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Summary In this study, the effects of high‐pressure homogenisation (HPH) treatment on structural and functional properties of mussel protein isolate (MPI) were investigated. HPH treatment did not modify the protein profiles of MPI, but caused changes in secondary, tertiary and quaternary structure. HPH treatment improved functional properties of MPI such as solubility, foaming ability, emulsifying activity and stability. This preliminary study demonstrated the potential of HPH technology to process MPI due to improving its functional properties.

In this study, the effects of limited hydrolysis and/or high-pressure homogenization (HPH) treatment in acid conditions on the functional properties of oyster protein isolates (OPI) were studied. Protein solubility, surface hydrophobicity, particle size distribution, zeta potential, foaming, and emulsifying properties were evaluated. The results showed that acid treatment led to the dissociation and unfolding of OPI. Subsequent treatment such as limited proteolysis, HPH, and their combination remarkably improved the functional properties of OPI. Acid treatment produced flexible aggregates, as well as reduced particle size and solubility. On the contrary, limited hydrolysis increased the solubility of OPI. Furthermore, HPH enhanced the effectiveness of the above treatments. The emulsifying and foaming properties of acid- or hydrolysis-treated OPI significantly improved. In conclusion, a combination of acid treatment, limited proteolysis, and HPH improved the functional properties of OPI. The improvements in the functional properties of OPI could potentiate the use of oyster protein and its hydrolysates in the food industry.

Oyster protein isolate (OPI) suspensions (6.19 % ± 0.82 %, w/v) were treated by high-pressure homogenization (HPH) at 0 (control), 20, 40, 60, 80 or 100 MPa for three cycles. Protein profiles, secondary structure, free sulfhydryl, surface hydrophobicity, particle size distribution, zeta-potential, solubility, water and oil holding capacity (OHC), emulsifying and foaming properties of the obtained suspensions were analyzed. The results showed that HPH treatment did not cause changes in protein profiles of OPI, but caused changes in secondary structure, content of α-helix decreased but content of β-turn and random coil increased significantly (P < 0.05). Free sulfhydryl and surface hydrophobicity all increased significantly (P < 0.05) after HPH treatment, indicating that tertiary and quaternary structures changed. Functional properties of OPI significantly (P < 0.05) improved after HPH treatment, such as zeta-potential (from −12.67 to −33.57 mV), solubility (from 20.24 % to 57.99 %), OHC (from 981.77 % to 1229.40 %), foaming ability (from 17.50 % to 35.00 %), foaming stability (from 44.49 % to 66.60 %), emulsifying activity index (from 8.87 to 17.06 m2/g) and emulsion stability index (from 14.65 to 41.68 min). At 60 MPa and 80 MPa, the improvements were more remarkable. However, HPH treatment significantly (P < 0.05) decreased particle size (from 200–500 nm to 0–200 nm) and water holding capacity (from 341.15 % to 216.96 %). These improvements were closely related to structural changes and reduction of particle size. Application of different pressures affected functional properties of OPI. These results could provide information for determining HPH applying condition in OPI modification.