Modulation of viscosity, swallowability, and stability of starch-based thickener: The effect of konjac gum and xanthan gum.

Hydroxypropyl distarch phosphate (HDP), as a commonly used starch-based thickener in dysphagia dietary interventions, is highly susceptible to enzymatic degradation by amylase. Although polysaccharides can improve the viscosity of starch, their effectiveness varies depending on the type of polysaccharides. This study investigated the effects of konjac gum (KG) and xanthan gum (XG) on the physicochemical properties of HDP. Both KG and XG increased the pasting viscosity, dynamic modulus, and apparent viscosity of HDP in a concentration-dependent manner. The flexible long chains of KG were conducive to the increase of HDP viscosity and reduced the viscosity loss caused by shear. The rigid structure of XG increased the elasticity of HDP but intensified the shear-thinning behavior. Furthermore, KG and XG reduced free hydroxyl groups and free water content of HDP while promoting the formation of intramolecular/intermolecular hydrogen bonds and bound water, thereby stabilizing the network structure. According to the International Dysphagia Diet Standardization Initiative (IDDSI) framework and in vitro oral simulation, HDP-polysaccharide composite pastes were assessed as IDDSI levels 3-4 and exhibited resistance to viscosity loss under artificial saliva exposure, indicating suitable swallowing performance. This study provides a theoretical basis for improving the viscosity stability of starch-based thickeners and offers practical guidance for developing dysphagia-friendly foods.