A wine lacking and adequate amount of acids tastes flat, “lifeless”, and generally has a relatively short shelf life.
On the other hand, a wine that has too much acidity fails to please the palate. Balance of all components in a wine is crucial for its appeal, quality, and popularity.
Acids may be fixed (i.e tartaric acid etc), or volatile ( i.e acetic acid aka vinegar). Acid is a substance which reacts with a base and generally has a sour taste. Acids occur in liquids, or solids, or in gases.
There are three common definitions of acids – Arrenhuis defines acids as substances which increase in concentration of hydronium ions in solutions, Brunsted – Lowry’ definition is “substances which can act as protone donors”.
Most acids are aqueous solutions or can be dissolved in water.
They measure between 0 – 7 on the pH scale. The pH scale contains 14 grades. 0-7 is acid, and 8-14 alkaline. The lower the pH level of a wine is, the better it ages.
The strength of acidity refers to it tasting sharper than others/
Wines contain many acids, the most important of which are tartaric, malic, lactic, and citric acids.
Tartaric acid is the most important of all and provides stability. Its level depends on grape variety, type of soil, weather conditions during the growing season, and harvest time.
Tartaric acid binds with lees and tannins forming harmless shards, which accumulate on the cork, but do not affects the taste. In most wineries tartaric acid is reduced by running the wine through super cold tubes ( – 4 C) to extract it. A wine so called “crystals” has not been subjected to this process.
Malic acid smells and tastes like green apples and generally displeases many, if not most North American wine drinkers. However, acid-driven wines complement creamy and/or fatty foods by cleansing the palate between bites and enhancing the taste of the food.
Barbera, carignan, riesling, sauvignon blanc are naturally high in malic acid. The acidity of a wine can be reduces by subjecting it to malo-lactic fermentation, during which half the malic acid is converted to lactic acid, which is mild.
Lactic acid is mild and has a “milky” flavour.
Chardonnay wines, put through malo-lactic fermentation before barrel aging, becomes “soft” and acquires a creamy mouth feel. Citric acid, tastes mild and provides citrusy aromas, and flavours. Citric acid occurs in less than five per cent of tartaric acid in proportion.
The white wines of most cool climate regions contain more citric acid than those from warm regions.
Ascorbic acid ( vitamin C) is an antioxidant and may be added during bottling.
Butyric acid causes the wine to smell rancid.
Sorbic acid may be employed to sweeten or preserve a wine, but can precipitate rancidity.
Tannins are bitter plant phenols that bind and precipitate to the bottom of red wines. Tannins are in the skins, stems, and pips of grapes. Removing berries from the stem and pressing the juice from skins after the fermentation (red wines only) reduces tannin content, but also reduces shelf life. Tannins are bitter, pucker the mouth, and are perceived towards the end of the tongue before entering the esophagus.
Tannins hydrolize and polimerize; resulting in large molecules consisting of a chain formed by a catalyst.
For all the above reasons, the balance of wine is very important.
Flavour is the term used for the combination of taste and smell. Smell is the main determinant of flavour, followed by taste, which is limited to sweet, sour, bitter, salty, and savoury aka umami.