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).

Calculation of the molar absorptivity of polyphenols by using liquid chromatography with diode array detection: the case of carnosic acid.

Antioxidant activity of vegetable extracts is related to the nature and the amount of active components, mainly polyphenols; therefore, a correct quantification of these molecules should be required to define their concentration in such kind of vegetable extracts. A fast and accurate method to calculate molar absorption coefficients (epsilon), by using HPLC, has been tested on standard polyphenols and caffeine, and should be widely adapted for standardless quantitative analysis. Molar absorptivity (epsilon) of carnosic acid (CA) was determined from 200 to 300 nm, by the proposed method and those values were compared to tert-butyl-hydroxytoluene (BHT) ones for further comparative quantification.

Atmospheric pressure chemical ionization (APcI) liquid chromatography-mass spectrometry: characterization of natural antioxidants.

The combination of liquid chromatography with mass spectrometry (LC-MS) allows non-volatile and thermally sensitive compounds to be handled. The key feature, regarding LC flowrate and MS vacuum requirements, is the LC-MS interface system. Atmospheric pressure chemical ionization (APcI) is a sensitive and widely applicable method which gives primarily molecular weight information with the ability to provide structural information if required. Applications concerning the characterization of natural antioxidants from rosemary, sage and barley are reported: the main functional groups of diterpenes (rosmanol and derivatives), the aglycone part of glycosylated flavones and the different units of polymers of flavan-3-ols (procyanidins, prodelphinidins) are shown.