Abstract: In this paper, soy protein isolate (SPI) was hydrolyzed by pepsin and then used to establish a stable SPI enzymatic hydrolysate-phospholipid complex emulsion system, aiming to find out a natural carrier that remains stable when passing through the stomach. Based on microscopic observation, particle size, potential, emulsion emulsification activity index (EAI), emulsion stability index (ESI) and creaming index (CI), we applied single factor experiment and orthogonal array design to determine the optimum composition of composite emulsions at pH 2.0 and 7.0. The results showed that the hydrolysis process was completed in 120 min. With increasing concentration of the protein hydrolysate, the stability of complex emulsions increased first and then remained unchanged. Maximum stability was observed for the complex emulsion with phospholipid concentration of 0.001 0 g/mL. With the increase of oil phase volume fraction, the stability of composite emulsions increased first and then remained unchanged. The emulsion with SPI hydrolysate concentration of 0.020 0 g/mL, phospholipid concentration of 0.000 5 g/mL and oil phase volume fraction of 10% was the most stable at pH 2.0, as determined by orthogonal array design

Key words: soy protein isolate; phospholipid; stability