Structural and functional properties of perilla protein isolate extracted from oilseed residues and its utilization in Pickering emulsions

Abstract

The objective of this study was to investigate the effects of defatting methods (hot-pressing, cold-pressing and solvent-extraction) on the functional and structural properties of perilla protein isolate (PPI) extracted from oilseed residues. Cold-pressing residues isolated protein (CRIP) exhibited the highest foaming ability (90.67%), emulsification capacity (3390.09 m2/g) and water holding capacity (2.17 g/g), which were attributed to its high surface hydrophobicity (119.29) and solubility (78.71%) and small particle size (318 nm). However, the oil holding capacity of CRIP (2.31 g/g) was slightly lower than that of hot-pressing residues isolated protein (HRIP). Furthermore, the water/oil holding capacity, foaming capacity and emulsifying stability of CRIP and HRIP were significantly higher than that of solvent-extraction residues isolated protein (SRIP). Interestingly, there were no significant differences in the secondary structure and ternary conformation among CRIP, HRIP and SRIP. At the oil-water ratio of 5:5 and PPI nanoparticles concentration of 2.0%, the creaming index of CRIP, HRIP and SRIP nanoparticle-stabilized Pickering emulsions after 7 d of storage were 26.01%, 29.42% and 31.45%, respectively. The emulsifying stability of CRIP nanoparticle-stabilized emulsions was better than that of HRIP and SRIP nanoparticle-stabilized emulsions, which was ascribed to the small droplet size (27.55 μm) and high ζ-potential (−52.74 mV) of CRIP nanoparticle-stabilized emulsion. These results indicated that PPI extracted from cold-pressing residues demonstrated excellent functional properties and could be used as a potential food-grade emulsifier for Pickering emulsions fabrication.