Oral environment responsiveness of switchable water-in-oil high internal phase emulsions-based sodium salt carrier mediated by gelatin: Temperature sensitivity, phase inversion, and saltiness perception

Water-in-oil high internal phase emulsions (W/O HIPEs) with oral environment responsiveness were constructed based on the internal aqueous phase gelation by gelatin for switchable delivery of sodium chloride. The effect of gelatin addition on the physical stability, saltiness perception, rheological behavior, and microstructure of W/O HIPEs was investigated. The formation of the three-dimensional gel network structure of the internal aqueous phase fortified by gelatin contributed to increasing the apparent viscosity and reducing the water-oil mobility of W/O HIPEs, thereby enhancing their stability. During oral processing, the presence of gelatin extended the duration of saltiness perception of W/O HIPEs (T_max ≥ 14.7) without affecting its intensity (I_max = 5.9), which was related to the melting temperature of gelatin being close to physiological temperature (37 °C). Under the combined action of mucin, α-amylase, temperature, and intensive tongue-palate operations, the phase inversion from W/O to W₁/O/W₂ emulsion, encouraged the sodium salt to burst release, enhancing the saltiness perception. Furthermore, the hydrophobic interaction between gelatin and mucin impaired the stability of W₁/O/W₂ emulsions, accelerating the occurrence of phase inversion. Altogether, these findings offer valuable insights for developing novel reduced-fat and reduced-salt food products.