Laccase-aided modification: Effects on structure, gel properties and antioxidant activities of α-lactalbumin

- Formation of large cross-linking α-LA-FA products with incubation time increased.
- Gel properties of laccase-catalysed α-LA-FA conjugates remarkably increased.
- Laccase-treated α-LA system with FA exhibited strong antioxidant activities.

Effects of laccase-catalyzed cross-linking on the structure, gel properties and antioxidant activities of α-lactalbumin (α-LA) were investigated in the presence of ferulic acid (FA). Particle size of laccase-catalysed a-LA-FA congugates became significantly larger with the increasing incubation time. Size exclusion chromatography showed that FA monomers disappeared almostly in the presence of laccase and high molecule polymers were formed with increasing incubation time. α-LA treated with laccase and FA led to the formation of oligomers and polymers by SDS-PAGE analysis. Moreover, intrinsic fluorescence intensity and surface hydrophobility of laccase-catalysed α-LA-FA conjugates remarkably increased from approximately 600 to 1200 A.U. and from 304.1 to 481.3, respectively, corresponding the incubation time from 0 to 24 h, compared with three control systems. After α-LA was treated by laccase and FA, its stronger gel strength and higher water holiding capacity were achieved, and had positive correlation with incubation time. Meanwhile, DPPH radical scavenging activity and ferrous reducing power of laccase-catalysed α-LA-FA conjugates significantly increased with the incubation time increased. Therefore, laccase catalyzed cross-linking of α-LA in the presence of FA could change α-LA structure, and enhance its gel properties and antioxidant activities.