Wine phenolics: Chemistry, biosynthesis and effects on health

Wine contains many phenolic components, most of which originate in the grape cultivars. They contribute to sensory characteristics such as color, flavor, astringency and hardness of wine directly or by interaction with proteins, polysaccharides, or other phenolic compounds. The main phenolic compounds deriving from grape can be divided in two groups, non-flavonoid and flavonoid (anthocyanins, flavan-3-ols and flavonols) compounds. The non-flavonoid phenolic constituents present in wine are mainly hydroxybenzoic and hydroxycinnamic acids as well as volatile phenols, stilbenes. Moreover, even if those compounds are colorless or slightly yellow, they have an important role in red wine color since they are known to enhance and stabilize the color of red wines by intra- and intermolecular reactions. They furthermore contribute to wine flavor and some of them also exhibit potent biological activities. Anthocyanins are the main pigments responsible for the color of the grapes and young red wines. They are localized in the solid parts of cluster and are extracted by maceration in the fermenting must. Flavan-3-ols (monomeric catechin and proanthocyanidins) are another large family of polyphenolic compounds in wines, which are mainly responsible for the structure of wines such as astringency and bitterness. The last groups of flavonoids present in wines are the flavonols such as quercetin, myricetin, kaempferol, isorhamnetin and their glycosides. The biosynthesis of the phenolic compounds begins with the aromatic amino acid phenylalanine, a product of the shikimate pathway. Red wines have a higher content of total phenolics and contain a wider spectrum of phenolics than the white wines. The total content of phenolics in wine depends on a number of factors such as types of grapes (red or white) used for vinification and their extraction (temperature and maceration time), procedures employed for wine making and chemical reactions that occur during the aging of wine. A complex relationship exists between the factors that influence wine quality. A large number of epidemiological and experimental studies have shown that the moderate consumption of wine, particularly red wine, helps to prevent coronary heart disease and some types of cancers. Wines, especially red wines, contain a large variety of antioxidants including resveratrol, catechin, epicatechin and proanthocyanidins. Of all the components of wine, especially resveratrol, which is a natural component specifically present in wine, has been identified as being mainly responsible for these health-promoting properties. This present chapter explains the chemistry, occurrence and health properties of wine phenolic compounds. © 2012 Nova Science Publishers, Inc. All rights reserved