Originally Posted by WilliamSlayer
I've read that the gravity of a wine will RISE as the sugars dissolve out of tthe solid fruit. Good rule of thumb is to not add any extra sugar till you have taken a gravity reading AFTER you have removed the fruit pulp. Hope it turns out tasty! :-)
Well, once it starts to ferment then the OG would be incorrect even if you get more sugars out of the fruit.
It's true that the fruit will give up a bit more fermentable sugar as it breaks up, but not usually a meaningful amount unless the fruit is rock hard when you start. "Mushy" fruit can be smashed up a bit and the OG reading at that time is pretty close to the actual amount of sugars that will ferment.
Edited for clarity- When I mix up the must, I always wait 24 hours before adding yeast. So the must is made up, the fruit smooshed up in the bag (or whatever I've got in there), and pectic enzyme added. The OG is taken the next day before adding yeast. It may not be 100% of the fermentable sugars, but it really seems to be "close enough" as most fruits don't have all that much sugar left in them to make a big difference.