When measuring the acidity of a wine, reference is often made to its pH. This index measures the quantity and strength of the organic acids present in the wine in terms of liberated hydrogen ions and therefore represents a measure of the “real” acid strength of that wine. Its value can vary between 2.8-2.9 (high acidity) and 3.8-3.9 (low acidity).
The pH normally has a value that is in inverse proportion to that of the fixed acidity of the wine (the higher this is, the lower the pH).
Sensory effects
It presents the same characteristics as the total acidity (being merely another way of measuring it), with a faintly biting, fresh sensation especially on the sides of the tongues when it is well-balanced (pH 3.1–3.4 for whites, 3.4–3.6 for reds) and sensations of sourness, harshness, acerbity and hardness if the pH is very low, or those of a flat, tired wine if the pH is too high. It also represents a reinforcing element for the astringency of the wine.
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