Food formulation: rheological and tribological determinants of oral processing and flavor perception

Understanding how food behaves during oral processing requires going beyond its chemical composition to integrate rheological and tribological determinants that shape texture, mouthfeel, and ultimately flavor perception. This review examines how viscosity, microstructure, and flow properties govern aroma release and taste perception across liquid, semi-liquid, solid, and emulsion-based foods, while oral tribology elucidates lubrication regimes that drive sensations such as creaminess, smoothness, or astringency during mastication and bolus formation. Particular emphasis is placed on the interplay with saliva, whose proteins and physicochemical properties critically modulate lubrication and sensory dynamics. By combining rheological and tribological approaches termed "rheo-tribology" with sensory analysis, this work highlights integrated mechanisms of flavor release, from controlled diffusion in viscous matrices to tribological transitions at oral surfaces. Formulation strategies using hydrocolloids, proteins, fat replacers, and emulsifiers are detailed, showing how textural engineering can tailor perception and consumer acceptance, particularly in plant-based or reformulated products. Overall, the integration of rheology and tribology provides a comprehensive, physiologically relevant model of oral processing, offering predictive power for designing sensory-optimized foods that balance nutrition, functionality, and pleasure while addressing current challenges in health-driven reformulation and sustainable food innovation.