Emulsification capacity of pectin extracts from persimmon waste: Effect of structural characteristics and pectin-polyphenol interactions

Abstract

Polyphenol-rich pectin extracts obtained from persimmon waste might have great potential due to their emulsification capacity. Their emulsion stabilizing properties may be influenced by pectin molecular structure and pectin-polyphenol interactions which in turn can be determined by the extraction conditions. Hence, this work aimed to study the influence of the molecular structure characteristics and their respective pectin-polyphenol interactions of three polyphenol-rich persimmon pectin extracts obtained by three different extraction conditions. Low, medium and high severity extraction conditions resulted in covalent phenolics-extract (CP-E), non-covalent phenolics-extract (NCP-E) and free phenolics-extract (FP-E), respectively. The electrical charge of pectin was strongly dependent on the pH, becoming more negative at increasing pH due to carboxyl group dissociation. CP-E and NCP-E in solution had more expanded conformations than FP-E, with greater intermolecular distances and hydrodynamic diameters ranging from 1089 to 1791 nm for CP-E and NCP-E, whereas from 529 to 782 nm for FP-E. Their interfacial layer thickness was thicker at pH 3 than at pH 7, probably due to multilayer organization as a result of less repulsion between pectin chains. All pectin extracts were able to decrease the interfacial tension of an oil droplet from 35 to at least 25 mN/m, with FP-E at pH 3 being the most efficient (13.89 ± 1.07 mN/m). Even so, submicron O/W emulsions with negative ζ-potential values could be formed with all pectin extracts. However, CP-E rendered O/W emulsions with higher colloidal stability than FP-E or NCP-E, which showed aggregation and creaming. These findings provide novel insights to re-valorize pectin from persimmon waste