Effect of controlled hydrothermal treatment, drying temperature, de-husking and decortication on phenolics characteristics and functional properties of foxtail millet flour

Abstract

Present study explores the impact of hydrothermal treatments (soak-boil & soak-steam) and subsequent grain drying on the in-vitro antioxidant activity, bioactive profile and bio-accessibility assay of polyphenol extracts of de-husked/decorticated foxtail millet flour and its functional characteristics. A total of seven phenolic compounds were detected by HPLC analysis in which ferulic acid, syringic acid and gallic acid contribute majorly. In-vitro antioxidant activity, measured using DPPH and FRAP assays, indicated highest values of 68.29 % and 55.79 (mg AAE/100g) for soak-steam (SS40) de-husked millet flour samples, respectively. Simulated in-vitro digestion further revealed enhanced bio-accessibility, with SS40 showing the highest bio-accessibility index (59.56 %) for total phenolics. Phenolic compounds like gallic acid and ferulic acid exhibited higher bio-accessibility of 67.63 % in soak-steam treated (SS40) flour as compared to 43.93 % in untreated samples. The overall bio-accessibility increased significantly after soak-steam treatment for several phenolic compound such as gallic acid (53.91 %), p-coumaric acid (40.37 %), vanillic acid (49.48 %), and ferulic acid (26.07 %). In the study of functional properties, a significant (p ≤ 0.05) difference was observed with higher water absorption capacities (159.81 g/100g), oil absorption capacities (168.65 g/100g), and improved foaming capacity for de-husked and decorticated SS40 flour dried at 40 °C. These results highlighted the potential of parboiled foxtail millet grain (particularly soak-steam treatment) as an ingredient in the gluten-free and other functional products.