Improved Bioactivity and Functional Qualities of Millet Protein Enzyme Hydrolysates by Ultrasonication

Ultrasound (US)-extracted browntop millet protein isolates (UBMPIs) were modified by combined US pretreatment (at 200 W and different time levels 0, 5, 10, 15, and 20 min) and controlled bromelain hydrolysis, and functionalities and bioactive properties of BMPH (BMP hydrolysates) and UBMPH (US-pretreated BMPH) were investigated. Compared with the controls, browntop millet protein isolates (BMPI) and BMPH, UBMPH-15 (US pretreated at 200 W for 15 min) was capable of significantly enhanced degrees of hydrolysis (65.68%), emulsifying activity (20.26 m2/g), free sulfhydryl content (9.09 μM/g), and protein digestibility (84.13%). However, UBMPH-10 also showed higher hydrophobicity (18.13 μg/g), solubility (88.02%), and foaming capacity (18.52%). In addition, UBMPH-15 and UBMPH-10 enhanced the in vitro antidiabetic activity with inhibition toward α-amylase (0.47 mg/mL) and α-glucosidase (0.68 mg/mL), respectively. Moreover, UBMPH-15 showed the highest antilipidemic activity with greater inhibition of cholesteryl esterase (0.34 mg/mL) and lipase (0.51 mg/mL) and displayed significant scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals (73.43%). All these results suggest that UBMPHs could be potential sources of bioactive hydrolysates with enhanced antilipidemic, antidiabetic, and antioxidant activities.