The importance of shear and extensional rheology and tribology as the design tools for developing food thickeners for dysphagia management

Food texture manipulation and modification is a practical strategy to reduce the risk of aspiration for dysphagia management. Addition of thickening agent to thicken liquid can increase the bolus transit time, thus, potentially leading to safer swallowing. The important bolus characteristics for safe swallowing include viscosity, hardness, cohesiveness, and adhesiveness, which can be related to the rheological and tribological properties of bolus. Therefore, this work highlights the importance of shear and extensional rheology and tribology as the design tools for developing dysphagia food thickeners. A range of commercially available thickening powders (xanthan gum-, guar gum-, and modified starch-based) was studied to create baseline rheological and tribological data. In general, it was observed that the increase in thickener concentration led to increases in shear viscosity, viscoelastic properties, and extensional viscosity, but the impact on tribological behavior was varied depending on the type of thickener and lubrication regime. It was also revealed that, at the same liquid consistency based on IDDSI classification, xanthan gum-based thickener showed the highest low shear viscosity, extensional viscosity, and lubricating capacity than the other thickeners. More specifically, modified starch-based thickener showed the poorest extensional property and could be the least effective thickener for promoting safer swallowing. The proposed design tools may be used beneficially to tailor novel thickeners for dysphagia management based on the obtained baseline data. Nonetheless, in-depth knowledge on the relationship between these properties and in-vivo measurements of swallowing is still required and is key to achieve the most effective therapeutic strategy in the dysphagia treatment.