Ultrasound-induced structural modification and thermal properties of oat protein

Abstract

The objective of this study was to characterize the solubility, structural, thermal, and aggregation properties of oat protein under high-intensity ultrasound (HIU) treatment. Suspensions of oat protein isolate (OPI) at pH 2.0–8.0 were subjected to HIU for 5 min at 70% amplitude; solubility, particle size, surface attributes, UV–Vis absorption, intrinsic fluorescence, polypeptide profiles, calorimetric properties, and thermal aggregation were determined. The HIU treatment significantly reduced particle size (up to 37%) and increased surface charge of OPI leading to solubility increases (up to 48%, P < 0.05) at pH 2.0–3.0 and pH 5.5–8.0. However, HIU did not alter the protein profile nor disrupt disulfide linkages between α and β subunits. Reduced enthalpy of denaturation with no shift in thermal transition temperature were observed in HIU samples unless disulfide bonds were pre-cleaved. While control OPI displayed variable changes in particle size upon heating from 20 to 95 °C, the HIU sample maintained a relatively uniform and smaller particle size. The findings indicate that protein particle disruption and weakening of intermolecular forces by HIU improved physicochemical and thermal properties of OPI, which are of value to processing oat protein-based beverages and other food products.