Tailoring the high-protein texture-modified foods for the dysphagia elderly by heating whey protein isolate-pectin complexes

Abstract

Adequate dietary protein intake is an effective way to combat muscle wasting disorders in the elderly, who are highly susceptible to dysphagia due to declining physiological functions. Herein, whey protein isolate (WPI) and pectin electrostatic complexes were chosen to prepare texture-modified foods with high protein (15%, w/v) for dysphagia elderly. Firstly, the region of soluble complex formation was initially identified as pH 4.2–5.5 by determination of the zeta potential of both biopolymers. Following this, it was found that the stability of WPI-pectin complexes was significantly dependent on the increase in the amount of pectin (from 1.0 to 2.0 %, w/v). However, the viscoelasticity and the degree of WPI aggregation of these complexes after heat treatment (90 °C, 20 min) both showed the lowest level at pH 4.6 (it was fluid state) regardless of the pectin content, and the degree of protein aggregation weakened with the increase of pectin content. Additionally, the shear viscosity, yield stress, and tribological properties of the thermal complexes were also positively correlated with the degree of protein thermal aggregation. Moreover, based on the dietary texture classes developed by the International Dysphagia Diet Standardisation Initiative (IDDSI), unlike pure WPI thermally-induced gels that are attributed to level 6, the WPI-pectin thermal complexes can achieve texture class coverage from level 3 to level 6. These findings suggest that by modulating the electrostatic binding strength and positive-negative charge balance between WPI and pectin, tailored design of high-protein diets for elderly people with varying degrees of dysphagia may be achieved.