Antioxidant activity of Vigna unguiculata L. walp and hard-to-cook Phaseolus vulgaris L. protein hydrolysates

Recent research, using model systems, has shown that enzymatic hydrolysis of food proteins can make them act as direct scavengers of diverse free radicals. This study aimed at the characterization of protein hydrolysates with antioxidant properties from Vigna unguiculata L. walp and hard-to-cook Phaseolus vulgaris L. protein concentrates. The maximum values obtained for all the assays were 15.1 mM/mg of protein for Trolox-equivalent-antioxidative capacity, 98.2% for percentage of 2,2-diphenyl-1-picrylhydrazyl (DPPH) discoloration, 70.1% and 71.4% for iron and copper chelating activities, respectively. The reducing power of hydrolysates was higher than butylated hydroxytoluene (BHT) (control). The antioxidant activity of the hydrolysates may be a result of enzymatic hydrolysis generating peptides that exhibit this type of activity. The hydrolysates showed an increase of amino acids that have been associated with the biological activity of peptides with antioxidant activity, such as hydrophobic residues: Ala, Phe and Ile; hydrophilic: Lys and neutral: Ser and Gly.