Think this equation makes sense?

[Sreidy12]

I'm brewing a Fruit pLambic and trying to figure out how to determine the abv of the final product. I'm thinking something like this:

OG=Postboil gravity
SG1=Gravity before racking to secondary
SG2=Gravity after mixing in fruit puree to secondary
FG=Gravity once fermentation has finished

( ( ( OG-SP1)/7.5) + ( (SG2-FG)/7.5) ) )/7.5

So basically I'm finding the ABV of the intial beer and adding it to the results from the secondary fermentation. Does this seem logical to anyone else?

 

[COLObrewer]

It's all greek to me, or actually it looks sort of "alien" . . . . . . . but then I'm more of a hands on guy when it comes to brewing, The computer does all my cumputing.

Brew on my friends

 

[bartyen82]

I don't think you need to divide by 7.5 the very last time. The way I see it,

Alcohol Content = Primary + Secondary

Primary = (OG-SG1)/7.5
Secondary = (SG2-FG)/7.5,

assuming that OG, SG1, SG2, and FG are in points (50 points, not 1.050 SG, for example).

 

[Sreidy12]

Yea good point, Idk why I decided to divide the whole equation by 7.5. Think I need to incorporate volume because of the addition of raspberries? If so how would that figure in?

 

[bartyen82]

Nope - the only thing that matters are the total number of points of sugar dissolved homogeneously in your wort/beer.

 

[dcp27]

You may have an easier time just calculating the amount of sugar added from the berries since there may be mixing issues. According to this source ( http://hbd.org/brewery/library/SugAcid.html ) raspberries are 7% sugar by weight, so you can do (OG + 0.07*lbs berries*40/volume - FG)/7.5

I don't know what ppg fructose actually is so I guessed 40ppg, at 7% by weight it won't make much difference.

 

[Sreidy12]

Good point, plus that'll let me avoid stirring the raspberries and aerating the wort. Looks like it'll raise the ABV about .7%. This sound right assuming the volume is 4 gallons?

 

[ajf]

I'd use (OG + (SG2 - SG1) - FG) * 131
Without the addition, (OG - FG) * 131 gives a very good estimate.
With the addition, you just increase the OG by the points added by the addition.

-a.