Extraction and physicochemical characterization of Tenebrio molitor proteins

This study focused on the extraction and physicochemical characterization of proteins from larvae and larvae meal of Tenebrio molitor. The larvae were subjected to a protein extraction process which involved a thermo-mechanical pre-treatment to produce the larvae meal. Soluble proteins from larvae and from larvae meal were subsequently extracted by solubilisation at an alkaline pH. The products obtained were then characterized and compared. The larvae and larvae meal were rich in protein (65.6% and 71.6% respectively) and displayed good essential amino acid (EAA) profiles. They contained all EAA and in sufficient quantities to meet the dietary requirements of both humans and salmon, except for a deficiency in methionine. The EAA profile of the larvae meal was also comparable to those of fish and soya meals used for feed. At pH10 and 45°C, the protein extraction yield of larvae (59.9%) was two-fold that of larvae meal (26.4%). The soluble proteins had protein contents on dry matter of 84% and 80% from larvae and larvae meal respectively. Molecular weights ranged from ≤14 to 100kDa but the two soluble proteins differed. The soluble proteins had a solubility which was highly pH-dependent, with a low solubility at pH3 to 5. Their surface charge depended on both the pH (in particular) and the NaCl concentration. The surface hydrophobicity at pH7 of soluble proteins from larvae (670.3) was higher than that of soluble proteins from larvae meal (102.5). These soluble proteins lowered the water surface tension to 42mN/m and 32mN/m for the soluble proteins from larvae and from larvae meal respectively. Chemical compounds used in this work. Glycine (PubChem CID: 750); Glycerol (PubChem CID: 753); Tris-(hydroxymethyl)aminomethane (PubChem CID: 4468930); Sodium chloride (PubChem CID: 5234); Ethanol (PubChem CID: 702); Monosodium phosphate (PubChem CID: 23672064); Disodium hydrogen phosphate (PubChem CID: 24203); 2-mercaptoethanol (PubChem CID: 1567); Hydrochloric acid (PubChem CID: 313); Bromophenol blue (PubChem CID: 8272); Sodium hydroxide (PubChem CID: 14798); Sodium dodecyl sulphate (PubChem CID: 3423265).