Decreasing the pH value would improve the swallowing characteristics of whey protein isolate-enriched thickened fluids for dysphagia populations.

The global aging of the population is accelerating, and dysphagia poses a threat to the health of the elderly. Thickened fluid foods prepared from polysaccharides and proteins could address dehydration and protein deficiency in the elderly dysphagia population. In this work, the structural characteristics, rheological properties, and swallowing characteristics of complexes formed by whey protein isolate (WPI) and polysaccharides (xanthan gum (XG), λ-carrageenan (λC), and konjac glucomannan (KGM)) at different pH values were investigated. As the pH decreased, there was a decrease in the charge of WPI, which weakened the electrostatic interactions resulting in the higher turbidity and particle size of complexes. At near pH 4, the XW complex had a moderate level of yield stress, zero-shear viscosity, and adsorption height, which resulted in moderate oral transit time, stretch length, and residual rate during swallowing, making it more potential as dysphagia foods. However, at pH near 4, λW and KW complexes had lower viscosity, adsorption height, and IDDSI levels, making them less suitable for dysphagia foods. The above results suggest that in WPI-enriched thickened fluids, the pH value could be appropriately adjusted to change the rheological properties and swallowing characteristics of the thickened fluids, thereby producing products adapted to elderly people with dysphagia.