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09-21-2012, 07:39 AM   #1
Unferth
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 Calculating complicated abv

Every time I rack my wines, I top up. With my juice wines, I top up with, you guessed it, more juice because store bought wine in Canada is priced like liquid gold, and in Vancouver it's like liquid platinum in diamond wine bottles.

So, how do I calculate abv after I add sugars in the middle of fermentation?

For instance, I racked an apple wine with an OG of 1.085 onto a can of concentrate, then I racked it a month later onto a liter of apple juice. Before I added the AJ I got a reading of .995.

This is way too much math for a humanities major.

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09-21-2012, 12:22 PM   #2
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Just assume that you got somewhere between 11 and 13 percent and don't worry too much about it.

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09-21-2012, 01:15 PM   #3
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I guess it depends on when you're going to stop it. If you are back-sweetening, then take another reading when you're done.

If you back-sweetened and then added chemicals to kill yeast without letting it ferment, then just pointing out obvious it didn't add anything.

If it's above 0.995, then that difference is subtracted from the total sugar points it was going to add, bc it didn't contribute to the alcohol. Is that confusing? Now that you have that you just need to know how much sugar was in the juice, and figure out how many points that would be in your batch.

I wouldn't worry too much about the differences in volume since you added concentrate.

So, figure out how many points that can of concentrate would be and spread that out over the total volume you've got, and there is the last number you need.

Really I would agree with not worrying about it though. Unless you are adding a lot of volume, why bother?

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09-21-2012, 02:50 PM   #4
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Also if my brain serves me well... if you top up with juice having the same SG as your starting solution and allow the yeast time to eat the sugars you can ignore the addition in your calculation and just do an OG and FG to get the ABV.

(yay abbreviations!)

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09-21-2012, 03:14 PM   #5
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You will need to figure out how many grams/liter of sugar your additions provide and determine the S.G. or Brix that the addition adds to the overall volume. And ultimately those points get tacked on to the original S.G. figure, then allow ferment to finish fermenting (if you topped up a still fermenting, unstabilized wine). Take your final S.G. and you will be able to determine ACV.

FWIW, one can of apple concentrate may contribute a S.G. of 0.020 to one gallon. Did the wine start fermenting again after you added the juice? Did you happen to take a S.G. reading after you added the juice?

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09-21-2012, 03:17 PM   #6
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Quote:
 Originally Posted by mbobhat I guess it depends on when you're going to stop it. If you are back-sweetening, then take another reading when you're done. If you back-sweetened and then added chemicals to kill yeast without letting it ferment, then just pointing out obvious it didn't add anything. If it's above 0.995, then that difference is subtracted from the total sugar points it was going to add, bc it didn't contribute to the alcohol. Is that confusing? Now that you have that you just need to know how much sugar was in the juice, and figure out how many points that would be in your batch. I wouldn't worry too much about the differences in volume since you added concentrate. So, figure out how many points that can of concentrate would be and spread that out over the total volume you've got, and there is the last number you need. Really I would agree with not worrying about it though. Unless you are adding a lot of volume, why bother?
Yep, think I got it. Really I just wanted to see if I can do it... I was just worried that if I keep racking it and adding sugar, the my ABV will get higher than I want. The concentrate added like 1/2 a percent, and the regular AJ a minuscule amt.

I think I'll just add AJ now on.

Thanks all!
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09-21-2012, 03:21 PM   #7
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Quote:
 Originally Posted by saramc FWIW, one can of apple concentrate may contribute a S.G. of 0.020 to one gallon. Did the wine start fermenting again after you added the juice? Did you happen to take a S.G. reading after you added the juice?
Thanks, it did start fermenting again, actually and has been dropping lees like crazy, I think it was the bentonite.

I didn't take a reading after the juice.
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09-21-2012, 05:19 PM   #8
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Quote:
 Originally Posted by brazedowl Also if my brain serves me well... if you top up with juice having the same SG as your starting solution and allow the yeast time to eat the sugars you can ignore the addition in your calculation and just do an OG and FG to get the ABV. (yay abbreviations!)
yea that makes sense to me (hamster wheel's a turnin') you would just have more delicious goodness to drink. mmmmmmm
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09-21-2012, 07:16 PM   #9
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Quote:
 Originally Posted by mbobhat yea that makes sense to me (hamster wheel's a turnin') you would just have more delicious goodness to drink. mmmmmmm
My thoughts exactly
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09-25-2012, 02:34 AM   #10
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It's really not that bad of a calculation. Most juices are around 1.050 SG, so that's what ill use here in an example, but you could easily measure the sg of your juice, and substitute appropriately.

Ex: after racking, you have 5.75 gallons, with a sg reading of 0.995. You add a quart of juice that has a sg of 1.050, the final gravity is:

5.75(0.995) + 0.25(1.050) = 6.00(x)

Where x is the new gravity reading. In this case, divide both sides by 6.00, x = 0.997. Not a huge increase in sg.

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