Impact of thermal treatment on proanthocyanidin-pectin binary complexes: Insights from structural, rheological, antioxidant, and astringent properties

In this study, the effects of thermal treatments on the structural, rheological, water mobility, antioxidant, and astringency properties of proanthocyanidin (PA)-pectin binary complexes were investigated. Thermal treatments (25, 63, or 85 degrees C) significantly decreased the particle size but increased the molecular weight of PA-pectin complexes, which indicated that heating altered the intermolecular and intramolecular interactions between PA and pectin. The thermal treatments reduced the apparent viscosity of both pectin and PA-pectin complexes, but the presence of proanthocyanidins (PAs) increased the apparent viscosity and water mobility of the PA-pectin complexes. Antioxidant activity analysis showed that the presence of pectin slightly reduced the antioxidant activity of the PAs, but there were no significant changes in the total phenolic content and antioxidant activity after thermal treatment. Finally, we found that pectin reduced the astringency of the PAs by forming PA-pectin complexes. Moreover, the thermal treatments also significantly reduced the astringency of the PA-pectin complexes.