Antioxidant activities of lupin (Lupinus angustifolius) protein hydrolysates and their potential for nutraceutical and functional foods

Bioactive peptides are the compounds used as medicines, nutraceuticals and food preservatives. In this study, lupin protein hydrolysates were produced by enzymatic hydrolysis using pepsin, pancreatin and flavourzyme and antioxidative activities of the hydrolysates were measured. Protein was isoelectrically isolated from the lupin seed flour and enzymatically hydrolysed. The hydrolysates were ultrafiltered using molecular weight cut-off (MWCO) membranes. Fractions with masses of <2 kDa, 2–3 kDa, 3–5 kDa and 5–10 kDa were separated from the hydrolysates obtained at different hydrolysis times and then subjected to further fractionation by Size Exclusion Chromatography. Radical scavenging activities against DPPH·, ABTS·+, OH· and Fe2+ chelating abilities of these peptide fractions were measured. The best iron chelating, OH•, DPPH• and ABTS•+scavenging activities (IC50) were 30 ± 5.3, 40 ± 3.9, 60 ± 3.9 and 90 ± 8.2 µg/mL respectively. Pancreatin and Flavourzyme have produced more fractions with best scavenging activities after 3–4 h of hydrolysis (IC50 values in the range of 40–110 µg/mL). Generally Size Exclusion purified fractions displayed superior activities than the parent fractions. Several lupin peptide fractions showed comparable antioxidant capacities to those derived from soybean protein and displayed superior activities when compared with chickpea derived peptide fractions. Therefore, lupin protein hydrolysates are a potential source for nutraceuticals and functional foods.