Signs of Fermentation: How to Determine if Your Kombucha is Done?

May 22, 2025

Brewing kombucha at home can be exciting and daunting, especially for newcomers. Seeing the SCOBY floating on the tea might be a relief, but how do you tell if kombucha is fermenting? Are there any subtle cues that indicate your brew is transforming into that tangy, fizzy delight you're hoping for?

This blog is your guide to decoding the signs of successful kombucha fermentation. From understanding the visual indicators to trusting your taste buds, you'll learn how to journey through this delightful process and become a more skilled brewer.

So, let's learn to read the language of your brew!

What is kombucha?

Kombucha is a fermented tea beverage that has been enjoyed for centuries. It is traditionally crafted by brewing sweetened black or green tea and then introducing a Symbiotic Culture of Bacteria and Yeast, often called a SCOBY.

During the first fermentation, which typically lasts 7 to 12 days, the SCOBY consumes the sugar in the tea. This leads to the production of various beneficial compounds, including organic acids like acetic acid and lactic acid, carbon dioxide, and trace amounts of alcohol.

The fermentation process gives kombucha its characteristic features:

Taste: Kombucha has a signature tangy and acidic taste with subtle hints of sweetness.
Fizz: The fermented tea is naturally bubbly due to the carbon dioxide produced during fermentation.
Probiotics: Kombucha contains a diverse range of live and active cultures (bacteria and yeast) that may contribute to gut health.

Wondering how your gut makes a difference to your overall health? Watch the video below to gain expert insights on how The Good Bug’s carefully crafted probiotics can support your gut.

With this understanding of kombucha, let’s see how you can tell if your home brew is hitting all the right notes!

Also read: Is Kombucha Good For You: Unlock the Benefits of Fermented Tea

How to know if your kombucha is fermenting?

Making kombucha at home requires patience, but your brew will offer subtle clues that the fermentation magic is happening. Let’s explore these visual and sensory cues to help you understand how your sweet tea transforms into tangy kombucha.

Visual cues

Keep a close eye on your fermentation vessel! Your kombucha will often provide visible hints that the process is underway:

SCOBY formation: If you notice a thin, jelly-like layer forming on the surface of your brew, which is a new baby SCOBY, it’s a sign of kombucha fermenting. Don't worry if your SCOBY sinks to the bottom, floats on top, or hangs somewhere in the middle; it’s all part of the normal brewing process.
Bubbles: Tiny bubbles gently rising within the liquid or clinging to the sides of the jar are a telltale sign of fermentation. This indicates the production of carbon dioxide, a natural byproduct of the SCOBY's activity.
Sediment accumulation: It's perfectly normal to see stringy, brownish sediment forming at the bottom of your jar. These are yeast strands, and their presence indicates that your kombucha is actively fermenting.
Cloudiness: The clarity of your sweet tea will likely change as the yeast and bacteria ferment the tea. The liquid may become slightly cloudy, a natural part of the fermentation process.

Sensory cues

Even if the visual cues are not noticeable in the initial stages, you can always rely on your senses:

Vinegar-like smell: As the fermentation progresses, you'll likely notice a gradually increasing vinegary or acidic aroma emanating from your brew. This indicates the production of organic acids, a hallmark of kombucha fermentation.
Tangy, acidic taste: Over time, you might notice the brew becoming less sweet and developing a slight tartness or acidity. This indicates that the sugars are being consumed effectively.

Important note: Fermentation speed can vary based on temperature (ideal temperature is around 75–80°F or 24–27°C). Warmer conditions can foster quicker fermentation, shortening the process to around 7 days, while cooler temperatures may extend it to 14 days or more. These external factors can affect how rapidly visible changes occur, such as the SCOBY's thickness or the carbonation level.

You've got your eyes and nose tuned in, but what about your taste buds? Let's explore how tasting is crucial to your kombucha brewing journey!

How and when to taste kombucha?

Besides determining when kombucha is done fermenting, tasting helps you tailor the brew to your taste preferences. Here are some important guidelines to follow for successful sampling when brewing kombucha at home:

Patience first: Resist the urge to disturb your kombucha's initial fermentation for at least the first 5 days. This undisturbed period allows the SCOBY to establish itself and begin the fermentation process effectively.
Timing your first taste: Experienced brewers often begin their first tasting around day 7 or 8 of the fermentation process. However, the ideal timing can vary depending on the ambient temperature in your area.
Sanitation is key: Always use clean and sanitised tools when sampling your brew. This helps prevent unwanted bacteria or mould, ensuring a healthy fermentation.
Tasting methods: Consider using a fresh straw or sanitised ladle for each test. One approach is gently inserting the straw, covering its top with your finger, and drawing out a small sample to taste. Discard this sample after testing.

Now that you've got a taste for when it's ready, let's examine another key aspect—monitoring pH levels!

Are pH levels an indicator of kombucha fermentation?

Monitoring the pH levels of your kombucha undoubtedly provides insights into its acidity and safety. Generally, a pH range between 2.5 and 3.5 is considered ideal for a fully fermented brew. It creates an environment hostile to harmful microorganisms, making your kombucha safe to drink.

However, hitting this pH range doesn't necessarily mean your brew is perfectly fermented for your taste preferences. The balance between sweet and tart is primarily a matter of taste and is not solely determined by pH levels.

Therefore, trusting your taste buds through careful and regular sampling remains the most accurate and enjoyable way to determine when your kombucha has achieved its optimal flavour profile.

Also read: Can Kombucha Ferment Too Long: Turning Mistakes into Magic

Before you become a kombucha connoisseur, learn what to look for to ensure your brew stays trouble-free!

Things to watch out for during fermentation

While you're eagerly anticipating the signs of successful kombucha fermentation, it's equally crucial to be vigilant for any indicators that something might be amiss. Early detection of potential issues can save you from disappointment and ensure a healthy brew.

Mould: If you see fuzzy or discoloured growth (blue, green, black, or pink) on the surface of your SCOBY or the liquid, it is a clear sign of mould contamination. If you spot mould, it's essential to discard the entire batch immediately, including the SCOBY and starter liquid, and thoroughly sanitise your brewing vessel.
Lack of SCOBY growth: A new baby SCOBY doesn't always form visibly, However, a complete absence of thickening or change on the surface of your brew after a week or more could indicate that your SCOBY is inactive or that the fermentation conditions are not favourable.
Overly strong vinegar smell: A mild vinegary aroma is a normal sign of fermentation. However, an overwhelmingly pungent vinegar smell developing early could suggest an imbalance in your culture or overactivity. While the brew might still be safe, it could quickly become unpleasant.

Also read: The Expiration Question: Can Kombucha Go Bad?

You've made it this far in ensuring your kombucha is brewing safely, and now comes the fun part—flavouring your freshly fermented batch!

What to do after your kombucha is fermented?

Once your kombucha has reached that perfect balance of sweet and tart, it's time to halt the first fermentation and prepare it for the next stage: bottling and flavouring. Here, you can get creative and experiment with different flavours.

Flavouring: Add your favourite fruits, juices, herbs, or spices to your bottled kombucha and seal it tightly.
Natural carbonation: The remaining yeast and bacteria will consume the residual sugars from the first fermentation and the sugars in added flavourings. This creates natural carbonation, resulting in that delightful fizz.
Transfer to refrigerator: Once you achieve the desired level of carbonation, transfer the bottles to the fridge. This slows down fermentation, prevents unpleasant explosions from too much fizz, and allows the flavours to meld beautifully.

Here are a few flavour ideas to infuse your brew:

Ginger and lemon for a zesty kick.
Mixed berries for a sweet and tangy delight.
Mango and chilli for a tropical heat.
Fresh mint or basil for an aromatic coolness.

Also read: Beyond Plain: Exploring Unique Kombucha Flavours

Pro tip: Before you bottle your delicious brew, reserve about 1-2 cups of the finished kombucha. This reserved liquid acts as your starter culture for your next batch, providing the necessary acidity and beneficial microbes to kickstart the fermentation process anew.

Making kombucha involves a fascinating blend of patience and observation. By watching out for those subtle signs, you’ll learn to tell if kombucha is fermenting and become a confident brewer. Trust your senses, and don't hesitate to experiment with different fermentation times and flavour combinations to discover your perfect kombucha.

Are you looking for delicious, expertly crafted kombucha to inspire your home-brewing adventures or simply enjoy right away? Explore the refreshing options from The Good Bug. Visit our website to grab your favourite flavours and enjoy sipping them from your home!