Effect of Extrusion Processing on Phenolics, Flavonoids and Antioxidant Activity of Millets

The study was aimed to evaluate the effect of different extrusion treatments on total phenolic content, total flavonoids and antioxidant activity of finger millet and sorghum. The flours were subjected to eight different extrusion treatments at varying feed moisture, die head temperature and screw speed. Statistical analysis revealed that the total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity (FRAP, DPPH, TEAC) of extruded finger millet and sorghum flours was reduced significantly (p < 0.05) over their native counterparts. However, extrusion at high feed moisture, low temp and high screw speed (HM/LT/HS) retained considerable percentage of bioactives. Maximum retention of TPC, TFC and FRAP was observed as: 54%, 78% and 57% in finger millet respectively and 87%, 89% and 86% in sorghum, respectively. High retention of bioactives in extruded millet flours demonstrated their enormous potential for the development of phenolic and antioxidant rich ready-to-eat snacks.