Antioxidant properties of digestive enzyme-treated fibre-rich fractions from wheat, finger millet, pearl millet and sorghum: A comparative evaluation

Whole grains are rich in antioxidant components (AC), most of which are bound to fibre fraction and released during digestion. The study investigated the effect of digestive enzymes on the antioxidant properties of fibre-rich fractions from wheat (Triticum aestivum), finger millet (Eleusine coracana), pearl millet (Pennisetum typhoides) and sorghum (Sorghum bicolor). Coarse (CF) and fine fractions (FF) of milled flour were separated using a standard sieve and analysed for nutritional composition, AC extractable in different solvents and antioxidant activity (AA) in untreated and enzyme-treated fractions. The CF had a higher range of insoluble dietary fibre (17.26–20.93%) than FF (10.65–17.29%). The highest amount of polyphenols and flavonoids was extractable in different solvents from finger millet and pearl millet, respectively. FF of pearl millet showed higher total AA in all solvents. Enzyme-treated samples had a much higher content of AC as well as higher total AA. Free radical scavenging assay revealed that enzyme-treated millet flours had higher activity in comparison to wheat. Between fractions, wheat exhibited variable results. Among millets, CF of finger millet and FF of pearl millet and sorghum had higher AA. In conclusion, digestive enzyme treatment released more AC from grains, and exhibited a higher AA.