Antioxidant activities of rapeseed peptides produced by solid state fermentation

In this study, rapeseed peptides (RPs) were prepared by solid state fermentation with Bacillus subtilis followed by evaluation of peptide antioxidant activities (scavenging of DPPH, ferric reducing power, ferrous ion-chelation and ability to inhibit linoleic acid autoxidation, in vitro). The content of soluble peptides increased rapidly within the first 2 days of fermentation, which suggested high susceptibility of the rapeseed proteins to microbial proteases. After 3 days of fermentation, RPs were composed mainly of five peptide fractions within the 180-5500 Da size range; however, proportion of peptides with < 3000 Da size decreased significantly (p < 0.05) after 5 days of fermentation. Glutamic acid (19.5%), lysine (7.6%) and proline (7.3%) were the most dominant amino acids present in the RPs but serine (1.5%), tryptophan (1.3%) and cysteine (0.5%) were present in least amounts. A concentration-dependent effect on antioxidant activities was present in RPs, which showed high activities of scavenging free radical, reducing power, and inhibition of lipid peroxidation, but low ferrous ion-chelating activity. We concluded that fermentation provided a suitable medium for converting rapeseed meal into antioxidant peptides that may be used to formulate functional foods and nutraceuticals.

► Rapeseed meal was converted to peptides by solid state microbial fermentation. ► Peptides were high in glutamic acid, a known potentiator of antioxidant activity. ► Peptides effectively scavenged free radicals and inhibited linoleic acid oxidation.