High-intensity ultrasound modification of techno-functional and structural properties of white finger millet protein fractions.

In this study, albumin, globulin, and glutelin were extracted from white finger millet, and their amino acid content, functional and structural properties were investigated. The protein concentration of albumin, globulin, and glutelin were 76.01%, 74.32%, and 69.55%, respectively. The results showed that all the fractions had a significant amount of essential amino acids. Aqueous protein dispersions (10%, w/v) were treated for 12 min at different ultrasound power levels (100, 200, and 300 W). The solubility, emulsifying, and foaming properties of albumin and glutelin were significantly (p < 0.05) improved after ultrasound treatment (20 kHz) which indicates that ultrasound could unfold protein aggregates. A decrease in particle size, increase in surface hydrophobicity, and zeta potential correlated with improved functional properties. Ultrasound treatment reduced the size of all proteins except for fractions at 300 W and also sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a significant change in the molecular weight of albumin and glutelin at 300 W. Scanning electron microscopy of treated protein fraction showed distinctive microstructure with irregular structure compared to untreated protein fraction. Although Fourier transform infrared spectroscopy spectra of proteins were similar after ultrasonication, a partial increase in the intensity of the Amide A band was observed. In conclusion, the ultrasound-treated protein fraction can be used as a high-value plant-based emulsifier.