@Scooter68 Do you think a refractometer used on the peach nectar pre-fermentation might be an option? I have a whole bunch of peaches in my freezer patiently waiting to be turned into wine and I intend to use all juice, no additional water.
As much as I'd like to give an answer - my experience with a refractometer is non-existent perhaps someone else will chime in. The method I use with my peach pudding must (Yeah it; starts out about that thick) may be incorrect but the wine has been turning out well.
So I put the hydrometer in the testing tube and quickly turn the tube between my hands trying to be like a vibrating machine. When it stops going down I measure it. At first it will only go in so far on it's own with the must so thick._
Then I push the hydrometer as far down into the tube as it will go and repeat the "vibrating' action. When it stops rising I take that measurement.
Then I split the difference Lets say first is 1.090 and the second is 1.094 - then I use 1.092 as my starting SG.
Now there will be some saying the solids are what I am measuring not the actual SG. Perhaps but it has been working for me so far.
I lost a small batch once when I tried waiting until the must broke down a bit so hit the must with K-meta when I prep it and make sure I get it started within 48 to 60 hours. I take one last measurement just before I pitch the yeast.
NOW - lets hear from others with better ideas, more experience. I don't want to filter my must to measure because I know that there is lot of sugar captured in the solids that will be released as the ferment progresses. BUT I am open to improving my processes so like OP I'm open to suggestions.
Oh blueberries - yeah we enjoy them. BUT this past year we had no crop due to late freeze then my wife went vegan to fight cancer and has been going thru our stored frozen blueberries a lot. So I hope we have good crop this year or the freezer will be empty of blueberries.
Agree about the other berries. If you can get some answers about those fruit types on her that might help you. Just post a new thread "Acid levels of XX XX and XX fruits. Keep in mind that there may be some published data but a lot depends on the local sources you get your fruit from.
I've had some EXCELLENT wines and some so-so batches but only a few losers along the way. 50 batches to date. (From 1 gallon to 4 gallon batches)