Homogenization pressure and soybean protein concentration impact the stability of perilla oil nanoemulsions

Perilla oil (PO) nanoemulsions (PON) were prepared using different concentrations (2, 3, and 4%) of soybean protein isolate (SPI) at different homogenization pressures (80, 100, 120, and 140 MPa). The stability of the PON and the interaction between interfacial protein structure and stability were investigated. The results showed that SPI concentration changed the particle size, zeta-potential, and interfacial protein concentration of the PON, but the SPI concentration did not change the interfacial protein structure. The PON from the 3% SPI group had the smallest particle size, the highest absolute zeta-potential, and the highest interfacial protein concentration. Physical stability and oxidant stability of the PON were best with 3% SPI. However, homogenization pressure not only changed the stability but also changed the structure of the interfacial proteins. Taken together, the PON at 120 MPa of pressure were the most stable. As homogenization pressure increased, the alpha-helix and beta-sheet contents of the interfacial protein decreased, and random coil content increased. The SPI unfolded on the surface of the oil droplets, increasing the flexibility of the SPI, so that the protein was more easily adsorbed on the surface of the oil droplets, thereby increasing the stability of the PON.