Kombucha Fermentation & Temperature

Temperature is crucial to your ferment!

We get a lot of questions here at the brewery about kombucha and temperature -- and whether or not you need to monitor and/or control it during fermentation.  The most common one is “do I really need to monitor my brew's temperature?”  Like most things in life, the answer for the home brewer isn’t always black and white, but here’s the philosophical question: “do you want your brew to taste great every time, be consistent every time, and make sure you never lose a batch?”  Of course you do!  One of the keys to that is monitoring and (if necessary or desired) controlling your fermentation temperatures.  The easiest way to do that is with our adhesive thermometers. Kombucha and temperature are closely related, as the temperature of the kombucha will affect its fermentation, flavor, pH, carbonation levels, and safety.  Nearly every aspect of kombucha is affected, and most importantly, the temperature of the kombucha will affect the rate and quality of the fermentation process.  At warmer temperatures, the bacteria and yeast will be more active and will ferment the kombucha faster and more completely. This will produce a more carbonated and flavorful kombucha, with a higher acidity and a stronger aroma. However, if the temperature is too high, the bacteria and yeast may become stressed or damaged, and the kombucha may become overly sour or undesirable.  It's important to maintain the temperature within a certain range, to ensure that the kombucha ferments properly and produces high-quality kombucha. The optimal temperature range for kombucha fermentation is between 74-84°F, so it's important to monitor the temperature of your brew during fermentation.

Why you should monitor temperature during fermentation.

It's important to monitor the temperature of kombucha because the temperature will affect the rate and quality of the fermentation process.  The bacteria and yeast in the kombucha will be more active at warmer temperatures, and they will ferment the kombucha faster and more completely.  This will produce a more carbonated and flavorful kombucha -- and more importantly finish it faster.  And 80°F will finish your brew about twice as fast as 74°F, so if your goal is brewing kombucha (and not waiting), heat mats are totally worth it for the increase in speed and brewing consistency.  Here at the brewery, we like to say that not using a heat mat is like jumping over dollars to get to pennies ????. In addition to affecting the fermentation and flavor of the kombucha, the temperature can also affect its safety.  At improper temperatures, the kombucha is exponentially more susceptible to contamination mold.  And while it's generally harmless, mold can produce toxins or other harmful substances that could make the kombucha unsafe to drink -- and definitely don't taste very good.  It's important to maintain a safe temperature range for the kombucha, to prevent contamination and ensure that it is safe to drink. To monitor and control the temperature of the kombucha, you can use a thermometer, a temperature controller, or other tools that are designed for this purpose. It's important to check the temperature regularly, and to make adjustments as needed, in order to produce high-quality and safe kombucha.

Why do warmer temperatures increase fermentation rates?

Warmer temperatures can increase fermentation rates because they speed up the metabolic reactions of the bacteria and yeast that are responsible for fermentation. The bacteria and yeast that are used in kombucha fermentation, such as Gluconobacter, Acetobacter, and Saccharomyces are living organisms that require a certain range of temperatures in order to grow and reproduce.  When the temperature is within this range, the bacteria and yeast will thrive -- and consume the sugars in the kombucha and produce the characteristic flavors. At warmer temperatures, the bacteria and yeast will be more active and will reproduce more quickly. This will increase the rate of fermentation, and the kombucha will ferment faster and more completely. The warmer the temperature, the faster the fermentation will be. However, if the temperature is too high, the bacteria and yeast may become stressed, damaged or die, which could seriously slow or stop fermentation altogether. It's important to maintain the temperature within a certain range, to ensure that the kombucha ferments properly and produces high-quality kombucha. Bottom line: trying to ferment outside of proper temperature ranges is definitely not brewing like a pro...

So you want to brew consistently like a pro?

It’s easy!  All you need to do is:

1. Start with a strong culture like Gaia or Honey
2. Use pH test strips to always test your brew's starting pH and finishing pH
3. Use an adhesive thermometer to monitor your brew's fermentation temperature
4. Start your brew at a pH of 4
5. Keep your brew between 74-84°F during fermentation (remember consistent temps produce consistent results from batch to batch)
6. Finish your brew at a pH of 3

It’s that simple.  Happy brewing, Booches!