Na+ saltiness perception strongly depends on its diffusion and retention within the salivary layer, processes modulated by mucoadhesive polysaccharides. However, the underlying saltiness-enhancing mechanism of soy hull polysaccharide (SHP) remains unclear due to its compositional and structural heterogeneity. SHP was separated into neutral (SHP-N, hemicellulose) and acidic (SHP-A, RG-I-enriched pectin) fractions. Salivary mucoadhesion of Na+ and SHP were investigated. Compared to SHP-N, negatively charged SHP-A exhibited a stronger saltiness-enhanced effect by accelerating Na+ diffusion and prolonging retention, which is not mainly attributed to viscosity changes. The electrostatic screening effect of Na+ promoted stable mucoadhesion of SHP-A on the mucin layer. Strong hydrophobic interaction as the dominant force is primarily mediated by protein domains within the rhamnogalacturonan I (RG-I) region of SHP-A. Strong SHP-mucin affinity may influence Na+ adsorption-desorption dynamics and accelerate its penetration. This work reveals key structural domains of polysaccharides responsible for saltiness enhancement and their mucoadhesive driving forces in salivary layer.
Zhang et al. (Mon,) studied this question.