Abstract: In this work, we explored the effect of enzymatic hydrolysis time for preparing lysophospholipid on the interaction between soybean protein isolate (SPI) and lysophospholipid (LP) and the emulsifying properties of an SPI-LP composite emulsion system. Fluorescence quenching, binding sites and constant and interaction forces between SPI and LP were investigated based on the Stern-Volmer and Van’t Hoff equations by fluorescence spectroscopy. Furthermore, the emulsifying activity and stability were determined, and the microstructural change of emulsion was observed. The results showed that as the hydrolysis time by phospholipase A1 was prolonged, the interaction between SPI and LP first increased and then decreased, and so did the emulsifying properties, which suggested that the interaction had some effects on the emulsifying properties. Among five hydrolysis times tested, 4 h hydrolysis demonstrated the strongest interaction between SPI and LP and the best emulsifying properties indicating that lysophospholipid produced by moderate hydrolysis showed improved interaction with SPI to form a stable interfacial film at the water-oil interface for stable composite emulsion.

Key words: soybean protein isolate, lysophospholipid, interaction, emulsifying property