Ultrasound-assisted alkaline extraction of pearl millet protein: Characterization of physical, structural, thermal, and techno-functional properties

Abstract

Millets are gaining attention as nutritional cereal alternatives due to their functional and therapeutic properties, partly attributed to bioactive peptides in their native proteins. This study investigated the structural, functional, and thermal properties of pearl millet proteins (PMPs) treated with ultrasound (US) to enhance their food application potential. PMPs were isolated via acid-base precipitation from defatted flour, followed by US treatment (5, 10, and 15 min at 45 kHz). The control sample exhibited the largest particle size (1321 nm), whereas sample treated with US for 10 and 15 min showed significantly reduction particle size (789.30 nm). Additionally, the zeta potential shows increasing trends shifting from −15.20 mV in the control sample to −23.96 mV in the US10 treatment, which collectively indicates notable structural changes in the protein. FTIR and circular dichroism analyses revealed modifications in secondary protein structures, including α-helix and β-sheet content. XRD confirmed the presence of these structures, while SEM showed more uniform and compact protein fragments in US-treated samples. Thermal analysis highlighted degradation behavior, and NMR confirmed amino and organic acid presence. US treatment thus significantly enhanced the functional properties of PMPs, improving their potential for food applications.