Fabrication and Encapsulation of Soy Peptide Nanoparticles Using Ultrasound Followed by Spray Drying

Peptide aggregation inevitably occurs during hydrolysis, and insoluble peptide aggregates (ISPA) are used as feed for animals due to their poor water solubility and unpleasant bitter flavor. Ultrasound was used to fabricate soy peptide nanoparticles by reassembling ISPA, followed by spray-drying encapsulation to develop low-bitterness peptide microcapsules with soluble soybean polysaccharide (SSPS) and stevioside (STE) as wall materials. Powder properties, bitter taste, and the morphology of the microcapsules were evaluated. The formation of soluble peptide nanoparticles (<200 nm) was observed after ultrasound due to the reassembly of ISPA through the disruption of non-covalent intermolecular interactions. A gradual reduction in bitter taste was observed with increasing ultrasonic time. Moreover, spray-drying encapsulation with STE could effectively improve the flowability and wettability of the microcapsule powder owing to the rapid migration of surface-active STE to the atomized droplet surface, as evidenced by the lower angle of repose and wettability time. Peptide microcapsules with STE (spherical particles with smooth surfaces) exhibited lower density and reduced bitterness because STE (0-0.1%, w/w) exhibited an excellent bitter-masking effect. With high STE concentrations (>0.5%, w/w), microcapsules exhibited a higher bitter taste than unencapsulated peptides due to the increased surface distribution of STE on the microcapsules. These results provide an effective technique to improve the physicochemical properties of ISPA.