The thixotropic and rheopectic behaviour of maize starch and maltodextrin thickeners used in dysphagia therapy

The viscosity of starch-thickened foods is critical in managing dysphagia (impaired swallowing). These fluids are highly non-Newtonian and exhibit thixotropic behaviour. The thixotropy of the starch-based thickeners that are used to achieve this critical viscosity is presented. Two types of thickeners were evaluated; maize-based and maltodextrin-based. The thixotropy of these thickeners proved to be complex and the behaviour could be toggled between thixotropy and rheopexy by changing certain variables. The sol to gel transition favours low or zero shear rates when the initial viscosity is low (low starch concentration), but shearing is preferred for structure formation of high viscosity (concentrated) samples. This is likely to be due to Brownian motion being restricted in thicker samples due to less solvent between starch molecules. This may also cause starch granules to be sheared open causing more amylose to enter the viscous matrix.