The effect of the oxidation state of iron ions on the competitive complexation of malvidin by caffeic or ellagic acid

The complexation behavior of malvidin with ellagic and caffeic acid and ferrous and ferric ions was studied in model wine solutions by means of experimental photoluminescence studies and model calculations. Our results show the significant role of caffeic acid in the anthocyanin–polyphenol interaction (also known as copigmentation). According to our results in the presence of caffeic acid the impact of ferrous and ferric ions is negligible. These results also highlight the less important role of ellagic acid compared to caffeic acid in the formation of copigmentation complexes.