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Recently I made a belgian strong ale. In the secondary I added 7 pounds of fresh cherries that were pitted, frozen, thawed, and blended up. Is there a good way to at least estimate the additional alcohol that they produced?

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Some info, though no real answer per se -- brewadvice.com/questions/1285/… –  hookedonwinter Jun 23 '10 at 16:45
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4 Answers

up vote 4 down vote accepted

For fruit, get a refractometer. $50 or so online at williamsbrewing.com or other beer/wine shops. Mash up a handful of the fruit 'til it's juice and then dribble the juice on the refractometer lens. That will give you a brix reading. There's probably some formal math you can use to get exact numbers here, but here's some basic info: 24 brix when fermented dry will give you roughly 14% alcohol +/- 1% depending on just how dry it goes. So then it's some fairly basic math based on the amount of this juice you're using and the gravity of your brew.

You can achieve basically the same thing with a triple beam hydrometer that shows brix, but you'll need to mash up more of the fruit and I've found refractometer readings to be more accurate with pulpy fruit. Then again, more fruit will give you a more accurate reading because some cherries might be 15 brix, some might be 18 brix so you want a good "field sample".

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As long as you aren't getting any solids in the refract sample this is a pretty good idea,IMO. however, if you can sacrifice enough fruit, the solids play a minimal role in interfering with a hydrometer. once they settle out. good answer –  brewchez Jul 12 '10 at 22:37
    
I ended up going with brewchez's suggestion, but using the refractometer seems like a great idea. I'm going to give it a shot next time. –  Jordan Jul 13 '10 at 15:17
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For an estimate try this... Look up the nutritional values for cherries on a USDA or other calorie counting website. It will tell you the sugars per serving. From there you can estimate the weight of the sugar per unit serving weight and then get a ballpark idea.

I'm telling you now though, its significantly less than most other things we add like pure sugar or extracts. To the point where its probably not worth calculating. Especially, from an ABV standpoint. It'll change your ABV fractionally. That's from roughly calculating it in the past somewhere else.

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The only thing I can think of is putting some cherries (in whatever form you would use the in your beer) in water, leaving them for some time (could be your fermentation time) and then checking the water's gravity to see how much sugar has been extracted.

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Press some of the fruit to extract the juice and measure the SG with your hydrometer. Measure the SG of your beer. Then measure the volume change when you add the fruit to your beer and you'll have to determine the dilution of the sugar throughout your batch to figure out the actual increase in SG of the whole batch.

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This is a nice approach only if you assume that dropping fruit into secondary extracts the same amount of sugar as pressing the fruit. –  brewchez Jun 29 '10 at 19:39
    
so the yeast won't get into the fruit and ferment the sugar in there? I wonder how wine gets made? –  Mattress Jun 30 '10 at 15:47
    
I think brewchez is saying that you'll likely get more sugar in the beer if you drop whole fruit in as opposed to pressing first. The pomace left behind when you press still contains some sugar - sugar that has the potential to be fermented if the whole, crushed fruit is added to the fermenter. (FWIW, white wine is pressed before being fermented. Red wine is fermented as whole fruit, sometimes not even crushed. The yeasties have no trouble getting into the berries for their sugar fix.) –  JackSmith Jul 13 '10 at 15:34
    
@ Jack What??? I thought all wine was made from must. Must being the juice collected after cruishing. Maybe there may be some examples of making wine from whole crushed fruit. But I think the vast majority of wine (red or white) is made by fermenting the juice, not crush fruit. I don't think the whole fruit concept is right. –  brewchez Jul 15 '10 at 12:37
    
WHAT??? I don't think much wine is made from fermenting crushed fruit, red or white. Wine is made by fermenting must, which is the juice collected from the crushing process of the grape. There must be some special cases where wine is made by adding yeast directly to crushed fruit. But the vast majority of wine being made, red or white, at home or professionally is made from fermenting juice. –  brewchez Jul 15 '10 at 12:40
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