Talk to me about Kombucha

[mredge73]

My mother's inner hippy came out at some point and she bought a $200 kombucha kit from KombuchaKamp last year. She had never had kombucha nor has she ever a sustained a hobby very long. She decided that she didn't like how it taste so I have been gifted an old SCOBY and a bunch of other stuff that she never used.

I have never tried the stuff either but I have an addiction to fermentation and love tea.
I have been doing a lot of reading lately on this but much of what I read is littered in hippy nonsense with incorrect assumptions and poor advice based on my knowledge of fermentation and vinegar making. I have a few questions that I haven't run across the answers for yet.

Is there a "style guide" for kombucha?

Why a SCOBY; why wouldn't you conduct these two different fermentations separably to better control the variables and improve consistency?

WLP600 looks to be the only available SCOBY created in a lab by actual technicians. Is this beverage too new and community too sparse that variation hasn't occurred yet? You cannot use the same yeast strain to make a Bud Light and then a Trappist beer; why would you use the same SCOBY to ferment an English breakfast tea and then a green tea?

There are no nutrient additions mentioned so what is in the tea that the yeast are using for reproduction?

What keeps the yeast from falling to the bottom like in a beer/wine fermentation (yeast attenuation)?

Why must I add "starter fluid" to a new batch? Is it because of yeast attenuation?

Acetobacter looks to be the dominate bacteria turning most of the alcohol produced to vinegar; what roles do the other bacteria strains carry?

This appears to be a beverage with a short life span, at some point the entire thing will turn to vinegar. Is this a correct statement or is my assumption wrong?

I am thinking that I will want to bottle and carbonate some of this, what VOL should I aim for?
I am thinking that 1.5vol maybe?

Is there a water chemistry that works best? Most reading does agree that chlorine must be eliminated, however I plan to use RO water. Should I use the same mineral cocktail that I would use with a pale ale or something different? Maybe the tea contributes enough minerals?

Have anyone here done some scientific experimentation with kombucha on this forum?

In beer making there is a such thing as too much yeast. This is because many of the flavors produced by yeast are done when oxygen is present and the yeast colony is growing. So why would many of these kombucha stores recommend a continuous brew using massive SCOBYs that cover the entire top keeping oxygen away from the yeast so all they do is produce alcohol that is then eaten by the bacteria happily sitting on top? I would image these being very vinegary and less complex; am I correct?

Thanks for reading and satisfying my curiosity.

 

[SanPancho]

Theres no style guide. Less acid, less vinegar, more residual sugar is like beginner kombucha. Super acid/vinegar with little residual sugar is hardcore kombucha. Some folks make kombucha with like 5% alcohol, so maybe thats a style?

The scoby is symbiosis, they work together because they help ech other. Technically you could do it separately but thats extra work. White labs has a culture because selling cultures is what they do. You are free to find your own, many companies develop their own cultures over time like bakers with mother dough. But if your culture goes off in a direction you dont like, a culture banked with a lab is a way to hit reset.

No nutrients necessary. It just eats sugar. Some oxygen will help with gluconic acid production. The yeast mostly floats as it inhabits the scoby, which a cellulose type scaffold it shares with bacteria.

Starter fluid is to drop ph to avoid infection as well as innoculate the new batch. Aceto will dominate with time, but its not dominant at the start.

Carb is personal preference. It will self carb if you bottle prior to full ferment. It will go to vinegar, but the time scale slows by a factor of about 30 if refrigerated.

Minerals are part of recipe design. Try for yourself and see. Continuous ferment can produce either a sweet/sour product or vinegary product depending on temp and how fast you drink/replenish fresh tea/sugar. Kombucha yeast generally arent known for adding flavor.

Thses answers are my best recollection from kombucha seminar at white labs in 2016.

 

[Calder]

Kombucha yeast generally arent known for adding flavor.

Can you add a different yeast that develops flovors? It may not survive too well in the low ph environment, but might work for a few batches. Might be worth a try. Any reasons not to try it?

 

[SanPancho]

well there are plenty of yeasts that will handle low pH, so its definitely possible. but brewers yeast will outcompete the bacteria and ferment prettty fast. I dont recall exactly but there was a reason why it didnt work that well. You can always blend two batches though.

 

[Calder]

brewers yeast will out compete the bacteria and ferment pretty fast. I don't recall exactly but there was a reason why it didn't work that well. You can always blend two batches though.

Unless you have significant alcohol, I don't think the yeast competes with the bugs. They work with each other. The yeast produces the alcohol, and the bugs convert the alcohol to acid.

If you boost the sugar to up the alcohol level, the yeast will certainly grow faster, and rapidly produce alcohol; and the high alcohol environment may inhibit the bugs.

It was just a thought, if anyone wanted to get some esters from the yeasts. Not something I am ready to try - trying my best to not screw up a batch while I learn the basics.

I have made a number of Berliners, and the ph is usually down somewhere around 3.0 - 3.2, and I have to pitch a high amount of yeast to ferment the sugars as most brewers yeasts don't reproduce well at that low a ph (some are better than others).

 

[SanPancho]

You are talking about brewers or vintners yeast no? Otherwise what yeast are you going to add for esters? An unknown yeast?

Both types are highly evolved to produce alcohol. The random yeasts in kombucha are not the same.

Thats what was stated in the class. Take it or leave it.

 

[FatDragon]

Kombucha is not new. According to Wikipedia, it's at least a couple hundred years (and possibly thousands of years) old.

I've definitely seen places selling SCOBYs they claim work better with various types of tea. There's also jun, which is made with honey instead of sugar and a SCOBY that can handle the antimicrobial properties of the honey. It's a much smaller market than beer or wine, though, which would account for the relative lack of work into commercializing various SCOBY strains. Perhaps the recent rise to popularity will drive more research and innovation into kombucha culturing, but there's probably not much money in it since SCOBYs beget SCOBYs so most kombucha brewers probably wouldn't be buying new SCOBYs as regularly as beer brewers buy yeast.