The improvement of the oxidative oat (Avena sativa L.) protein based on ultrasound treatment: Study of structural, emulsifying, and rheological properties

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Oat protein (OP) inevitably suffers oxidative attack during long-term storage to form oat oxidized aggregates (OOPA), thus causing deterioration of emulsification properties, so modification of OOPA to enhance their emulsification properties is essential to expand the application of emulsions in the food industry. In this experiment, OOPA was sonicated using ultrasound at different lasted times to obtain ultrasonic oxidative oat protein aggregates (UOOPA) in order to investigate the effects of ultrasound on the structure, emulsification properties and interfacial properties of the OOPA, and to establish the structure-activity association between the structure and emulsifying properties of OOPA under ultrasound by correlation analysis. Based on the physical structure analysis, ultrasound treatment at 25 min led to the reduction of particle size and disulfide bond (S–S) content, exposure of the hydrophobic group, an increase of ζ-potential absolute value. The Fourier transform infrared (FTIR) spectroscopy analysis and atomic force microscopy (AFM) observation also suggested ultrasound-induced depolymerization behavior, improvement of flexibility, and reduction of the roughness of OOPA. The emulsifying properties were optimized when ultrasound treatment lasted for 25 min; the emulsifying activity (EAI) and emulsifying stability (ESI) increased by 2 times and 1 time, compared with the OOPA. Then, viscosity curve and frequency sweep oscillatory experiments proved the ultrasound improved the rheological properties of OOPA and the observations of the confocal laser scanning microscope (CLSM) further provided visual evidence. In general, these results further confirmed the role of ultrasound in promoting the emulsifying properties of OOPA.