Measures of the yield stress fluids oriented for dysphagia management using steady-state shear, transient shear, and large-amplitude oscillatory shear (LAOS)

Dysphagia has become a highly prevalent and ever-growing disease among the elderly in today's society. Polysaccharide-thickened food with yielding features oriented toward dysphagia management has been recognized as a suitable diet capable of alleviating the swallowing risk by allowing the swallow-related muscles to coordinate this activity with appropriate timing. However, the divergence of different measures and the resultant discrepancy between yield stress values remains that experimentally and theoretically impedes the understanding of yielding features of food on the efficiency of dysphagia management. Herein, we compared the typical rheological approaches to yielding measurement, including steady-state shear, transient shear rate ramp, and large-amplitude oscillatory shear (LAOS), based on three polysaccharide-thickened solutions and nutrition emulsions. As a hallmark of thixotropy properties, the hysteresis loop was quantitatively illustrated for the three polysaccharide emulsions to distinguish them as simple or complex yield stress fluids. The Herschel–Bulkley model was employed to obtain the dynamic yield stress in steady-state shear mode. Yield stress estimated by transient shear and small oscillatory shear methods is comparable. Importantly, different from the common approaches that acquire only one critical yield stress value, the stress bifurcation method from LAOS employed in this work enabled us to estimate the yielding onset and end in the solid–liquid transition process of the fluids, which may bring new insight and motivate innovative idea in the diet design in dysphagia management.