ABV guesstimating

[Booch before hooch]

Good day,

Does anyone have a "great" online resource or calculator for kombucha ABV guesstimating?

Would be appreciated,
Thanks

 

[BobBailey]

A pound of sucrose in a gallon of water will have an original gravity of 1.046 and ferment very close to a final gravity of 1.000. This would produce very close to 6.0% ABV. With a little math, and this information you should be able to guestimate your ABV. Better yet, spend 6 or 8 bucks on a hydrometer.

 

[DIYer]

Commercial kombucha is usually less than 1%. I've never measured SG (either OG or FG) on my homemade stuff. I figured it was about the same. Might have to try next time just for kicks, although with kombucha, alcohol is not the only byproduct of fermentation. There's also acetic acid, etc., and I don't know how those other byproducts might affect gravity readings. You can do a second fermentation and get the ABV up a bit if that's what you are looking for (google "champagne kombucha").

 

[FatDragon]

...with kombucha, alcohol is not the only byproduct of fermentation. There's also acetic acid, etc., and I don't know how those other byproducts might affect gravity readings...

This is crucial. With the acetic acid being produced in booch, a hydrometer reading probably won't do you much good. In the event that you do want to get information from a hydrometer reading, you'll want to know the SG of pure ethanol (0.79) and acetic acid (1.049 @25C, both according to a quick search). That would suggest that a bone-dry kombucha with 100% fermentation of its sugars would need about 4x as much acetic acid as alcohol to measure at 1.000 SG, though that's probably complicated by other stuff in the booch and the swing between various proportions of alcohol and acetic acid would be far less dramatic than those numbers suggest since the majority of the booch is water.

 

[Scoby Keeper]

I'm interested in this as well. I'm working at a small kombucha brewery in Canada, and I'm trying to figure out a reliable method to estimate ABV without relying on lab testing. I've been using a simple kit to test for titratable acidity, and removing that from the specific gravity equation determined by hydrometers and refractometers, but I'm not entirely convinced about my results.

 

[thebuchaman]

I just send mine to a local lab. I need as close to exact numbers as I can get.