For my upcoming raspberry wheat recipe I plan to secondary the beer on top of a raspberry puree for 2-3 weeks. Likely going to use 3lbs. Is there a way (or a reason) to account for the fermentation of raspberry sugars contribution to the alcohol level or is it negligible?
It would require math.
Fruit contributes both sugars and volume too complicate that. I think it is often a wash.
You can take a small amount of the puree and mix it with a measured amount of water, take the OG and then calculate the OG of the puree itself. From there you can calculate what the new OG of the beer will be.
I would bet fruit would usually lower the alcohol, since fruit is mostly water with a bit of sugar.
Beer Smith has a grain addition of fruit based on the US average brix (% sugar, ) of the fruit.
Bottom line, unless your wort is pushing 100% fruit very little impact
Raspberries have an average potential of 5 pppg so you are adding 3lbs* 5 pppg = 15 gravity points, so for the same volume in a 5 gallon batch your OG will go up 15/5 = .003, This will increase abv by about .4%abv
I am doing the same thing now with blackberries, so this is helpful information!
The volume of the puree is important to account for. If you’re going from a 6.5 gal carboy to a 5 gal, make sure you have enough room for the fruit and a bit of headspace for another (albeit small) fermentation. I used fermcap-S because the 3068 I used can be a very foamy fermenter!
Necro post, apologies.
Been trying to find answer for this myself. I cannot find the grain entry in BS you mentioned. Where did you find the average potential pppg of raspberries, and do you have a list for other fruits? I am curious if fresh vs puréed fruit has different pppg value due to cell wall breakdown.
I notice that the displacement or volume of the fruit or purée has not been accounted for. I think there is a complicated way to calculate this as I have seen on Belgian candi syrup packaging.
I looking for pppg for blueberries,rhubarb, and white fleshed peaches if you happen to know the pppg.
Thanks
TD