Phenolic Compounds and Wine Color

Abstract

Grapes and wine contain a large array of phenolic compounds. Derived from the basic structure of phenol (hydroxybenzene), the term “phenolic” refers to any compound with a phenol-type structure. Singleton (1980) describes the classes of phenolics in terms of chemical structures that range from relatively simple to complex. One phenolic group is composed of the nonflavonoids, which are derivatives of cinnamic and benzoic acid. Members of the group include hydroxycinnamates and benzoates (and their derivatives), as well as tyrosol. Additional group members are other lower molecular weight phenolics similar to those described, but probably arising from higher molecular weight forms as a result of degradation. These compounds include the volatile phenolics, hydrolyzable tannins, and benzene derivatives. A second large group of phenolics includes the flavonoids. This group encompasses catechins, flavonols, and anthocyanins. A third group is recognized in wine, and represents a composite of phenolic-protein-polysaccharide complexes. Representative structures of these major classes of phenolics are presented in Fig. 7-1.