Beyond viscosity: Saliva‐driven oral processing of commercial dysphagia foods through rheology, tribology, and mucoadhesion

Designing safe and acceptable foods for individuals with dysphagia requires understanding oral processing beyond viscosity-based descriptors. Saliva plays a central role in bolus behavior by modulating lubrication, friction, and food–mucosa interactions. In this study, commercially available soft-solid and gel-like dysphagia-oriented foods (pasta-based puree, chicken-based puree, apple-based puree, vanilla-flavored pudding, and orange-flavored thickened water) were characterized through oscillatory rheology, three-interval thixotropy, tribology, IDDSI testing, and ex- vivo mucoadhesion on porcine tongue, in the absence and presence of simulated saliva. All products exhibited weak-gel behavior, supporting a balance between bolus cohesion and deformability. However, their functional response was strongly affected by saliva-mediated interfacial phenomena. Tribological measurements showed a marked reduction in friction over most of the investigated sliding-speed range, especially in the boundary and mixed lubrication regimes. Ex- vivo mucoadhesion showed product-dependent reductions in peak detachment force and/or work of adhesion under salivary conditions, indicating that the salivary pellicle can limit direct food–mucosa interactions. These findings support a mechanistic view in which the oral behavior of dysphagia-oriented foods arises from the coupling between bulk structure and saliva-driven interfacial mechanisms. Adhesion, lubrication, structural recovery, and IDDSI consistency should therefore be considered alongside viscosity. Because salivary flow and composition are frequently altered in dysphagic populations, saliva represents a major source of variability in product functionality. Incorporating saliva into experimental protocols can improve the physiological relevance of in vitro characterization and guide the rational design of safer and more acceptable dysphagia-oriented foods.