Relationships between shear rheology and sensory attributes of hydrocolloid-thickened fluids designed to compensate for impairments in oral manipulation and swallowing

Thickened fluids are commonly used as a therapeutic intervention for various swallowing impairments (dysphagia). However, there is little understanding around rheological properties of thickened fluids that are relevant to dysphagia. This study compared shear rheology of thickened fluids with sensory properties during oral preparation and swallowing. Fluids were thickened with different concentrations of three hydrocolloids (xanthan gum, starch, carboxymethylcellulose gum) to provide a range of viscosities at different shear rates, and yield stresses. Perceived oral cohesiveness, propulsion effort, stickiness, and oral residue were quantitatively assessed by a specially trained sensory panel, and data correlated with rheological measurements. Very strong correlations were found between fluid viscosities at shear rates of 10 s-1 for oral cohesiveness (r = 0.97), and 50 s-1 for propulsion effort (r = 0.97). Strong positive correlations were found between viscosities at 100 s-1 and perceived stickiness and oral residue (r = 0.78 and 0.80, respectively). Yield stress was not a direct indicator of any sensory attribute studied. Measurements of fluid viscosity at representative shear rates 10, 50 and 100 s-1 provide a sound basis for investigating the impact of a 2.5 mL bolus size on sensory performance of thickened fluids during oral preparation and propulsion. Different hydrocolloids produce differing sensory profiles, providing important consideration for selecting thickeners for dysphagia