Preparation and Properties of Tenebrio molitor Protein Hydrolysates

Abstract

Proteins hydrolyzed by enzymes were biologically active. The protein-rich, defatted Tenebrio molitor was used as raw material and hydrolyzed by alkaline protease. The effects of temperature, time, pH, liquid-to-feed ratio, and enzyme addition were investigated with degree of hydrolysis (DH) as an index; the enzymatic hydrolysis process was optimized using one-way and response surface experimental methods, and the antioxidant, physicochemical properties, and amino acid compositions of the hydrolysates were analyzed. The results showed that the optimum process conditions for the preparation of enzymatic hydrolysates were at 52°C for 120 min, pH 7.5, a dosage of enzyme of 5000 U/g, and a liquid-to-material ratio of 30:1, under which the DH was 13.82%. Antioxidant analysis revealed that the hydrolysates exhibited a scavenging ability for free radicals. The scavenging rate of DPPH· reached 47.51% when it was 0.4 mg/mL, and its IC50 was 427.51 mg/mL. When its concentration was 0.2–0.6 mg/mL, the scavenging rate of OH· increased from 50.41% to 92.17%, and its IC50 was 158.4 mg/mL. The physicochemical properties of the hydrolysates differed from those of the Tenebrio molitor protein. The solubility of Tenebrio molitor protein reached a maximum of 38.97% at pH 11.0, whereas that of its hydrolysates peaked at 40.36% at pH 5.0. The hydrolysates exhibited higher values at pH 2.0 and 10.0, with foaming capacities of 26.58% and 25.14% and foaming stabilities of 61.43% and 53.73%, respectively. The EAI and ESI of the hydrolysates were optimal under alkaline conditions, with maximum values of 0.82 and 44.5 m²/g, respectively, at pH 10.0. The hydrolysates contained a variety of amino acids, as well as aromatic amino acids (17.32%) and hydrophobic amino acids (37.51%). Essential amino acids in hydrolysates accounted for 37.91%, and the EAAI value of hydrolysates was 0.7187; the protein quality of hydrolysates significantly improved. The hydrolysates had better solubility and can be used as an effective antioxidant, and the study could provide a theoretical basis for the development and utilization of Tenebrio molitor.