Abstract: In this study, the emulsifying properties of porcine bone protein hydrolysates (PBPH) with different degrees of hydrolysis (DH) were determined. Porcine bone protein was hydrolyzed by alkaline protease for 0, 1, 2, 3, 4, and 5 h, yielding DH of 0%, 5.6%, 7.8%, 11.1%, 14.3% and 17.2%, respectively. The emulsifying activity, emulsion stability and microstructure, zeta potential, and molecular mass distribution of active peptides of PBPH were measured. The results revealed that the emulsifying activity index and emulsion stability index of hydrolysates were increased at the beginning and then decreased with increasing DH (P < 0.05), and the highest emulsifying stability was obtained at a DH value of 11.1%, which was presumably related to the highest surface hydrophobicity and zeta potential, the smallest mean particle size and the uniform droplet size distribution. The results of size exclusion chromatography proved that the content of large peptides was decreased and the content of small peptides was gradually increased with the increase of DH. The hydrolysis process was accompanied by cleavage of polypeptide chains and aggregation of proteins. The functional properties of PBPHs with different DHs were affected by the changes in protein structure, which may be the reason for the changes of the emulsifying properties. It can be concluded that the PBPH obtained after 3 h hydrolysis (DH = 11.1%) had the best emulsifying properties and could be used as an emulsifier in emulsions with good physical stability.

Key words: porcine bone protein, hydrolysate, degrees of hydrolysis, oil-in-water emulsion, emulsifying properties