Abstract: This work studied the effect of high pressure treatment (60, 100 and 140 MPa) on the formation of composite emulsions of 0.5% soybean lipophilic protein (LP) and different concentrations (0%, 0.01%, 0.05%, 0.1% and 0.2%) of hydroxypropyl methylcellulose (HPMC) at different homogenization pressures, and it also revealed the relationship between the structural changes of LP and emulsion stability. Dynamic laser scattering (DLS), contact angle measurement and infrared spectroscopy were employed to investigate the hydrodynamic radius and interfacial adsorption characteristics of the composite emulsions as well as the changes in protein secondary structures. The results showed that the emulsions had lower emulsifying capacity, storage stability and interfacial adsorption capacity at 60 MPa than at other pressures. As the pressure increased, the particle size of the emulsions became smaller, the shape of the droplets was regularly and evenly distributed, and the negative charge on the emulsion surface increased. At 140 MPa and 0.1% cellulose concentration, the emulsification activity and emulsion stability were as high as 223.05 m2/g and 290.5 min, respectively. The high pressure treatments changed the secondary structures of LP, affecting its combination with HPMC and consequently the adsorption characteristics of the formed emulsion at the oil-water interface. The emulsion had the best hydrophilicity at 0.1% cellulose concentration.

Key words: soybean lipophilic protein, hydroxypropyl methylcellulose, emulsion, high pressure homogenization, stability