THE ACIDIC FOODS..

The Acidic foods are those have a pH of 4.6 or lower.
Acidic foods include most fruits, pickled vegetables, jams, and jellies.

Grapes contain Malic, Citric, and Tartaric acids.
Naturally found acid in grapes, is essential component
as it contributes to the crispness, sourness, sharpness,
and tartness of a wine.
Acid can balance the sweetness of a wine.
Acid is necessary for a wine to age well.