Relationships Among Rheological, Sensory Texture, and Swallowing Pressure Measurements of Hydrocolloid-Thickened Fluids.

The objective of this study was to examine the relationships among three categories of measurements (rheological, sensory texture, and swallowing pressure) from fluids thickened to two different viscosities with 15 different hydrocolloids. Fluids at viscosities of 300 and 1500 cP (at 30 s(-1)) were targeted because these are the viscosities corresponding to the barium standards used in radiographic dysphagia diagnosis. Within the low viscosity (nectar) fluids (300 cP), the sensory properties thickness, stickiness, adhesiveness, mouth coating, and number of swallows were highly positively correlated with each other and highly positively correlated with the flow behavior index, n value (an indicator of shear-thinning behavior). Within the higher viscosity (thin honey) fluids (1500 cP), the sensory textures of adhesiveness, stickiness, mouth coating, and number of swallows correlated positively with rheological measures of n value. Swallowing pressures measured in the anterior oral cavity correlated negatively with the consistency coefficient k [shear stress/(shear rate) (n) ]. Samples that were more shear thinning (lower n values, higher k values) were generally perceived as less thick, with less adhesive properties (stickiness, adhesiveness, mouthcoating, and number of swallows). This information can be useful for selecting thickeners for people with dysphagia. A desirable thickener for many dysphagic patients would be one that allowed for a safe swallow by being viscous enough to reduce airway penetration, yet pleasant to drink, having the minimal perceived thickness and mouthcoating associated with greater shear thinning.