Ultrasonic treatment influences the compactness of quinoa protein microstructure and improves the structural integrity of quinoa protein at the interfaces of high internal phase emulsion.

For native quinoa protein with a loose disordered structure and low structural integrity, once the protein is absorbed to the oil-water interface, the stress of interfacial tension and hydrophobic interaction can easily trigger the conformation change and denaturation of quinoa protein, leading to the instability of high internal phase emulsion (HIPE). Ultrasonic treatment can induce the refolding and self-assembling of quinoa protein microstructure, which is expected to frustrate the disruption of protein microstructure. The particle size, tertiary structure, and secondary structure of quinoa protein isolate particle (QPI) were investigated by multi-spectroscopic technology. The study demonstrates that QPIs prepared with ultrasonic treatment of 5 kJ/mL exhibit more robust structural integrity compared with native QPIs. The relatively loose structure (random coil, 28.15 ± 1.06 %∼25.10 ± 0.28 %) transformed to a more ordered and compact form (α-helix, 5.65 ± 0.07 %∼6.80 ± 0.28 %). Through the addition of QPI-based HIPE as an alternative for commercial shortening, the specific volume of white bread was increased (2.74 ± 0.35 ∼ 3.58 ± 0.04 cm/g).