Moldy Kombucha: A Fermented Drink's Worst Nightmare

Kombucha is a fermented tea drink that has gained popularity in recent years. However, brewing kombucha at home can lead to the growth of SCOBY mold, which can ruin the entire batch. Mold is an overgrowth of bad bacteria or fungi, and while it is avoidable, it can develop when brewing conditions are not optimal. The presence of mold indicates that the kombucha and the SCOBY used to ferment it have been contaminated with unwanted and harmful fungi. This article will discuss the causes of mold, how to identify it, and the steps to take if mold is found.

What does mold on kombucha look like?

While mould on kombucha is rare, it's important to know what to look out for. Mould on kombucha looks like mould on any other food: it's colourful, fuzzy, and spreads quickly. It can be white, green, black, blue, or grey, and it will develop on the top of your brew, where it's exposed to oxygen.

Mould typically grows in clumps, circles, or rings with visible thread-like structures at the base. These threads can crisscross from one cluster to another. The hair-like structures are thin and soft, often with a fuzzy texture. Upon maturing, the hair-like structures will develop spores, which are as fine as dust.

Mould can be confused with a growing baby SCOBY or leftover specks of tea leaves. However, mould only grows on the upper surface of the brew, and it gives off a distinctive musty odour that's reminiscent of mildew.

How to prevent mold on kombucha

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What to do if you find mold on your kombucha

Finding mold on your kombucha is disappointing, but it's not the end of the world. Here's what you need to do:

Discard the batch

Throw away the SCOBY and any liquid that it has come into contact with. Do not ingest any of it or try to salvage it. A moldy brew is a lost cause, and you cannot save a SCOBY that's already been infected with mold.

Clean and sterilize your equipment

Clean and sanitize/sterilize all equipment that has come in contact with your kombucha. Use boiling water and distilled white vinegar to sterilize everything very well.

Start fresh with a new SCOBY

Get a new SCOBY and start a new batch of kombucha, making sure to follow all the prevention steps outlined below.

How to prevent mold in your kombucha:

• Use a good amount of starter tea to acidify your brew. The starter tea helps bring the pH down to a low enough level where mold can’t thrive.
• Don’t refrigerate your SCOBY, starter tea, or brewing vessel. Keep the temperature in the mid- to high-70s, as temperatures below 65 degrees make the yeasts and bacteria go dormant.
• Don’t keep your brewing vessel in a moist area with poor air circulation, or anywhere there might be mold, like near your fruit basket or house plants.
• Fully strain your tea. If too many solid tea dregs or other particles get into your brew vessel with your SCOBY, it could attract mold.
• Use the right kind of tea and sugar for your brew. Black tea and cane sugar are best. Do not use herbal teas or different types of sugar, as these can weaken the SCOBY over time.
• Avoid flavored teas with essential oils and other chemical flavorings, as these can hurt the SCOBY's natural protective barrier.
• Keep your kombucha somewhere with good airflow to ensure proper oxygen levels during fermentation.

How to identify mold on kombucha

Firstly, it's important to note that kombucha mold is extremely rare and avoidable, and the chances of it occurring are low if you're brewing kombucha properly. However, it's still useful to know how to identify it.

Kombucha mold is an overgrowth of bad bacteria or fungus, similar to the mold that might grow on old bread. It usually occurs during the first fermentation when the kombucha acidity isn't high enough to stop it from growing.

• Mold will usually be located on the surface of the kombucha, as it needs air to survive.
• It will often appear in concentric circles, but not always.
• It will have a fuzzy or dry appearance.
• It can be white, green, black, blue, or red. Bright colors are a bad sign.
• It will look similar to the mold you might find on bread, cheese, or fruit.

If you're still unsure, it's recommended to isolate the kombucha from your other vessels and wait a few days. If it's mold, it will continue to grow and become more obvious.

If you do identify mold, it's important to throw away the SCOBY and any liquid it has come into contact with. Clean and sanitize all equipment, and start over with a new SCOBY and starter tea.

What causes mold on kombucha

Kombucha is a fermented, fizzy, tea-based drink made using a combination of bacteria and yeast. While mold is rare, it can develop on the top of your brew, where it is exposed to oxygen. If you do experience mold, you must discard everything and start again with a new SCOBY and starter liquid.

Common causes of mold on kombucha

• Not enough starter liquid: The starter liquid is one of the most important ingredients in your kombucha brew as it helps to acidify and jump-start the fermentation of new sweet tea. If you don't use enough, your kombucha may not be acidic enough to defend itself from mould strains.
• Temperature too low: If the temperature is too low, the bacteria and yeast go dormant. This means they can't acidify your kombucha, and mould may grow.
• SCOBY stored in the fridge: SCOBYs and their starter liquid should always be stored at room temperature. If they are refrigerated, the yeast and bacteria will go dormant, and your kombucha will be more susceptible to mould.
• Using the wrong ingredients: Substituting non-tea botanicals or other sugar types in the initial brewing stage may result in mould.
• Brewing location: Airborne contaminants from garbage, compost, fruit bowls, or other fermentation projects can contaminate your kombucha.
• Brewing equipment not clean enough: Mould spores may have slipped in through your supplies, such as a dirty sponge used to clean the jar.

Frequently asked questions