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04-05-2009, 04:35 AM   #1
daveooph131
Recipes

Mar 2009
Dallas, TX
Posts: 1,112
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When looking at a recipe calculator what does it mean by "apparent attenuation"?

04-05-2009, 05:37 AM   #2
android

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Jan 2009
Ames, Iowa
Posts: 3,062
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from Specific Gravity and Attenuation

Attenuation

Attenuation is a measure of how much of the sugar in the wort has been fermented by the yeast.

In home brewing, we usually deal with apparent attenuation:

apparent attenuation = ( ( OG in points - FG in points ) / OG in points ) x 100

Apparent attenuation is different (higher) than the actual attenuation, because the alcohol produced during fermentation is lighter than water, and throws the reading off.

The apparent attenuation you will get on a given batch depends on a number of factors, including the types of grains/extracts used, mash temperature (if brewing all-grain), and the strain of yeast. Typically, apparent attenuation will range from 65 to 80%. Beers with a lower apparent attenuation will be sweeter, fuller-bodied, and lower in alcohol. Higher apparent attenuation will result in a drier, thinner, higher alcohol brew.

Example:

What is the apparent attenuation of a beer with an OG of 1.055 and a FG of 1.016?

( 55 - 16 ) / 55 x 100 = 71%
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04-05-2009, 06:16 PM   #3
daveooph131
Recipes

Mar 2009
Dallas, TX
Posts: 1,112
Liked 35 Times on 28 Posts

So when the beer recipe calculator asked for apparent attentuation without the OG and FG you can't really calculate correct?

So if you are using the calculator to build a recipe I assume aparent attenuation is just speculation unless you were to use the target OG / FG?