Fabrication of water-in-oil high internal phase emulsions containing astringent compounds for enhanced oral sensation

Abstract

This study aimed to mitigate astringency sensation from tannic acid (TA) or Rosa roxburghii Tratt juice (RRTJ) by incorporating them within the internal aqueous phase of water-in-oil high internal phase emulsions (W/O HIPEs).HIPEs with TA concentrations ranging from 0% to 0.4% were prepared using 2% lecithin and 3% PGPR as emulsifiers. Increasing TA content reduced the droplet size (1.4-3.5 μm) and enhanced physical stability, as reflected by a low instability index (<0.01) after centrifugation and a TA retention rate >90% over 28 days of storage. Rheologically, the HIPEs exhibited solid-like behavior (G′ > G″) and pronounced shear thinning. During simulated oral processing, emulsion droplets aggregated and increased in size. Molecular docking confirmed strong binding between TA and mucin (-12.913 kcal/mol), primarily via hydrogen bonding. Tribological tests showed that saliva-mixed HIPEs had only a slightly elevated friction coefficient, as the oil phase provided viscous lubrication that limited lubrication loss. Sensory evaluation confirmed effective astringency masking (astringency score <4) and improved flavor with added RRTJ, together with good spreadability. These findings demonstrated that W/O HIPEs can successfully reduce astringency and show potential for use in nutritious, fruit-enriched spreads.