Physical and Oxidative Stability of Low-Fat Fish Oil-in-Water Emulsions Stabilized with Black Soldier Fly (Hermetia illucens) Larvae Protein Concentrate

The physical and oxidative stability of fish oil-in-water (O/W) emulsions were investigated using black soldier fly larvae (BSFL) (Hermetia illucens) protein concentrate as an emulsifier. To improve the protein extraction and the techno-functionality, defatted BSFL powder was treated with ohmic heating (BSFL-OH) and a combination of ohmic heating and ultrasound (BSFL-UOH). Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were performed in order to characterize the secondary structure and thermal stability of all protein concentrate samples. The interfacial properties were evaluated by the pendant drop technique. The lowest interfacial tension (12.95 mN/m) after 30 min was observed for BSFL-OH. Dynamic light scattering, ζ-potential and turbiscan stability index (TSI) were used to evaluate the physical stability of emulsions. BSFL-OH showed the smallest droplet size (0.68 μm) and the best emulsion stability (TSI = 8.89). The formation of primary and secondary volatile oxidation products and consumption of tocopherols were evaluated for all emulsions, revealing that OH and ultrasound treatment did not improve oxidative stability compared to the emulsion with untreated BSFL. The results revealed the promising application of BSFL proteins as emulsifiers and the ability of ohmic heating to improve the emulsifying properties of BSFL proteins.

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Characterisation of black soldier fly larva protein before and after conjugation by the Maillard reaction

Journal of Insects as Food and Feed ◽

10.3920/jiff2021.0017 ◽

2021 ◽

pp. 1-16

Author(s):

B. Zozo ◽

M.M. Wicht ◽

V.V. Mshayisa ◽

J. van Wyk

Keyword(s):

Maillard Reaction ◽

Protein Extraction ◽

Structural Difference ◽

Principal Component ◽

Protein Molecule ◽

Nutritional Composition ◽

Gravimetric Analysis ◽

Protein Extract ◽

Scanning Calorimetry ◽

Black Soldier Fly

Black soldier fly has been proposed as an alternative protein source sustainable for both food and feed due to its nutritional composition. The functional properties of this protein can be improved by inducing the Maillard reaction (MR) in protein-sugar mixtures. This study focused on the conjugation and characterisation of black soldier fly larvae (BSFL) proteins and conjugates. The defatted BSFL larvae were subjected to protein extraction at an alkaline pH. The protein extract was then conjugated with glucose. The BSFL protein and glucose were mixed at (2:1 w/w, pH 9), incubated at 50, 70, and 90 °C for 30, 60, 90 and 120 min. The products obtained were then characterised and compared. The changes were confirmed by universal attenuated total reflectance Fourier-transform infrared spectroscopy (UATR-FTIR), scanning electron microscopy, thermal gravimetric analysis and differential scanning calorimetry. UATR-FTIR combined with principal component analysis monitored the protein-sugar conjugates, to show the structural difference among heated proteins and conjugates. The heating treatments resulted in the unfolding and reduction of the protein molecule aggregation. The protein extract from the larvae was rich in protein content (67±0.78%) and displayed good essential amino acids (EAA) in sufficient quantities to meet the dietary requirements for humans. The EAA quantities of the conjugates decreased due to the MR treatment. The conjugates showed a significant decrease in the lysine content as a function of reaction temperature and time at 90 °C and 120 min, respectively. FTIR indicated that the amide I and II bands of the protein were altered by the MR. The increased Tmax (the temperature at which decomposition is completed) demonstrated that the conjugation of the protein with glucose improved the thermal stability, remarkably. These results suggested that MR with glucose can be a promising way to improve the thermal properties of BSFL protein.

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