Abstract: This study was undertaken in order to investigate the effect of jet cavitation on physicochemical and functional properties of a soy protein isolate (SPI)-phosphatidylcholine (PC) stabilized emulsion. The conformational changes of the composite system were characterized by fluorescence spectroscopy, and the creaming index, particle size, microstructure, surface hydrophobicity and emulsifying activity and emulsion stability were analyzed. The results showed that jet cavitation significantly improved physicochemical and emulsifying properties of the composite emulsion. The emulsifying activity index (EAI) and emulsion stability index (ESI) of the composite emulsion treated at 0.2 MPa for 10 min were 82.7% and 10.43-fold higher than those of the single SPI stabilized emulsion, respectively. The average particle size of the composite emulsion system became smaller and surface hydrophobicity became higher after jet cavitation as examined by dynamic light scattering and optical microscopy. The lowest average particle size and the highest surface hydrophobicity were obtained with the 0.2 MPa/10 min treatment. Thus, we concluded that jet cavitation could cause the exposure of hydrophobic groups in the interior of the protein, increasing the interaction between the protein and PC. Fluorescence spectroscopy indicated that cavitation force had a quenching effect on the fluorescence intensity of SPI.

Key words: jet cavitation, soy protein isolate-phosphatidylcholine, fluorescence spectrum, emulsifying activity, emulsion stability