Thermal and light stability of pelargonidin-3-glucoside and catechin copigmentation complex from high-pressure processing: effects of high-pressure processing conditions on complex conformation and structure characteristics

Former research has shown that high-pressure processing (HPP) accelerates copigmentation reaction rates between pelargonidin-3-glucoside and catechin, increasing solution absorbance. However, the structural characteristics of these complexes and HPP's effects on their conformations remain unclear. This study prepared pelargonidin-3-glucoside and catechin complexes under varying pH, molar ratios, and high pressures, followed by separate light and heat treatments. Solution absorbance was measured, and molecular cluster structures and corresponding characteristics were analyzed to explain stability under HPP conditions. The results indicated that HPP-induced copigmentation complexes show reduced thermal and light stability, along with increased conformational diversity and a decreased proportion of dominant structures (from 41.99%−88.92% to 22.56% at pH 1.5, and from 26.48%−34.56% to 15.53% at pH 3.6). The primary interaction between catechin and Pg-3-Glc was van der Waals forces unaffected by HPP. Additionally, HPP lowered excitation energies in flavonoid cations (pH 1.5) and increased energies in hemiketals (pH 3.6).