Ultrasound-assisted preparation of nanoemulsions co-stabilized by immature nectarine polysaccharide and soy protein isolate

This study isolated and characterized polysaccharides from immature nectarines (INP) and constructed nanoemulsions co-stabilized with soy protein isolate (SPI). The results showed that arabinose and galactose were the main monosaccharides in INP, which was identified as a pectic heteropolysaccharide with a high molecular weight (M w = 9.26 × 10 5 Da) and high polydispersity (PDI = 11.42). INP exhibited a compact random coil conformation and a loose, porous morphology. The incorporation of SPI effectively reduced the interfacial tension of the SPI-INP composite system, significantly enhancing the stability of the resulting nanoemulsions. The concentration of the INP-SPI mixture, the SPI/INP mass ratio, and ultrasonic conditions significantly influenced the formation of the nanoemulsions. Based on the results of single-factor experiments and response surface analysis, the optimal process parameters for nanoemulsion preparation were determined as follows: INP-SPI concentration 1.6%, SPI/INP mass ratio 2.1:1, ultrasonic power 500 W, and ultrasonic time 5.3 min. Validation experiments confirmed that under these conditions, the average droplet size of the obtained nanoemulsion was 214.10 ± 1.74 nm, which closely aligned with the model-predicted value (216.33 nm). The superior stability of the INP-SPI nanoemulsion under various pH (6.0–9.0) and salt (0–100 mM NaCl) conditions was attributed to the formation of a robust interfacial layer providing steric stabilization, as validated through droplet size analysis and environmental stress testing. This research promotes the in-depth utilization of immature nectarine resources and provides a reference for the construction of food-grade nanoemulsions.