Characterization and bioactive protein hydrolysates from two-spotted cricket (Gryllus bimaculatus De Geer) and short-tail cricket (Brachytrupes portentosus Lichtenstein)

The two-spotted cricket (Gryllus bimaculatus) and short-tail cricket (Brachytrupes portentosus) are economically significant edible insects in Thailand, boasting up to 60% protein content. This study investigates the effects of different types of proteases on the production of protein hydrolysates and biological activities from two cricket species, divided into 4 groups based on extraction and digestion methods as proteins extracted by heat at 100°C, proteins digested with the protease SD-AY 10, pepsin, and a combination of protease SD-AY 10 and pepsin. None of the 4 protein groups inhibited pathogenic E. coli, Salmonella enteritidis, and Salmonella typhimurium. The total antioxidant capacity (TAC) assessment showed that proteins from G. bimaculatus digested with SD-AY 10 had a significantly higher antioxidant level (5.5 nmol/µl), while proteins from B. portentosus digested with pepsin had a similarly high antioxidant level (5.59 nmol/µl), both significantly higher than other groups (p<0.05). Proteins from both crickets digested by enzymes were safe for RAW 246.7 macrophage cells at concentrations from 1.56 to 25% (v/v) and effectively inhibited nitric oxide production. Protein hydrolysates from G. bimaculatus and B. portentosus inhibited nitric oxide production at a concentration of 25% (v/v) equivalent to ß-glucan. Phagocytic activity was also observed in protein hydrolysates from both cricket species, stimulating RAW 246.7 cells at concentrations of 1.56-25% (v/v). However, protein hydrolysate from B. portentosus, digested with pepsin at a concentration of 1.56-12.5% (v/v) showed higher phagocytic activity values (152.52-163.86%) compared to ß-glucan (149.18%). The results showed that protein hydrolysates from two cricket species, digested by enzymes, exhibited antioxidant activity, inhibited nitric oxide production, are safe for cells, and hold potential as future supplements for human food and animal feed additives.