Calculating gravity after fruit addition

[ABarritt]

So I brewed an amber ale with an O.G. of 1.069, then after about 13 days I racked it onto 1lb of cherries. Gravity at transfer was 1.013. Question is...is there a way to calculate how much this raised my gravity, and therefore when I take my final grav reading to adjust for this in ABV? Any thoughts or equations are helpful.
Thanks

 

[JustLooking]

In most cases the liquid in the fruit will balance out any sugars, so you're estimated OG will be unchanged.

 

[ABarritt]

Very good thank you. Would I need to adjust anything to calculate for my FG/ABV to account for additional sugars being consumed by the yeast? Or should I just expect a lower FG/higher ABV...

 

[JustLooking]

It really depends on the fermentability of your original wort. If it was low, your attenuation may go up, but I doubt you'll see much change.

Just noticed that your beer went from 1.069 to 1.012 before the fruit. That almost 83% attenuation. I believe fructose potential is about 1.046. I don't know the amount in 1lb of cherries, but still don't think you'll see any change in FG or %ABV. It's more about the flavor you'll gain.

 

[ABarritt]

Right on thank you sir. 1st fruit beer attempt so we'll see

 

[Calder]

Actually, in most cases, the effective OG will go down with the addition of fruit. The amount of sugars in the fruit compared to the volume of the fruit will have a lower volume sugar content than your original wort.

Fruit has roughly 10% sugar. That is, 1 lb of fruit will have roughly the sugar content as 0.1 lbs of plain sugar.

Therefore in 5 gallons, 1 lb of fruit will add roughly .001 to the gravity, but since the overall volume increases too, the gravity in most cases goes down.

I just ignore the fruit addition and use my OG and FG measurements as normal

 

[Hujo]

It depends on the fruit, grapes have 16% sugar, cherries 12, and raspberries as little as 3! There are lots of lists online.

 

[eadavis80]

If you drink 4 or more in a sitting and are smiling at the end, then you added the right amount of fruit.