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Making Kombucha

Contents

Goal

What is Kombucha

Equipment

Ingredients

Method

References

Goal

I recently discovered that I like the flavor of Kombucha and that it might be a healthy, probiotic drink if the residual sugar can be minimized. The commericial Kombuchas that I have tried are too sweet, and rather expensive as well. I decided I would make my own to experiment with getting a higher conversion of sugar to vinegar than usual. I’ve also been interested in finding a non-sucrose way to brew the Kombucha, because sucrose is a disaccharide of fructose and glucose, and fructose is one of the unhealthiest sugars, so I would rather any residual sugar not be fructose. Yeast preferentially ferments glucose over fructose, and so fructose would likely be the source of residual sweetness.

What is Kombucha

Read the Wikipedia article or Cultures for Health article for details, but briefly Kombucha is the result of fermenting sugar tea with a symbiotic culture of bacteria and yeast (SCOBY) that results in the sugar being converted into alcohol by the yeast, and the alcohol being converted into acetic acid (vinegar). Secondary fermentation in a sealed glass bottle can make it a fizzy drink when the CO2 produced by the fermentation is retained in the bottle.

While the details are given below, basically I do bulk fermentation of sugar tea for 12-14 days, and then bottle with a 10% addition of fruit juice for a 6-7 day secondary fermentation.

Cultures For Health is an excellent source of information about Kombucha. I recommend their many pages of information on it, which may be found at Cultures for Health > Learn > Kombucha.

Equipment

I have ended up with a fair amount of Kombucha-specific equipment for this project. Here is what I use:

Some of these items I already had for other purposes (such as one filter for making cold brew coffee, stock pot, funnel, kitchen scale, kitchen thermometer, quart mason jars). So basically I spent around $200 to equip myself for making Kombucha. I will probably take about four months to break even given the above.

The quart mason jar is helpful for rehydrating a purchased SCOBY, if you get one that way, and for experiments with small batches.

If the distiller is included, then the cost is significantly higher, around $450. Not counting the electricity it uses, the distiller itself will take 16 months to break even on compared to buying a gallon of reverse osmosis water each week, but it is much more convenient. With the cost of the electricity to run it, the distiller never breaks even, so it is entirely about convenience. The distiller turns out to be useful for more than Kombucha as well (e.g. tea and coffee, soy milk). I use it every night, and buying seven gallons of water a week would be inconvenient. I could never go back to just filtered water in the kitchen after seeing the residue left behind in the distiller. I also insist my water be kept in glass or stainless steel, not plastic, which rules out many water options.

I hope that someday I can replace the distiller with a product from Water Harvesting Inc. to pull moisture from the air to create pure water.

Ingredients

Each 6-7 days I use:

This results in eight bottles of Kombucha, for a cost of about $14.40 per week, or $1.80 per bottle. With cane sugar instead of glucose, it would be $10.80 per week, or $1.36 per bottle. (I should probably use a cheaper tea, but it is one I buy for drinking as well.)

I also use a small amount of organic white vinegar to clean the distiller, but the cost of this is tiny. Vinegar is also called for when rehydrating a purchased SCOBY.

Culture for Health Formula

For reference here are the Cultures for Health Kombucha Ingredient Ratios:

One-Quart Batch Half-Gallon Batch Gallon Batch
1½ teaspoon loose
OR 2 tea bags
1 tablespoon loose
OR 4 tea bags
2 tablespoons loose
OR 8 tea bags
¼ cup sugar ½ cup sugar 1 cup sugar
2–3 cups water 6–7 cups water 13–14 cups water
½ cup starter tea
or vinegar
1 cup starter tea
or vinegar
2 cups starter tea
or vinegar

In metric this would be approimately, with my formula appended:

One-Quart Half-Gallon Gallon Adjusted
loose tea 4g 8g 16g 16g
sugar 60g 120g 240g 225g
water 475–700mL 1.4–1.6L 3.1–3.3L 3.5L
starter 120mL 240mL 480mL 500mL

Method

I brew my Kombucha for 12-14 days on a heating mat set to 23.5–24.5°C (74–76°F). I divide it into two sets of three half-gallon jars. Three jars are processed on even weeks and three jars on odd weeks. This yields about 3.6–3.8 L (15–16 cups) of flavored Kombucha a week (3.2 L of kombucha tea, 0.4 L of fruit juice), or eight bottles of 450 mL (15 fl oz).

On Friday night, distill 3.8–4 L (1–1.1 gallon) of water to use in the morning.

On Saturday morning, create 3.5 L (15 cups) of sugar tea from 3.8 L (1 gallon) of distilled water, cool, mix to fill three half-gallon brewing jars. The tea will be reduced from the water due to evaporation, etc. Mix remaining Kombucha with pomegranate juice to fill eight flip-top bottles.

  1. Put 16 grams (0.56 oz) (2 tablespoons) of tea into the two filters (8 grams (0.28 oz) each).
  2. Heat 3.8 L (1 gallon) of distilled water in stock pot to tea brewing temperature — 90°C (194°F) for oolong, 100°C (212°F) for black tea.
  3. Add filters with tea to stock pot. Set timer to 5 minutes.
  4. After 5 minutes of brewing tea, add 225 grams of glucose powder, and stir to dissolve.
  5. Set thermometer to alert when sugar tea temperature falls to 28°C (82°F).
  6. Decant three half-gallon jars of 12-14 day fermented Kombucha through cheesecloth and plastic strainer(s) into temporary containers (I use two one-gallon jars). The fermented tea should no longer be sweet, but instead fairly sour. If not, you may need to ferment longer or at a higher temperature. If you have pH test strips, you can test the fermentation that way (it should be 2.5 – 3.5).
  7. Remove SCOBYs from their containers and rinse the jars.
  8. Each jar will probably have two SCOBYs: the original, and the new baby SCOBY. Discard the least healthy-looking SCOBYs (or give to someone who wants to start their own kombucha production). Fill through plastic strainer and cheesecloth again to just above 250 mL (8.5 fl oz) (there should be a mark on one side). You can substitute white vinegar if there is not enough fermented tea. Add one SCOBY back to each cleaned half-gallon jar.
  9. Move previous weeks’ eight flip-top bottles to refrigerator.
  10. Set out eight 500 mL (17 fl oz) empty flip-top bottles. Using the scale and funnel, pour 400 grams (14 oz) of Kombucha into each bottle. Next add 50 grams (1.8 oz) of pomegranate juice, and seal. Set these bottles on the heating mat to ferment for another week to covert some of the pomegranate juice sugar into fizz. The pomegranate juice contains about 5.8 grams (0.2 oz) of sugar per bottle, which will fuel the bottle fermentation.
  11. When sugar tea has cooled to approximately 28°C (82°F), fill each half-gallon jar to approximately (or just below) the 1500 mL (6.3 cups) mark (about 1150 mL of addition to each, or 3.5 L combined). Use the remaining sugar tea, if any, to top up the previous week’s three jars (which will have lost some kombucha to evaporation).
  12. Put the three half-gallon jars back on the heating mat and let brew for 12-14 days.

I estimate that the 3.8 L (1 gallon) of sugar tea produced will yield about 3.2–3.5 L (14–15 cups) of unflavored Kombucha two weeks later due to evaporation and spillage during filtering and bottling, or about 400 mL (14 fl oz) per bottle. To this is added about 50 mL (1.7 fl oz) of juice for the second fermentation, bringing the total to 450 mL (15 fl oz), a bit less than the 475 mL (16 fl oz) in a supermarket product like GT’s.

A total of 272 grams (9.6 oz) of sugar was the input to the two stages of fermentation, or 34 grams (1.2 oz) per bottle; how much was converted to alcohol and vinegar is uncertain. Commercial Kombucha (e.g. GT’s) contains 16-20 grams of sugar per bottle; I hope mine is much less.

References