Abstract text: Pectins are major structural polysaccharides of plant cell walls and as functional biopolymers due to their gelling, thickening, and emulsifying properties. These functions are closely linked to molecular architecture. The diluted alkali-soluble pectin (DASP) fraction displays a characteristic architecture in which rhamnogalacturonan I (RG-I) regions are interspersed within a largely linear homogalacturonan (HG) backbone.
The aim of this study was to evaluate how RG-I structure influences the emulsifying performance of DASP. Native DASP isolated from apple cell walls was compared with an enzymatically modified fraction in which RG-I side chains were selectively degraded. Monosaccharide analysis revealed a marked decrease in arabinose and galactose contents, accompanied by an increase in uronic acids and higher polymer linearity.
These structural changes were reflected in rheology, as enzymatically modified DASP exhibited lower viscosity and stronger pseudoplastic behavior. Native DASP, characterized by a longer backbone and abundant RG-I side chains, formed dense networks in the continuous phase and at the oil–water interface, enabling effective electrosteric stabilization supported by weak electrostatic interactions. This resulted in a lower and more stable creaming index, particularly under acidic conditions. In contrast, the modified, more homogalacturonan-rich fraction stabilized emulsions mainly electrostatically, leading to gradual droplet flocculation at neutral pH and increased creaming..