Ultrasonic-assisted alkali extraction of quinoa polysaccharides: Yield and structural characterization

Abstract

Given that extraction methods affect the structural and functional properties of polysaccharides, four different extraction techniques, hot water extraction (HWE), alkali extraction (AE), ultrasound-assisted extraction (UE), and ultrasound-assisted alkali extraction (UAE), were employed to extract quinoa polysaccharides, and their yield, structural characteristics, and morphology were compared using a range of chemical and instrumental analysis techniques. The results revealed that UAE achieved the highest yield of quinoa polysaccharides at 7.13%, surpassing the other three methods. Particle size analysis showed polysaccharides ranged from 301 to 693 nm by four methods. Molecular weight analysis demonstrated that polysaccharides extracted by UE and UAE possessed higher molecular weights than those extracted by AE and HWE. Additionally, the viscosity of polysaccharides decreased as molecular weight decreased. Furthermore, the study found no evidence of triple-helical structures in polysaccharide fractions extracted by the four methods. Morphologically, all extracted polysaccharides exhibited distinct features, and their functional group characteristics were comparable. Notably, polysaccharides extracted by AE contained a minor amount of protein. Overall, UAE emerges as a promising extraction method based on the yield, purity, and structural characteristics of quinoa polysaccharides. These findings provide a robust experimental basis for understanding quinoa polysaccharide extraction, utilization, and potential applications in product development.