Utilization of potato protein fractions to form oil-in-water nanoemulsions: Impact of pH, salt, and heat on their stability

The plant-based foods market has grown rapidly due to increasing consumer concerns about the ethics, sustainability, and nutrition of the modern diet. However, it is challenging to create plant-based foods with good physicochemical, functional, and sensory properties. In this study, we investigated the emulsifying properties of two potato protein fractions: PP-200 (patatin) and PP-300 (protease inhibitor). The size, surface, charge, and microstructure of corn oil-in-water emulsions produced using these proteins were measured when they were exposed to changes in pH, ionic strength, and temperature. Both protein fractions successfully formed emulsions containing small droplets under suitable conditions, but the PP-200 required less protein (0.5%) and produced smaller droplets (230 nm). The proteins had different isoelectric points (pH 5 for PP-200 and pH 8 for PP-300), which caused the emulsions formed from them to be unstable to flocculation over different pH ranges (pH 4–5 for PP-200 and pH 6–8 for PP-300). The addition of salt screened the electrostatic repulsion between the droplets, causing them to become unstable to aggregation. The level of salt required to promote aggregation depended on protein type: ≥50 mM NaCl for PP-200 and ≥200 mM NaCl for PP-300. Both emulsions were stable to heating in the absence of salt. However, in the presence of 100 mM NaCl, the PP-200 emulsions were unstable when heated above 60 °C, while the PP-300 emulsions remained stable. In summary, both potato protein fractions have good emulsifying properties, but they are suitable for use under different environmental conditions, especially pH ranges. [Display omitted] •Patatin and protease inhibitor from potato protein were used to form emulsions.•The isoelectric point (pI) of patatin and protease inhibitor were pH 5 and 8, respectively.•Emulsions formed from both proteins aggregated around their isoelectric points.•Emulsions formed from both proteins were unstable to salt addition (>100 mM NaCl).•The heat stability of protease inhibitor-emulsions was better than patatin-emulsions.