Influence of ultrasonic pretreatment on structural properties and biological activities of lupin protein hydrolysate

Abstract

This study examined how application of ultrasound pretreatment (UP) (400 W, 20 kHz for 5, 10 min) influenced the structural characteristics, molecular weight distribution, amino acid composition and biological activity of hydrolysate prepared from lupin protein using protamex enzyme. Circular dichroism (CD) and Fourier transform infrared (FTIR) techniques revealed changes in secondary structure after UP, while changes in molecular weight pattern were revealed by SDS-PAGE and MALDI-TOF analyses. Also, the crystallinity and surface hydrophobicity of the hydrolysates were affected by UP. The amino acid compositions of the hydrolysate varied, especially glutamic acid, arginine and aspartic acid. In vitro biological assays showed that antioxidant, α-glucosidase, α-amylase and ACE inhibitory activities significantly improved in sonicated hydrolysates compared with non-sonicated samples, and this may be linked to the structural modifications caused by UP. Hence, the application of UP to lupin protein could en hance the biological activity of its hydrolysate.