Fermentation - Kombucha


Kombucha is a probiotic beverage that has been consumed for centuries, perhaps millenia, by people in China and Russia. It is made by fermenting sweetened green or black tea with a culture called a SCOBY (symbiotic culture of bacteria and yeast); the result is a tart and delightfully effervescent beverage loaded with beneficial microorganisms. Kombucha can be served warm or cold and custom flavors can be created with the addition of different fruits or fruit juices.

The Basics: Make a pot of black or green tea, add sugar and a scoby, and wait while the scoby microorganisms convert the sugar into acids and effervescence.

Check out our blog post Kombucha 101 for a descriptive walk-through of the process... or keep reading for step-by-step instructions.

Quick Reference
Batch Size Tea Sugar Starter Tea
1 qt. 2 bags (or 2 tsp. looseleaf) 1/4 cup 1/2 - 1 cup
1/2 gal. 4 bags (or 4 tsp. looseleaf) 1/2 cup 1 - 2 cups
1 gal. 8 bags (or 8 tsp. looseleaf) 1 cup 2 - 4 cups
  • fermentation vessel (glass jar or plastic pitcher)
  • breathable jar cover
  • large pot for brewing tea
  • steeping bag or strainer (if using loose leaf tea)
  • stirring spoon (preferably wooden or plastic)
  • tea (black or green)
  • sugar (real cane sugar, no artificial sweeteners or sugar substitutes)
  • starter tea reserved from previous batch or vinegar
  • swing-top glass or plastic soda bottle(s)
  • funnel with tip narrow enough to fit bottlenecks
  • SCOBY (Symbiotic Culture Of Bacteria and Yeast)
  1. When using a dried scoby, follow the manufacturer's instructions for activation. (The first few batches will require the use of vinegar to acidify the tea, since sufficiently acidic starter tea won't be available.) Once you have a fully active scoby, you may proceed to brew regular batches with the following instructions.
  2. Make pot of tea using water and tea amounts according to desired batch size.
  3. Add sugar while tea is still hot and stir to dissolve.
  4. If using loose leaf tea without a steeping bag, strain leaves out once tea has steeped.
  5. Let tea cool to room temperature. Cover if cooling overnight, or place pot in large bowl of ice water and stir to cool quickly.
  6. Once tea has reached room temperature, combine it with reserved starter tea and SCOBY in fermentation vessel. A SCOBY can ferment any size batch of tea, it just might take a little longer for larger batches.
  7. Cover with breathable jar cover (or use muslin held in place with a rubber band) to keep out dust and flies and store at room temperature, out of direct light.
  8. Allow to ferment undisturbed for 7-14 days, depending on how tart you like it. If you're totally new to this, pour off a small amount after 7 days and every other day after to taste it.
  9. When the balance of sweet and sour is to your liking, it's ready to drink! Or, if you prefer a bit of fizzy effervescence, funnel kombucha into swing-top glass bottles or plastic soda bottles and leave out for another 2-3 days. Remember to save some of your completed kombucha to use as starter tea for your next batch! As the tea continues to ferment, carbon dioxide (carbonation) will build up in the bottles.
  10. Refrigerate the completed kombucha and enjoy!
Frequently Asked Questions

Can I use alternative sweeteners to make kombucha?

Understandably, many people are trying to reduce the amount of sugar in their diets, but SCOBY microorganisms are not in this camp. They depend for their survival on an intake of real sugar (not sucralose or saccharine, etc.) and they're the ones actually consuming the sugar, not you. Depending on how long you allow it to ferment, your finished kombucha will only have a gram or two of sugar per cup; it will become progressively more sour the longer you let it ferment, as more sugar is converted to acid.

Is there any risk of glass bottles shattering due to the pressure of carbonation?

Glass bottles are plenty strong enough to contain a few day's worth of built up carbonation pressure. However, if you forget how long they've been out, you can't gauge the pressure inside except by opening them, which can lead to an explosive mess on your kitchen ceiling. When in doubt, open bottles outside. With plastic bottles, you can give them the "squeeze test." When they're firm, they're ready to refrigerate. If you forget to refrigerate carbonated plastic bottles in time, the seal in the cap is more likely to fail than the bottle itself and you'll just end up with leaky tops.

Can I use fruits or fruit juices to flavor kombucha?

Absolutely! To avoid possible contamination or damage to the SCOBY, it's recommended to brew the kombucha as described above and add fruit or fruit juice when you bottle it for the second stage of fermentation (carbonation). As a rule of thumb, use 1 tablespoon fresh fruit, frozen fruit, or fruit juice for each cup of kombucha.

What's the starter tea for?

The starter tea is already acidic from being previously fermented and serves to acidify the new batch of tea, which prevents contaminants from moving in before your SCOBY microorganisms have time to take hold. If you don't have enough starter tea, such as when starting with a dried SCOBY, vinegar may be used to acidify the tea. Starter tea also boosts the number of microorganisms: the more starter tea you use, the quicker your kombucha will ferment.  Vinegar does not add microorganisms.

Additional Resources

www.thekitchn.com/how-to-make-kombucha-tea-at-home-cooking-lessons-from-the-kitchn-173858 An awesome reference for all things culinary. Easy-to-follow instructions from the author of True Brews, Emma Christensen.

http://www.westonaprice.org/health-topics/flavored-kombucha-a-home-brewers-guide/ A detailed guide to using fresh fruits, fruit juices, and dried fruits to customize the flavor of your kombucha. Also discusses the use of extracts, infusions, and medicinal herbs in kombucha.

Christensen, Emma. True Brews: How to Craft Fermented Cider, Beer, Wine, Sake, Soda, Mead, Kefir, and Kombucha at Home. An excellent reference for making all kinds of fermented beverages. Great ideas for fruit flavor combinations, as well as instructions for growing your own SCOBY if you can't get one from a friend and/or don't want to buy one.

Kombucha Supplies