Читать книгу Wine Faults and Flaws - Keith Grainger - Страница 77

Acidity is detected, particularly on the sides of the tongue and cheeks, as a sharp, lively, tingling sensation. Medium and high levels of acidity encourage the mouth to salivate.

Of course, all wines contain acids: whites generally more than reds, and those from cooler climates more than those from hotter regions. In the grape ripening process, as sugar levels increase, acidity levels fall (mostly due to a reduction in malic acid), and pH increases. Thus, a cool climate white wine might have a pH of 2.8, whilst in a hot climate, the pH of red wine might be as high as 4. Uniquely amongst fruits of European origin, grapes contain tartaric acid: this is the main wine acid, although malic and citric acids are also important. These three acids account for over 90% of the total level of acidity. The other acids present may include lactic, ascorbic, sorbic, succinic, gluconic, and acetic acids. A high level of volatile acetic acid is most undesirable. At an extreme, it will impart a nose and taste of vinegar. Accordingly, excessive volatile acidity is generally regarded as a fault. If the grape must is deficient in acidity, the winemaker may be allowed to add acid, usually in the form of tartaric acid. Within the EU, such additions are only permitted in warmer, southern regions.

Perception thresholds for various acids vary according to the individual, with under 50% of tasters detecting tartaric acid in concentrations of 0.1 g/l or less, and the remainder between 0.1 and 0.2 g/l. However, sweetness negates the impact of acidity, and vice versa, and the relationship between these is one of the considerations when considering balance, as discussed below.