If you've started researching kombucha, you've probably come across the term SCOBY. Unfortunately, there is a surprising amount of confusion about what the term "SCOBY" actually means. Some people use the term for the rubbery biofilm floating on top of the tea, while others mean the entire community of bacteria and yeast living throughout the brew. In reality, both ideas contain part of the truth.
For a few years we made чайный гриб (pronounced chai-knee grib), the traditional Russian fermented tea drink. The name literally translates as "tea mushroom", and the drink itself is sometimes simply called grib, meaning "mushroom" or "fungus". I have read online that it is also affectionately called gribok ("little mushroom"), although I have never heard anyone use that term. In Australia, however, many people call it kombucha.
Kombucha is sweetened tea fermented by a SCOBY (Symbiotic Culture of Bacteria and Yeast). It is inexpensive to make at home and surprisingly simple once you understand the basics. Many people flavour their kombucha with fruit, herbs, or spices after fermentation, but I generally prefer drinking it plain.
In this article I'll explain what a SCOBY actually is, how it differs from the kombucha biofilm/pellicle, why people disagree about the terminology, and which parts are best for beginners to use when brewing kombucha at home.
What is a Kombucha SCOBY
SCOBY is an acronym for Symbiotic Culture of Bacteria and Yeast. Researchers have identified hundreds of bacterial and yeast species in kombucha cultures. The exact number varies depending on the individual culture and changes over time. Kombucha often contains around 200 species with 20 bacteria and 16 yeast being the most dominant.
Other studies that were conducted over three years have recorded kombucha containing 320 different species. This study clearly demonstrates that the number of species, and abundance of each type, fluctuates significantly over time, and that the number of species/abundance of species is different in the liquid than it is in the pellicle/biofilm.
In practical terms, a healthy kombucha culture consists of three connected parts: the microorganisms (the SCOBY), the starter tea they live in, and the cellulose raft that many of them inhabit. Although these parts can be discussed separately, they normally function together during fermentation.
What is Symbiosis
People often like to think that symbiosis means all the organisms working together in balanced harmony to benefit each other. The truth is far less romantic. Symbiosis only means different organisms living together for a period of time, symbiosis does not have to be mutually beneficial, or beneficial to one species, or even beneficial at all.
The microorganisms are not simply cooperating. They are constantly competing for survival, adapting, and interacting, with some relationships being beneficial to some species while others are neutral or even harmful. Some of the studies I link to in this post indicate that some species even entrap and almost 'farm' others.
These organisms competing for survival make the environment too harsh for many non-beneficial organisms, while adding health benefits to the drink. It is a fascinating subject that is poorly researched, and no two scobys are exactly the same.
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| kombucha jellyfish |
Kombucha biofilm/pellicle
When making kombucha at home it often has a 'biofilm' which is also known as a 'pellicle' or a 'mother'. The biofilm/pellicle is a flat thing that looks a bit like a pancake, or a jellyfish, (or a placenta). Some people refer to the pellicle as the scoby, while others aggressively attack them for using this term as it is not strictly accurate.
The pellicle is largely made of cellulose that is built by bacteria. The scoby lives in and on and under the pellicle, you could not separate them if you tried. The pellicle helps to protect the scoby, and helps the scoby survive if conditions are not ideal. Kombucha pellicles have been tested in the international space station to see how it protects against radiation etc - it is a fascinating subject. We don't fully understand how the pellicle works, or exactly what it does, but we know it has a role for the microorganisms interacting with each other and it has a role for protecting the microorganisms. While the pellicle is not the scoby, I don't see much harm in calling the pellicle the scoby, to me it seems like semantics.
While not ideal, it is possible to brew kombucha by simply adding a pellicle to sweetened tea.
This is possible, and I have done it, but things could go wrong. The main problem is the liquid will generally not be acidic enough to prevent undesirable microorganisms from growing in the liquid. Another issue with using the pellicle only is in the early stages most of the scoby are in/on the pellicle rather than mixed through the liquid. If starting kombucha with only using the pellicle, by the time enough of the scoby are thoroughly mixed through the liquid, and the pH is low enough, there may also be other microorganisms that have started to grow.
For this reason you should always include at least some starter tea when brewing kombucha. Most people add about 10% starter to 90% sweet tea, but I include a lot more starter. You could only use the pellicle and add something acidic to lower the pH, but it is easier and better to just include some starter tea.
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| Kombucha looks like a monster in a jar |
Kombucha starter tea
It is possible to brew kombucha by simply adding some starter liquid to sweet tea. I am told the finished kombucha brew tastes different than when the pellicle is also added. There is a higher chance of losing some species of microorganisms from your scoby when only using starter tea and not including any biofilm.
Fermenting kombucha using only the liquid and no pellicle works well enough because this liquid is often too acidic for many harmful microorganisms to thrive, the scoby are mixed through the liquid, and the scoby can multiply quickly and make the environment too harsh for other microorganisms to get a foothold.
Interestingly, the only times I have heard of kombucha going wrong was when people batch brew and/or are using only starter tea. Perhaps the pH is slightly too high, or there are not enough scoby living in the liquid and they struggled with cold temperatures, which allows mold to develop.
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| kombucha jellyfish in a jar |
For those who disagree with me that the pellicle/biofilm can be used effectively as an inoculum to brew kombucha, I thought I would include a link to a paper on this topic.
That microscopy study found the pellicle develops in layers. Yeasts become trapped within the bacterial cellulose, while living bacteria remain concentrated in different regions of the biofilm. These interactions may help explain why the pellicle contributes to the stability of the kombucha culture.
Some people brew kombucha without ever using a pellicle, and throw away every pellicle they see. While this seems to work well enough for them, they are reducing the metabolic interplay in their kombucha even if they don't know it. They are also slowly reducing the number of different species of microorganisms that are present.
Brewing kombucha using both starter tea as well as the pellicle is the traditional way that stood the test of time because it is very simple, and it has been demonstrated to produce a healthy result. Using both pellicle and starter tea is the traditional way to make kombucha, it helps maintain the highest diversity of microorganisms, and it is really hard for anything undesirable to start growing. In my experience, I have not encountered problems when both starter tea and the pellicle were used together to brew kombucha.
For someone who is just starting out brewing kombucha, it is easiest and safest to use both pellicle and starter tea.
The pellicle and the starter liquid both contain live SCOBY, and including both when brewing kombucha is simple and makes success much more likely for beginners. Including both the pellicle and starter tea is likely to preserve a greater diversity of microorganisms over time, it will have the maximum number of beneficial microbes, and it gives the best chance that they will be interacting in ways you want them to. The linked paper above demonstrates that in some years some species were present in biofilm that were not present in the liquid, other years they were present in the liquid but not the biofilm, other years they were present in both but at vastly different concentrations.
Once you have done a few kombucha brews and have a feel for how things should progress, as well as what looks normal, feel free to discard the pellicle and only brew using the liquid (which is simple), or to only use the pellicle (but only if you are very confident you know what you are doing). When you are still learning, or if you are planning on sharing your kombucha scoby with others, I strongly suggest using both the liquid and the pellicle.
If you are new to kombucha, and are buying scoby to get started, don't just buy a pellicle. Make sure you get pellicle and some of the starter liquid. While you can begin a kombucha brew with either just the biofilm, or just some starter liquid, it is better and easier to use both.
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| Kombucha |
My Recommendation for Beginners
If you're making kombucha for the first time, I recommend using:
- starter tea
- the biofilm / pellicle
- freshly prepared sweet tea
This gives the culture the best chance to establish, provides an acidic environment that discourages unwanted microorganisms, and is likely to preserve a greater diversity of microorganisms than relying on either the biofilm/pellicle or starter tea alone.
Once you're familiar with how a healthy kombucha culture behaves, you can experiment with brewing using only starter tea or only the pellicle if you wish.
Kombucha continuous brew method
There are plenty of kombucha recipes on the internet. They all work because it is hard to go wrong brewing kombucha when you use both pellicle and starter liquid.
I tend to do continuous brew rather than messing around with batches and bottling and using fridge space. Continuous brewing is the traditional approach and has worked well for generations. It's also the method I prefer because I find it simple, cost effective, and reliable.
Other people prefer batch brewing. This usually works for them, and they are often happy with the result.
They are both good methods, they both work, it is mostly personal preference.
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| Continuous brew чайный гриб |
You can see in the photo above I have a large jar that has a tap. It is simple, and is very forgiving unless the jar gets smashed or the tap falls out.
I don't put the lid on the jar as the scoby needs some air. I tend to keep a cloth on top of the jar, this keeps out insects and dust. I used to hold the cloth on with a rubber band, but stopped bothering with that a few years ago and it still does the trick.
You can see there are a bunch of pellicles in my jar. Once or twice a year I remove most to free up jar space for more liquid. Leaving the extras causes no problems, it helps things brew a little faster, and it ensures the diversity of microorganisms isn't slowly being reduced.
If you'd like to start brewing your own kombucha, I've written a separate guide showing the continuous brewing method I use at home, including the equipment, ratios and routine that have worked well for me.
Further Reading
If you'd like to learn more about brewing kombucha and other fermented foods at home, these guides may be helpful:
- How to Make Kombucha: My Simple Continuous Brew Method - The straightforward method I use to keep kombucha brewing with very little effort.
- Making Milk Kefir at Home: Simple Instructions From Years of Experience - A complete beginner's guide to another easy cultured dairy drink.
- Filmjölk: The Easiest Fermented Milk I've Made (How to Make It at Home) - Learn how to make this mild Swedish cultured milk using only a starter culture and fresh milk.
- Kefir Vs Filmjolk (which is easier for beginners) - my comparison of making these two fermented milks at home
- For Sale Catalogue - where I sometimes sell Kombucha SCOBY, and active cultures of milk kefir, and filmjölk
Many of these cultures rely on stable communities of bacteria and yeast. While each works differently, understanding one fermented food often makes the others much easier to understand and maintain.
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