Shear Rate Evaluation for the Viscosimetry of Thickened Liquids by a Sensory Test Using Five Concentrations of Newtonian Fluids / The Japanese Journal of Rehabilitation Medicine

Objective：The aim of this study is to obtain information for setting a common shear rate for the viscosimetry of thickened liquids.Materials & Methods：The panelists (healthcare professionals involved in dysphagia) drank five maltose syrups, and organized them in the order of viscosity based on their pharyngeal sense. Then, they drank three thickened liquids, i.e., 1.4% and 0.95% xanthan gum (XAN) solutions, and 1.4% guar gum (GUA) solution, and aligned them with the maltose syrups. We carried out the test twice using different concentrations of maltose syrups and obtained 126 answers. Results：Of all panelists, 77% could correctly arrange the five maltose syrups in the order of viscosity. The answers of the panelists who could serialize the five maltose syrups and the two XAN solutions were as follows. There were few answers that corresponded to shear rate of less than 11 sec^-1 for each of the thickened liquids. Meanwhile, most frequently answers corresponded to the shear rates of 61-140 sec^-1, 80-240 sec^-1, 210-620 sec^-1 for 1.4% XAN, 0.95% XAN, and 1.4 GUA solutions, respectively. Conclusion：The common shear rate for the viscosimetry of thickened liquids was not equivalent to the shear rate of 3 sec^-1 historically adopted in Japan；it was at least 50 sec^-1 according to the results of the sensory evaluation.