Fruit Addition Adjustment

[Brett Wilford]

I have enjoyed fruit beers and an starting to brew my own. I have done a few but not worried too much about the specific ABV. I have just made a raspberry blonde using 9 pounds of fresh raspberries in 6 gallons of beer. It was added 3 days after the yeast was pitched. I have been trying to figure out what my final ABV will be but struggling with the math. I found a calculator to give me the approximate sugar addition form the raspberries but not sure how it works exactly. The OG on my blpnde was 1.047 with an FG target of 1.011 to get an ABV of 4.73. Based on the fruit calculator I should add 2.28 GU or .30% ABV but not sure how to actually do this. I do not understand how the 2.28 lines up with .30% ABV so it seems wrong to me.

This is the calculator I used: Fruit Gravity / Alcohol - CraftBeerTraders

 

[VikeMan]

I'll just say this... without knowing the gravity and attenuation of your base beer (or the ABV of your base beer), it can't possibly know whether the "with fruit" ABV will be higher or lower, let alone by how much. I see in the notes that it says it takes the fruit's water into consideration (which is great, because most don't), but it's still seriously flawed.

 

[catalanotte]

I have enjoyed fruit beers and an starting to brew my own. I have done a few but not worried too much about the specific ABV. I have just made a raspberry blonde using 9 pounds of fresh raspberries in 6 gallons of beer. It was added 3 days after the yeast was pitched. I have been trying to figure out what my final ABV will be but struggling with the math. I found a calculator to give me the approximate sugar addition form the raspberries but not sure how it works exactly. The OG on my blpnde was 1.047 with an FG target of 1.011 to get an ABV of 4.73. Based on the fruit calculator I should add 2.28 GU or .30% ABV but not sure how to actually do this. I do not understand how the 2.28 lines up with .30% ABV so it seems wrong to me.

This is the calculator I used: Fruit Gravity / Alcohol - CraftBeerTraders

I just went through this process and used the following approach that comes close to what you have.
There are charts of the % sugars by weight for various fruits like this one: Determining the Sugar Contribution of Fruit in Beer | MoreBeer
Raspberries are about 4.3% sugar by weight. Sugar contributes about 44 GU per pound/per gallon (different from article above, but what I use)
9 lbs of raspberries x 4.3% sugar x 44 GU/lb/gal / 6 gallons of beer = 2.8 GUs

If you add the GUs to you OG and assume the same attenuation, you can see the difference in ABV.
Ex 1.047 + .0028 = 1.050 OG
Assuming 77% attenuation based on your original FG target of 1.011 target, the new target FG 1.012. (1.050 attenuated 77%)
Use an ABV calculator:
1.047 to 1.011 = 4.73%
1.050 to 1.012 = 4.99% (Increase of .26%)

These number are close enough to yours to show the calculations, although not the exact same as yours

 

[VikeMan]

@catalanotte I don't see where you are accounting for the increased water from the fruit.

I kid you not, many fruit additions actually decrease the ABV. It depends on the beer and the fruit.

 

[catalanotte]

@catalanotte I don't see where you are accounting for the increased water from the fruit.

I kid you not, many fruit additions actually decrease the ABV. It depends on the beer and the fruit.

Good point, hadn’t thought about side of the equation. Guess you would need to estimate the liquid yield from the fruit. Any resources for water yield from various fruits?

 

[VikeMan]

Good point, hadn’t thought about side of the equation. Guess you would need to estimate the liquid yield from the fruit. Any resources for water yield from various fruits?

I don't know of a good central resource. I did a lot of googling of "fruitX* water content" for water and "fruitX* nutrition" for sugars and carbs.

*Where "fruitX" is raspberries, cherries, or whatever.

 

[day_trippr]

I can say with confidence that adding a pound of raspberry puree to a gallon of pretty much any beer is going to lower the ABV. Which is why I build my base wheat beer to at least 6.5% (on paper, of course) so the finished product will end up in the 5s...

Cheers!

 

[VikeMan]

@Brett Wilford here's a screenshot from BrewCipher 6.5, showing a solution to your fruit addition.

edit: replaced w/ corrected version.

 

[Brett Wilford]

@Brett Wilford here's a screenshot from BrewCipher 6.5, showing a solution to your fruit addition.

edit: replaced w/ corrected version.

Thank you for this. Where can I get Brew Cipher from?

 

[VikeMan]

Thank you for this. Where can I get Brew Cipher from?

It can be downloaded from -> Google Drive <- or -> DropBox <-.

 

[Brett Wilford]

@VikeMan thanks for the link