A friend gave me 2 qts of ripe fresh picked blackberries, which I
promptly froze. I tested a couple then and they seemed rather sour,
but were indeed ripe. My friend told me later that the owner of the
bushes had started to complain that the berries didn't taste "right"
any more.

I defrosted them tonight, crushed them and they are drippin' for jelly
right now. How do I sweeten/perk up/adulterate them if possible for a
nice finished product? I got 2 cups of raspberry/mullberry juice
tonight and was going to mix them in but no way. The R/M juice is
outstanding!

Suggestions for Blackberry Rx?