Great Question: Fruit beers and gravity potential

Hi everyone! I just finished a brown ale this weekend that i intend to add some fig puree to. I am curious to know if anyone has any formula or idea as to how much alcohol or gravity potential added fruit brings to a recipe. For instance: I am adding about 5 lbs of fig puree to my secondary ferm. Any idea on how this will influence the %abv?

Thanks folks!

Ok. So I did some math of my own and am hoping that if I'm incorrect, some of you can correct me. Here is my logic: On average figs way about 50 grams. Of that 50 grams about 9 grams are sugar. I'm putting 5lbs of figs in which would be 2240 grams of figs. Since figs are about 18% (9/50) sugar by weight, I would be adding 403.2 grams of sugar via the figs. This would equate to adding .011 to specific gravity per gallon by my calculations. Does this sound right?

Are these dried figs or fresh ones? Dried ones are almost 55% sugar. Of course, they'd suck up a lot of beer re-hydrating.

These would be fresh figs.

OMG So many responses!

Sounds about right but of those sugars how many are fermentable??

Good question. I'm not sure at all. This requires more research....

I put 5 gallons of a whit on top of a 5lb puree of apricot, I measured the gravity after adding the beer on top of the fruit and did not notice an increase in gravity, as well the final gravity did not change much as well. I saw some activity but not a whole lot. I had the beer on the puree for 14days, now it's in a bright tank for 7, and will keg it tonight.

I think for the most part the sugar in the fruit wont dissolve too easily into the beer at fermentation temps. If your looking to get the sugar content out you should add it fruit to the boil, but then you loose flavor and aroma.

Bsquared said:

I put 5 gallons of a whit on top of a 5lb puree of apricot, I measured the gravity after adding the beer on top of the fruit and did not notice an increase in gravity, as well the final gravity did not change much as well. I saw some activity but not a whole lot. I had the beer on the puree for 14days, now it's in a bright tank for 7, and will keg it tonight.

I think for the most part the sugar in the fruit wont dissolve too easily into the beer at fermentation temps. If your looking to get the sugar content out you should add it fruit to the boil, but then you loose flavor and aroma.

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While the sugars won't dissolve easily into the beer when you rack onto the fruit the yeast will have no trouble finding the sugars and converting them.

Does your fig puree package have nutrition information? The sugars should be fructose which is highly fermentable.

dantodd said:

While the sugars won't dissolve easily into the beer when you rack onto the fruit the yeast will have no trouble finding the sugars and converting them.

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True, but I thought he was asking on what to expect for a change in gravity by adding fruit. My observation is that you can not see much of a change in gravity when doing a secondary fermentation on fruit, and any estimation of potential from the fruit will be a SWAG at best.

You might be able to get a better idea , If you have a refractometer, know your starting gravity and have a sample that did not have fruit added to it.

e.g.
Measure the FG of both beers using a hydrometer,
1). 1.011 (no fruit)
2). 1.012 (Fruit)

Measure the Brix of both beers
1). 6.5
2). 7.5

Calculate the predicted gravity of the beer from the Brix reading (I used beer alchemy assuming a 1.050 SG)

1). 1.011
2). 1.017

from this you could estimate that the fruit imparted .005 units to your beer.

estimating ABV at
1). 5.2%
2). 5.7%

This is just an Idea of how to figure it out, I'm sure there are other ways that are more accurate, like a mass spectrophotometer .

Bsquared said:

True, but I thought he was asking on what to expect for a change in gravity by adding fruit.

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Ahhh..... there's the problem, he wasn't asking about measured gravity, he was asking about ABV.

Dantodd is correcto!

can't believe nobody has linked this yet: http://brewery.org/brewery/library/SugAcid.html

so take the weight of the fruit, multiply it by the % of sugar, then calculate the amount of gravity added if you were adding that much sugar, easy peasy.

Freezeblade said:

can't believe nobody has linked this yet: http://brewery.org/brewery/library/SugAcid.html

so take the weight of the fruit, multiply it by the % of sugar, then calculate the amount of gravity added if you were adding that much sugar, easy peasy.

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3 years later, great link. Thanks.

a year later... this link is in fact cool... but is the product of the the formula grams? i am assuming grams. thanks.