Hydrogel foam with designed structural properties of egg white protein through building aggregates as potential dysphagia food

Abstract

To address the growing demand for texture-modified foods (TMFs) among individuals with dysphagia, the structural properties of alkali-heat treated egg white protein aggregates (AHEWP) were investigated to developed hydrogel foams as suitable soft gels. The results showed that AHEWP presented partially unfolded and higher content of β-sheet structures. The alkaline shift suppressed thermally denatured molecular unfolding (exposing aromatic and hydrophobic amino acids) and blocked hydrogen bonding, leading to the generation of small-sized AHEWP. Within the pH range of 10.5–11.25, raising temperature promoted more covalent bonding to produce structurally compact aggregates. Compared to EWP, AHEWP exhibited remarkably stable foams (85.62–91.99% of FS) and could form Ca2+ crosslinked cold gels, which were contributed to the formation of hydrogel foam. The alkali-heat treatment of high intensity gave a less increase in surface tension and richer interfacial proteins. SEM and microrheology revealed that the alkaline shift transformed the hydrogel network of AHEWP into a “sheet-like” stacking structure, accompanied by a rise in the macroscopic viscosity index and a change of gelation rate. At pH 11.0 and 11.25, the higher temperature, the denser the pore and the lower the elasticity index. The self-supporting property and water loss of AHEWP hydrogel foam reduced, and their time stability enhanced with increasing pH and/or temperature. According to IDDSI, AHEWP hydrogel and hydrogel foam were attributed to level 4–7 and 4–5, respectively. Overall, AHEWP has the potential to establish hydrogel foam systems that will serve as a valuable reference for designing protein-based soft gel TMFs for dysphagia diets.