Comparison of Rheological and Tribological Properties of Cold Thickened Beverages for Dysphagia Management

This study investigated the rheological and tribological properties of cold beverages [bottled water (BW), sports drink (SD), orange juice (OJ), and whole milk (WM)] thickened with various concentrations (1%, 2%, and 3%, w/w) of xanthan gum-based food thickeners. All thickened beverages exhibited high pseudoplastic behavior, with increasing thickener concentration leading to higher viscosity and viscoelastic moduli and a lower flow behavior index. Thickened BW, SD, and WM exhibited typical Stribeck curves covering the boundary, mixed, and hydrodynamic lubrication regimes. However, thickened OJ displayed a different curve pattern comprising five regimes because of the presence of small pulp and gel particles. As the thickener concentration was increased, the maximum friction coefficient (μ) values of thickened BW, SD, and OJ decreased, whereas that of thickened WM increased because of the depletion flocculation of emulsion particles. The maximum μ values of thickened beverages, except for thickened WM, were positively correlated with n and tan δ values with increasing thickener concentration. Thus, the tribological characteristics of cold thickened beverages had a good relationship with their rheological properties, which were greatly influenced by the thickener concentration and beverage type.