Calculating ABV after backsweetening?

[BadgerBrigade]

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...

 

[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.

 

[BadgerBrigade]

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...

 

[Randzor]

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.

 

[Pratzie]

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.

 

[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

 

[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....

 

[Pratzie]

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!

 

[BadgerBrigade]

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

 

[BadgerBrigade]

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...

 

[Hello]

I realize this thread is somewhat old but I figured I'd ask here.

If my OG was 1.070 and my FG was 1.010, when I added juice at bottling and took a reading with my hydrometer, the FG was 1.022. But based on the above, I cannot just take the OG to the FG (post juice) and call it a day, right?

Instead, I need to figure my 1 gallon batch of cider (128 oz) and get the fixed volume of alcohol and then work the above equation, right? So taking the reading after adding juice is wrong?

For my 1 gallon batch I added 16 oz of juice. So I have this:

128*.0788 = 10.086 volumes of alcohol in the batch.
So I take my (10.09*100)/144 (volume plus juice) and I get 7.01% (if I round). Right?

 

[BadgerBrigade]

I realize this thread is somewhat old but I figured I'd ask here.

If my OG was 1.070 and my FG was 1.010, when I added juice at bottling and took a reading with my hydrometer, the FG was 1.022. But based on the above, I cannot just take the OG to the FG (post juice) and call it a day, right?

Instead, I need to figure my 1 gallon batch of cider (128 oz) and get the fixed volume of alcohol and then work the above equation, right? So taking the reading after adding juice is wrong?

For my 1 gallon batch I added 16 oz of juice. So I have this:

128*.0788 = 10.086 volumes of alcohol in the batch.
So I take my (10.09*100)/144 (volume plus juice) and I get 7.01% (if I round). Right?

Just saw this post...
I think your ABV (Before you backsweetened) was 7.96%...
Sorry, doing math out loud ... Lol...
You sound about right

 

[Iceman9818]

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....

This is great, found your post while searching for something similar. I’m wanting to know about calculating the sugar content after sweetening. I just made a wine SG 1.074 FG 0.996. I haven’t yet but I am planning to backsweeten (not planning on measuring the sugar, just sweeten til it tastes good) and pasteurize. What I’m wanting to find out is the end sugar content per serving. I feel ok figuring out the total amount of sugar I add by taking another gravity reading and calculating the total amount of sugar that way but I’m a little lost on taking that down to per ounce (this is for letting the diabetics in my life know how much sugar is in a glass)

 

[marc1]

This is great, found your post while searching for something similar. I’m wanting to know about calculating the sugar content after sweetening. I just made a wine SG 1.074 FG 0.996. I haven’t yet but I am planning to backsweeten (not planning on measuring the sugar, just sweeten til it tastes good) and pasteurize. What I’m wanting to find out is the end sugar content per serving. I feel ok figuring out the total amount of sugar I add by taking another gravity reading and calculating the total amount of sugar that way but I’m a little lost on taking that down to per ounce (this is for letting the diabetics in my life know how much sugar is in a glass)

If you have the total amount of sugar, divide it by the total volume, and that will give you sugar per volume.

For example, you have 100 Oz total volume after the sweetening, and you had added 50 grams of sugar, you would have 50/100 or 0.5g sugar per ounce. Just keep your units consistent.

If you weigh the sugar you add you don't even need to check the gravity to get sugar by volume of the final wine.

 

[marc1]

You can tell how much sugar you add even without pre planning the specific amount by weighing by difference.

Fill a container with more than enough sugar and weigh it. Write it down. Add sugar to the wine from that container. When you are done, weigh the container again. Subtract the end weight from the start weight; this is how much sugar you added.

If you want to be extra accurate, measure the volume of your wine after the sugar addition to account for the increase in volume due to the sugar addition, and use that volume in the calculation in my previous post.