Nutritional composition and in vitro bioaccessibility of minerals in the developed composite flours from Teff millet (Eragrostis tef) & guava leaves (Psidium guajava)

In the present study, combination of Teff flour and powdered guava leaf was utilized to develop composite flour mixes. Effect of two different drying techniques of hot air oven and solar drying was assessed on the guava leaves for the composition. The composite flour mixes were evaluated for physical, nutritional, mineral, anti-nutritional, phenolic and antioxidant components. Among the physical properties, the bulk density, tapped density, Carr index, Hausner ratio, water absorption capacity, swelling index, foaming capacity and water solubility index were evaluated. Protein was found to be highest in Teff flour (13.41 g/100 g) and among the combination of composite flours it ranged between 12.19 to 12.89 g/100 g. Whereas, the total dietary fiber among the composite flours was found to be between 4.18 to 5.04 g/100 g. The anti-nutrients of phytic acid and total tannin content among the analyzed samples was ranging from 0.48 to 0.66 g/100 g and 1.40 to 3.40 mg CE/g, respectively. The Fe and Zn content among the analyzed samples were ranging between 8.01 to 10.99 and 0.69 to 3.56 mg/100 g, respectively. Among the analyzed samples, the highest total phenolic content (TPC), total flavonoid content (TFC), total anthocyanin content (TAC), and total carotenoid content (TCC) was found in solar dried guava leaf (SGL) sample with 18.99 g GAE/100 g, 5.36 g CE/100 g, 1.48 mg/g, and 20.96 mg/100 g, respectively. Concurrently the highest antioxidant activity assessed by DPPH, ABTS and FRAP assay methods was also found in SGL sample with 94.59% inhibition, 98.10% inhibition and 6.01 M Fe+/g, respectively. Solar drying method retained higher nutritional and phenolic components in comparison to the hot air oven drying method. In the present study, the composite flour combinations containing Teff flour and guava leaf powder provided optimum nutrients and bioaccessibility of minerals. Also, incorporation of guava leaf powder increased the phenolic components and the antioxidant activity of the formulated products.