Bottle conditioning - why no more alcohol?

[3dB Brewing]

Yeast eats sugar, and excretes CO2 and alcohol (simplified).

We read FG at the end of fermentation and calculate ABV. Then we add priming sugar and bottle. A few weeks later the beer is fizzy.

So the priming sugar reactivates the yeasties and they make more CO2, which is trapped in solution because the volume is fixed.

Why don't they also make more alcohol?

 

[VikeMan]

Why don't they also make more alcohol?

They do.

 

[3dB Brewing]

They do.

Then bottled beer is always more alcoholic than the ABV we calculate from OG-FG (which is read prior to bottling)???

 

[VikeMan]

Usually, unless you add a lot of water as part of the priming solution.

If you want to estimate the net impact on ABV for your batch, download the FruitCalc spreadsheet from this page:

http://sonsofalchemy.org/library/
Put your base beer's information in, then select Sugar from the "fruit" dropdown and enter the amount. Select Water from the next "fruit" dropdown and enter the amount you used in your priming solution.

 

[AntonioMartins]

If you you use 5g/l sugar for priming, your ABV will increase about 0,3%

 

[3dB Brewing]

Ah. So ABV for a hypothetical batch went from 6.64 to 6.7.

Not enough to worry about, I guess, but it makes sense there is some change.

Thanks!

 

[VikeMan]

Ah. So ABV for a hypothetical batch went from 6.64 to 6.7.

Not enough to worry about, I guess, but it makes sense there is some change.

That sounds like a really small increase, much smaller than avg. What were your particulars?

 

[AntonioMartins]

That sounds like a really small increase, much smaller than avg. What were your particulars?

I took this information from wine producers, they did some calculations and assume by their experience that 17 g/l of sugar will increase 1% ABV (on wine).

So

g/l - %ABV
--------------
1 - 0,06
2 - 0,12
3 - 0,18
4 - 0,24
5 - 0,29
6 - 0,35
7 - 0,41
8 - 0,47
9 - 0,53
10 - 0,59
...

 

[VikeMan]

I took this information from wine producers, they did some calculations and assume by their experience that 17 g/l of sugar will increase 1% ABV (on wine).

So

g/l - %ABV
--------------
1 - 0,06
2 - 0,12
3 - 0,18
4 - 0,24
5 - 0,29
6 - 0,35
7 - 0,41
8 - 0,47
9 - 0,53
10 - 0,59
...

Thanks. I was actually replying to @3dB Brewing's post about 6.64% to 6.7%, i.e. only a 0.06% increase.

 

[3dB Brewing]

I just ran the default numbers in that spreadsheet, and entered 5 oz sugar and .05 gal H20 (prob on the low side; it was a SWAG), then compared the result to an ABV calculator on the web.

I recently went to kegging so I doubt I'll run actual numbers from an actual batch; I just always wondered why the bottle conditioning didn't (I assumed) increase the alcohol. So it does, a little. Cool. Just one of those random little questions rattling around my brain, that's now resolved. Y'all rock.

 

[VikeMan]

I just ran the default numbers in that spreadsheet, and entered 5 oz sugar and .05 gal H20 (prob on the low side; it was a SWAG), then compared the result to an ABV calculator on the web.

Hmm... the default numbers for the base beer come out to 6.3% ABV (at one decimal). Adding 5 oz table sugar and 0.05 gallons water results in 6.7% ABV (at one decimal). I wonder if you typo'd something. If not, I'd like to have a look at a copy of your sheet. Thanks!

 

[3dB Brewing]

Yes, that's what I got from the spreadsheet, 6.7%.

Then I put OG=1.060 and FG=1.012 into the ABV calculator at brewersfriend.com and... it now says 6.51% (alternate equation). Changing FG to 1.011 yields 6.64, so I must have made that typo earlier.

FG=1.012 and the standard equation yields 6.3%.

 

[bwible]

Yeah the amount of water you dissolve the priming sugar in pretty much negates the little bit of extra sugar. Then there’s gelatin. I see people saying dissolve gelatin in a cup of water and add to the beer. That would be lowering your gravity by a small amount.

 

[VikeMan]

Yeah the amount of water you dissolve the priming sugar in pretty much negates the little bit of extra sugar.

I'd say that depends on what you mean by pretty much negates, but for example... Imagine 5 oz of table sugar (and no water) added to 5 gallons of a 5% abv beer. Once that sugar ferments out, the ABV is going to be a bit over 5.4%. With 1 pint of water along with the sugar, we're looking at a hair over 5.3%.

 

[bwible]

Table sugar is about 45 points per pound. 5 oz is .31 lb. 45 x .31 = 13.95. So you’re adding about 14 extra points to a 5 gallon batch. But it’s really 5 gallons plus an extra pint because of the water. So if you have say an average 1.050 beer thats not really adding anything.

 

[VikeMan]

Table sugar is about 46.21 points per pound, so 5 oz is more like 14.4 points, but that's almost beside the point. That 5 ounces plus a pint of water has an OG of about 1.098. And it's more fermentable (122% Apparent Attenuation) than the beer wort. It really is adding something. In my example above, it's adding about 0.3% ABV.

 

[bwible]

Table sugar is about 46.21 points per pound, so 5 oz is more like 14.4 points, but that's almost beside the point. That 5 ounces plus a pint of water has an OG of about 1.098. And it's more fermentable (122% Apparent Attenuation) than the beer wort. It really is adding something. In my example above, it's adding about 0.3% ABV.

Yeah I’ll buy that. A negligible increase