Well, not quite what you're asking about but along the same sort of lines, I made seedless apple and blackberry jam yesterday.
Then cooked all the peelings and cores from the apples and tipped in the blackberry seeds for the last few minutes of cooking. Dripped it through muslin and got some nice apple and blackberry jelly as a bonus :happy:
I would try anything you can think of and learn from the result.
Had about half pint of stewed apple left over this morning, mashed it up a bit, added an egg white and turned it into a very nice sorbet. The handful of blackberries left from yesterdays jam has made a coulis to pour over. :happy:
Just go with what ever and dont forget to tell us if it works