It all depends what kind of wine you are making. I don't believe I've
ever seen a recipe that called for the addition of red grape juice.

Unless you like the taste of Concord a lot don't use it. I don't know
what you are making but white concentrate is usually Niagara which is
more neutral, I would use that, honey or table sugar before I used
Concord. Concord is very assertive and grapey, if that is your goal,
go ahead.

Joe



Joe