Effect of Natural Fermentation on Antioxidant Activity of Pearl Millet (Pennisetum glaucum)

Abstract

Background: Millets are small-seeded cereals having excellent nutritional quality. They are comparable or superior to some commonly consumed cereals like wheat and rice. Millets are gluten-free, have low Glycemic Index and are a good source of calcium, iron, potassium, zinc magnesium and B vitamins. Natural fermentation of millets can improve their lower cooking quality, taste, low bioavailability and palatability. Objective: This study was undertaken to evaluate the effect of natural fermentation on antioxidant activity of Pearl millet (Pennisetum glaucum). Methods: The present work has been done to standardize the natural fermentation process of pearl millet using response surface methodology for enhanced iron content and antioxidant activity. Pearl millet was treated with natural fermentation process at varying temperature (30-50°C), time (4-12 hrs) and pH (3-7). The effect of these fermentation treatments were studied on total reducing sugar, iron content, antioxidant activity (Total Phenolic content and DPPH), tannin content and antinutritional factors of pearl millet using a second order central composite design. Results: The cofficient of determination, R2 values for Total reducing sugar, iron content, antioxidant activity and tannin content was greater than 0.900. Statistical analysis showed that sugar, iron content, antioxidant activity and tannin content varied significantly (p <0.05) with a change in pH, temperature and time. pH was found to be the most important factor affecting the quality parameters of the pearl millet during fermentation as it exerted a strong influence (p < 0.01) on all the dependent variables. Conclusion: Increase in total reducing sugar, iron content, antioxidant activity and decrease in tannin content of pearl millet were observed along with a decrease in pH and temperature of fermentation. On the basis of response surface and contour plots, the fermentation conditions of pearl millet were optimized at a temperature of 40°C, pH 5 and time duration of 8 hours.