Transformation of stacked π-π-stabilized malvidin-3-O-glucoside - Catechin complexes towards polymeric structures followed by anisotropy decay study

The temperature-dependent transformation of π-π-stabilized stacked malvidin-catechin structures towards polymeric-type structures was studied by photoluminescence (PL) and anisotropy decay studies. The results show an immediate decrease of the anisotropy decay after elevating the temperature from 293 K to 303 K or 313 K, while only a very slow increase in the anisotropy decay could be observed when the samples were kept at these elevated temperatures for a longer time such as a few days. The slow polymerization of the malvidin-polyphenol system could be identified as the main process responsible for the change in optical properties by the comparison of the time-dependence of the anisotropy decay with the change observed in the PL intensity. Measurements were also conducted in red wines, where we observed similar results. This suggests a possibly broader relevance of our results for all systems, where anthocyanins and polyphenols are present in considerable concentrations.