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Old 05-25-2012, 05:11 PM   #1
Zapped
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Default How to measure sugar and alcohol content

I've searched through this site (using keywords separately, also joined by a + symbol, and also with the kombucha keyword added), but I still can't find a definitive answer to my question.

How do I directly measure the sugar content in my Kombucha after 2nd ferment is complete and I'm ready to drink it? How do I directly measure the alcohol percent by volume?

All I've been able to dig up here and elsewhere on the Interweb is folks arguing about Brix refractometer readings and how the mix of some residual sugar and alcohol make hygrometer readings inconclusive. I read second-hand anecdotes that there is "almost no" sugar left when the yeast has done the sugar-->alcohol tango and "less than 0.5%" alcohol when the bacteria has drunk its fill and spit out acetic and gluconic acids. But nothing definitive.

Personally I try to avoid sugar but I'm not so strict that I expect Kombucha to be sugar-free. I have no aversion to alcohol at all. I just want to know what's in what I'm drinking and be able to answer the reasonable questions I'm asked when I share the drink.

Can anyone explain how to test for sugar and alcohol content in Kombucha?



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Old 05-30-2012, 10:03 PM   #2
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If you want to measure for yourself, first you need to find out how specific gravity is affected by pH levels perhaps?

Generally a regular KT ferment doesn't go over 2%. Often I believe it's significantly less than %2. Probably more like 0.5%

Consider also, the sugar to alcohol conversion isn't one to one.

Also, you can use other sugars than refined white sugar. Albeit some sugars (like brown) may induce molding.

I'm going to try to make a KT using unhopped malt syrup or powder extract soon. I just need to put a little time in to calculating the amount to use. Likely it will be 20% more than regular sugar.

I know that you can use maple syrup.

Good luck searching for specifics



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Old 06-02-2012, 12:47 AM   #3
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Have you tried a hydrometer? Take a sample before brewing and when finished and you can calculate ABV. Same with refractometers however you'll need to input the values into a separate spreadsheet to compensate for the gravity of alcohol.

Hydrometers are cheap and useful.

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Old 06-04-2012, 06:47 AM   #4
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I think the short version is that it's not easy, and if you want exact figures, tough, you're not likely to get them.

I think there's still a reasonable amount of sugar left when you drink it. If you doubt that, consider that when you're drinking it, it's all nice and pleasant, but if you leave it to ferment for another few weeks it keeps changing (sugar keeps being used up) and if you leave it a further month or two it will change more, so there is still a reasonable amount of sugar left even well after you could drink it. Whether that's 20% or 50% or even outside that range I don't know, but there's definitely more than 'almost none'. My guess is that more than half the sugar is gone by the time most people would want to drink it.

Testing using specific gravity isn't going to work well I wouldn't think. The specific gravity is going to be affected by alcohol and other things. With multiple things affecting the specific gravity you have no way to quantify how much any one specific thing is doing.

As for alcohol, I've never felt at all intoxicated from it, even when I've consumed close to a litre/quart. I'm making no more than a poorly-educated guess here, but I believe alcohol peaks early, would probably usually not get to more than 1-2%, and by the time you're drinking it would be about 0.2% That's largely guesswork. Sometimes I can smell the cultures getting alcoholic early in, sometimes not. I assume/guess that sometimes the yeast kicks in quickly and the bacteria takes a while to catch up, and other times the bacteria does a better job of keeping up. I've never tried drinking more than about a shot glass of the alcoholic-smelling early stage kombuchas because they're just too sweet.

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Old 06-22-2013, 09:28 PM   #5
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Zapped, just curious if you ever got anywhere with this? I buy my bottled KT w/ ~1.5% ALC by volume and would love to know what the Alcohol content will be for my home brew. Also, my husband is diabetic, so it would be nice to know sugar content of home brew as well.

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Old 06-23-2013, 03:03 AM   #6
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I'm actually glad you bumped this year-old thread because I never did find any specific methods to measure either alcohol content or residual sugar content in my home-brewed Kombucha. Still hoping someone has some detailed information.

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Old 07-27-2013, 01:51 AM   #7
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I know if you add one 1 cup of sugar to a gallon of water for a kombucha recipe that'd give you a starting gravity of 1.023. No matter what no more sugar will be introduced so kombucha wouldn't ever be over 3% ABV if the finishing gravity was 1.000.

Since most commercial versions are only .5% I'd say that you can take gravity readings along the way to see how yours is doing.

I have heard also that parts of the scoby feed off of the alcohol so even if you hit 3% it might not be that at all when its done.



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