Characterization of (+)-Catechin−Acetaldehyde Polymers: A Model for Colloidal State of Wine Polyphenols

Abstract

The (+)-catechin−acetaldehyde condensation was studied as a model for tannin polymerization and precipitation in red wines. It was shown by using LSIMS that reaction products are catechin polymers with CH−CH3 bridges at two reaction sites. Before the end of monomer conversion into polymers there is an aggregation followed by a phase separation. Particle mean diameter was measured by dynamic light scattering directly in reaction medium. Comparison between particle and polymer sizes showed that polymers aggregate into colloidal intermediates before a large polymerization degree is reached. These particles then coagulate further, which leads to polymer precipitation. This colloidal behavior is explained by hydrophobic forces since aggregates and precipitate redissolve in ethanol. Keywords: Tannin; wine aging; colloid; catechin; acetaldehyde