Phenolic compounds in quinoa and amaranth grains: Composition, biological properties and processing effects

Free and bound phenolic compounds including various phenolic acids and flavonoids contribute to the super-grain status of quinoa and amaranth. There were significant genetic diversity and similarities in the phenolic profiles of the grains of quinoa and different amaranth species. These phenolics significantly contributed to the health-promoting properties such as antioxidant, antihyperglycemic, and anti-inflammatory effects. Processing methods such as germination, fermentation, roasting, boiling, extrusion, microwave and radiation changed the phenolic profiles and related biological functions of the grains. Data inconsistencies among different studies were attributed to differing extraction and quantification methods, unit reporting, and limited genotype and species used, making direct comparisons across studies difficult. Furthermore, studies on biological activity of the phenolics remain limited to in vitro models and are scarce in in vivo or clinical trials. There is a need for standardized methodologies and optimized processing operations related to quinoa and amaranth phenolics for food and nutritional applications.