Nutritional and functional properties of amaranth grain flour fractions obtained by differential sieving

Amaranth grain, a gluten-free grain was milled to flour and differentially sieved to coarse and fine fractions. The whole flour and fractions thereof were analyzed for the nutrient composition, antinutrients, total and bioaccessible minerals, fatty acids, and amino acid profile and functional properties of flours. Results indicated that the fine fraction representing 44% of the whole amaranth flour contained higher protein (19.7%), fat (8.54%), minerals (3.46%) and dietary fibre content (20.09%) as well as a higher overall amino acid profile with lysine as its major essential amino acid. Linoleic acid (44.8%) in fine flour whereas oleic (29.4%) and palmitic acid (29.6%) in coarse flour was the predominant fatty acid found in amaranth flour fractions. Minerals were variedly distributed in analyzed fractions as iron was found majorly in fine flour and calcium in coarse flour. A similar trend in mineral bioaccessibility was observed. The in vitro protein digestibility of amaranth flour samples ranged from 59.8-72.5%. Functional properties revealed that higher values of water and oil absorption capacity were characterized in the coarse fraction, while whole flour showed higher foaming capacity and stability. Thus, differentially sieved flour fractions of amaranth grain showed a wide distribution of nutrients and in particular, the finer fraction was nutrient-dense. It was found to be an excellent source of nutrients and could be incorporated as a functional ingredient in the development of nutrient-rich products.