Synergistic pH-shift and heat treatment for the recovery of protein isolates from ham processing brine: evaluation of protein ingredient quality, structure, and functional properties

Ham processing generates significant volumes of brine, a saline wastewater with untapped potential. This study compared three protein recovery methods: direct centrifugation, moderate heat treatment (75 °C), and a combined pH-shift-mild heat (PSMH) approach (65 °C). Both the PSMH method and moderate heat precipitation produced protein concentrates with the highest initial protein contents (62.15%–62.81%), which increased to 91.65%–95.59% purity after desalting, with NaCl levels reduced to <1.5%. Amino acid analysis revealed that PSMH-derived proteins had the highest total amino acid content (96.58 g/100 g). Sodium dodecyl sulphate-polyacrylamide gel electrophoresis confirmed improved recovery of muscle proteins, while Fourier transform infrared spectroscopy indicated that moderate heat treatment reduced the α-helix/β-sheet ratio. Proteins recovered using PSMH exhibited the highest water and fat binding capacities and maintained solubility across a broad pH range. They also exhibited strong foaming ability, although they showed slightly lower foam stability than proteins recovered by other methods, and they demonstrated emulsifying properties that were optimal under mildly alkaline conditions. Overall, PSMH presents a sustainable and efficient strategy for recovering functional proteins from ham brine for use in food and feed applications.