Isolation and Identification of Antioxidant Peptides Derived from Cricket (Gryllus bimaculatus) Protein Fractions

SIMPLE SUMMARY: The consumption of crickets, like that of other insects, has beneficial effects such as improving gut health, ameliorating chronic diseases because of their bioactivity, and aiding food products when crickets are used as a protein ingredient, such as in baked foods. However, it has not been generally accepted globally as an alternative protein to the mainstream. In this study, a new way to utilize cricket protein as a functional ingredient was explored. The antioxidant activity of cricket protein hydrolysates prepared by different proteases was analyzed and the identification of amino acids sequence responsible for the increased bioactivity of peptides after purification was conducted. The results showed that cricket proteins can be an alternate source of edible protein and bioactive peptides in addition to the mainstream. ABSTRACT: Crickets contain high protein content that can be used to improve nutrition but are less exploited. This study was conducted to isolate different Cricket Protein Fractions including albumin, globulin, glutelin, and prolamin. All fractions were characterized and hydrolyzed by commercial enzymes. The results showed that the glutelin fractions had the highest extraction yields with 53.9 ± 2.12% (p < 0.05). Moreover, glutelin hydrolysate fraction prepared by Alcalase with a 16.35 ±0.29% hydrolysis degree was selected for further purification because of their high antioxidant activities, including ABTS radical-scavenging activity (0.44–0.55 µmol Trolox eq./g) and metal chelating activity (1721.99–1751.71 µmol EDTA eq./g). Two active fractions, GA-1 (<3 kDa) and GA-2 (<3 kDa), were collected from the consecutive purification of glutelin hydrolysates, which included processes such as membrane ultrafiltration and gel filtration. The fractions were analyzed by LC-MS/MS to obtain 10 peptides with 3–13 amino acids identified as TEAPLNPK, EVGA, KLL, TGNLPGAAHPLLL, AHLLT, LSPLYE, AGVL, VAAV, VAGL, and QLL with a molecular weight range of 359.23–721.37 Da in the two fractions. The amino acid sequence shows a prevalence of hydrophobic amino acids (50–100%) such as valine and leucine in the peptide chains, accounting for its high antioxidant activity. In conclusion, cricket glutelin hydrolysate prepared by Alcalase can serve as an alternative source of potent edible bioactive peptides in functional food products.