Abstract: In this work, the application of soy protein isolate (SPI)-steviol glycosides (STE) mixtures as natural stabilizers to prepare nanoemulsions was evaluated. The effects of stabilizer composition, homogenization parameters and oil phase concentration on the formation of nanoemulsions were investigated. The storage stability and microstructure of nanoemulsions were characterized. The results showed that when the oil phase concentration was 10%, the particle size of emulsion prepared with pure SPI (1%) was larger (d43 = 0.548 μm) while the emulsion stability was poorer. When 0.25%–1% STE was added, the particle size distribution of emulsions stabilized by SPI-STE mixtures was more uniform and the particle size was smaller. The droplet size of the emulsions with 0.5% or 1% STE was smaller than 200 nm, and these nanoemulsions showed good storage stability for 30 days. The addition of 2% STE resulted in the complete replacement of proteins on the surface of droplets, thereby weakening the long-term stability of emulsions. The increase in homogenization pressure, number of homogenization cycles and STE concentration could reduce the particle size of emulsions, whereas the increased oil phase concentration had the opposite effect. Further, the nanoemulsions were freeze-dried, yielding a well-structured oil powder with high oil content. Compared to the pure SPI-stabilized oil powder, the structure of oil powders prepared with SPI-STE mixtures was more compact, and the powder surface was less viscous.

Key words: nanoemulsion, soy protein isolate, steviol glycosides, stabilization