Bioactive compounds, antioxidant activity and consumer acceptability of porridges of finger millet (Eleusine coracana) flours: effects of spontaneous fermentation

The flours of finger millet (Eleusine coracana) from light brown and dark brown varieties fermented spontaneously for 96 h were evaluated for their bioactive compounds, antioxidant activity and physicochemical properties. The consumer acceptability of the fermented porridges was also determined. Bioactive compounds of finger millet (FM) flours significantly (p < .05) increased with fermentation time, total polyphenolic content increased from 166 to 488 mg/100 g (light brown) and 420 to 606 mg/100 g (dark brown) and total flavonoid content increased from 160 to 330 mg/100 g (light brown) and 249 to 465 mg/g (dark brown). However, the total anthocyanin content of FM flours decreased with fermentation time. The DPPH activity of FM flours significantly (p < .05) increased with fermentation time from 52 to 58% (light brown), 53 to 59% (dark brown) and inhibitory effect on lipid peroxides significantly (p < .05) increased from 0.9 to 1.3% (dark brown) and 1.7 to 4.5% (dark brown). Fermentation significantly increased the crude protein of FM flours (light brown, 7.12 to 9.43%) and (7.80 to 9.53%, dark brown). Dietary fiber, fats, moisture and carbohydrates significantly (p < .05) decreased. Total titratable acid significantly (p < .05) increased from 0.49 to 1.77 g/100 g (light brown) and 0.47 to 1.58 g/100 g (dark brown). Fermentation resulted in the decrease of FM flours pH values. However, the total soluble solids were significantly (p < .05) different in both flours. Fermentation caused the lightness (L*) and redness (a*) to decrease and the yellowness (b*) of both flours to increase with time. The textural properties of the FM porridges decreased with fermentation time. The FM flours of both varieties which were fermented for 24 h resulted in porridges with the best sensory attributes. The results suggest that spontaneous fermentation could be an effective way of improving the bioactive compounds and antioxidant activity of FM flours.