How I Make Kombucha

There are hundreds of sites with instructions on how to make kombucha, and I hadn’t originally anticipated that someone would want that information from me. Generally speaking, my blog is for my own use, primarily recording my experiences for future reference, and secondarily for sharing those with my friends and family.

Nevertheless, those who end up here may like to know exactly how I make kombucha, so I’ll try to document it. At some point I’ll probably reread this and rediscover something I’d forgotten. I’ll try to describe things without getting into the weeds on technical details like the ratio of volume to open surface.

The gear I use:

  • gallon jars (large pickle jars, w/ lids)
  • quart canning jars, wide-mouth (for my small-scale experiments)
  • drug store heating pad
  • large, plain, white coffee filter
  • large rubber bands
  • aquarium thermometer on one gallon jar
  • wine-range pH strips

The gear I’d like to use, or may eventually use:

  • 1 gallon or 2 quart canning jars
  • 5 gallon bucket (food grade) w/ spigot and mesh lid
  • An autosiphon
  • A refractometer (for measuring sugar content)
  • A good digital pH meter

My usual food ingredients:

  • 1 cup white sugar
  • 2 family size decaf black tea bags (I change it up with a new loose tea every fourth batch)
  • 1 cup plain kombucha tea
  • 1 scoby
  • 3-4 quarts distilled water (reverse-osmosis + carbon filtering is probably fine)
    • Apparently, fluoride and chlorine kills the kombucha microbes, so the point is to use water that contains little or none of these chemicals. When in doubt, call the source for actual fluoride and chlorine levels.

My process:

  • boil water in a large saucepan on back burner (1-3 quarts)
  • add tea, cover and turn off
  • let it steep until room temperature (~3 hours)
  • squeeze last bit of fluid out of tea bags and pour tea into pickle jar
  • add sugar to jar and stir
  • add plain kombucha to jar
  • add scoby to jar
  • top off jar with water
  • cover jar with coffee filter and rubber band
  • label jar
  • put jar on heating pad
  • wait

From what I’ve read, it seems like it takes unusually long for my kombucha to ferment. Maybe I like it stronger than most, or maybe there’s something unique to my culture or process. Fermentation speed is affected by temperature. My first summer, I just kept my kombucha in the garage. When it started getting cold out, I introduced a heating pad, and eventually moved it all inside. Get an aquarium temp sticker for your fermentation jar and shoot for 68-86°. Generally speaking, the warmest location will be the most efficient, as long as it stays within the comfort rage of the yeast and bacteria.

I use little paper stickers to put the date on the jar when I start it, as well as any notes about what might be different about the brew (gunpowder tea, piloncillo sugar, etc). Although I generally drink 1 gallon a week, I’ve built up a small bit of reserve, so I label the quart jars in of bottled kombucha in my fridge so that I can identify the base and any added flavors. I use a sharpie for this, because the paper labels are more prone to getting soggy from condensation or dripping.

I should probably transition to continuous brewing soon. Then I’ll use that for my usual stuff, and pickle jars for experimentation. It’s hard/bad to experiment with continuous brew since there’s no clear break from one batch to the next, and there’s potential to ruin your culture if the experiment goes wrong. It’s pretty easy to find 1-2 gallon jars with a spigot, but since I drink ~1 gallon a week with a three week ferment, I expect to need at least a 3 gallon container. If fermentation speeds up, I may need less, but if it slows down I’ll need more. Thus, I’m considering something like a 5-gallon bucket with spigot.

I use decaf tea, but many people use regular (thinking they must). Many people also think (falsely) you can decaffeinate regular tea, or that kombucha made with regular tea is caffeine-free. The studies I’ve seen have had mixed results about the amount of caffeine left in the finished kombucha. The leading hypothesis seems to be that, depending on the exact microbes in a particular culture, caffeine can be consumed (it’s high in nitrogen, the vital nutrient), but may not be consumed until preferred (easier to metabolize) nitrogen sources are consumed. Personally, I use decaf because I want to be able to drink it at any time, and to be able to give it to anyone. Caffeine has no useful effect for me, so I might as well avoid it when convenient.

If you do use caffeinated tea and want to see how much you might be drinking, it should be easy to estimate the theoretical max. Just take the amount of caffeine in the tea you used, divide by the 128 ounces in your gallon of finished kombucha (or whatever volume you end up with), and multiply by the number of ounces you are drinking. This is only a rough estimate. Actual starting caffeine will depend on what the tea leaves/bag actually contained, how much was extracted by your steep, and how much was broken down during fermentation. The caffeine should be further diluted by the volume of whatever flavoring you may add.

I steep the tea for a long time, because I’ve found that the resulting kombucha has a richer flavor. I imagine that it would also increase the extraction of caffeine, but since I use decaf tea, this doesn’t concern me.

Many people add the sugar to the tea as it steeps. I don’t, simply to avoid the chance that sugar will caramelize. Since water boils at 212° and sugar caramelizes at 340°, it shouldn’t happen except where the sugar touches the pan itself. Even if it did, I don’t know that it would hurt anything. I’m sure I’ll try it someday, but I haven’t yet. Along those lines, I should also try making a batch with intentionally caramelized sugar.

I save one cup from each batch as a starter for the next. It seems like the bottom of the jar is more cloudy, so I imagine it has more yeast and bacteria. Thus, the cup for the next batch comes from the (strained) dregs at the bottom of the last. I have a spare jar full of old scobys (scoby hotel) and some of each previous batch of kombucha, giving me a very strong pseudo-solera kombucha tea. I use this jar to get the cup of kombucha and the scoby that starts each new batch. So the process of bottling adds scoby+kombucha to the jar. The process of brewing removes scoby+kombucha from the jar. I have to “clean it out” occasionally, as each week the hotel adds its own fresh 1/4 inch scoby to the top of the jar.

If the old scoby floats, the new scoby will become attached to it when it grows. If you want, you can pull them apart when you bottle. The old scoby can also sink. I generally prefer that, just so that they stay separate. I like this just so that I can easily see how the new scoby is growing, but also because sometimes they can tear when separating. Tearing isn’t a practical problem, just an aesthetic one for me. Generally speaking, a scoby is a three-dimensional cellulose matrix with yeast and bacteria trapped within its structure: you can cut a scoby into pieces and it will be fine.

Once a week, I poke at the scoby to make sure that it isn’t stuck to the sides of the jar and to push out any air bubbles that may be under the scoby. I know that the scoby isn’t stuck if it will rotate (radially) in the jar. Air bubbles can push the scoby out of the kombucha, and can make the scoby stick to the sides where they get dry. All of this increases the potential evaporation, so you lose more to the air. Since I have a jar to bottle every week, I poke and prod with the straw that I’ll eventually use to taste the kombucha that’s been fermenting for two weeks. Sometimes the fermentation can be quicker or slower, so I always taste at two weeks and each subsequent week. I’ve read that it’s a good idea to gently press down on the scoby every few days, just enough to wet the surface of the scoby (to inhibit mold) and to press out any air bubbles. I’ve done this sporadically, but haven’t decided if I like the practice.

How can you tell when the kombucha is done? Ultimately, by tasting it. Feel free to smell it, but don’t make any decisions based on scent. When the flavor is somewhere between “tastes good enough” and “tastes a little too strong”, it’s probably done. Your first taste should be by dipping a straw into the jar, filling it, and dropping the straw-full onto your tongue. Use the straw to gently push aside the scoby enough to fit the straw down the inside edge of the jar. If it seems to taste good, carefully pour off a little (2-4 oz) so that you have enough to see how it tastes as a real drink. If it still tastes good, bottle your kombucha and put it into the refrigerator.

The flavor will change when it’s refrigerated. In my experience, the flavor simplifies. Usually, it’s just a matter of some flavor nuances disappearing, but occasionally the disappearances of some flavors mean that other flavors will become more noticeable. You’ll have to learn how it changes to your palate, adjust however you see fit, and perhaps adjust your next batch to ferment longer, with less sugar, etc. I actually prefer my kombucha warm over cold just because the flavor is richer. The difficulty lies in the fact that warm kombucha continues to ferment. Since I don’t want pressure to build in my bottles (risking explosion), and I don’t want to pasteurize the drink to halt the process, I refrigerate it. Continuous brewing should also help with this.

After bottling, I leave it in the refrigerator until it’s cold, and then taste it again. Based on the cold flavor, I’ll usually add a tea bag to incorporate a complementary flavor. If my timing was off and the kombucha is a little too sweet or sour, I’ll pick a contrasting flavor in an effort to provide some semblance of balance. I usually leave the tea bag steeping for 24 hours, squeeze the fluid it’s holding into the bottle, and throw the bag away. I’ve found that 24 hours is almost always enough time to extract the flavors I want, and that longer steeps can extract flavors I don’t want. I always leave 8oz plain (and unrefrigerated) to start the next batch of kombucha.

Some people like to use a secondary fermentation for added fizziness and other flavor options. I have never tried it, and don’t anticipate trying it since I’m happy with my “plain” light fizz and would rather avoid the added sugar that’s usually part of the process. You can search the web and decide for yourself.

I bottle into quart jars for sheer convenience. I already had quite a few and they are easy to pour into and out of. It would be easier if I had an autosiphon, but I’ve not yet invested in it. If you’d like to bottle into Grolsch-style bottles (advisable with secondary fermentation), get an autosiphon.

When I bottle, I pour the kombucha though a fine strainer. It’s not required, but the floaty bits gross me out a little, so I remove them. I use the same strainer when I’m pouring myself a glass from the bottle. Even though the cultures should be inactive and hibernating from the cold, it’s pretty clear that there’s still some activity while it’s in the refrigerator.

After I bottle the kombucha, I rinse off the scoby and the jar with cold tap water, and start a new batch. Rinsing the scoby isn’t required, and some people advise against it. I like to get all the loose bits off. Note that while I always brew with distilled water, that’s the only place I use it. Many people caution against using tap water for cleaning, etc, but this is one place I’ve thrown caution to the wind. I also use cold tap water for rinsing the jars, strainer, and everything else. I know my tap water is chlorinated and fluoridated, but it doesn’t seem to be hurting my kombucha production at all.

That’s all I have for now. If you have a question, or think of something I’ve forgotten, please comment. Happy brewing!

17 thoughts on “How I Make Kombucha

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