Enzymatic Preparation and Antioxidant Activities of Protein Hydrolysates from Tenebrio molitor Larvae (Mealworm)

The present study was carried out to evaluate the applicability of Tenebrio molitor larvae (mealworm) as a health functional food material in order to contribute to the development of the domestic insect industry and health functional food industry. Protein hydrolysates were prepared from mealworm powder by enzymatic hydrolysis using five different proteases (alcalase, bromelain, flavourzyme, neutrase, and papain), and the hydrolysates were then tested for their antioxidant activities. Based on available amino group contents and sodium dodecyl sulphate-polyacrylamide gel electrophoresis analyses, mealworms treated with alcalase (4,781.39 microgram/mL), flavourzyme (5,429.35 microgram/mL), or neutrase (3,155.55 microgram/mL) for 24 h showed high degree of hydrolysis (HD) value, whereas HD values of bromelain (1,800 microgram/mL) and papain-treated (1,782.61 microgram/mL) mealworms were much lower. Protein hydrolysates showing high HD values were further separated into greater than 3 kDa and less than or equal to 3 kDa fractions by a centrifugal filter system and then lyophilized, and the production yields of the low molecular weight protein hydrolysates (less than or equal to 3 kDa) by alcalase, flavourzyme, and neutrase were 42.05%, 26.27%, and 30.01%, respectively. According to the RC50 values of the protein hydrolysates (less than or equal to 3 kDa) obtained from three different antioxidant analyses, all three hydrolysates showed similar antioxidant activities. Thus, alcalase hydrolysates showing the highest production yield of low molecular weight protein hydrolysates were further tested for their inhibitory effects on peroxidation of linoleic acid by measuring thiobarbituric acid values, and the results show that peroxidation of untreated linoleic acid increased dramatically during 6 days of incubation. However, pretreatment with the hydrolysates (100∼800 microgram/mL) significantly inhibited linoleic acid peroxidation in a dose-dependent manner over 6 days.