Kombucha Conundrums, with Jo Webster and Caroline Gilmartin
Last week I posted a report on a fermentation test of commercial kombucha that fermentation experts Jo Webster and Caroline Gilmartin conducted in England. This was preceded by an hour-long video on their substack channel [subscription required – low £20 annual fee to access] where they tasted a range of UK commercial brands. Their opinions are grounded in their knowledge of fermentation and their preferences as consumers. This edited transcript of the video includes time codes. I strongly encourage everyone to subscribe and then through to substack and watch the entire video which is informed by their delightfully English sense of decorum and humor.
Intro: In Search of Authentic Kombucha
There’s a lot of kombucha out there. How do consumers know that what they’re getting is the real deal? Or, more to the point, what do you want to get? Your priorities might be different from others. You might only care if it tastes good or you might prefer authentic, traditionally made kombucha, and you might care about its potential health benefits. On the other hand, you might just want something quick in a sachet to fling in a cup because it will do some good.
The reality is that there’s no clear standard stating what kombucha is!
Jo: I could put drain water in a cup and call it kombucha because it’s not a protected term. So that means people can call pretty much anything kombucha if they want to.
We aim to share information to let you know what’s out there. Is the current information you’re getting enough to see that you’re getting what you want?
If you go to the supermarket, there are two places where you can find kombucha. Sometimes, it will be on the shelf at ambient room temperature and sometimes in the fridge. For example, Momo Kombucha [below] must be stored in the fridge because it is a live kombucha. One way to keep microbe activity at a minimum is by refrigerating it.
The Gold Standard: Jo’s Homebrew
I mostly use black or green tea, and I’ve got some rose hip, sugar, water, and the all-important backslop. You need starter kombucha to make new kombucha because that contains the microbes that you need.
At the end of the day, your kombucha brew will have lowish sugar and probably a little bit of alcohol in it. So, all these commercial kombuchas have actually got quite a high bar to jump over because few things are more delicious than homebrewed kombucha.
When you taste it, you can see that a lot is going on. There are different notes and tones. There’s the tang. There’s the fruitiness. The tea is astringent. There’s a depth to it.
Jo: The more that I read and the more research I do, the more I know diversity in our diet is good. And you can tell on your taste buds that a lot is going on in there.
Good kombucha is a balancing act between the yeast activity and the acetobacter gluconoacetobacter bacteria activity. Yeast sugar to alcohol, bacteria, alcohol to vinegar.
And that’s the challenge for commercial brewers because, at home, I’ve got no transport chain. I’ve got no storage issues. I’ve got a fridge right there. I can make my kombucha, decide when it tastes nice, and then refrigerate it. It hasn’t got to go anywhere.
Caroline: As a non-drinker, I absolutely love the slight acidity that you get in kombucha. Because in the absence of alcohol, for me, that is much more pronounced, and it’s tangy and it’s delicious, and it gives me a reason to drink it. But also, when I drink kombucha, it actually makes me feel–I don’t know–it gives me a little thrill, which might sound a bit odd.
Commercial Production Challenges
It’s a really hard job making commercial kombucha. So respect to all of the commercial kombuchas out there.
The bacteria or acetobacter gluconoacetobacter are aerobic. They like being in my nice airy jar under its little hat, and they will work away. But the yeast is anaerobic. They get more active when you’ve excluded oxygen, which is what can happen when you put them in a bottle. So, if there’s still sugar in there and you’ve bottled your kombucha to send to the shops on a long transport chain, the acetobacter doesn’t want to be as busy. But the yeast says, yes, this is party time!
If there are still sugars, the yeast can thrive, and alcohol levels can rise. And that’s a real concern for commercial producers.
Commercial producers must get the sugar levels right to manage the alcohol levels. So, how much sugar is in there will relate to how much alcohol is in the end product. And they’re looking at low alcohol of 1.2% to 0.5%. Most of the commercial brewers are trying to get under 0.5%. But to do that, you must do more stuff to it than you do to your homebrew kombucha.
They’ve got to think about the yeast. Then they’ve got to think about the bacteria because customers don’t want to find that it tastes of vinegar, and most people don’t want a scoby in the bottle.
Unlike the home brewer, commercial brands must obsess about consistency. Consumers expect it to taste the same each time.
Commercial Production Solutions
Forced Carbonation: To avoid excessive alcohol, they’ve got to manage carbon dioxide levels.
Our homemade kombucha is slightly flat. But most commercial ones will be quite fizzy because of forced carbonation. They put carbon dioxide in as part of the process to make it fizzy, but it also stuns the remaining yeast when putting it in the bottle. And remember, they don’t want the yeast in the bottle to eat more sugar because the alcohol levels will increase. Forced carbonation can suppress microbial growth as well.
Filtration: Filtering removes a proportion of the microbes so that they cannot make alcohol. You can generally tell when filtration has gone on by seeing how cloudy a kombucha is. Some do large yeast filtration for clarity.
The Science & Health Benefits of Kombucha (13:50)
Our study is vital if you want to know what tastes good in terms of kombucha: if you’re interested in what’s being made traditionally authentically, if you’re interested in who’s being transparent about what they’re doing, and if you’re interested in potential health benefits. But there’s limited data. There is some information mostly about blood glucose regulation and blood lipid regulation. But the more things that have been done to manage the kombucha in an ambient situation, or the long transport situation, the further away you’re getting from the traditionally produced kombucha that humans have enjoyed for thousands of years and that is most likely to be related to health benefits.
There’s little research on whether the microbes or the microbial products of metabolism are the most crucial thing in kombucha. So, it might be that the benefit of kombucha is actually in the glucuronic acid it contains, which could be significant. So, it might not be as important if there are a lot of microbes in there.
Jo: That’s an important thing to remember because part of my research at the moment originated from an interest in postbiotics, which is the idea that microbes don’t need to be alive to benefit health. So when we go on in a minute to talk about the yeast being filtered out and the microbes being filtered out in some situations, remember that there is this whole body of research in that area–it’s young, but it’s really developing. It might be that if there’s metabolites, if there’s the by-products of microbial activity in their little chemicals components, that those might be the benefits. It’s not the end of the world if some microbes have been filtered out.
Real Drinks (10:20 & 23:20)

Real Drinks don’t call their product kombucha. They are transparent that their beverage is about occasion, not health. Real Drinks are clear about what they’re doing and why. And we like that because it’s clear and transparent. It’s a fantastic, delicious drink.
They make it in a winery using stainless steel wine barrels. They’re conscientious about the microbes they use. It’s a very managed process, and they’re completely transparent about it. They’re taking microbes that they know will do the job–that will turn sugars into alcohol and then taking other microbes that will turn alcohol into vinegar–and they’re balancing them very carefully and not using a cellulose SCOBY mat.
It is presented in a wine bottle that would be tempting to leave as a gift, like Chardonnay. It looks crystal clear.
Equinox Kombucha (17:00)

Jo: I’m actually really into Equinox at the moment. It definitely tastes good. They do a really nice range of flavors–the Sicilian orange one is delish and fizzy. What’s nice about their website is they are clear that they filter and they do force carbonate. They add fizz, and they say so on their website.
Caroline: It’s nice, but it doesn’t taste anything like kombucha. It literally tastes like a bottle of ginger beer. I get no hint of tea whatsoever.
Jo: It’s like the homemade, but that complexity is different. I’m not a downer on this.
Caroline: I love it. It’s perfectly nice. It just doesn’t taste it doesn’t taste the same as the homebrew.
Jo: They’re really good and clear on their website. They do a nice range of flavors.
Momo Kombucha (18:00)

They do not force carbonate. It’s completely unfiltered. You can see how cloudy it is.
I wrote to Momo asking how they control their process, and they said they only control the sugar level when they bottle it. It must be refrigerated since sugar is food for yeast that loves to go crazy in anaerobic bottles. They’re managing the yeast by managing the cold chain. They test their batches for how much alcohol is produced, so they’ve found that three percent sugar is not enough to take your alcohol level above 0.5%.
It’s not a surprise that it tastes like our homebrew kombucha.
They brew in 10-liter jars. Their Instagram shows racks of 10-liter jars–like home brewing on a much larger scale. Other brands ferment in enormous vats.
There are hints of elderflower, and it smells slightly yeasty.
Twisted Kombucha and Zak’s Kombucha (21:00)

Twisted Kombucha also does it without any intervention at all. It’s pretty clear on their website. I think they lightly filter it.
Zak’s Kombucha does force carbonate to help put the yeast to sleep.
I would say if you care about authenticity and the health factor, I would look at the websites of the ones you’re interested in because you can pretty soon tell the sentiments and the spirit of the people making it.
Nania’s Vineyards (21:50)

I’ve never heard of them, and they’re just down the road in Bristol.
I went to their website, and it really looks great. The artwork is fantastic. They use oak barrels for an almost wine approach. They don’t force carbonate and do put it in cans, but they’re not massively filtered.
It says it is “canned conditioned,” so it can potentially have a slightly higher alcohol level, which it says on the tin.
What’s super interesting is their money-back guarantee that you can take one of their cans and use it to make your homebrew kombucha. If it does not work, they’ll give you your money back.
Lo Bros / Remedy / Captain Kombucha (23:50)

Lo Bros, Remedy, and Captain Kombucha are everywhere. We’ve only got a sample of Remedy. I looked around their websites, and there’s a different vibe–how they word things is entirely different, and their process is completely different.

I couldn’t properly work out what’s going on with these three brands. But when I looked at the ingredients, I began to see what they do. They probably use a fine-micron filter to remove most of the microbes.
The Remedy label says that there’s no sugar. I’m curious–how is that? The sugar content of Momo is 2.8 percent sugar, and Equinox is three percent sugar.
Remedy states “no sugar” on the label, yet kombucha is sugar-sweetened fermented tea. So how do they do this?
We’d be very interested if anybody from Remedy could contact us to explain their process.
Caroline: The reason I ask is that when you make homebrew kombucha, you find that even if you leave that kombucha sitting for months and then check the sugar level using a hydrometer, there will always be some residual sugar, typically two percent. We don’t understand how they can claim no sugar. They must have added some acetic acid bacteria to eat the sugar up or some yeasts that have metabolized absolutely everything. They must be able to tolerate high levels of acetic acid because that’s what stops most of the yeasts in kombucha from fermenting out all the sugar because the acetic acid bacteria produce a certain amount of acidity. Most of the yeasts in kombucha cannot handle that high acidity. What I’m saying is they’ve found a way around the natural system.
As the acetobacter goes up, the yeast goes down, and you’re left with no sugar.
The label also states they have stevia glycosides. These are non-fermentable sugars that are used together with erythritol.
Jo: It’s clever in a way because if the yeast can’t ferment the sugar, you’re not going to get alcohol, which they don’t want. You’re not going to get a ton of carbon dioxide, which is associated with yeast activity. So you’re not going to get exploding bottles, either. If you can see stevia glycosides, or erythritol on the label, then you know they use non-fermentable sugars to manage the process.
Also, you might see bacillus coagulans has been added. They filter all the microbes from the ferment and then add heat-resistant spore-forming microbes. Then, they can pasteurize with microbes that can tolerate pasteurization and will then reactivate in your gut. The idea is that it’s still healthy because it has microbes in it, but they’ve put those microbes in so they can tolerate the process.
It sounds a very long way away from what kombucha actually is.
We’ve worked out that Remedy do an original traditional kombucha that they ferment to concentrate for a long time. Then, they dilute it with sparkling water or some raw kombucha flavor enhancer. The long ferment makes it very, very concentrated to get rid of all the sugar, and then they add things back to make it taste like a perfectly nice gingery drink. But it lacks complexity. It lacks depth. But it’s fizzy. So, if fizzy is important to you, choose this one, unlike my homemade kombucha and Momo, which are slightly flatter. I’m sure it must be forced carbonated.
Caroline found Remedy had more flavor than Equinox. Jo disagreed and preferred the Equinox. She found Remedy one-dimensional, compared to homemade kombucha which is 3D, “maybe four of you tip it over yourself.”
They could taste the lemon, which gives it a little earthier taste but is very fizzy.
The natural ginger flavoring doesn’t quite taste authentic. Now, it is almost universally true, that something called “natural ginger flavoring” is not related to ginger. They extract things using solvents.
Captain Kombucha added bacillus coagulans, stevia, raspberry flavor, carrot, apple, and currant extracts. It looks like another brand where the sugar’s been fermented away, and then they add in other ingredients.
Jo: The fact is, it’s hard to tell from their websites because they’ve got so many sound bites and sexy things that if you weren’t discerning, you’d think it was great. It does taste good. It’s nice and fizzy. But unlike Equinox, unlike Momo, unlike Twisted Kombucha, it’s not clear from the website what they are doing. And we’re not saying that all these other things are bad. We’re just saying we should be allowed to know if they’re force-carbing, filtering, pasteurizing, adding in other microbes.
Caroline: Obviously, it’s up to you if you want to eat additional flavorings and things like that. To my mind, Momo and Equinox are showing you that you can actually make kombucha on a very large scale, as close to the original as possible. This leads one to think that Lo Bros, Remedy, and Captain Kombucha have a different approach, but it’s not an approach that I prefer. I probably prefer having a little bit of sugar to having some erythritol and stevia-like additives.
Cidrani (33:30)

Cidrani sells a pouch of concentrated liquid kombucha. The ingredients are super interesting– it doesn’t look like they’ve used green or black tea. They list peppermint, fennel, anise, caraway, thyme, hops, yarrow, cardamom, and cardamom powder, which is interesting, especially for me as a herbalist. But it’s not generally what traditional kombucha is. And apparently, it’s “fermented, reinvented.” It’s the next level!
There’s lots of diversity in this. The more products you put in something and then ferment them, the wider the range of end products of metabolism. They make water kefir as well.
We should add 250ml of water, but we could try it neat. It tastes like apple cider vinegar with flavoring in it. Also syrupy. It says no refined sugars. What does that mean? Honey? That’s what I can taste.
Once diluted, it tastes very sweet. It tastes vinegary. It has a range of funny flavors and is completely flat. And I think it’s the complete lack of any form of carbonation that maybe means I need to try with some sparkling water.
I actually quite like the taste undiluted. It’s nicer undiluted than diluted.
It tastes like shrub to me. It tastes like a vinegar. It doesn’t taste like a kombucha. I can’t get any hint of tea. I actually quite like it neat. I don’t think this tastes horrible.
So it’s got loads and loads of different things in it. None of them are billed as tea. So, if you were trying to avoid tea or caffeine for some reason, you might find that this was it. It’s worth looking at the website. Suppose you want to be able to carry things easily around. But is it kombucha?
I don’t think so. I really don’t think it’s kombucha.
Manna-K (38:00)

There’s a wave of Manna-K crossing the world. Do you know how many ones they’ve got now? They’ve got Manna-K, Manna-KN, Manna-KX, and Manna-FIR.
This is very concentrated, long-aged, and almost a vinegar used to make kombucha. And their sales patter is “long-aged, fermented kombucha base, the most efficient way to make kombucha. It enables you to brew and package in as little as 24 hours. It reduces your production time, saving your money and effort, and you use it as a 5% base”– so sort of similar to what Cidrani has done–and you add to it, you add water or flavorings. “No need for lengthy fermentation process or quality concerns.”
As we said before, brewing this stuff commercially is not straightforward, and this is one solution that some have come up with.
Caroline: As an end-user, would somebody have to tell me whether they’ve used that in their kombucha?
Jo: No, because as I told you, I could get my drain of water and say, Caroline, here is some delicious kombucha. So, this is where we have a choice. You can just keep drinking the ones that you think taste nice, but if you care about these other things, then have a little root around for information or just listen to us.
Purearth (39:38)

I’m researching powder ferments and was excited to discover Purearth: kombucha in a sachet.
I know from my research that powdering changes the constituent profile to some extent and will inactivate microbes.
Their website states, “kombucha powder is a concentrated form of kombucha offering the same probiotic and antioxidant benefits in an easily accessible and portable format.” That’s not what I’ve seen in my research on vegetables.
I’ve contacted them, and I hope they will show me their data. I’ll be super excited if they’ve done research. I want to know their process because it would be helpful in my PhD research.
However, there isn’t enough evidence to suggest that many of the microbes in your kombucha are probiotic. So perhaps it isn’t. Perhaps that’s their get-around.
While microbes can be freeze-dried, you lose potency. I’ve done the CSU count.

Jo: It’s not the same probiotic, and it’s not the same antioxidant. It contains trademarked InstaKombu powder. It also has erythritol, inulin, and bacillus coagulans. They’ve bought some InstaKombu, made by a nutraceutical powder company, which interests me because of my research. They’ve spray-dried it, and then they’re basically offering it as a meal replacement. They’re basically taking kombucha and powdering it, and then this company, Purearth, is adding stuff like tapioca soluble fiber.
The bottom line is I don’t think it tastes like kombucha. The process is different. And if they had the data on their website to show me that the microbial count was the same and the antioxidant profile was the same, then I would be like, wow. I want to get in touch with these people and find out what process they’ve used because it’s going to be super interesting.
Caroline: I don’t drink inulin because, in a study on rats, they found that if you give people loads of inulin, it’s terrible for you. If you have tiny amounts in your everyday diet, it’s kind of okay. We think, oh yeah, inulin–inulin is what gut bugs like. Therefore, we should mainline inulin, and you can actually find inulin powder. It’s a bad idea. Moderation is key in everything, and sometimes, we just try to be too clever.
Is it kombucha?
Caroline: It’s very sweet. It’s anise-y, and I don’t like it. It has to be the bottom of the pile. I think it’s really horrible. It’s so horrible I don’t want to drink it. I’m sorry, Purearth.
Conclusion (45:00)
We don’t mind what you buy. But we would like producers to be transparent with consumers so consumers get what they want and know that they’re getting what they want.
To be honest, because companies aren’t allowed to make health claims about food and beverages, not one of them actually says anything at all.
Given a choice, if I were traveling and I had a kombucha habit that I had to support, I’d probably take Cidrani and drink it neat.
Caroline: That’s what I do with my homebrew kombucha. I over-brew my kombucha, and then I dilute it with sparkling water. It gives it a lower sugar concentration because it’s more acidic. It’s too acidic to drink as it is. There will still be some residual sugar in it. I normally find around two percent. If I take a fifth of a glass, put my concentrated kombucha in, and then dilute it with four parts water, I will then reduce the sugar amount in that whole glass to about 0.4% sugar.
We mentioned Nanja Vineyards’ claim that kombucha from one of their cans would make starter liquid for home-brewed kombucha. We plan to take each of these that we’ve talked about today and set up our jars. We’re going to make some tea, add sugar, and then we’re going to backslop each of these into our jars. And our next little get-together will be about looking at what’s happened and tasting those.
Caroline: While shopping for the kombucha we discussed today, there were only two small areas of the supermarket shelf that had ambient kombucha. The first was Jonny Wilkinson’s One Living, and the other was Remedy. The rest of the shelf was dedicated to Monster Drinks and Red Bull. So the point is: Is Remedy better or worse than picking up that than a Monster Drink? I’m going to say any of these are probably better than Monster Drinks, which is basically speed in a can. Any of these is better than Coke or Pepsi, Monster Drinks, or Red Bull.
So, for all that, we might appear to be coming down hard on the ones that have taken sugar out.
Jo: We just want you to know and to be able to make choices about what you want to drink. And sometimes, it takes a bit of effort to look at websites or listen to us.
If you are interested in what we’ve discussed, ask us a question. We love questions. So please send us your questions, and we will answer them. We will see you again here before too long for another fascinating chat about the joys of our fermentation obsessions.
Disclaimer
The views and opinions expressed in this posting are solely those of the original authors. These views and opinions do not necessarily represent those of this publication.