Just as alcohol gives wine a pseudocaloric sensation, so acids induce a papillary sensation that can be perceived as freshness. The gustatory freshness of a wine is a sensation induced by fixed acids, which counteracts, by balancing them, the sensations of warmth and softness induced by alcohol and sugars. The scale of the freshness (acidity) of the wines is the following: flat wine (low acidity) fairly cool wine fresh wine acidic wine (acid beyond measure) Source 4calici