Effect of microwave and hot air radiofrequency treatments on physicochemical and functional properties of foxtail millet flour and its protein isolate

Abstract

The current study investigated the impact of microwave (MW) and hot-air assisted radiofrequency (HARF) technologies on physicochemical characteristics of foxtail millet (FM) flour. Besides, the physicochemical characteristics of foxtail millet protein (FMP) from MW and HARF treated FM flour were also evaluated. Residual relative lipase activity (LA) (10.86%) was least at 15% moisture (w.b.) for two passes-28 min treatment in HARF, while the MW heating showed lower LA at 786.80W power level for 6 min (0.27%) and 4 min (8.17%). Peak viscosities of MW and HARF treated FM flour exhibited a decreasing trend compared to untreated. An increase was observed in emulsifying, and oil/water absorption properties of MW and HARF treated FMP in comparison with the untreated sample, while it was vice versa with the foaming properties, and protein purity. This changes can be attributed to the decrease in relative crystallinity and modifications in the secondary structural elements (i.e., increase in β-turn, and decrease in α-helix, β-sheets), as confirmed by FTIR and XRD analyses performed.