ABSTRACT
Due to their protein content and balanced amino acid profile, edible insects have been described as an excellent alternative protein source to combat malnutrition. As the global population continues to grow, edible insects such as the black soldier fly larvae (BSFL) may contribute to food security. The effect of different protein extraction methods, i.e., alkaline solution and acid precipitation (BSFL-PC1) and extraction with an alkali (BSFL-PC2), on the nutritional, techno-functional, and structural properties of BSFL flours and protein concentrates were studied. The highest protein content (73.35%) was obtained under alkaline and acid precipitation extraction (BSFL-PC1). The sum of essential amino acids significantly increased (p < 0.05) from 24.98% to 38.20% due to the defatting process during extraction. Protein solubility was significantly higher in protein concentrates (85−97%) than flours (30−35%) at pH 2. The emulsion capacity (EC) was significantly higher (p < 0.05) in the protein concentrates (BSFL-PC1 and BSFL-PC2) compared to the freeze-dried and defatted BSFL flours, while the emulsion stability (ES) was significantly (p < 0.05) higher in BSFL-PC1 (100%) compared with BSFL-PC2 (49.8%). No significant differences (p > 0.05) were observed in foaming stability (FS) between freeze-dried and defatted BSFL flours. Fourier transform infrared spectroscopy (FT-IR) analysis revealed distinct structural differences between BSFL flours and protein concentrates. This was supported by surface morphology through scanning electron microscopy (SEM) images, which showed that the protein extraction method influenced the structural properties of the protein concentrates. Therefore, based on the nutritional and techno-functional properties, BSFL flour fractions and protein concentrates show promise as novel functional ingredients for use in food applications.
ABSTRACT
This study aimed to assess the nutritional information and structural overview of the BSFL (black soldier fly larva) flours (full fat and defatted). The BSFL flours were obtained by freeze-drying the larvae and the removal of fat using hexane and isopropanol ratio of 3:2 (v/v), these solvents were used due to their defatting efficiency and because they are less toxic. Nutritional and structural analyses were conducted using standard methods. The full-fat and defatted flours had high protein content (45.82% and 56.11% respectively). Defatting significantly (p < 0.05) increases the protein content by approximately 10%, while the fat content decreased from 25.78% in full-fat larvae to 4.8% in defatted larvae. The compositional data were qualitatively confirmed with Universal Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (UATR-FTIR) mainly in the amide I and II regions. Thermal gravimetry (TG) and differential scanning calorimeter (DSC) analysis, showed the conformational physical changes induced due to removal of fat which affected protein denaturation. DSC analysis displayed curves of both endothermic and exothermic reactions. During the first heating program, both samples had wide endothermic heating peaks ranging from 42 to 112 °C, which may be attributed to the water content in the samples evaporating. The first stage of the decomposition process was important, with loss of free and loosely bound water up to 150 °C, according to TGA curves. Protein and carbohydrates volatilized during the second stage of decomposition. The third level may be linked to polypeptide decomposition. FTIR revealed that the defatting process induced structural modifications on the amide I (1650 cm-1) and amide II (1540 cm-1) regions. Defatting has a significant effect on the functional groups and nutritional value of the BSFL. Defatted as well as full-fat flour both show good nutritional and structural characteristics for use in many food applications, however the improved proximate composition of the defatted BSFL can be applied to food products using BSFL flour as an alternative ingredient.
ABSTRACT
Black soldier fly (Hermetia illucens) has received considerable interest as an alternative protein source. Aqueous solutions of black soldier fly larvae (BSFL) protein and glucose (2:1 w.w-1, pH 9) were heated at 50, 70 and 90 °C, for 2-10 h at 2 h intervals, respectively. The zeta-potential (ζ) of BSFL-Glu conjugates heat-treated at 70 °C ranged from -10.25 to -25.25 mV while the native BSFL protein ranged from -12.84 to -16.70 mV. The ζ-potential analysis revealed that the glycation reaction modified the surface charge density of the BSFL protein as a function of reaction time and temperature. In addition, an increase in thermal stability of the BSFL-Glu conjugates was observed by means of Thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Fourier transform infrared spectroscopy (FT-IR) analysis indicated that the most apparent structural changes in the BSFL protein were in the amide I and amide II region. Well-separated clusters permitting differentiation between native BSFL and BSFL-Glu conjugates were observed by using principal component analysis (PCA) on FT-IR spectra. At 50, 70 and 90 °C the first two principal components (PC1 and PC2) showed an accumulated total variance of 91, 96 and 95%, respectively. A classification efficiency of 91% was obtained when using soft independent modelling of class analogy (SIMCA). Infrared spectroscopy combined with SIMCA is a powerful tool to monitor the formation of edible insect protein-sugar conjugates by Maillard reaction. As a result, combining FT-IR spectroscopy with multivariate techniques (PCA and SIMCA) exhibited a strong potential to differentiate between native and glycated protein samples from black soldier fly larvae.
