High hydrostatic pressure enhances the interaction, antioxidant activity, stability, between endogenous pectin and malvidin in‘Beibinghong'grapes

This paper studies the physicochemical properties, and structural characterization of endogenous pectins (GP1, GP2, GP3) extracted from ‘Beibinghong’ grape pomace using three techniques (high hydrostatic pressure extraction, high hydrostatic pressure cellulase extraction, and microwave-assisted extraction) and the interaction mechanism between the three pectins (GP) and malvidin (MV) was also explored under high hydrostatic pressure (HHP). GP1, GP2 and GP3 are all high methoxyl GP with HG regions as the main body, mainly containing galacturonic acid. GP1 and GP3 are similar, with large linear and regular smooth pectin structures, high esterification degree and high molecular weight. However, GP2 has more RGI regions, a more complex and branched structure, and a smaller esterification degree and molecular weight. At pH 4, time 15 min, mass ratio 1:9 (w/w) and pressure 350 MPa, the binding with MV, among which the binding rate of GP2-MV (56.35 ± 1.03 %) reached the maximum. UV–Vis, FTIR and XRD results showed that new intermolecular associations were formed between GP and MV through hydrophobic interactions and hydrogen bonds under HHP treatment. Zeta potential, Molecular adsorption docking confirms that GP and MV can bind through electrostatic interactions with van der Waals and that the pectin GP2-MV has the lowest adsorption binding energy (−250.1 kcal/mol) suggesting that MV adsorbs optimally to GP2. In addition, HHP treatment improved the storage stability, antioxidant activity and gastrointestinal stability of the complex. This study contributes to an in-depth understanding of the interactions between endogenous GP and MV molecules in HHP-treated ‘Beibinghong'grapes.