Investigation of antioxidant capacity of peptide fractions from the Tra catfish by-product-derived proteolysate using Flavourzyme® 500 mg

In this study, the antioxidant potential of peptide fractions isolated from the Tra catfish (Pangasius hypophthalmus) by-product-derived hydrolysate using ultrafiltration centrifugal devices with 3 distinct molecular-weight cutoffs (MWCOs) of 5KDa, 10KDa, and 30KDa was investigated. Firstly, the chemical composition of the Tra catfish byproducts was analyzed. The result showed that the Tra catfish by-products contained 58.5% moisture, 33.9% crude protein, 50.1% crude lipid and 15.8% ash (on dry weight basis). Secondly, the effects of enzyme content, hydrolysis time on the antioxidant activity of the hydrolysate were studied using DPPH• (2,2-diphenyl-1-picrylhydrazyl) radical scavenging method (DPPH• SM), and FRAP (ferric reducing antioxidant potential) method. Flavourzyme® 500 MG was used for hydrolysis. The result revealed that the antioxidant activity of the proteolysate reached the peak when the hydrolysis time was 3h, enzyme/substrate (E/S) ratio was 25 U/g protein, hydrolysis temperature was 500C, pH was 7, and the degree of hydrolysis (DH) of the hydrolysate reached 37.4%. Next, the proteolysate was further fractionated using MWCOs of 5KDa, 10KDa, and 30KDa and the peptide fractions were investigated for their antioxidant activity. The result showed that the <5KDa fraction showed strongest antioxidant activity with the 50% DPPH• inhibition concentration (IC50) of 3079.34±75.29 μg/mL and FRAP value of 611.28±4.5 μM Trolox equivalent. The second strongest fraction was 5-10KDa with the IC50 and FRAPS value of 4709.3 ± 222.22 μg/mL and 323.62±2.54 μM Trolox equivalent, respectively. The 10-30KDa fraction showed weakest antioxidant capacity with the IC50 of 5847.73 ± 128.68 μg/mL and FRAP value of 291.4±2.65 μM Trolox equivalent. The antioxidant peptides derived from Tra catfish by-products proteolysate have the potential to be used as natural antioxidant ingredients in pharmaceutical and food industry.