Effect of Differential Sieving of Amaranth, Buckwheat and Quinoa Flours on Antioxidant Properties of Flour Fractions

Pseudocereals, namely, amaranth, buckwheat and quinoa are gluten-free grains with high bioactive components and antioxidant properties. Differential sieving is a common pre-processing technique to obtain coarse and fine flours for specific uses. The present study aimed at determining the content and activity of antioxidant components extracted in acidified methanol and aqueous media in differentially sieved pseudocereal flours. Further, the antioxidant components were characterized and measured in each flour fraction. Buckwheat grain and its fractions showed the highest total phenolic and flavonoid content. Overall, the bioactive compounds were majorly present in fine flour fraction followed by whole and coarse flour. Free radical scavenging activity and ferric reducing antioxidant power was highest in quinoa flour fractions. Ferulic acid was predominant in amaranth and buckwheat, whereas for quinoa, it was gallic acid and catechin. The pseudocereal flours were rich sources of antioxidant components and showed considerable antioxidant activity, though there were wide variations in each of the flour fractions. Differential sieving influenced the antioxidant properties significantly and finer fractions appeared to be richer in antioxidant components. Quantification of phenolic compounds in this study describes the compositional distribution in flour fractions of pseudocereals along with assessment of their antioxidant potential using multiple assays. This would help in better understanding of antioxidant properties of pseudocereals and their potential utilization for development of products with improved nutritional profile. The pseudocereal flours can serve as functional food ingredients for development of novel products.