Pigeon pea enzymatic protein hydrolysates and ultrafiltration peptide fractions as potential sources of antioxidant peptides: An in vitro study

Pigeon pea protein isolate was hydrolysed using food grade enzymes (alcalase, pancreatin, pepsin + pancreatin). The resulting hydrolysates were fractionated by membrane ultrafiltration and evaluated for their antioxidant activities. Fraction with molecular weight < 1 kDa had the highest peptide yield (36.97%) for pepsin + pancreatin (PPHPp) hydrolysates, whereas fraction 1-3 kDa showed the highest yield (28.84%, 37.27%) for alcalase-derived peptide (PPHA) and pancreatin-derived peptide (PPHPa) respectively. Low molecular weight fractions of PPHPa showed highest inhibitory activity against DPPH center dot, superoxide (PPHA, PPHPa), and (OH)-O-center dot scavenging activities. However, high molecular weight peptides exhibited better radical scavenging activity (DPPH) and reducing property (FRAP) than the low molecular weight peptides. All fractions exhibited higher ferric reducing and ABTS(center dot+) scavenging activity than the crude hydrolysates. All the peptides also had a higher ABTS(center dot+) scavenging activity than GSH. The low MW fractions ( < 5 kDa) were able to inhibit the progression of lipid peroxidation during the first four days of incubation for most of the peptides. Our findings show that membrane ultrafiltration significantly increased antioxidant properties and the peptides have the potential to be useful as functional ingredient in food and nutraceutical industry to maximise the use of underutilised protein sources.