Calculating Final % after Fruit Additions

[Abraxas57]

Hi, may be a silly question, but i'm still quite inexperienced.

Recently made a mango sour, made the base beer first and calculated % from og/fg as usual. Then added fruit, which obviously added sugars, so took a new gravity and final gravity when it was completed fermentation, resulting in another %.

Is it a simple matter of combining the 2 percentages?
If so I've got a 9.5% mango sour... We did add a lot of mango.

 

[Donoroto]

Hi, may be a silly question, but i'm still quite inexperienced.

Recently made a mango sour, made the base beer first and calculated % from og/fg as usual. Then added fruit, which obviously added sugars, so took a new gravity and final gravity when it was completed fermentation, resulting in another %.

Is it a simple matter of combining the 2 percentages?
If so I've got a 9.5% mango sour... We did add a lot of mango.

Good question. I don't know. But it seems like it should be more complicated than that.

I know your situation is different, but if I made a 1.050 wort, fermented it to 1.020, then added more 1.050 wort, it would ferment down to 1.020 again. I would not have double the alcohol percentage, but the same, just more of it.

 

[Abraxas57]

Thanks, yeah it doesn't seem as simple as adding the 2.

 

[Bigbre04]

Generally the volume of water you add vs the volume of added sugar cancel out any practical gain in abv. That being said, if you had some absurdly sugary fruit addition to a low OG beer, you could gain ABV.

I dont ferment out my fruit, so i am diluting my beer when i add fruit, but its a negligible difference.

Plus you have to assume not all of the sugar in the fruit will ferment out so???

My fruit comes with a % sugar by volume, but i never really worry about it to be honest. but now i am curious and happen to have time on my hands...ill brb!

 

[Bigbre04]

So the mango puree that i use from oregon fruit is between 13-18 brix. Call that 15.5 on average. If i were adding the entire 42# box to my normal sour recipe, it changed the calculated abv from 5.67 to 5.98% according to the calculator in here. I'm not sure how the calculator handles the added volume of liquid?

The OG of that batch is 14p so adding about 4 gallons of liquid at 15.5p would bump it up slightly which would up the total abv. BUT i am not fermenting it out so it shouldnt add anything unless i were to leave a keg out of the cooler or loose power for a couple days, then i could have problems...but kegs can handle over 30 psi right??? Technically it is actually diluting out the total ABV, but again its so small that It doesnt really matter much.

If your fruit has a lower Brix then your starting gravity though it will actually lower your overall ABV by a small amount. It seems like there are a lot of fruits that have lower brix then mango.

https://www.brewersfriend.com/homebrew/recipe/embed/1383335

https://www.oregonfruit.com/fermentation/fermentation-products/?utm_term=oregon fruits&utm_campaign=Brand+-+Search&utm_source=adwords&utm_medium=ppc&hsa_acc=5465175317&hsa_cam=19927165360&hsa_grp=155097688729&hsa_ad=672991387894&hsa_src=g&hsa_tgt=kwd-298363908198&hsa_kw=oregon fruits&hsa_mt=e&hsa_net=adwords&hsa_ver=3&gad_source=1&gclid=CjwKCAiAg9urBhB_EiwAgw88mZb1j-nFA_XIsJgWgKZSH8lAxw1T6QSSFH7zA6FMm6tYQK31Je3LCRoCAJYQAvD_BwE

https://asepticfruitpurees.com/pages/resources

 

[Abraxas57]

The initial beer had OG 1.054 and FG 1.016, so 4.988%.

We added 6.8kg of mango pulp (so 6.8l of liquid added, which brought it up to a total of 28l). The cans had added sugar. Nutritional info suggests 204g of sugar per can, 1.632kg of total sugars.

The new OG was 1.046 and it finished at 1.012 so 4.5%.

 

[Donoroto]

21 liters at 4.988% (call it 5) combined with 6.8 liters at 4.5% gives us 4.84%. About.
(21*5 + 6.8*4.5)/28

 

[Bigbre04]

21 liters at 4.988% (call it 5) combined with 6.8 liters at 4.5% gives us 4.84%. About.
(21*5 + 6.8*4.5)/28

I spent some time chatting with a couple other brewer friends and we all basically came to the same conclusion. On the small scale with standard fruit purees(not concentrated) the overall changed to final ABV is within our +/- legally, so for most batches i dont bother to calculate the actual difference. Big guys will for sure have the gear and fucks to get it very accurate, but it doesnt really matter.