Study on Structure and Properties of Hydrolyzed Rice Protein with High Emulsification Properties

In order to explore the key components affecting the emulsification characteristics in hydrolyzed rice protein. rice protein was hydrolyzed by acidprotease, papain and trypsin, respectively. The relationships between the structural and functional properties of different hydrolyzed rice proteins were studied by surface hydrophobicity, Fourier transform infrared spectroscopy (FTIR), emulsifying activity index and emulsifying stability index. <5 kDa, 5~10 kDa, and >10 kDa were separated from the rice protein with degree of 2% treated with trypsin (trypsin 2%) by ultrafiltration. The interfacial tension, quartz crystal microbalance with dissipation (QCM-D), mean diameter particle, confocal laser scanning microscope (CLSM) and storage stability were measured to explore the influence of molecular weight on the interfacial characterization and emulsion stability. The results demonstrated that hydrolysates treated with trypsin exhibited the highest yield. Compared with the rice protein, the surface hydrophobicity of the enzymatic hydrolysis products declined significantly except for the rice protein with degree of 6% treated with trypsin (trypsin 6%). The secondary structure content revealed that the β-sheet contents of hydrolyzed rice protein significantly decreased, showing that the structure of hydrolyzed rice protein was more unfolded. The trypsin 2% exhibited the better emulsifying capacity. The mean diameter particle of <5 kDa-stabilized emulsions increased from 2.59 μm to 7.82 μm after 7 days storage. The result suggested that emulsion stabilized with <5 kDa had poor storage stability. >10 kDa had lower interfacial tension and thicker interfacial film than the others. The emulsion prepared by >10 kDa exhibited better emulsion stability. The results indicated that the emulsion stabilized by high molecular peptides was more stable than the smaller ones.