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-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.