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Is the Tea Really Needed?

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Chris Edward

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Hello all
I keep reading page after page on Kombucha brewing and they all pretty much parrot each other, but don’t really give a reason why the tea is necessary.

I am curious if the tea is even necessary?

Is it used because strong black tea is slightly acidic?

Does anyone have any links or PDF sources to research done, showing why the tea is necessary?

People have cited how the SCOBY uses the caffeine from the tea but I have also seen people cite reports (with no links to the reports) that say there have been tests on the caffeine on new tea and SCOBY tea and except for what would be expected to be lost due to oxidation from the tea sitting at room temperature for several weeks, the loss in caffeine wasn’t enough to cause an effect on the SCOBY.
Basically it seems like there's the same amount of caffeine is in the final brew as what goes into it.

Also I have witnessed the tea lightening.
I use a Whiskey color chart myself.
Found here:
http://malt-review.com/wp-content/uploads/2015/09/Colour-bar-Big-1024x214.jpg



My tea starts out as “burnt umber (1.7)” and a few days later it is “amber (0.7)" colored and pretty much stays that way through the rest of the brew.

This suggests that the color change has less to do with the SCOBY gaining some nutritive value from the initial tea but instead the acidic nature of the initial tea being added to the much more acidic SCOBY starter tea, causing a lightening of the color.

Any information other than opinion would be greatly appreciated.

I am sorry if this comes off rude, I am just trying to remove as many variables that can go wrong from my SCOBY brews as possible and I am just curious.

Thank you for your help
 

RPh_Guy

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I am curious if the tea is even necessary?

Is it used because strong black tea is slightly acidic?
No, it's not "necessary".
However, the tea provides flavor, mouthfeel (tannins), and nutrients (e.g. nitrogen, potassium) for the microbes.

The acidity is irrelevant.

You can certainly ferment plain old sugar water with some yeast nutrient if you really want. I've made wine from candy corn.
Basically it seems like there's the same amount of caffeine is in the final brew as what goes into it.
Yes, that's my understanding.
Also I have witnessed the tea lightening.
The light color is caused by the microbes suspended in the liquid. They reflect light.
 
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Chris Edward

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You can certainly ferment plain old sugar water with some yeast nutrient if you really want. I've made wine from candy corn.
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Thank you for your reply, I appreciate the "food for thought."

I am curious whether the tea acts in a similar way as adding humic acid in an aquaponcs system; to shade the liquid so things like algae don't have a chance to grow.
Plus it seems that the acidity makes for an environment that is tailor-made for the SCOBY.
 
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Chris Edward

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I reckon if you try it once without the tea the clear difference beyond the scientific stuff will be bland kombucha.
I would assume if you left out the black tea, that there would be nothing in the liquid to detract from the vinegary-ness and the resulting kombucha tea would be quite nasty, unless it was further processed....
I am not a fan of vinegary tastes and so I do my best to dilute the tea so I can't taste it but that sort of defeats the point of drinking it.
My goal is the SCOBY cellulose, as a natural fiber source, the tea for me is sadly a bit of a by product.
 

Andrew Hodgson

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If all you are after the is the cellulose from the SCOBY I would imagine there is some way to have a continuous SCOBY motel going and somehow process it how you want without the vinegary quality.

I will say that I have made some pretty bland kombucha by cutting the sugar and tea quantity way down, I think it can probably be done to your satisfaction, just have to dial it in.
 

RPh_Guy

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I am curious whether the tea acts in a similar way as adding humic acid in an aquaponcs system; to shade the liquid so things like algae don't have a chance to grow.
No, as I said, the acidity of the tea is irrelevant. The scoby culture you pitch will bring down the pH immediately even if you pitch into plain sugar water, because there's acid from the previous batch. Furthermore, both the yeast and the bacteria will adjust the pH downward fairly quickly -- within a matter of hours if the culture is healthy.

FYI, reducing oxygen exposure during and after fermentation will reduce the conversion of ethanol to acetic acid (less vinegar).

You're just eating the cellulose pellicle?

Cheers
 
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Chris Edward

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If all you are after the is the cellulose from the SCOBY I would imagine there is some way to have a continuous SCOBY motel going and somehow process it how you want without the vinegary quality.

I will say that I have made some pretty bland kombucha by cutting the sugar and tea quantity way down, I think it can probably be done to your satisfaction, just have to dial it in.
Awesome, thanks.
It would be interesting to try and figure out what the upper and lower limits of how much sugar is needed/tolerated, compared to the time necessary to complete a batch of tea (supposing temperature is kept constant).
But there are so many variables and everyone's taste of what is a completed batch is up to them...

This I suppose is both the beauty and for me anyway, the frustration of brewing kombucha...
 
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Chris Edward

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No, as I said, the acidity of the tea is irrelevant. The scoby culture you pitch will bring down the pH immediately even if you pitch into plain sugar water, because there's acid from the previous batch. Furthermore, both the yeast and the bacteria will adjust the pH downward fairly quickly -- within a matter of hours if the culture is healthy.

FYI, reducing oxygen exposure during and after fermentation will reduce the conversion of ethanol to acetic acid (less vinegar).

You're just eating the cellulose pellicle?

Cheers
I appreciate all of your help, but I fear you are getting caught up on the word acid in humic acid.
Humic acid is a very, very weak acid and the amounts needed to darken water will in no way alter it's pH.
A cup of tea would be much more acidic than water colored similarly brown by humic acid.


In the photos shown, this is considerably more than what would be needed to turn the water the light "tea" brown necessary for hydroponics and aquaponics.
For that you would need a pea sized amount for 950ml/32oz.
Humic acid is used to darken the water in hydroponics and aquaponics growing systems to keep algae from growing in the reservoirs and tubing.
I was merely suggesting that it could be used instead of tea, to act similarly as the tannins.

As far as consuming the the SCOBY pellicle,
I am grinding the SCOBY's up and using them as a fiber supplement.
It's much more palatable (when mixed with some food) than trying to consume them as dense rubbery pucks.
I haven't tried turning them into fruit leather, though at some point I want to try this.
It's much better then getting a fiber supplement with some chemically derived cellulose that has an unknown source.
Plus so far it seems much easier on my system, because commercial fiber supplements can be be a bit "rough."

Thank you for the suggestion about lower the oxygen during and after fermentation, I will see about trying this to make a less vinegary kombucha.

I am curious if adding something such as DAP would help lower the conversion to acetic acid as well (but speed up the conversion of alcohol).
I haven't taken the time to research what it is broken down into while fermenting, but seeing as how the process in wine making (where it is used quite a bit) is similar, I assume it should be fine to use in very small amounts for kombucha.
But until I can get some data verifying that it is safe to use, or I can find the time to do the research myself, I will not be using it.


Thank you again for all of your help!
 

RPh_Guy

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I appreciate all of your help, but I fear you are getting caught up on the word acid in humic acid.
You're right, I mistakenly assumed humic acid was just for acidification. I'll leave the hydroponics expertise to you, but there's certainly no risk of algae growth in kombucha.
The combination of acidification, alcohol, and low nutrients all help prevent unwanted microbial growth, generally speaking.

Tannins are mainly for flavor. They do have some anti-microbial properties but I doubt that's relevant.
I am grinding the SCOBY [pellicles] up and using them as a fiber supplement.
Interesting.

I am curious if adding something such as DAP would help lower the conversion to acetic acid as well (but speed up the conversion of alcohol).
Adding nutrient should indeed increase fermentation rate, but this isn't a good way to manage acetic acid production.
Acetic acid is only produced in the presence of oxygen. Remove the oxygen and you completely prevent acetic acid formation.

Yeast nutrient is safe to use. You can make your own since it seems like you're into that. :) Just bring the yeast sediment from a previous batch to a boil, or some bread yeast in water brought to a boil. Fermaid O is organic and works great too.

It will be more difficult to ferment plain sugar water without nutrients, so I'd definitely recommend using nutrients if that's your plan.
 
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