Compositional selectivity and quantitative interfacial adsorption of polyglycerol polyricinoleate in water-in-oil emulsions

Polyglycerol polyricinoleate (PGPR) is the most widely used lipophilic emulsifier for stabilizing water-in-oil (W/O) emulsions. Although its interfacial functionality has been extensively studied, quantitative information on the amount and molecular composition of PGPR interfacial adsorption remains limited. In this study, the calculated interfacial adsorbed amount of PGPR under different homogenization conditions and aqueous phase compositions was quantified, and the compositional selectivity of polyglycerol fractions during adsorption was evaluated. Increasing homogenization intensity significantly increased the calculated interfacial adsorption of PGPR, a trend consistent with the larger oil–water interfacial area associated with droplet size reduction. More importantly, analysis of the adsorbed polyglycerol composition revealed clear molecular selectivity of PGPR, with highly polymerized polyglycerol fractions preferentially enriched and lower-polymerized fractions depleted at the interface. The addition of different food proteins did not significantly alter the calculated interfacial adsorbed amount of PGPR at the investigated PGPR and protein concentrations, whereas increasing NaCl concentration slightly enhanced PGPR adsorption. These contrasting effects indicate that changes in the physicochemical properties of PGPR-stabilized interfaces are not necessarily accompanied by changes in PGPR interfacial occupation. Together, these findings provide quantitative insights into how emulsification conditions, molecular heterogeneity, and aqueous-phase composition influence PGPR interfacial adsorption and improve the understanding of its functionality in W/O emulsions.