Effect of ultrasound on structure and functional properties of laccase-catalyzed α-lactalbumin

The effects of ultrasound (400 W, for 0, 20, 40, 60, 80, or 100 min) pre-treatment on the physicochemical properties, functionality and structure of laccase-catalyzed α-LA in the presence of ferulic acid (FA), were investigated in this study. Size exclusion chromatography showed that α-LA monomers decreased significantly in the presence of laccase and FA, and its high molecule polymers were formed with increasing ultrasonic time. SDS-PAGE analysis also showed that ultrasound treatment contributed to the formation of oligomers and polymers of α-LA treated with laccase and FA. Surface hydrophobility and gel strength of laccase-catalyzed α-LA-FA conjugates were higher than that of three control systems, and gradually enhanced with the ultrasonic time increased. Moreover, ultrasound-treated α-LA with laccase and FA had greater G′ values than other three control systems according to the rheological measurements. Ultrasound treatment did not significantly changed conformational structure of laccase-catalyzed α-LA-FA conjugates, as demonstrated by CD spectra. Therefore, ultrasound contributed to form greater non-covalent and covalent interactions between α-LA molecules and aggregates, and could remarkably change physicochemical and functional properties of laccase-catalyzed α-LA-FA conjugates.