Study on Na⁺ Release and Saltiness Perception in High Internal Phase Emulsions During Oral Processing

High internal phase emulsions (HIPEs), defined as emulsions with a dispersed phase volume fraction exceeding 74%, are widely employed for modulating food texture and delivering bioactive compounds. To investigate the release kinetics of Na⁺ and saltiness perception in food systems, while achieving fat and salt reduction objectives, polyglycerol polyricinoleate (PGPR) was used as an emulsifier to prepare water-in-oil (W/O) HIPEs with an 80% aqueous phase volume fraction, and their behavior under simulated oral processing conditions was subsequently examined. Regarding matrix release, Na⁺ existed in a quasi-free ionic state within W/O emulsions, with its release rate significantly influenced by the dispersing medium and mastication duration. In salivary medium, salivary proteins initially restricted Na⁺ release. However, release progressively increased with prolonged mastication, and saliva markedly accelerated Na⁺ release compared to deionized water. Concerning oral transfer, elevated PGPR and NaCl concentrations prolonged emulsion retention on porcine tongue surfaces, whereas emulsions with lower aqueous phase volume fractions exhibited enhanced wettability by saliva and reduced mucoadhesion. Na⁺ diffusion through the mucin layer was primarily governed by the intrinsic structural properties of the emulsion and emulsion-mucin interactions. In terms of saltiness perception, W/O emulsions presented a relatively smooth, oily flavor profile, with saltiness perception being more susceptible to NaCl concentration. Emulsion texture also exerted a moderate influence on saltiness perception and overall acceptability. These findings demonstrated that modulation of PGPR concentration (4%-8%), aqueous phase volume fraction (30%-80%), and NaCl concentration (10-200 mmol/L) can optimize Na⁺ release behavior and oral mucoadhesion properties of W/O HIPEs, enabling sodium reduction without compromising saltiness. As a potential butter replacer, this system offered dual advantages of fat reduction and enhanced saltiness perception, providing theoretical foundations and technical guidance for the development of novel health-oriented food products.