Antioxidant Activity in Two Pearl Millet (Pennisetum typhoideum) Cultivars as Influenced by Processing

Research on the effect of processing on the retention of bioactive components with potential antioxidant activity is gaining importance. The objective of this investigation was to evaluate the effect of various processing methods (milling, boiling, pressure cooking, roasting and germination respectively) on the antioxidant components as well as the antioxidant activities in the commonly used pearl millet cultivars—Kalukombu (K) and Maharashtra Rabi Bajra (MRB). The methanolic extracts of processed pearl millet flours were analyzed for 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, reducing power assay (RPA) and ferric reducing antioxidant power (FRAP) assays respectively. The samples were also evaluated for tannin, phytic acid and flavonoid content which was then correlated with the antioxidant activity assayed using three methods. The results indicated that the bran rich fraction showed high antioxidant activity (RPA) owing to high tannin, phytic acid and flavonoid levels. Heat treatments exhibited significantly (P ≤ 0.05) higher antioxidant activity (DPPH scavenging activity and RPA) reflecting the high flavonoid content. Processing did not have any significant effect on the FRAP activity of pearl millet. The data on the correlation coefficient suggests that DPPH radical scavenging activity and reducing power assay in the K variety was largely due to the presence of flavonoid content, however in MRB, no relationship was found between antioxidant activities and antioxidant components.