Enhancement of macadamia protein solubility and functionality using combined pH-shift-heat treatment: Role of ionic...

This study aimed to enhance the physicochemical and functional properties of macadamia protein isolate (MPI) using a combined pH-shift-heat-treatment (PSHT), comparing protein dispersion in phosphate buffered saline (PBS) versus pure water (H₂O). PSHT reduced particle size and increased surface hydrophobicity of MPI colloidal particles. Functional improvements were greater in H₂O than in PBS, due to salt ions interfering with electrostatic interactions. Specifically, PBS treatment increased solubility from 9.24% to 55.96%, with emulsifying and foaming capacities rising 1.38- and 7.02-fold, respectively. In H₂O, solubility increased from 10.22% to 99.39%, with emulsifying and foaming capacities increasing 1.75- and 8.15-fold, respectively. Moreover, oil-in-water emulsions prepared with PSHT-H₂O-treated MPI consistently demonstrated superior overall emulsion stability. These outcomes corresponded with changes in protein secondary/tertiary structures and colloidal microstructure. In conclusion, the PSHT-mediated technique significantly enhancing the solubility and functionality of MPI, supporting their promising application as functional ingredients in high-protein beverages and emulsified food systems.