Accelerated Kombucha Success!

[Owly055]

In spite of everybody's lack of interest in my sugar reduction program, you SHOULD read this. While you may not be interested in Xylitol as a percentage of the sweetener, the success at accelerating the fermentation using invert sugar and aeration is nothing short of spectacular! I have a reputation here for doing off the wall experiments, and there seems to be little interest in many of them. I record them here ... both successes and failures so there is a permanent record for those few other true experimenters to use. I seem to be very much in the minority on HBT. Rocking the boat is not popular it would seem ;-)

We think of Kombucha as being a low sugar health drink.... It is not. The residual sugar is actually quite high, about 60% of what you put into it. About 30 calories per cup for store bought. That is the equivalent of drinking almost two teaspoons of sugar per cup. We can do better! It is also hard on your teeth. The acidity eats at the enamel on your teeth, and the sugar promotes dental decay. It's better than coke at about 100 calories per cup though. I'm looking at getting it down to about 5 or less calories per cup.

. In my quest to reduce residual sugar in kombcha by substituting 50% Xylitol.... a project that was greeted with a "resounding silence", I decided to do a new brew starting with GT's Original Plain. I began it with a quart of GTs and a quart of sweet tea....... sugar sweetened, giving me a gallon total. I just doubled it up to a gallon a few days ago. 5 DAYS TO MATURITY from 50%.

I accomplished this by inverting the sugar using citric acid, and cooking it down to an invert syrup, which I then diluted and brewed tea with. I then aerated the entire thing... GTs and sweet tea using an immersion blender to whip it to a froth. At the end of 5 days I had a lovely scoby.... not just as thin film, and it was nicely sour. I did aerate it a second time on day 2 That is 28% faster than normal!

I doubled it again the other day, using invert sugar and heavily aerating.... in my Ninja. I now have a gallon going, and will aerate about 1.5 qts per day drawing it out of the spigot and returning it to the jug... dumping it right over the scoby as I always do.

When this matures, I'll split it, half to a 2 gallon jug which will contain normal booch, and the one gallon jug will be recharged with 50/50 invert sugar and Xylitol. If this works, I will be left with booch that has only 10% remaining sugar... approximately..... after a few cycles.

H.W.

 

[Andrew Hodgson]

Sounds like a cool experiment, and agreed that most commercial booch is chock-full of sugar, probably because unfiltered "uncut" booch really isn't too palatable to most consumers, which is why I make my own as I like it raw and very sour. +1 for trying something new.

 

[Owly055]

Sounds like a cool experiment, and agreed that most commercial booch is chock-full of sugar, probably because unfiltered "uncut" booch really isn't too palatable to most consumers, which is why I make my own as I like it raw and very sour. +1 for trying something new.

Don't be fooled into thinking that your sugar content is far lower than commercial booch... just because you like it sour.... I do too. You can assume that you have somewhere between 50 and 60% residual sugar anyway.
I'm thinking that with the xylitol I can get that down to about 10% of the sugar I typically have.... The whole idea of the accelerated brew is to not only get a new batch started rapidly, but to use the same technique to facilitate the fermentation of the smaller amount of sugar I have.

The object of course is not speed, but minimal residual sugar....... maximum attenuation..... To accomplish this, perhaps fermentation should be separate with a high attenuation yeast. This would allow attenuation to be measured. A "normal" kombucha culture could be kept on the side to innoculate the fermented sugar water, at which point the xylitol would be added. From there the process would be subjective based on flavor.

Looking at Brewer's friend, one gallon of brew with the only fermentable being 1/2 C sugar (3.2 oz) would yield 1.21% ABV. We really don't want either sugar or alcohol. As far as I can find out, the calories per cup of vinegar are about half that of beer, and both start out at about the same ABV.

It is known that vinegar will reduce the glycemic index of a meal by about 30%

Temperature control and aeration, and high fermentability would seem to be the key. Vinegar production, which is much the same as kombucha production, has been done using surfaces exposed to air to accelerate it. Sometimes a pile of beechwood chips in a container and a circulating pump trickling the liquid over the chips.

I propose the following. Ferment a brew at about 3.6 percent using invert sugar and tea using a beer yeast.... Belle Saison would be my choice. Dilute to triple volume with water... or more tea, sweeten with xylitol at the rate of 1/2 cup per gallon, and innoculate with kombucha from a "mother culture" kept for just that purpose. Aerate daily until nicely soured. Actually a small amount of sugar might be a good thing to feed the beasties to achieve a good booch with an array of microbes.

H.W.

 

[Andrew Hodgson]

My route for controlling the sugar is much simpler, I use an extremely small amount of it, I have done gallon booch ferments with 2 tbsp and less, seemingly with no real consequences to the product or the SCOBY or seemingly anything, of course I have done ferments with 1/2 cup to 3/4 cup as well, which I would not assume have little sugar as the input is quite a bit of sugar for the volume.

Your experiments are interesting to me from an academic perspective but if I can make a 1 gallon batch with 2 tbsp of sugar and as you say 50%-60% is left, then I would be comfortable with with I would call an insignificant amount of residual sugar in the batch (and my above referred to confidence that my homebrewed booch has much less sugar per oz than the store-bought). I respect the amount of time and effort you are putting into the reduction of the residual sugars, I just find that for me greatly reducing the input leaves me with a product I still enjoy, I like to KISS for booch since it is really a side project compared to brewing beer for me.

I also use the opposite of a speedy approach, my batches will sit for 2-3 weeks sometimes or until I run out of the current batch. Sometimes if we go through it fast I might turn it in one week. I am interested in the idea of a high attenutation beer yeast in the booch process, I have been kicking around the idea of a mixed fermentation using a SCOBY and as you mention a saison yeast or the like. Sour, highly attenuated saison-booch? Seems like it could be a worthwhile venture to me.

 

[Owly055]

My route for controlling the sugar is much simpler, I use an extremely small amount of it, I have done gallon booch ferments with 2 tbsp and less, seemingly with no real consequences to the product or the SCOBY or seemingly anything, of course I have done ferments with 1/2 cup to 3/4 cup as well, which I would not assume have little sugar as the input is quite a bit of sugar for the volume.

Your experiments are interesting to me from an academic perspective but if I can make a 1 gallon batch with 2 tbsp of sugar and as you say 50%-60% is left, then I would be comfortable with with I would call an insignificant amount of residual sugar in the batch (and my above referred to confidence that my homebrewed booch has much less sugar per oz than the store-bought). I respect the amount of time and effort you are putting into the reduction of the residual sugars, I just find that for me greatly reducing the input leaves me with a product I still enjoy, I like to KISS for booch since it is really a side project compared to brewing beer for me.

I also use the opposite of a speedy approach, my batches will sit for 2-3 weeks sometimes or until I run out of the current batch. Sometimes if we go through it fast I might turn it in one week. I am interested in the idea of a high attenutation beer yeast in the booch process, I have been kicking around the idea of a mixed fermentation using a SCOBY and as you mention a saison yeast or the like. Sour, highly attenuated saison-booch? Seems like it could be a worthwhile venture to me.

It is worth mentioning that my kombucha made this way.... and I've only tasted samples.... has a lovely delicate fruity flavor.... I'm thinking it's the citric acid. It's a flavor that is nice enough to forego the typical addition of fruit flavor, etc. I keg mine, and often throw in some pure blackberry powder or sour cherry concentrate or some such.

I like your idea of greatly reduced sugar content.... Many people put twice the sugar per gallon in as I do. I've just always used one cup and 4 tea bags.... perhaps I'll try less sugar at the outset... something I have not done. Cutting it in half would yield 2.5T sugar and 2.5T Xylitol. I think for the moment I'll do one thing at a time... that is to say reduce sugar to 1/2C and 1/2C Xylitol..... see what I get and go from there......

Doing pre-fermentation may NOT be a good idea, as there are multiple microbes in kombucha, and many of them probably would not survive without some sugar. Perhaps keeping a mother culture (normal), and fermenting for a day or two, then pitching kombucha from the mother culture...........

H.W.

 

[hottpeper13]

I think that the micro feed on alcohol,so it might be a good idea to preferment. I would just use a low attenuater and forgo the added sugar.

 

[Owly055]

I think that the micro feed on alcohol,so it might be a good idea to preferment. I would just use a low attenuater and forgo the added sugar.

My concern is the array of microbes involved....If we were just looking at yeast and acetobacter, it would make a great deal of sense to change up the yeast and pre-ferment, but kombucha is not vinegar. The balance of the brew might be substantially changed.

Here (below) is a list of the primary organisms from a web site... Undoubtedly this composition varies. It is worth noting that the mistique of the "mushroom" /"scoby"/"mother" and it's role in kombucha is deeply embedded in kombucha culture. It is widely and erroneously believed to be a living organism, that actually produces kombucha. None of that is true. It is actually a pellicle, a byproduct of acetobacter fermentation consisting largely of microcellulose, and neither is it "alive", nor does it make kombucha. The microbes in the brew including yeasts and bacteria do the job. There are at least 3 acids produced by various microbes that give kombucha it's distinctly complex sour character. Throwing off the balance of the bacterial culture will effect this flavor development, and should be a concern. Creating a monoculture bacterial community.... or rather one yeast and one bacteria, or creating conditions to favor such development would be a bad thing IMHO. It would reduce the biological complexity, and simplify the flavor profile.
I'm even a bit concerned by my accelerated brewing with invert sugar and aeration.... it might favor one yeast over another, and likewise acetobacter over say gluconacetobacter for example. If the environment created by one microbe suppresses the development of another, that will change the character of the brew.... perhaps not for the better. Clearly the acid producing bacteria are critical. The lowered PH (acidic environment) they create suppresses growth of pathogens and mold, and my methods of aeration and use of invert sugar both should contribute to this... though what else results???

H.W.

Probiotics: Bacteria & Yeast
The specific bacteria and yeast strains in the kombucha are what make it act the way it does, and what produce the fizz and flavor of kombucha. Not all kombucha cultures will contain the exact same strains, but these are some that have been recorded in studies:

• Acetobacter [2] is an aerobic (requiring oxygen) bacteria strain that produces acetic acid and gluconic acid. It is always found in kombucha. Acetobacter strains also build the scoby mushroom. Acetobacter xylinoides and acetobacter ketogenum are two strains that you might find in kombucha.
• Saccharomyces [2] includes a number of yeast strains that produce alcohol and are the most common types of yeast found in kombucha. They can be aerobic or anaerobic (requires an oxygen-free environment). They include Saccharomycodes ludwigii, Saccharomycodes apiculatus, Schizosaccharomyces pombe, Zygosaccharomyes, and Saccharomyces cerevisiae.
• Brettanomyces [2] is another type of yeast strain, either aerobic or anaerobic, that are commonly found in kombucha and produce alcohol or acetic acid.
• Lactobacillus [2]: A type of aerobic bacteria that is sometimes, but not always, found in kombucha. It produces lactic acid and slime.
• Pediococcus [2]: These anaerobic bacteria produce lactic acid and slime. They are sometimes, but not always, found in kombucha.
• Gluconacetobacter kombuchae [2] is an anaerobic bacteria that is unique to kombucha. It feeds on nitrogen that is found in tea and produces acetic acid and gluconic acid, as well as building the scoby.
• Zygosaccharomyces kombuchaensis [3] is a yeast strain that is unique to kombucha. It produces alcohol and carbonation as well as contributing to the mushroom body.

 

[Owly055]

TRAIN WRECK !!!

I reached the point of adding Xylitol at 50% to my brew....jumped ahead and did this when doubling to 2 gallons..... Unfortunately it was not until after this, that I discovered that Xylitol has anti fungal properties .... Naturally Murphy dictated that I would not run across this bit of info until after I had done this. I inverted my sugar, dissolved the Xylitol in the sweet tea, and heavily aerated. This did not kill the kombucha, but put the yeast into low gear..... It was a failure, though I'm still fermenting it to see where it goes.

I started a new accelerated brew using GTs Original Plain last night.... 3 pints to a gallon of sweet tea... though with the sugar reduced from my one cup per gallon standard. I will continue aerating this once or twice a day, and encourage it to go far beyond the normal sourness, to the level of undrinkability, then temper it with Xylitol when it goes into the keg.

My accelerated method was inspired by the way vinegar is made, as well as my years of home brewing. Both the aeration and the use of invert sugar should stimulate both yeast and acetobacter production. The use of my blender for aeration is a bit inefficient, but it seems to work. Maintaining a fairly high temperature of around 90F should also help both, though perhaps the yeast will produce "off flavors"... but these will be submerged in the overall flavor profile. It isn't beer after all. Below are two methods used for vinegar production.
It is also worth considering that the acetic and gluconic and lactic acids probably all inhibit yeast production, and if the various microbes are converting the alcohol as quickly as it's being produced, this might actually work against the yeast breaking down the sugars. This points obviously to reducing sugar in the feed stock (sweet tea). Less sugar means less alcohol means slower acid production, allowing the yeast to do it's job more completely.... or that's how the theory (mine) goes.

H.W.

The submerged fermentation
method

1. The submerged fermentation method is commonly used in the production of wine vinegars. Production plants are filled with large stainless steel tanks called acetators. The acetators are fitted with centrifugal pumps in the bottom that pump air bubbles into the tank in much the same way that an aquarium pump does.
2. As the pump stirs the alcohol, acetozym nutrients are piped into the tank. The nutrients spur the growth of acetobacters on the oxygen bubbles. A heater in the tank keeps the temperature between 80 and 100°F (26-38°C).
3. Within a matter of hours, the alcohol product has been converted into vinegar. The vinegar is piped from the acetators to a plate-and-frame filtering machine. The stainless steel plates press the alcohol through paper filters to remove any sediment, usually about 3% of the total product. The sediment is flushed into a drain while the filtered vinegar moves to the dilution station.

The generator method

1. Distilled and industrial vinegars are often produced via the generator method. Tall oak vats are filled with vinegar-moistened beechwood shavings, charcoal, or grape pulp. The alcohol product is poured into the top of the vat and slowly drips down through the fillings.
2. Oxygen is allowed into the vats in two ways. One is through bungholes that have been punched into the sides of the vats. The second is through the perforated bottoms of the vats. An air compressor blows air through the holes.
3. When the alcohol product reaches the bottom of the vat, usually within in a span of several days to several weeks, it has converted to vinegar. It is poured off from the bottom of the vat into storage tanks. The vinegar produced in this method has a very high acetic acid content, often as high as 14%, and must be diluted with water to bring its acetic acid content to a range of 5-6%.
4. To produce distilled vinegar, the diluted liquid is poured into a boiler and
   
   The production of vinegar.
   brought to its boiling point. A vapor rises from the liquid and is collected in a condenser. It then cools and becomes liquid again. This liquid is then bottled as distilled vinegar.

 

[RPh_Guy]

I have some thoughts...

Oxygenation has long been known to help the yeast grow, and decreases lag time, increasing fermentation speed.
Oxygen is of course also required for acetic acid formation. Nothing new here.
An oxygen stone and oxygen tank are extremely efficient. You can also use an aquarium pump setup or a drill-powered stirring tool to aerate. Get a stir plate and a 5L flask constantly stirred if you really want one gallon done quick

The need for invert sugar is questionable. Yeast have an enzyme called invertase and are perfectly capable of breaking the disaccharide sugar into its components. There seems to be some debate on this topic.

There's one huge point you missed:
Add yeast nutrient. This will ensure 100% attenuation AND increase fermentation speed.

Since xylitol is unfermentable, just add it after fermentation when packaging if you want the added sweetness. No harm done.

I agree with Andrew. If you want less sugar/calories, just use less sugar. It's that simple.

You can assume that you have somewhere between 50 and 60% residual sugar

On what data are you basing this?
I'm gonna go out on a limb and say you're incorrect.
You can't simply use s.g. to determine attenuation because the acids are major fermentation products and are contributing to the density, among other things.

perhaps fermentation should be separate with a high attenuation yeast.

If the yeast in your SCOBY aren't up to the task of hitting 2% alcohol (which seems very unlikely), you can add literally any commercial yeast to your SCOBY -- Sacc, Brett, bread yeast, etc. Any will easily ferment to up 8% ABV.
Listed "attenuation" is meaningless with simple sugar, so a "high attenuation" yeast is not needed.
EC-1118 or Red Star Premier Cuvee would smash through that sugar like a wrecking ball, reaching 100% attenuation in 1-2 days or less.
Will this change the flavor? Probably. Try it and see whether you like it.

Cheers

 

[Owly055]

I have some thoughts...

Oxygenation has long been known to help the yeast grow, and decreases lag time, increasing fermentation speed.
Oxygen is of course also required for acetic acid formation. Nothing new here.
An oxygen stone and oxygen tank are extremely efficient. You can also use an aquarium pump setup or a drill-powered stirring tool to aerate. Get a stir plate and a 5L flask constantly stirred if you really want one gallon done quick

The need for invert sugar is questionable. Yeast have an enzyme called invertase and are perfectly capable of breaking the disaccharide sugar into its components. There seems to be some debate on this topic.

There's one huge point you missed:
Add yeast nutrient. This will ensure 100% attenuation AND increase fermentation speed.

Since xylitol is unfermentable, just add it after fermentation when packaging if you want the added sweetness. No harm done.

I agree with Andrew. If you want less sugar/calories, just use less sugar. It's that simple.


On what data are you basing this?
I'm gonna go out on a limb and say you're incorrect.
You can't simply use s.g. to determine attenuation because the acids are major fermentation products and are contributing to the density, among other things.


If the yeast in your SCOBY aren't up to the task of hitting 2% alcohol (which seems very unlikely), you can add literally any commercial yeast to your SCOBY -- Sacc, Brett, bread yeast, etc. Any will easily ferment to up 8% ABV.
Listed "attenuation" is meaningless with simple sugar, so a "high attenuation" yeast is not needed.
EC-1118 or Red Star Premier Cuvee would smash through that sugar like a wrecking ball, reaching 100% attenuation in 1-2 days or less.
Will this change the flavor? Probably. Try it and see whether you like it.

Cheers

None of this is news to me.... I don't happen to have yeast nutrient.... which is why I didn't use any. I do believe inverting helps. I have an aeration stone, but no aquarium pump... which is why I'm aerating the way I am.... My LHBS closed. I gave away my stir plate and flask when I quit brewing. My conclusion of 60% residual sugar is based on published calories for commercial kombucha.... not on using a hydrometer, as I am well aware of the issues caused by production of acetic acid. There is far more sugar in kombucha than we like to think... otherwise it would be like drinking vinegar. The sugar is needed to temper the acidity. Actually salt would also temper the acidity, and add a richer more complex taste. Try salt on grapefruit.... many folks use sugar... I use salt because it takes the sharp edge off and brings out a fuller flavor, which sugar does not. I would take issue with the idea that any yeast will rip through the sugar... or that this is desirable. First of all the PH will suppress yeast growth to varying degrees, dependent on the yeast. The yeasts in kombucha are adapted to the job.. note that there is even a brett there. Second I'm concerned that some of the other microbes may utilize the sugar to some extent, so going rapidly to alcohol may be detrimental to their metabolism.
The microbial community in kombucha is complex, and probably goes farther than what I copied above in most home brew cases. Inevitably there is a balance..... or more accurately a flux, as in nature in general. Any changes such as aeration or temp changes, could easily alter that balance/flux for better or worse. As with many things, slower may in fact be better....

H.W.

 

[RPh_Guy]

The commercial manufacturers intentionally interrupt fermentation to leave residual sugar. Therefore you can't extrapolate residual sugar in commercial kombucha to residual sugar in homebrew kombucha.
Same thing for commercial cider. Sooo many are sweet, unlike fully fermented home cider.

The pH in kombucha will not significantly suppress the ability of commercial yeast to ferment. Wine and sour beer easily and quickly ferment to completion.

I'm not meaning to be disagreeable, but you may be trying to overcome a problem that doesn't exist.
You can test my theory: Allow your kombucha to fully ferment as normal for your process. Take a gravity reading. Correctly rehydrate and pitch a packet of Premier Cuvee. Take a gravity 3 days later.
If the gravity is the same, then your SCOBY had already fermented it dry (no residual sugar).

Cheers

 

[Owly055]

The commercial manufacturers intentionally interrupt fermentation to leave residual sugar. Therefore you can't extrapolate residual sugar in commercial kombucha to residual sugar in homebrew kombucha.
Same thing for commercial cider. Sooo many are sweet, unlike fully fermented home cider.

The pH in kombucha will not significantly suppress the ability of commercial yeast to ferment. Wine and sour beer easily and quickly ferment to completion.

I'm not meaning to be disagreeable, but you may be trying to overcome a problem that doesn't exist.
You can test my theory: Allow your kombucha to fully ferment as normal for your process. Take a gravity reading. Correctly rehydrate and pitch a packet of Premier Cuvee. Take a gravity 3 days later.
If the gravity is the same, then your SCOBY had already fermented it dry (no residual sugar).

Cheers

The fact remains that kombucha must contain significant residual sugar to offset the sourness created by the acids...... Otherwise it would be like drinking lemon juice or vinegar. Gravity readings are questionable at best when alcohol is being converted to vinegar, but a relative gravity over a few days may be telling.

I don't have any yeast on hand as I quit brewing, and my LHBS in Bozeman closed down (U-Brew in Planet Natural). Anybody know where to get supplies now? I hope to get down to Billings in the next week or so, and will pick up some yeast. I have a couple 2 gallon brews of kombucha going and another 1 gallon jar that I will use for experiments.

Interestingly the Xylitol did not stop or slow the fermentation as I expected, but it was a fairly small percentage. I just drew off about 3/4 of the jar that had the xylitol into a keg (1.75 gallon keg), and refilled with sweet tea at a rate of about 1/2 cup of invert sugar per gallon, and aerated the bejesus out of it. I expect to have an aeration "stone" in it (brewing grade sintered stainless steel), shortly. I have an aquarium pump coming saturday.

I will be pre-fermenting in my gallon jug with beer yeast and invert sugar, then pitching kombucha at about 25% booch to 75% fermented liquor as an initial experiment. I'll ferment the original liquor out totally, but add a couple of tablespoons of table sugar with the booch. I'll also get some yeast nutrient when I hit the LHBS. Just as well try things...........

Note that I've been using freeze dried blackberry powder for flavoring lately, but as I am planning to buy a high grade masticating juicer (Omega NC900), this should open up some interesting options. I may even use some veggie juices initially in place of tea.... I'm no fan of tea, and use it minimally.

H.W.

 

[RPh_Guy]

The fact remains that kombucha must contain significant residual sugar to offset the sourness created by the acids.

Personal preference. Some of us rather enjoy sour taste

You could aim for less sourness by lowering the temperature, lowering oxygen exposure, and lowering the sugar. Also consider using water with low alkalinity such as RO or distilled, or perhaps a mix of tap and RO. This should reduce the lactic acid.

I use MoreBeer for supplies. Good selection, service, shipping, and prices.

Regards

 

[Owly055]

Personal preference. Some of us rather enjoy sour taste

You could aim for less sourness by lowering the temperature, lowering oxygen exposure, and lowering the sugar. Also consider using water with low alkalinity such as RO or distilled, or perhaps a mix of tap and RO. This should reduce the lactic acid.

I use MoreBeer for supplies. Good selection, service, shipping, and prices.

Regards

I tend to brew a more sour kombucha than most folks..... I like sour also. The reality is that kombucha normally will continue to sour well beyond drinkability if you allow it........ do you like drinking straight vinegar? Reducing the sugar up front obviously is going to reduce the ultimate sourness.