confused on ABV

[macaler]

I keep going around on this in my head.

So, lets say i start off with an OG reading of 1.05 on a 5gallon batch, drop my yeast and end up with a FG of 1.00 ... my ABV = 6.5%

As this is very dry and unsweet brew, I want to rack off to secondary and back-sweeten.

I like to leave my brew for a week or so before bottling (with airlock as I'm sure there's a little bit of yeast left in my concoction).

I will heat pasteurize right after I bottle.

How can I calculate the final ABV%?

Thoughts?

 

[FatDragon]

With backsweetening, the total alcohol doesn't change, but you'll be diluting your cider by the volume of whatever you're using to backsweeten. For a super simple example, let's assume you backsweeten a gallon of 10% cider with a gallon of unfermented apple juice. That would dilute your alcohol by 50%, so you'd end up with two gallons of 5% sweet cider. For five gallons of 6.5% cider where you add (let's say) a quart of frozen apple juice concentrate, you'd be diluting by 5% which should drop your ABV to approximately 6.2%.

However - I may be wrong because I've never made a cider - but if you backsweeten and then leave it for a week I would expect you'd restart fermentation and end up with a stronger, but not necessarily sweeter cider. Maybe I'm missing something, though - are you stabilizing before backsweetening, and if so, is pasteurization really necessary after bottling?

 

[brancaster]

I keep going around on this in my head.

So, lets say i start off with an OG reading of 1.05 on a 5gallon batch, drop my yeast and end up with a FG of 1.00 ... my ABV = 6.5%

As this is very dry and unsweet brew, I want to rack off to secondary and back-sweeten.

I like to leave my brew for a week or so before bottling (with airlock as I'm sure there's a little bit of yeast left in my concoction).

I will heat pasteurize right after I bottle.

How can I calculate the final ABV%?

Thoughts?

First off, what are you using to backsweeten? (Juice, concentrate, honey etc.)

Second, if you backsweeten then leave in secondary for a week you're going to skew your numbers greatly and I'm not sure there's an exact way to calculate your true ABV% after that.

That being said, if I were just going to bottle and pasteurize without bottle carbonating like you seem to be doing, I'd let the cider ferment to completion, add the backsweetener and then bottle immediately. Your heat pasteurization method is going to stop any remaining yeast anyhow. This way you can calculate your final ABV% and be sure of it after you bottle.

If you're going to use more juice to backsweeten, then you'll be diluting your final product, as FatDragon said.

If that's the case (if you don't let it sit in secondary for a week and ferment further), then determining your final ABV% is a simple average of the two liquids.

The equation would look like this: (Volume1 X ABV1) + (Volume2 X ABV2) / (Volume1 + Volume2)

So lets say you want to backsweeten your final product of 5 gallons at 6.5% with 1 gallon of apple juice. You're average would look like this:

(5 gallons x 6.5%) + (1 gallon x 0.00%) / (5 gallons + 1 gallon)
= (0.325)+(0) / 6
= 0.0541
= 5.41%

Using things like juice concentrate will not dilute as much, but you should be able to apply the same equation for averages.

 

[Arrheinous]

Add vodka to your backsweetening addition to conserve the % alcohol. Adding any volume of 6.5% ABV to a batch of 6.5% ABV cider won't dilute the alcohol.

I've got a sweet cider on tap that used generic sucralose/maltodextrin artificial sweetener to backsweeten. It's stable and people seem to like it.