Does anyone have an estimate of the potential gravity contribution for orange juice? I’m making a strong Belgian specialty, using the zest from Curacao oranges (bitter) in the boil, and I plan to add the juice to the secondary. How much I use depends on how it tastes.
According to this article:
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2621.1992.tb05499.x/abstract
“whereas the reduced acidity Sour orange juice was 7.4 “Brix”, that’s about 1.030
But that’s all google will show me. I don’t have access to the full article though, maybe someone else does.
I found another article that had an average over 10 years of 10.4 brix, so about 1.041 SG.
From "Evaluation of rootstocks for the Cyprus local lemon variety ‘Lapithkiotiki’ "
I think your best bet is to just measure it with a refractometer or hydrometer. I’d be more worried about the bitterness than the sugar though, they are called bitter oranges too and I don’t know how that will carry over into the finished beer :) The bitterness might come from just the peel and the walls so maybe it won’t be an issue depending on how you plan to juice them.
Just polling the first few google results, it looks like OJ has about 21 g of sugars per 8 fl oz. That’s 8.75 °Bx, or about 1.035 SG.
Or you could just measure the juice…
I like Denny’s response ;D
http://www.honeycreek.us/brix.php
6 to 20+ brix with an average of 11brix (US 11.8)(%sugar)
the potential in PPPG is 1.006, that is add 1 pound of OJ to make 1 gal of fluid you get about 1.006
Fred
Yeah, good idea Denny! I can’t believe no one else suggested that . . . ;D
Pragmatism, dude…it’s the way to go! 
:
Thanks for the estimates!
And just to be clear, I do plan to measure the juice, I just don’t have it yet. I was looking for a figure for planning purposes. For weird reasons (to be explained at a future date), I really want to hit my gravity exactly with this batch. I also plan to taste the juice before using it. That will determine how much or even whether I use it at all.
DOH! Read too fast and missed that! Good idea, Tom! 
I think you’ve just been skipping over mine - too many posts to read all of the way through
For the record, the juice was 10.7 brix, which works out to 1.041. Three oranges gave me 14.4 ounces (weight) of juice, and 1.64 ounces of fresh zest.
Thanks for the update, Rob. Did you use it all?
I used all of the zest in the boil. When I rack to the secondary I plan to taste what I’ve got, and make a decision then. If the orange character is already fairly strong I won’t add any juice, but if it’s weak I may add some or all. If it does get added, the juice is quite red, and that should give an interesting color to the beer.