While attending Mass at a parish out of town, my girlfriend received the chalice (I have not done so in a long time) and told me afterward that it had a strong peach taste. I remember attending Mass there sometimes in the past, when I still received from the chalice on occasion, and having some very strong and unusual (and admittedly delicious flavors) – sometimes peach, sometimes apple, etc. No other parishes in the area seem to use such wines for Mass.
This seems really curious to me, as I know liturgical law requires altar wine to be 100% grape, so that wine made of peaches or apples would be absolutely forbidden. Is there some way, then, to introduce such flavors to grape wine without adulterating it to the point of its becoming invalid matter?