Antioxidant Properties of Peptide from Cowpea Seed

The amino acids, hydrophobicity, preparation technology, and antioxidant activity of peptide from cowpea seed isolated protein were investigated. The ratio of essential amino acid to total amino acid of cowpea seed and cowpea seed isolated protein were 35.60 and 36.27%, respectively, and the essential amino acid to non-essential amino acid were 55.27 and 56.96%, respectively. The mole ratio of hydrophobic amino acids and branched chain amino acids in cowpea seed isolated protein were 38.10 and 31.75%. The hydrophobicity value of cowpea seed isolated protein was 5.01 KJ/ mol. The optimum hydrolyzing parameters obtained from orthogonal experiment (L₉(3)⁴) were as follows: hydrolyzing temperature, 50°C; cowpea seed isolated protein concentration, 5%; pH, 9.0; and hydrolyzing time, 2 h. Under optimized conditions, the degree of hydrolysis was 26.85%. Available data obtained with in vitro models exhibited that peptides had significant inhibitory effects on 2,2-diphenyl-1-picrylhydrazyl and hydroxyl radical with half inhibitory concentration (IC₅₀) values of (6.38 ± 0.15) mg/mL and 2.03 mg/mL, respectively, suggesting that cowpea seed peptide possessed higher antioxidative activity and could be used as a potential functional food ingredient.