The present study examined the influence of malting on the phenolic composition of two cultivars of finger millet using an ultra-performance liquid chromatography mass spectrometer. Total polyphenols and antioxidant activities of the grains were also evaluated using sorghum as an external reference. Catechin, epicatechin, quercetin, taxifolin, and hesperitin were isolated flavonoids, whereas protocatechuic acid was the phenolic acid detected in finger millet malt. Increases in the content of catechin, epicatechin, and protocatechuic acid were observed for 72 h and 96 h for brown finger millet and sorghum malt. Complete loss of taxifolin and hesperitin were observed with the malting period for finger millet cultivars. A similar loss was noted in the proanthocyanidin A1/A2 and catechin content of sorghum with malting time. The grain malt exhibited 2,2-diphenyl-1-picrylhydrazyl,2,2'-azinobis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) radical scavenging and iron reducing activities. Increased ABTS and iron reducing activity with malting time were observed for the finger millet cultivars. The study demonstrates the presence of hesperitin in finger millet, and also shows that 72 h and 96 h of malting enhanced the catechin, epicatechin, and protocatechuic acid content, in addition to the antioxidant activity of the grain.
Keywords: Eleusine coracana; UPLC-MS; antioxidant activity; malting; phenolic compounds.