready and active enough to start producing kombucha for you. This may be a conservative estimate, however; the one I tested started picking up with fermentation after a couple of weeks of rehydration.


As I hope you’ve gleaned from the multiple symbiotic fermentations happening in kombucha, it can be unstable stuff. It’s not as predictable as bottle conditioning homebrew. The risk of bottle bombs is a pretty serious reality. For that reason, I strongly recommend plastic PET bottles designed for carbonated beverages. Not only will they hold tremendous pressure and not cause serious damage to life and property if they do happen to explode, but they can also be gently squeezed during bottle fermentation to determine, or at least approximate, the level of carbonation. PET bottles also have twist tops, so if you are concerned too much pressure is building up, you can burp them as needed.

I recommend buying a case of inexpensive sparkling water, enjoying the contents (while taking care to never drink directly from the bottles), and using the clean empties as dedicated kombucha bottles. Fill them with fermented tea, keep them in a warm spot, give them an occasional squeeze, and when they feel nice and tight, move them to the fridge, where the low temperature will halt any further gas buildup. Then you can enjoy your fizzy, tart, healthy beverage within a couple of weeks without fear of detonation.

Basic Kombucha Recipe

Below is a is a simple kombucha recipe that can be enjoyed as-is or act as the base for flavor additions. Check out the article You’ve Tried Making Kombucha, Now Let’s Make It Delicious for flavored kombucha recipes.

Batch volume: 4 liters (1.06 US gal.)


  • 200 g (7 oz.) sucrose (table sugar)
  • 20 g (0.7 oz.) tea leaves (bagged or loose)


  • 1 fully hydrated, active kombucha SCOBY


  • 4 liters (1.06 gal.) filtered, chlorine-free water
  • distilled white vinegar as needed to adjust pre-ferment pH
  • other flavorings to add at bottling: fruit purees, spices, herbs, etc. (optional)


  • pH meter or test strips in the 2.8 to 4.4 range
  • wide-mouth 1.5-gallon (5.7-liter) jar or bucket to use as a fermenter
  • coffee filter or tight-weave cloth and rubber band to cover fermenter
  • pressure-ready PET bottles


Boil water and add tea leaves. Steep 1–5 minutes, depending upon tea variety. Remove tea leaves and stir in sugar until it dissolves. Cover tightly with a lid or plastic wrap and allow to come to room temperature (70–80°F or 21–27°C). Add sweetened tea to sanitized fermenter, then add SCOBY and 2 cups of starter kombucha (or ¼–½ cup distilled vinegar). Stir well, then remove a small sample and test pH. If below 4.5, cover fermenter with screen material and secure with rubber band. Keep fermenter in the correct temperature range for 7 days.

Take a small sample, smell, and taste. If you are happy with the flavor and acid balance, use a sanitized funnel to fill your bottles. Don’t worry about splashing—Acetobacter likes air. Leave about an inch (2.5 cm) of head space in each bottle. If your tea is still too sweet, ferment a few days more and taste again.

To carbonate, there’s no need to add additional priming sugar—your tea should still have plenty of sucrose. Just keep the bottles at the same temperature for 3–7 days, squeezing them gently every day or two to gauge the level of condition. When fully carbonated, transfer to the fridge and enjoy cold.

Source: homebrew association official website

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