Homebrewers Association | AHA Forum

General Category => Yeast and Fermentation => Topic started by: rbowers on May 12, 2012, 09:41:56 PM

Title: Accounting for fruit contribution to alcohol level
Post by: rbowers on May 12, 2012, 09:41:56 PM
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?
Title: Re: Accounting for fruit contribution to alcohol level
Post by: Jimmy K on May 12, 2012, 09:48:28 PM
It would require math.

Fruit contributes both sugars and volume too complicate that. I think it is often a wash.
Title: Re: Accounting for fruit contribution to alcohol level
Post by: tschmidlin on May 13, 2012, 05:59:30 AM
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.
Title: Re: Accounting for fruit contribution to alcohol level
Post by: nateo on May 13, 2012, 03:51:47 PM
It would require math.

Fruit contributes both sugars and volume too complicate that. I think it is often a wash.

I would bet fruit would usually lower the alcohol, since fruit is mostly water with a bit of sugar.
Title: Re: Accounting for fruit contribution to alcohol level
Post by: bonjour on May 13, 2012, 04:09:15 PM
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
Title: Re: Accounting for fruit contribution to alcohol level
Post by: kylekohlmorgen on May 14, 2012, 02:39:23 PM
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!
Title: Re: Accounting for fruit contribution to alcohol level
Post by: trickydick on May 07, 2014, 02:34:20 PM
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

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