Fermenting in Winter: Why and How to Keep Kombucha Warm

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Ferment your kombucha between 68 and 78 degrees Fahrenheit for best results. Higher or lower temperatures can interrupt the fermentation process or even introduce bacteria. Brewing kombucha and maintaining the correct temperature can be more challenging during the winter. 

What Temperature Should Kombucha Be Fermented At?

Kombucha should ferment between 68 and 78°F. The SCOBY (symbiotic culture of bacteria and yeast) is a living culture and needs an adequate temperature to ferment the sweet tea correctly. Temps between 68 and 78°F allow the proper ratio of acids, probiotics, and enzymes to grow and create a healthy fermented tea. If you have to choose one end of the spectrum, warmer is better.

If the temperature is too low, the SCOBY won’t be able to ferment your brew. It may turn sour or grow mold. The yeast may grow too fast if the temperature rises beyond 85°F. This can result in over-fermentation or kombucha vinegar.

9 Ways to Keep Kombucha Warm While Fermenting in a Cold Environment

Fermenting kombucha in the winter months presents the challenge of keeping your brew warm while your house is cooler. Try these suggestions to continuously brew your kombucha, even in the winter.

  1. Put your homebrew in the warmest room in your house.
  2. Place your kombucha in a high cabinet or on the refrigerator since warm air rises.
  3. Place your kombucha in your oven and turn the oven light on. Just make sure you remove it before you (or a household member) preheats the oven.
  4. Put your kombucha near a lamp that’s almost always on.
  5. Wrap your homebrew jug in a towel to provide some insulation.
  6. Use a seedling mat to heat your fermenting jar.
  7. Use a heating pad to provide extra warmth. This one is made explicitly for fermenting. It has a built-in thermostat and auto shut-off.
  8. Buy a heating belt for your kombucha jar. It’s designed for optimum temperature control.
  9. Get a heating wrap for your brew. It wraps around your brewing vessel to keep your kombucha warm.

Jun kombucha ferments at a colder temperature than regular kombucha. If you live in an especially cold environment, try Jun kombucha. It ferments with green tea, honey, and a SCOBY.

What Temperature Kills Kombucha?

Temperatures higher than 95°F will kill the living cultures in your kombucha. If you use a kombucha heating pad or heating mat to keep your brew warm, ensure you track your brew’s temperature. Attach a temperature strip to your brewing vessel so your kombucha stays in the ideal temperature range.

Temperatures below 65°F can also harm your batch of kombucha. The SCOBY needs a warm brewing temperature to stay active and healthy. Temps below 65°F will cause the SCOBY to get sluggish. You’ll notice that the fermentation time is taking longer than it should.

Prolonged cold temperatures will starve your SCOBY, making your brew unsafe. Cold temperatures won’t kill your SCOBY like hot temperatures but will damage your SCOBY. If you need to take a break from brewing your kombucha, set up a SCOBY hotel instead of storing your SCOBY in the fridge.

Temperatures higher than 90°F can kill the SCOBY. Ensure your starter tea cools to room temperature before adding your SCOBY at the beginning of the fermentation process. Adding hot tea to your SCOBY is a sure way to kill it.

When Should You Put Homebrewed Kombucha in the Refrigerator?

Put homebrewed kombucha in the fridge after the second fermentation. Kombucha goes through two different fermentation processes. The first fermentation lasts between 7-21 days. Then the kombucha is bottled and fermented a second time for 3-5 days. The second fermentation fills your booch with carbonation. You can also add fruit or herb flavors during the second fermentation.

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Second fermentation

You must put your brew in the fridge to stop the fermentation process. Your kombucha has fermented plenty by this time. If you keep it at room temperature, it may over-ferment. Before putting it in the fridge, ensure your kombucha is sealed in a glass bottle. Even in a cold environment, kombucha should be stored in the refrigerator. Storing ready-to-drink kombucha in a place that is under 40°F is ideal.

Taste your brew every day during the second ferment. Once the taste is to your liking, your kombucha is done! Put it in the fridge to help preserve the flavor.

Sarah Pearce

Sarah first tried kombucha in 2015 and she was hooked. Her favorite flavor is ginger, but cranberry comes in a close second. She made her own for many years and loved experimenting with fruit flavors.

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