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

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−CH 3 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.