

07172013, 01:35 AM

#1

Dec 2011
Monterey, Ca
Posts: 953
Liked 61 Times on 49 Posts

I asked this question once I didn't understand the answer at the time. I've been brewing a little more and I think I'm going to pose the question again.
How do you calculate the ABG change after back sweetening?
P.s.
I plan to filter out or killed the yeast.
Maybe we can use these examples:
3 gallons at 8% ABV....
Question one: What would happen if you added half a gallon of fresh juice
Question two: What would happen if you added a quarter of a gallon of fresh juice
Question three: Three quarters...
Question four: a full gallon...
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07172013, 01:54 AM

#2

Nov 2011
, The south
Posts: 761
Liked 61 Times on 53 Posts

It's my understanding that if you backsweeten you are adding sugar post fermentation in a way that it will not ferment as well (pasteurization, splenda, lactose). So the added sugars will not ferment into alcohol, co2 and other products; resulting in something slightly sweeter but with no more alcohol.
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07172013, 02:35 AM

#3

Dec 2011
Monterey, Ca
Posts: 953
Liked 61 Times on 49 Posts

Quote:
Originally Posted by CBMbrewer
It's my understanding that if you backsweeten you are adding sugar post fermentation in a way that it will not ferment as well (pasteurization, splenda, lactose). So the added sugars will not ferment into alcohol, co2 and other products; resulting in something slightly sweeter but with no more alcohol.

No no, I'm totally with you as far as the adding the sugar.... I plan on killing the yeast, I just need to know calculation wise...
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07172013, 03:17 AM

#4

Jun 2013
Posts: 510
Liked 43 Times on 36 Posts

The easy way would to take a reading at the time of pasteurization(when you kill the yeast). This will give you the final alcohol content and no more need for a specific gravity reading.



07172013, 03:26 AM

#5

Sep 2012
Northeastern Pennsylvania
Posts: 1,557
Liked 161 Times on 113 Posts

Ur gonna need to get a FG reading of the cider before sweetening, then take a gravity reading of the juices ur using to back sweeten. Post those and someone can prob do the calculations for u... Im uber math stupid or else I would but ur gonna be diluting ur cider's current ABV with sugars in a percentage based on the amount u add to the amount u already have. I hope that makes some sense, it does in my head...
Edit: Add ur starting grav too.
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07172013, 03:43 AM

#6

Feb 2012
Asheville, NC
Posts: 22
Liked 4 Times on 3 Posts

You shouldn't need a gravity reading after adding the juice or whatever you you use to back sweeten as long as no more fermentation is taking place. You just need the volume of liquid added. From there it's just a simple dilution factor based on your original alcohol content and volume added



07172013, 04:00 AM

#7

Nov 2010
Madison, WI
Posts: 180
Liked 17 Times on 14 Posts

3 g x 128 oz = 384 total oz, 8 % of which are alcohol. 384 * .08 = 30.72 oz of alcohol in 3 gallons. This volume of alcohol doesn't change by adding fluid, it only becomes a smaller percentage of the new volume. Basic algebra allows you to calculate the new abv.
3.25 gallons = 416 oz. however there are still only 30.72 oz of alcohol. so what percentage of 416 oz total volume is that 30.72oz fixed known volume of alcohol?
Formula is 30.72 (fixed volume of alcohol) over 416 (total new volume) = x (unknown new abv) over 100 (100 percent of).
Solve for x  (30.72*100)/416=7.38. This 7.38 is the new % abv.
3.5 gallons = 448. (30.72*100)/448 = 6.85% abv.
Etc.
The constant is the 8% of the original volume expressed as a actual volume, and then calculate what percentage of any total volume that actual volume is....



07172013, 04:37 AM

#8

Sep 2012
Northeastern Pennsylvania
Posts: 1,557
Liked 161 Times on 113 Posts

Quote:
Originally Posted by Doongie
3 g x 128 oz = 384 total oz, 8 % of which are alcohol. 384 * .08 = 30.72 oz of alcohol in 3 gallons. This volume of alcohol doesn't change by adding fluid, it only becomes a smaller percentage of the new volume. Basic algebra allows you to calculate the new abv.
3.25 gallons = 416 oz. however there are still only 30.72 oz of alcohol. so what percentage of 416 oz total volume is that 30.72oz fixed known volume of alcohol?
Formula is 30.72 (fixed volume of alcohol) over 416 (total new volume) = x (unknown new abv) over 100 (100 percent of).
Solve for x  (30.72*100)/416=7.38. This 7.38 is the new % abv.
3.5 gallons = 448. (30.72*100)/448 = 6.85% abv.
Etc.
The constant is the 8% of the original volume expressed as a actual volume, and then calculate what percentage of any total volume that actual volume is....

I knew a math wizard would follow thru. Hope this helps, I didn't read it cuz the math gives me a headache!
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07172013, 05:59 AM

#9

Dec 2011
Monterey, Ca
Posts: 953
Liked 61 Times on 49 Posts

Quote:
Originally Posted by WoodAle
You shouldn't need a gravity reading after adding the juice or whatever you you use to back sweeten as long as no more fermentation is taking place. You just need the volume of liquid added. From there it's just a simple dilution factor based on your original alcohol content and volume added

Can you show an example please
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07172013, 06:06 AM

#10

Dec 2011
Monterey, Ca
Posts: 953
Liked 61 Times on 49 Posts

Quote:
Originally Posted by Doongie
3 g x 128 oz = 384 total oz, 8 % of which are alcohol. 384 * .08 = 30.72 oz of alcohol in 3 gallons. This volume of alcohol doesn't change by adding fluid, it only becomes a smaller percentage of the new volume. Basic algebra allows you to calculate the new abv.
3.25 gallons = 416 oz. however there are still only 30.72 oz of alcohol. so what percentage of 416 oz total volume is that 30.72oz fixed known volume of alcohol?
Formula is 30.72 (fixed volume of alcohol) over 416 (total new volume) = x (unknown new abv) over 100 (100 percent of).
Solve for x  (30.72*100)/416=7.38. This 7.38 is the new % abv.
3.5 gallons = 448. (30.72*100)/448 = 6.85% abv.
Etc.
The constant is the 8% of the original volume expressed as a actual volume, and then calculate what percentage of any total volume that actual volume is....

PERFECT! Got it! Thank you...
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