Performance evaluation of heated rice protein/konjac glucomannan mixtures as dysphagia diets

Neutral polysaccharide konjac glucomannan (KGM), characterized by its exceptional high viscosity, was selected to enhance the stability of rice protein (RP) with poor water solubility. This enabled the preparation of a high-protein, fluid RP/KGM mixtures through thermal processing (100 °C, 30 min), offering a safe and convenient diets for elderly individuals with dysphagia. The results revealed that adding 0.5% KGM was sufficient to provide excellent stability for RP dispersions (5%, 10%, 15%, w/v). Shear rheology results revealed that, regardless of RP content, the yield stress and apparent viscosity at a shear rate of 50 1/s for heated RP/KGM mixtures significantly increased with rising KGM content (from 0.5% to 1.5%), corresponding to ranges of 0.12∼42.0 Pa and 0.49∼12.3 Pa s, respectively, as well as thixotropy, viscoelasticity, and cohesiveness. Similarly, the extensional viscosity (from 1 to 6 Pa s) of heated RP/KGM mixtures increased significantly with rising KGM content, while the contribution of RP was minor. However, lubricity assessments found that the high viscosity of KGM caused the friction coefficient of heat-treated mixtures to increase markedly with polysaccharide content in the elastic-hydrodynamic regime. According to the IDDSI framework, mixtures containing 0.5% and 1% KGM fall within level 2∼3 and level 3∼4, respectively. Samples containing 1.5% KGM may cause airway obstruction due to excessive viscosity, yield stress, and cohesiveness, and thus may not be suitable for elderly individuals with dysphagia. These findings lay the foundation for designing protein-rich, convenient-to-consume, easy-to-swallow liquid foods using RP/KGM mixtures.