Sensory and rheological characteristics of thickened liquids differing concentrations of a xanthan gum-based thickener

Abstract

The objectives of this study were to develop and compare sensory characteristics of beverages and soups thickened with different concentrations of a xanthan gum-based thickener, and to examine, using rheological measurement, whether the viscosity of the thickened liquids conformed to the recommendations of the National Dysphagia Diet (NDD) Task Force. Beverages tested included water, apple juice, orange juice, soymilk, and Yakult. The thickening agent was added to samples at concentrations of 1, 2, or 3%. Addition of the thickening agent had a significant effect on the appearance, texture, and starchy flavor, which were evaluated by descriptive sensory evaluation. The reference standards of viscosity used in sensory descriptive analysis could be useful to practitioners who have to make dysphagia diets and need to learn to make them properly. In rheological measurement, viscosity of thickened liquids in stationary state would be perceived as higher compared to that while swallowing, because of the shear thinning property. This could lead to noncompliance of the medical advice or malnutrition. It is necessary to determine optimal proportion of xanthan gum-based thickener or uncover alternatives, which have shear thinning properties lower than those of xanthan gum, for the acceptance of dysphagia patients. There was no pudding-like viscosity as classified by NDD, when prepared following instructions. Future studies should include higher concentrations of thickener to find out the concentration of the thickener resulting in pudding-like viscosity as recommended by NDD.

Practical applications: When a manufacturer modifies or develops a xanthan gum-based thickener, findings from this study can be utilized to understand sensory and rheological characteristics of thickened liquid. For practitioners who have to make dysphagia diets, the reference standards of viscosity used in sensory descriptive analysis could be helpful for deciding the viscosity level of thickened liquids based only on visual evaluation. This study suggests manufacturers should provide clear direction for viscosity range and thickener concentration. Medical doctors should pay close attention to the risk of aspiration when prescribing pudding-like viscosity. Dietitians should understand the variability in achieving different levels of viscosity and should educate preparers who are responsible for making dysphagia meals.

Keywords: descriptive analysis; dysphagia; rheological measurement; thickened liquid; viscosity; xanthan gum-based thickener.