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Kombucha Commercial Brewery Alcohol problem

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Boer

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Hi, I am a Kombucha brewer that provides 4 different flavoured Kombucha products for Food stores throughout South Africa. I have no background in actual food science so my knowledge regarding live organisms and interactions with each other is limited to the internet.

Firstly- Primary fermentations:
  • I use both Rooibos tea and Ceylon tea as base flavours for my primary ferment. The Ceylon tea usually takes about 10 days to achieve an alcohol of 0.5%. But these batches's TA (titrable acidity) is 1 g/L (very littlle). So I was wondering if anyone can help me to find a way to slow down alcohol production and fasten Total Acidity production.
  • I know that Ceylon (black) tea has much more caffeine than Rooibos so I also want to know if this may be a reason why the Ceylon often has a problem with alcohol?
My fermenting batches are 1000 liters. In A grade plastic flowbins.
My boss (who has a masters degree in Microbiology), told me we need to do an anaerobic fermentation but after my own research I wonder if this is not ideal- especially for alcohol production.

I have a lot of other questions, so I would appreciate some help :)
 

RPh_Guy

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So I was wondering if anyone can help me to find a way to slow down alcohol production and fasten Total Acidity production.
If you want more lactic acid you could buffer it, with calcium carbonate for example.

To produce more acetic acid it needs to be aerobic during/after the yeast fermentation completes.

I know that Ceylon (black) tea has much more caffeine than Rooibos so I also want to know if this may be a reason why the Ceylon often has a problem with alcohol?
To my knowledge, caffeine does not affect the microbes whatsoever.

However, polyphenols (tannins) in tea do have an anti-microbial effect, so that may possibly account for the difference between different teas. There may also be differences in nutrient content; I'm not sure.
 
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Boer

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To produce more acetic acid it needs to be aerobic during/after the yeast fermentation completes.
Hi, thank you for the reply. As I produce the Kombucha to stores I have to comply with a certain set of specifications (alcohol <0.5% and a completely natural fermentation) so it isn't possible for me to add other ingredients like calcium carbonate. Just out of curiosity, what will be the difference in taste if I somehow manage to benefit my lactic acid bacteria?

This makes sense but I have a few questions:

I read somewhere on the internet that the function of the cellulosic pellicle is to suffocate yeast. So how I understood it is that the yeast is in a state of reproduction (when it has O2) but fermentation only happens when there is no O2 available, so in other words untill the new new pellicle forms it will reproduce?

But then I read somewhere else that yeast can ferment without O2- which makes sense when you read up on how beer brewers ferment. What is the function of the pellicle then? Is it plainly a byproduct of the bacteria feeding on some of the Glucose and ethanol?

Lastly: is there any airborne yeast present in Kombucha that may contaminate my filling area? As I have struggled with bottles ferment after Filtration, Cooling and Carbonation. Keep in mind that I use a .45 micron filter so there should be no yeast present in my blend.
 

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it isn't possible for me to add other ingredients like calcium carbonate.
If you want increased lactic acid you need to find a way to increase the buffering capacity of your beverage that complies with regulations.

what will be the difference in taste if I somehow manage to benefit my lactic acid bacteria?
It will taste more sour.

I read somewhere on the internet that the function of the cellulosic pellicle is to suffocate yeast.
Exactly why microbes form pellicles isn't well understood. While some microbes may have a competitive advantage by excluding oxygen from the other microbes, other microbes simply like to be at the surface in order to access oxygen.
Many yeasts form pellicles, so a pellicle's function isn't to "suffocate yeast" generally speaking.

So how I understood it is that the yeast is in a state of reproduction (when it has O2) but fermentation only happens when there is no O2 available, so in other words untill the new new pellicle forms it will reproduce?
Yeast are very capable of depleting oxygen from the fermentation medium without the presence of a pellicle. Furthermore, yeast certainly can ferment in the presence of oxygen, although oxygen does increase cell growth.

But then I read somewhere else that yeast can ferment without O2- which makes sense when you read up on how beer brewers ferment.
Yeast fermentation is an anaerobic process.

is there any airborne yeast present in Kombucha that may contaminate my filling area? As I have struggled with bottles ferment after Filtration, Cooling and Carbonation. Keep in mind that I use a .45 micron filter so there should be no yeast present in my blend.
Airborne microbes are always present everywhere. You should consider pasteurization, assuming you can't add preservatives.
Make sure your cleaning and sanitation procedures are thorough in your bottling line post-filtering, and that your bottles and closures are sanitized.
 
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Boer

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It will taste more sour.
Thought that the sour taste of Kombucha was due to the Acetic Acid Bacteria, or is it both? I do Water Kefir ferments as well to make fermented soda's and the Kefir has Lactic Acid bacteria but the liquid after the primary ferment is just sweet not sour at all!
 

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It's my understanding that the microbes responsible for the acids are more active at higher temps. When my primary's exceed 78*F it's done much faster and is quite a bit tarter. The Big Book of Kombucha, which I recommend, states that you can go as high as 86*. When I did that the end product was very tart and done in a very short time (was awhile ago) and I didn't think is very tasty. Also I have a water source high in calcium, maybe you can find one that complies.
 
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How would you describe the kombucha fermentation process? In as much detail as possible.
If you want increased lactic acid you need to find a way to increase the buffering capacity of your beverage that complies with regulations.


It will taste more sour.


Exactly why microbes form pellicles isn't well understood. While some microbes may have a competitive advantage by excluding oxygen from the other microbes, other microbes simply like to be at the surface in order to access oxygen.
Many yeasts form pellicles, so a pellicle's function isn't to "suffocate yeast" generally speaking.


Yeast are very capable of depleting oxygen from the fermentation medium without the presence of a pellicle. Furthermore, yeast certainly can ferment in the presence of oxygen, although oxygen does increase cell growth.


Yeast fermentation is an anaerobic process.


Airborne microbes are always present everywhere. You should consider pasteurization, assuming you can't add preservatives.
Make sure your cleaning and sanitation procedures are thorough in your bottling line post-filtering, and that your bottles and closures are sanitized.
 

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Thought that the sour taste of Kombucha was due to the Acetic Acid Bacteria, or is it both?
Both, to some extent. The acids taste differently. The majority of sourness/tang is from the acetic acid.

the liquid after the primary ferment is just sweet not sour at all!
Sweetness means that fermentation is in fact not complete, or it has stalled (e.g. due to lack of nutrients). Sweetness also overpowers acidic taste, so you wouldn't necessarily be able to taste a low level of acidity if it is sweet.

It's my understanding that the microbes responsible for the acids are more active at higher temps.
This is certainly true.

How would you describe the kombucha fermentation process? In as much detail as possible.
Here's an overview. I can answer specific questions but I'm not going to write a novel here.

Lactic acid bacteria make lactic acid from sugar.
Yeast make alcohol and CO2 from sugar (anaerobic)
Acetic acid bacteria make acetic acid from alcohol (aerobic).

Cheers
 

ahnavbilauvaq

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Hello, fellow kombucha brewer here. From what I learned, kombucha's main processes is alcohol and acetic acid fermentation. Yeasts produce alcohol while acetic acid bacteria (AAB) produces acetic acid. I never heard myself that lactic acid bacteria as a main process in Kombucha, but there may be a negligible amount of LAB.

AAB fermentation occurs aerobically (with O2), from what I read the bacteria produces AA + cellulose pellicles (the SCOBY) from the alcohol. That's why new SCOBY forms on the surface of the wort while fermenting. Yeasts fermentation on the other hand occurs anaerobically.

Tea (with its variants) provides kombucha with nutrients and anti-microbial properties (that helps certain microbes to thrive while killing others). Changing tea also means changing nutrients and the microbes.

To answer your question: you can lower the alcohol level by lowering the amount of yeasts present (I don't know how to) and allowing more aerobic fermentation to occur (by fermenting in larger vessel so it has more surface area). You can maybe also do it by oxygenating the wort as in theory it will allow more aerobic fermentation to occur (tho I never tried it that way, pls take this last advice with a grain of salt).

I found that this journal helps tremendously to at least learn a little about kombucha: Error - Cookies Turned Off . Good luck!
 

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To answer your question: you can lower the alcohol level by lowering the amount of yeasts present (I don't know how to) and allowing more aerobic fermentation to occur (by fermenting in larger vessel so it has more surface area). You can maybe also do it by oxygenating the wort as in theory it will allow more aerobic fermentation to occur (tho I never tried it that way, pls take this last advice with a grain of salt).
There's really no need to inhibit the yeast in any manner (even if you could). Alcohol level is easily controlled by adjusting the amount of sugar.

Using a larger vessel actually lowers the amount of surface area relative to the volume. Square–cube law - Wikipedia

Oxygenating the tea prior to fermentation will speed up the yeast fermentation. Oxygenating the kombucha after the yeast fermentation will speed up the acetic fermentation.
 

ahnavbilauvaq

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There's really no need to inhibit the yeast in any manner (even if you could). Alcohol level is easily controlled by adjusting the amount of sugar.

Using a larger vessel actually lowers the amount of surface area relative to the volume. Square–cube law - Wikipedia

Oxygenating the tea prior to fermentation will speed up the yeast fermentation. Oxygenating the kombucha after the yeast fermentation will speed up the acetic fermentation.
What I meant by larger vessel was a vessel with bigger surface area with the same volume. What is the perfect term to describe it? Broader? Sorry I don't speak English as first language. What I meant was kinda like "you're better off using 1L jar with wide mouth rather than 1L bottle with narrow mouth".

I guess adjusting alcohol level by adjusting the amount of sugar works with alcoholic fermentation right? In Kombucha, we're not only adjusting the sugar but also the pH. My suggestion to inhibit the yeast is to adjust the speed of alcohol fermentation by comparison to AAB.

Oxygenation in kombucha wort is a thing I never tried, although my understanding is AAB thrives in rich-oxygen situation. I'm not really well-versed in alcohol making but from what I know yeasts ferment in anaerobic condition, am I wrong?
 
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What I meant by larger vessel was a vessel with bigger surface area with the same volume. What is the perfect term to describe it? Broader? Sorry I don't speak English as first language. What I meant was kinda like "you're better off using 1L jar with wide mouth rather than 1L bottle with narrow mouth".

I guess adjusting alcohol level by adjusting the amount of sugar works with alcoholic fermentation right? In Kombucha, we're not only adjusting the sugar but also the pH. My suggestion to inhibit the yeast is to adjust the speed of alcohol fermentation by comparison to AAB.

Oxygenation in kombucha wort is a thing I never tried, although my understanding is AAB thrives in rich-oxygen situation. I'm not really well-versed in alcohol making but from what I know yeasts ferment in anaerobic condition, am I wrong?
Hi, sorry for the late reply.

I have 2 questions:

What effect does the sugar have on the tea's pH- assuming this is before the starter inoculation?

What is the most effective way to speed up the alcohol fermentation? Temperature control? So, should I should increase my brewing room temp from 23 C to about 30C?
 

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What effect does the sugar have on the tea's pH- assuming this is before the starter inoculation?
None.
What is the most effective way to speed up the alcohol fermentation?
Keeping it warm, providing yeast nutrition, providing adequate aeration, pitching a healthy culture.

30C will result in faster fermentation, but it may change the flavor produced by the microbes (for better or worse). You may want to be cautious.
 
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Boer

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Many yeasts form pellicles, so a pellicle's function isn't to "suffocate yeast" generally speaking.
Is the other pellicles found in beer ferments also a cellulosic pellicle or is that unique to Kombucha? So do the yeast and bacteria work together then to form the new pellicle?
 

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Is the other pellicles found in beer ferments also a cellulosic pellicle or is that unique to Kombucha? So do the yeast and bacteria work together then to form the new pellicle?
Generally other pellicles produced by yeast are much less thick that what's normally found on kombucha. Their composition varies.
 
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pitching a healthy culture.
I take it you are referring to the culture as only the liquid from previous batches, or with the pellicle as well? How would you know this liquid is healthy?
 

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The sediment at the bottom will be mostly yeast, so that's probably a large portion of the yeast biomass.
There are many factors that can affect yeast health. Generally a recently grown culture with access to quality nutrients and oxygen is the most healthy. On the other hand, yeast that's been sitting for days-weeks-months in a warm acidic nutrient-depleted environment is less healthy.
 
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Yes, I know. So the ethanol will form a curve like the graph shows (possible mistake from the source?). But the ABV wil not fluctuate and instead keep climbing?
 
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How can the ABV (alcohol percentage) decrease as the fermentation goes on longer?
 
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Ok so in other words if my ABV do not decrease, is there a problem with my Acetic Acid bacteria then? If that is the case, is there anything I can do to "treat" my bacteria? I know that previously in the post it was mentioned I should oxyginate the kombucha, but how will this work is practice? Do I need to disperse O2 bubbles through the whole batch from the bottom?
 

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If that is the case, is there anything I can do to "treat" my bacteria? I know that previously in the post it was mentioned I should oxyginate the kombucha, but how will this work is practice? Do I need to disperse O2 bubbles through the whole batch from the bottom?
Warm it up after the yeast finish. Bacteria like it warm!

One option to continually aerate is to use an air pump like for an aquarium. Use an inline HEPA filter to keep out airborne contaminants. Otherwise you can agitate it, manually or otherwise. Look at modern commercial vinegar production. Kombucha is basically a vinegar made from tea.
 
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Warm it up after the yeast finish. Bacteria like it warm!

One option to continually aerate is to use an air pump like for an aquarium. Use an inline HEPA filter to keep out airborne contaminants. Otherwise you can agitate it, manually or otherwise. Look at modern commercial vinegar production. Kombucha is basically a vinegar made from tea.
Thank you, vinegar production explained so much to me now? So one of the specifiactions my kombucha need to comply with, is a Total Acid of 3g/L. So in other words as I understand it: if the TA is still low after 3 weeks fermentation the ABV will be high (>0.5%) as the Bacteria struggles to convert the ethanol into Acetic Acid?

One of the sources I read now, says that vinegar has a minimum of 4% volume Acetic Acid. Does this mean that, since Vinegar is a process like Kombucha, if the Acidity is lower than 4% there is more alcohol present?
 

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So one of the specifiactions my kombucha need to comply with, is a Total Acid of 3g/L. So in other words as I understand it: if the TA is still low after 3 weeks fermentation the ABV will be high (>0.5%) as the Bacteria struggles to convert the ethanol into Acetic Acid?
3g/L of what? TA is expressed in terms of a specific acid.

Yes, if alcohol is present in significant amounts, then the acetic fermentation is not complete.

One of the sources I read now, says that vinegar has a minimum of 4% volume Acetic Acid. Does this mean that, since Vinegar is a process like Kombucha, if the Acidity is lower than 4% there is more alcohol present?
Not necessarily. A low amount of sugar would lead to a low amount of ethanol, which will lead to a low amount of acetic acid.
 
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3g/L of what? TA is expressed in terms of a specific acid.
What is the difference between Titratable acidity and total Acidity? Is Tit. acidity also specific to one type of acid?
 

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Is Tit. acidity also specific to one type of acid?
I was referring to TA as titratable acidity, since that's what we measure.
AFAIK total acidity would be difficult or impossible to measure without advanced tools (GC/MS or HPLC).
However, the values should be close.
 

ahnavbilauvaq

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Hi, sorry for the late reply.

I have 2 questions:

What effect does the sugar have on the tea's pH- assuming this is before the starter inoculation?

What is the most effective way to speed up the alcohol fermentation? Temperature control? So, should I should increase my brewing room temp from 23 C to about 30C?
Hello, sorry for the late reply. The starting pH from the tea doesn't really matter much before the innoculation. Though, for me below pH 4 is best (to ensure fermentation success).

I've been busy researching the alcohol content problem (it's also a problem in my brewery), so here's some things I've found helped me:

1. Agitating and oxygenating the fermentation (by stirring or oxygen pump) helps to lessen the alcohol fermentation and boost the acetic acid fermentation. Some big kombucha brewery actually do this to ensure less fermentation. This also cancels the dimension problem of kombucha fermentation vessel.
2. Cleaning the batch every fermentation helps to lessen alcohol fermentation, as yeasts will pile up at the bottom of the fermenter. This also means you can't use SCOBY continuously.
3. If you can force-carb (or don't need carbonation in your product), you can use 1 micron filter to filter out the yeasts. Bacteria is less than 1 micron in size and yeasts is more than 1 micron.

My cheap way to do it is to stir vigorously the fermentation every 1-2 days (I'm still using 20L jars, . This helps to degas and oxygenate it, thus lowering the alcohol fermentation and yeasts reproduction. SCOBY won't form, though, but for me it makes it easier to clean up each batch.
 
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