How do you get ABV with a fruit beer?!

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Homebru358
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Joined: Thu Jul 08, 2004 9:26 am
Location: Garfield, NJ, US

How do you get ABV with a fruit beer?!

Post by Homebru358 » Fri Jul 09, 2004 4:44 pm

I'm still very new to home brewing and I will be working on my third batch, but fruit beer is what I have been interested in the most. I've done research on fruit beers but there's one thing I haven't been able to find - a formula to figure out ABV when adding your fruit to the secondary, which is what many brewers do! I know some home brewers don't care as much about what the alcohol is on their beers, but for me it's very important since I plan on making higher alcohol fruit beers. And, of course, a lot of the alcohol will come from the fruit that is added. Does anyone know how to figure this out? I know there's formulas out there.

Brewer2001
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Gravity...a perplexing subject.

Post by Brewer2001 » Sat Jul 10, 2004 11:04 pm

Bru,

The only way that the 'true' alcohol level of a fermented product can be determined is by distillation. Far removed from what a homebrewer and most small craft brewers can do or afford.

I have trained and worked a pro brewer but this is one of those subjects that is still muddy.

The problem is that, as you pointed out, 'full' bodied beers contain polysacarides that change the viscosity of the finished beer. If measured (or calculated) using a hydometer will produce an error. The thickness of the finished beer will tend to give you a higher final gravity.

But in answer to your question on calculation I use the following:

OG - FG * 0.105 = ABW: ABW * 1.25 = ABV

This works for most beers. Most of the micro and brewpubs report their alcohol content using this method but this is just a guess. As I said earlier only the lab distillation will give you the precise reading.

Good brewing,

Tom F.

Homebru358
Posts: 2
Joined: Thu Jul 08, 2004 9:26 am
Location: Garfield, NJ, US

About your calculation

Post by Homebru358 » Sun Jul 11, 2004 8:45 pm

Brewer,
So this formula works to determine
ABV even when adding fruit (or any other fermentable) on secondary fermentation?

Brewer2001
Double IPA
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Posts: 170
Joined: Fri Sep 07, 2001 1:56 am

No, this formula approximates the ABV.

Post by Brewer2001 » Mon Jul 12, 2004 1:51 am

Bru,

When a hydrometer is used to measure gravity there are three things that need to be taken into account. First is temperature (60 deg F for SG readings and 20 deg C for Brix or Plato readings), second is carbonation (de-gas the sample by agitation) lastly is the amount of unfermented sugars that are left in solution.

The hydrometer measures apparent degree of fermentation. The Brix or Plato scales should have less error when measuring higher viscosity solutions. I will recheck my notes for the correction factors. But lab tests are the only real way to get an accurate measurement.

Good brewing,

Tom F.

fitz
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Clear as mud

Post by fitz » Tue Jul 13, 2004 10:16 am

You can take an educated guess by doing a reading for OG then two readings at secondary before and after the addition of the fruit, and then one at the end. Do the calculations for the ABV on both the secondary before the addition, and at the end and combine for the abv it isn't exact, but should get you close.

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