Drying methods affect physicochemical and functional properties of quinoa protein isolate

Abstract

Quinoa protein possesses great amino acid profiles and can be a potential food ingredient with broad applications. The objective of this study was to investigate the effect of different drying methods, namely freeze drying, spray drying, and vacuum drying on the functional and physicochemical properties of quinoa protein isolate, e.g., morphology, amino acid composition, SDS-PAGE profile, sulfhydryl/disulfide content, secondary structure, surface hydrophobicity, and thermal stability. The freeze-dried protein exhibited the highest emulsification capacity and stability and oil binding capacity, which was contributed to its higher surface hydrophobicity, while the spray-dried sample had the highest solubility and water absorption capacity at pH 7. Gels (8%) prepared with the freeze-dried protein had higher elastic and viscous modulus than that from others. The freeze-dried protein had the highest maximal denaturation temperature but lowest enthalpy, which may be attributed to its higher amount of random coil but lower percent of regular α-helix and β-sheet structures. Overall, quinoa protein isolate from different processing methods demonstrated distinct functional properties. This information will be useful to optimize quinoa protein production and benefit its applications.