Bio-enrichment of phenolics and antioxidant activity of combination of Oryza sativa and Lablab purpureus fermented with GRAS filamentous fungi

Abstract

Cereal and legumes meet a considerable requirement of protein and carbohydrate of the local population. Most of the foods are cereal based but some cereal/legume or legume based foods are also common in many countries of Asia and Africa. In present study, the effect of fermentation on total phenolics, antioxidant activity and α-amylase enzyme activity of ethanolic extracts of each of seeds and flours combination (1:1) of Oryza sativa (rice) and Lablab purpureus (seim) was determined. The percentage inhibition of free radicals formation by DPPH and ABTS assays was found maximum i.e. 80.66 ± 0.21, 97.67 ± 0.35 on 4th day of incubation of combined sample of rice and seim seeds fermented with Aspergillus oryzae and Aspergillus awamori, respectively. The increased percentage inhibition of free radical formation of fermented samples was found greater than the non-fermented samples (65.88 ± 0.15, 42.00 ± 0.63). The TPC of substrate i.e. rice:seim seeds (1:1) was also found maximum i.e. 47.53 ± 0.20 on 5th day of fermentation with A. awamori. α-amylase activity of fermented samples was also found higher than that of non fermented samples. Almost similar results were obtained in combined flour extract of both the substrates. Increase in level of α-amylase enzyme during SSF indicates that enzymes produced by microorganisms were responsible for release of bound phenolics which may be responsible for increase in antoxidant activity of extracts of fermented seeds and flour combination a cereal and a legume.