Influence of phenolic compounds and tannins on wine-related microorganisms

Abstract

Polyphenols represent an important family of compounds found in grapes and wine. To date, a plethora of polyphenols has been identified in various parts of the grape, although typically only 20-30 polyphenols are identified in grapes and must using standard analytical methods, such as HPLC/UV-Vis. The biosynthesis of these compounds follows the route: the shikimic acid, the phenylpropanoid, and the flavonoid pathway. The products of these pathways are the hydroxybenzoic and the hydroxycinnamic acids, the stilbenes and the flavonoids. The occurrence and the typical concentrations of the different polyphenols in grapes, grape musts and red and white wines are reported here. One of the best analyzed polyphenols in grapes and grape products is trans-resveratrol. It is biosynthesized from p-coumaryl-CoA and malonyl-CoA resulting in the stilbene derivative. It has been found in nearly all grape varieties and their respective products in various concentrations. Yet, the highest amounts were detected in red grapes and respective wines. Beside antioxidative effects polyphenols also show antimicrobial effects. These have been proven for several polyphenols, above all for trans-resveratrol. The antimicrobial effect of salicylic acid is used to induce systemic acquired resistance (SAR) in plants. Plants are treated with salicylic acid, which then produce more polyphenols in return. This leads to a higher resistance against bacterial or fungus attacks. Some polyphenols are formed not until the grapes are crushed for fermentation. Typical examples are tyrosol, which is formed from the amino acid tyrosine, and the so-called grape reaction product (GRP), which is formed from caftaric acid and glutathione. They have been used as indicators for a oxidative production technique. Recent research has shown that several yeast strains can have an effect on polyphenol content of wine. According to literature some polyphenols can be depleted by more than 50% through reactions between yeast and the respective polyphenol. For trans-resveratrol it has been proved that it possesses a life span-increasing effect on Saccharomyces yeast. © 2009 Springer-Verlag Berlin Heidelberg. All rights reserved.