Effect of High Hydrostatic Pressure Intensity on Structural Modifications in Mealworm (Tenebrio molitor) Proteins

Abstract

Processing edible insects into protein extracts may improve consumer acceptability. However, a better understanding of the effects of food processing on the proteins is needed to facilitate their incorporation into food matrices. In this study, soluble proteins from Tenebrio molitor (10% w/v) were pressurized using high hydrostatic pressure (HHP) at 70–600 MPa for 5 min and compared to a non-pressurized control (0.1 MPa). Protein structural modifications were evaluated using turbidity measurement, particle-size distribution, intrinsic fluorescence, surface hydrophobicity, gel electrophoresis coupled with mass spectrometry, and transmission electron microscopy (TEM). The observed decrease in fluorescence intensity, shift in the maximum emission wavelength, and increase in surface hydrophobicity reflected the unfolding of mealworm proteins. The formation of large protein aggregates consisting mainly of hexamerin 2 and ⍺-amylase were confirmed by protein profiles on gel electrophoresis, dynamic light scattering, and TEM analysis. The typical aggregate shape and network observed by TEM after pressurization indicated the potential involvement of myosin and actin in aggregate formation, and these were detected by mass spectrometry. For the first time, the identification of mealworm proteins involved in protein aggregation phenomena under HHP was documented. This work is the first step in understanding the mealworm protein–protein interactions necessary for the development of innovative insect-based ingredients in food formulations.

The Review of Cooking, Drying, and Green Extraction Methods on General Nutritional Properties of Mealworms and Locusts

“…On the other hand, HHP is a nonthermal technology utilizing several thousand atmospheric pressures to inactivate microbiological contaminations and preserve the food components such as color, nutrition, and flavor. In a study by Boukil et al ( 2022 ), soluble proteins from mealworms were shown to be unfolded/denatured, leading to increased surface hydrophobicity by exposing hidden hydrophobic amino acid residues to a more polar environment. The increased hydrophobicity was also seen during heating (H. Lee et al, 2019 ) and USE treatment (Rivero-Pino et al, 2020 ) of mealworm proteins.…”

“…Together, these phenomena can lead to a lower degree of protein hydrolysis (Dion-Poulin et al, 2020 ). Mealworms are rich in fibrous proteins (muscle), hemolymph proteins (hexamerins), and enzymes, causing them to be more susceptible to high pressure promoted by the presence of myosin and actin, which aid the formation of intermolecular S-S bonds (Boukil et al, 2022 ). To reduce the molecular weight and enhance the bioavailability of nutrients, further treatment using enzymatic hydrolysis might be needed (Urbina et al, 2021 ), which can lead to higher antioxidative capacity (Kim et al, 2021 ), solubility (Dion-Poulin et al, 2020 ), and reduced allergenicity (Boukil et al, 2020 ) of mealworm hydrolysates.…”

Edible Insects in Thailand: An Overview of Status, Properties, Processing, and Utilization in the Food Industry

“…High-pressure applications ranging from 100 MPa to 800 MPa, and sometimes up to 1000 MPa, result in non-covalent bond instability. High hydrostatic pressure does not affect the covalent bonds of proteins but causes the exchange of disulfide bonds, especially when proteins with free thiol are pressed under high pressure [20,99].…”

Conformational Stability and Denaturation Processes of Proteins Investigated by Electrophoresis under Extreme Conditions

“…Identification of a stable denatured ( D ) state, dissociated oligomers, or irreversible aggregates of unfolded proteins after single or combined action of heat, pressure, ultrasound, chemical, and solvent denaturation can be performed by PAGE under standard conditions [ 203 , 233 , 234 , 235 , 236 ]. Then, protein staining, immunoblotting, or affino-immuno-electrophoresis reveals the threshold of enzyme dissociation/inactivation or loss of immunoreactivity.…”