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The Age Old Fear: Kombucha Mold

Mold!  Argggghhhhh!

The word alone strikes terror into the heart of any newbie Kombucha brewer.

Yet this fear is mostly unfounded as moldy Kombucha is extremely rare. In 6 years of brewing, I have encountered it only ONCE. It was plainly obvious and, yes, disheartening for a moment. Nobody likes to fail and the sight of that fuzzy blue mess was intimidating. Yeck.

no SCOBY ever grew but mold came in

Mold may grow if the brew is under-acidified or too cold.

If there is one mold warning I urge you to take seriously, it’s this one:


If you have determined it is contaminated, THROW IT AWAY. Start over with a new one, and try the tips at the end of the article to avoid mold in the future.

However, before throwing that culture away, make sure it is mold. Oftentimes a newbie will mistake normal SCOBY formation or a stray tea leaf lodged in the SCOBY as mold.  Feeling frustrated, they destroy a perfectly good culture out of ignorance. To avoid such a tragedy, lean down and take a closer look at MOLD (but don’t inhale!)

Okay wait…What is mold?


Molds (or moulds) are fungi that grow in the form of multicellular  filaments called hyphae.  In contrast, microscopic fungi that grow as single cells are called yeasts. A connected network of these tubular branching hyphae has multiple, genetically identical nuclei and is considered a single organism, referred to as a colony.

Molds do not form a specific taxonomic or phylogenetic grouping, but can be found in the divisions Zygomycota, Deuteromycota and Ascomycota. Some molds cause disease or food spoilage, others play an important role in biodegradation or in the production of various foods, beverages, antibiotics and enzymes.


Obviously then, Kombucha is somewhat related to mold. Single cell mold is called yeast, which of course is the ‘Y’ in SCOBY. In fact, the most literal translation of the Chinese characters for Kombucha might be “red mold tea.”

However, the type of mold we are discussing here is definitely to be avoided.  The most typical types of mold that may infest a Kombucha culture are the same as those you would find on bread or fruit or other decaying food items.  While not deadly, they do produce an off-taste and can cause allergic reactions or sickness.

Here are some photos of moldy cultures.

Looking at a Kombucha brew from above, large foul circles of blue and black mold have taken over almost half of the Kombucha mushroom culture.

Major mold-function!

More than a dozen blue, quarter-sized circles of mold sit on top of a ruined Kombucha brew.

Note the blue color

Mold can be contained to one small section of the SCOBY as it is here, but the whole SCOBY Mushroom and batch must always be thrown away.

Mold forming on the left hand side of the Kombucha culture

What do you notice about these pics?  What color is the mold? Where is the mold located? What texture is the mold?

Almost all Kombucha mold is:

  • blue or black and fuzzy
  • located on top of the culture – not under it nor embedded in a layer
  • looks exactly like the type you have seen your whole life

Trust your instincts. If you have any question or doubt, you can always submit a photo on the KommUnity Forum or Kombucha Kamp Facebook Group for an opinion.

But my SCOBY looks funny!

Now, just because it is not moldy, that doesn’t mean your SCOBY will form in a perfect smooth pancake. The shape and color of your newly growing cultures is not necessarily indicative of the quality of your brew. Odd looking cultures can make a fantastic tasting kombucha, and great looking ones can fail.

Depending on many factors, SCOBY formation can be quite unusual looking yet completely normal. Sort of like people. (Kombucha and people are very similar in many ways. Don’t get me started.)

Here are some photos of normal SCOBY formation and yeastie bits.

Brownish yellow cobweb like strands of yeast form in the Kombucha and often cling to the bottom of the Kombucha SCOBY mother.

Yeast strands are brown and sometimes clumpy

Little white dots are one way a SCOBY might begin to form and is not indicative of mold.

Early SCOBY formation takes a variety of shapes – note the white color of the many dots they will gradually all connect

A milky and uneven Kombucha mushroom begins to form on the Kombucha.

the culture forms unevenly, some parts are more opaque than others while the layer forms

The SCOBY may grow transluscent at first, even bumpy or shiny, but this is normal growth.

The new SCOBY growth is still translucent

Click here to see more photos of developing cultures and moldy cultures submitted by readers.

To the untrained eye, these odd looking formations can seem startling at first, but over time, they become the familiar process of new SCOBY growth.  This is why I instruct newbies not to look at or disturb their Kombucha for at least 7 days.

Why does mold occur in the first place?

To better understand, let’s review the brewing process. The standard recipe for Kombucha calls for a 90% nutrient solution of sweet tea and 10% Mature KT starter liquid. That starter liquid is the key to protecting the culture from mold.

This mature Kombucha Tea has a pH of 3.0-2.5, low enough to create a natural anti-microbial barrier which inhibits the growth of any foreign micro-organisms.  The starter liquid acts as a protective layer until the entire sweet tea mixture is converted to young Kombucha (about 3 days), defined as when the mixture’s pH drops to 3.0 or below. It is only during that approximately 3-day period that there is the potential for mold to grow.

Mold spores are not visible to the human eye and can lay dormant or survive in extreme conditions. That is why it is impossible to simply wash off the culture in water or vinegar.

Once again: if you do end up with mold, get rid of your culture, toss the tea and start over fresh from your SCOBY Hotel.

How can I prevent mold?

If you find you are getting mold repeatedly, you are in unfortunate rare company. Clearly there is something in the environment that is contributing to the problem. Is your water clean? If you aren’t sure, boil it without a lid for 10 minutes.

Some other causes for mold include cross-pollination from house plants, cigarette smoke, excessive humidity and cold temperatures (keep your cultures out of the fridge!).

Tips to prevent mold from recurring:

  • Use starter liquid from your SCOBY Hotel (or any very old KT)
  • If you don’t have strong starter liquid, use more of your regular starter per batch or
  • Sprinkle 1-2 tablespoons of distilled vinegar on top of the brew
  • Use a heating pad or other warming method during cold months
  • Remove house plants from the vicinity
  • Make sure there is plenty of air flow – open the cupboard or move to a counter top
  • Do not expose to cigarette smoke

Over time you will discover that mold is very rare and easy to spot.  There is definitely  no need to fear mold – or new SCOBY formation.  The more you observe your culture, the more you will understand its unique process.

Hannah Crum, the Kombucha Mamma!Hannah Crum is The Kombucha Mamma, founder of Kombucha Kamp, Industry Journalist & Master Brewer, educating others about Kombucha since 2004. Connect with her on Google +