Charge-Symmetry-Mediated Liquid-Liquid Phase Separation Enables Tailored High-Protein Food Models.

Precise control of the matter state and dynamics is a key challenge in developing novel food matrices using concentrated protein coacervates. Herein, we report a pH-driven liquid-gel-solid transition of protein coacervates composed of β-lactoglobulin (BLG) and lysozyme (LYS). The terminal relaxation time of the coacervate extended from 0.17 ms to 267 s during the phase transition due to increased affinity. Spin-spin relaxation data, hydrogen bond competition experiments, and molecular dynamics simulations revealed that increasing the pH from 6 to 8 shifted the BLG/LYS stoichiometric ratio from 3:1 to 1:1. The enhanced charge symmetry expanded the interaction interface between BLG and LYS by 1.8 times, thereby promoting the desolvation of bound water and the formation of protein-protein hydrogen bonds that consequently slowed the dynamics of the BLG-LYS coacervates. Overall, this study introduces a new class of protein-based food models with tunable physical properties and offers valuable insights into their precise control.