4 Best Ways to Prevent Kombucha Contamination & Mold

avoid kombucha scoby mold

Whether you are an experienced brewer or this is your very first batch of kombucha, we have all taken a long look at our growing SCOBY and said “Is it supposed to look like that?”

Your SCOBY will grow in many shapes and forms, and that is completely natural when you are brewing of a living probiotic drink. It may be perfectly ivory colored and uniform, there may be various clear or brown spots throughout the SCOBY, and there may even be brown tendrils hanging down into the batch. This article will discuss how to spot a good batch from a bad, and goes through our best tips for limiting the risk for contamination or mold to form.

How to Identify Mold

We’ve established that kombucha can take on a wide range of appearances as your SCOBY is starting to grow. That being said, if your batch is developing mold it is relatively easy to spot. Mold usually takes the form of fuzzy, dry spots on the top of your culture. The tendrils or brown globs growing down into your batch are just yeast bits, and help with your fermentation. Mold frequently grows in rings, and could be white, blue or black. It will look very similar to the type of mold you have seen on bread or cheese your whole life. At the end of the day, trust your instincts.

How Does Kombucha Naturally Defend Against Mold?

The good news is that your SCOBY is a fighter, and can out-compete just about every other microorganism out there. The yeast growing in your culture takes the early lead in protection, by converting sugar into alcohol. This inhibits most bacteria and mold from growing (but not your SCOBY!) The acetobacter in your SCOBY then takes that alcohol and converts it into vinegar acids, dropping the pH and further protecting your batch against nasties. Remember, kombucha has been brewed for over 2,000 years! You don’t make it that long in the microbiology world without some tricks up your sleeve.

Overall, mold growth is relatively rare, and your risk can be reduced even further by taking just a few steps:

  • Brew a strong batch of starter tea!

  • Make sure you are using enough ingredients for your batch. The more nutrients your SCOBY has to feed on, the quicker it will grow and protect itself. We always recommend at least 1 cup of sugar per gallon and a minimum of 12 grams of real tea. Most tea bags contain 2-3 grams each, but we have seen some examples with only 1 gram per bag. We also recommend that you bring your water to a full boil before adding the tea.


  • Ferment in a warm place.

  • Ideal temperature for SCOBY growth is from 70 – 85 °F. Warmer temperature speeds up the brewing process and keeps your probiotics active and viable. Mold on the other hand can thrive at low temperatures (think of the mold growth you have seen in your fridge)! We recommend that you NEVER refrigerate your SCOBY.


  • Make sure you drop your starting pH and pitch with a healthy SCOBY.

  • Dropping the pH as it produces vinegar is one of the primary ways that your SCOBY defends against mold and other contaminants. Very few microorganisms can survive in the environment that it creates during fermentation. Getting a kick start by dropping your pH early is a great way to help.

    If this is your very first batch, our Kombucha Starter SeedTM is designed with a perfect blend of acid to get your pH into optimal range, and contains millions of viable SCOBY cells to get your fermentation going fast and strong.


  • Always keep your brew clean and covered.

  • During the brewing process, make sure to clean your fermentation vessel and all utensils that will be touching your liquid. This is very important though – avoid using soap to clean! Antimicrobial soap can damage your SCOBY and will slow the fermentation process. Instead, we recommend using distilled white vinegar for all of your cleaning needs. This does a great job at knocking down contamination. Once your batch is brewed, be sure to keep it covered with a clean cloth or filter.

    If your kombucha gets mold...

    Unfortunately, sometimes despite our best efforts even experienced brewers will get mold in their batch. It is all part of brewing a living beverage. If you do get mold it is best to pour out the batch, discard the SCOBY and start anew. It is never a bad idea to keep a backup SCOBY or Kombucha Starter SeedTM for just such an occasion. Whatever you do – don’t let one contamination encounter discourage you! Never stop brewing and learning.

     Learn: The easiest way to make kombucha at home →