Effect of ultrasound treatment on antioxidant activity and structure of β-Lactoglobulin using the Box–Behnken design

Effect of ultrasound treatment on antioxidant activity and structure of β-Lactoglobulin were investigated using antioxidant indexes and spectroscopy techniques. The 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities had been applied to the experimental response obtained by a three-factor-three-level Box–Behnken design. Results showed that ultrasound treatment significantly increased antioxidant activity (p < 0.05). The maximum DPPH radical scavenging activity of β-Lactoglobulin was 57.59% at the ultrasound conditions of 45°C, 20 min and amplitude of 30%. The ultrasound-treated β-Lactoglobulin exhibited higher 2,2ʹ-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical scavenging activity and oxygen radical absorbance capacity. Circular dichroism data indicated that ultrasound treatment increased both α-helix and β-sheet contents of β-Lactoglobulin and altered Trp residues, which resulted in the secondary and tertiary structure changes. Differential scanning calorimeter and scanning electron microscopy micrographs showed that ultrasound-treated β-Lactoglobulin contained larger aggregates than untreated. In conclusion, ultrasound treatment had considerable effects on antioxidant activity and structure of β-Lactoglobulin. Ultrasound treatment may expand the applications of β-Lactoglobulin in food industries