Comparative characterization of pectin fractions from pomegranate peel: Structure-Function relationships

This study evaluated structure-function relationships of four pectin derived from pomegranate peel: alcohol-insoluble residue (AIR), water-soluble pectin (WSP), homogalacturonan (HG)-enriched pectin, and rhamnogalacturonan-I (RG-I)-enriched pectin. AIR and WSP exhibited higher molecular weight (M _w) and moderate degree of methylation/acetylation (DM/DA), showing superior water- and oil-holding capacities (13.88-20.90 g/g and 4.14-4.65 g/g respectively), excellent emulsifying activity index and emulsion stability index (EAI: 12-16 m²/g, ESI: 80-91%), and strong antioxidant activity. HG-enriched pectin, rich in galacturonic acid (GalA) (74.24-89.94%) and low DM (<5%), formed strong calcium-induced gels (gel strength up to 190 g) but had limited emulsifying and holding capacities. RG-I-enriched pectin, with abundant neutral sugar branches, demonstrated moderate overall functionality. Structure-function correlation analysis revealed that high M _w, moderate DM/DA, and branching enhanced emulsifying, water-holding, oil-holding, and antioxidant properties, while linear HG structures promoted gel formation. These results support the targeted use of pomegranate peel pectin fractions as functional ingredients in food applications.