Never had them, looks unique. Use only the very ripest? Are the green ones still bitter, and have to be picked out?
This was my first go at Mustang grapes. I did some reading up while waiting for them to ripen. They are all very tart. Like lemon juice tart. Some of the green ones were still a bit hard and I culled those. Others were still quite green but were softer and they got processed. From my research, don't eat the skins raw, that's where the acid is. I did pop a few and ate insides and couldn't really tell much difference between the ones that were almost black and the softer green ones. Of the ones I tasted, I wouldn't say they were bitter, just damn tart. The jelly has a tart intense grape flavor. I canned it Saturday evening and let it sit overnight. Sunday morning the flavor had developed and I'll just tell you it is excellent. Wild plum jelly was my favorite until Sunday morning. I've had my fair share of homemade muscadine jelly from a family friend in Louisiana and the Mustang grape is better.
Since I was in the jelly making mode and had all of the gear out, I went ahead and made a batch of peach jam and strawberry jam too. Homemade jelly is just a way better than anything from the store.
I ended up with 9 cups of juice from 8lbs of grapes. I froze enough juice for two more batches of jelly.