0

votes

Kombucha home brew question

Answered on September 12, 2014
Created February 01, 2013 at 11:50 PM

I'm looking to measure my 'bucha's abv%... my question is if the data recorded with the hydrometer translates to abv% as it does with beer? Or, would there be a different equation to apply?

I'm sure with a little basic chemistry knowledge this is common sense... but that's just something I don't have...

Thank you

E687b5eb51456c9a0205aff406f44ca3

on February 03, 2013
at 02:41 AM

greymouser is probably correct about this! the vinegar and other compounds would interfere with the gravity reading, especially considering that the alcohol is pretty negligible. nonetheless, i have been carded when purchasing it!

Ebb10603524dd22621c1155dd7ddf106

(19150)

on February 02, 2013
at 07:02 PM

... and not to comment this into death, but put it this way: if you have an uncle that brought over "home made red wine vinegar" (yeah, no kidding it spoiled, since you still make wine the old fashioned way, Uncle Mike!) would you serve it to your kids? My parents did, and I started eating lettuce, spinach, and kale - 'cause EVOO + red wine vinegar tastes great! ... while "the creamy stuff" my mom and sister ate on salads horrified me as a youngster. (Actually it still does!)

Ebb10603524dd22621c1155dd7ddf106

(19150)

on February 02, 2013
at 06:59 PM

Also, I initially took the "egghead approach" to answering the question. If I knew there was a child consuming kombucha involved, I would have tried to answer that and not the particulars of fermentation! :-)

Ebb10603524dd22621c1155dd7ddf106

(19150)

on February 02, 2013
at 06:57 PM

I can't answer that for you, since I'm not a parent yet. However ... I'm a first generation 100%, thoroughbred Italian and I was given greatly diluted, homemade wine to drink when I was young. I don't think it's wrong for young people to try alcoholic products with their families, but I can't make that decision for anyone else. I think that the commercially made kombuchas are probably safer for a young child (wrt to alcohol levels), than homemade, as their creation is standardized (per producer at least), and they have been refrigerated (which slows/halts any sort of fermentation).

Ed7403e397077dd1acdbf25c7f6e56ce

(3452)

on February 02, 2013
at 06:48 PM

I downvoted. Apologies... without the further explanation it seemed like a lot of guesswork. Thank you for revisiting, very thorough. In your estimation, then, an average kombucha should be fine for a small child to sip on a few times a week? She really likes it and I suspect it's pretty healthy for her. Thank you again.

Ebb10603524dd22621c1155dd7ddf106

(19150)

on February 02, 2013
at 06:31 PM

Please note: I've added an explanation as to why this is wrong in my original answer. Please read and comment further.

Ebb10603524dd22621c1155dd7ddf106

(19150)

on February 02, 2013
at 06:09 PM

This is the equation for fermentation of **alcohol** from a sugary base. It *could* be used in kombucha brewing if you could account for two things: 1) the by products that are not alcohol or CO2 (i.e. subtract them), and 2) the amount of vinegar conversion the bacterial component of the culture created from any alcohol created.

Ebb10603524dd22621c1155dd7ddf106

(19150)

on February 02, 2013
at 06:06 PM

Have people who downvoted this ever brewed both wine (or beer) as well as kombucha? The by products **are not** the same.

5b9a25a1a676397a25579dfad59e1d7b

(2318)

on February 02, 2013
at 05:28 PM

Ahh ok, I see why you want to be so precise now. My bad.

Ed7403e397077dd1acdbf25c7f6e56ce

(3452)

on February 02, 2013
at 01:24 AM

I feed it to a six-year-old.

Ed7403e397077dd1acdbf25c7f6e56ce

(3452)

on February 02, 2013
at 12:57 AM

This sounds like it makes sense. What do you think of greymouser's objections?

  • Ed7403e397077dd1acdbf25c7f6e56ce

    asked by

    (3452)
  • Views
    3K
  • Last Activity
    1262D AGO
Frontpage book

Get FREE instant access to our Paleo For Beginners Guide & 15 FREE Recipes!

3 Answers

best answer

4
Ebb10603524dd22621c1155dd7ddf106

(19150)

on February 02, 2013
at 12:11 AM

No, it doesn't translate correctly.

The hydrometer readings taken before and after wine or beer fermentation are able to give an approximate abv% because nearly all the conversion is sugar into alcohol and CO2, and these give uniform, predictable result as they change.

With kombucha, the conversion is (usually) extremely light on the alcohol side and you have lots of other by products made, so I would wager that a hydrometer-abv% equation would yield a much higher result than you actually have.

I'm not sure if a vinometer would work, either. Assuming nearly all the sugars were converted so the vinometer could work at all, the other by products are bound to mess with the theory behind the vinometer: that the alcohol predictably interferes with the water's surface tension and the glass capillary it's in.

I'm not sure of any other easy home methods.

EDIT: I've had to add this information since some people don't understand the basic principles of wine/beer fermentation as well as the basics of kombucha.

Wine (or beer) pre fermentation is a juice (or mash). Water is added if the juice's sugar content is too high; sugar is added if the content is too low. The reason the sugar-strength is diluted or increased is because it is a control for two things: the residual sweetness of the wine (i.e. sugar left over) and the alcoholic strength of the wine. Both of these factors are also effected by the species of yeast used -- some types eat lots of sugar, produce more alcohol and CO2, and are able to survive longer in their own waste (i.e. fermentation continues longer).

The basic, physical approach to brewing kombucha is the the same as wine. You have a base (tea) to which sugar is added. However, instead of introducing yeast, one introduces the "SCOBY", which is an acronym, not a word: it means "symbiotic culture of bacteria and yeast".

Now, in general, the yeast are going to proceed as above with wine: they will eat sugar and produce CO2 and alcohol. If you took hydrometer readings before and after fermentation and used only yeast and not a SCOBY, you could calculate the hypothetical possible abv%. For common recipes for kombucha, I would estimate the theoretical maximum is 1-4% abv. (This is completely a guess.)

Now, if the story stopped there, you'd have your answer. However, it doesn't. The complementary bacteria in kombucha is acetobacter. Acetobacter is the bacterium that can ruin wines. It does this because it is an anaerobic bacterium species that eats alcohol and produces vinegar (technically it produces acetic acid). If you are making wine, you have to have good cleanliness and quality controls to avoid this. However, if you are making kombucha, you purposefully introduced acetobacter to digest the alcohol produced and produce vinegar and other by products.

It is the entirety of these by products for which kombucha is prized: trace alcohol, vinegar, and a plethora of proteins and vitamins produced by the yeast and the bacterium. There is certainly not 0% alcohol in kombucha, but the levels are most likely lower than a standard non-alcoholic beer (0.5% or so).

Summary of the edit: the equations for wine making that estimate potential abv% using specific gravity cannot be used to estimate abv% of kombucha.

Ed7403e397077dd1acdbf25c7f6e56ce

(3452)

on February 02, 2013
at 06:48 PM

I downvoted. Apologies... without the further explanation it seemed like a lot of guesswork. Thank you for revisiting, very thorough. In your estimation, then, an average kombucha should be fine for a small child to sip on a few times a week? She really likes it and I suspect it's pretty healthy for her. Thank you again.

Ebb10603524dd22621c1155dd7ddf106

(19150)

on February 02, 2013
at 06:06 PM

Have people who downvoted this ever brewed both wine (or beer) as well as kombucha? The by products **are not** the same.

Ebb10603524dd22621c1155dd7ddf106

(19150)

on February 02, 2013
at 06:59 PM

Also, I initially took the "egghead approach" to answering the question. If I knew there was a child consuming kombucha involved, I would have tried to answer that and not the particulars of fermentation! :-)

Ebb10603524dd22621c1155dd7ddf106

(19150)

on February 02, 2013
at 07:02 PM

... and not to comment this into death, but put it this way: if you have an uncle that brought over "home made red wine vinegar" (yeah, no kidding it spoiled, since you still make wine the old fashioned way, Uncle Mike!) would you serve it to your kids? My parents did, and I started eating lettuce, spinach, and kale - 'cause EVOO + red wine vinegar tastes great! ... while "the creamy stuff" my mom and sister ate on salads horrified me as a youngster. (Actually it still does!)

Ebb10603524dd22621c1155dd7ddf106

(19150)

on February 02, 2013
at 06:57 PM

I can't answer that for you, since I'm not a parent yet. However ... I'm a first generation 100%, thoroughbred Italian and I was given greatly diluted, homemade wine to drink when I was young. I don't think it's wrong for young people to try alcoholic products with their families, but I can't make that decision for anyone else. I think that the commercially made kombuchas are probably safer for a young child (wrt to alcohol levels), than homemade, as their creation is standardized (per producer at least), and they have been refrigerated (which slows/halts any sort of fermentation).

0
5b9a25a1a676397a25579dfad59e1d7b

(2318)

on February 02, 2013
at 01:01 AM

How about not over thinking it and just enjoy it?

5b9a25a1a676397a25579dfad59e1d7b

(2318)

on February 02, 2013
at 05:28 PM

Ahh ok, I see why you want to be so precise now. My bad.

Ed7403e397077dd1acdbf25c7f6e56ce

(3452)

on February 02, 2013
at 01:24 AM

I feed it to a six-year-old.

0
E687b5eb51456c9a0205aff406f44ca3

on February 02, 2013
at 12:12 AM

Yeah, I'm pretty sure it would be the same! Water is always heavier than alcohol, and sugar water is even heavier. So, I would just follow the same steps: 1. Measure with hydrometer/Calculate original gravity (OG) before fermentation 2. Calculate terminal gravity (TG) when degree of fermentation is reached 3. Alcohol content = ((1.05 x (OG ??? TG)) / TG) / 0.79

Ed7403e397077dd1acdbf25c7f6e56ce

(3452)

on February 02, 2013
at 12:57 AM

This sounds like it makes sense. What do you think of greymouser's objections?

Ebb10603524dd22621c1155dd7ddf106

(19150)

on February 02, 2013
at 06:31 PM

Please note: I've added an explanation as to why this is wrong in my original answer. Please read and comment further.

E687b5eb51456c9a0205aff406f44ca3

on February 03, 2013
at 02:41 AM

greymouser is probably correct about this! the vinegar and other compounds would interfere with the gravity reading, especially considering that the alcohol is pretty negligible. nonetheless, i have been carded when purchasing it!

Ebb10603524dd22621c1155dd7ddf106

(19150)

on February 02, 2013
at 06:09 PM

This is the equation for fermentation of **alcohol** from a sugary base. It *could* be used in kombucha brewing if you could account for two things: 1) the by products that are not alcohol or CO2 (i.e. subtract them), and 2) the amount of vinegar conversion the bacterial component of the culture created from any alcohol created.

Answer Question


Get FREE instant access to our
Paleo For Beginners Guide & 15 FREE Recipes!