Spectroscopic analysis of the effect of vitamin B12-soy protein isolate on the soy protein isolate structure

Insight into the interaction and binding mechanism of a natural nonnutritive sweetener mogroside V with soybean protein isolates based on multi-spectroscopic techniques and computational simulations

As a natural low-calorie sweetener, Mogroside V (Mog-V) has gradually become one of the alternatives to sucrose with superior health attributes. However, Mog-V will bring unpleasant aftertastes when exceeding a threshold concentration. To investigate the possibility of soy protein isolates (SPIs), namely β-conglycinin (7S), and glycinin (11S) as flavor-improving agents of Mog-V, the binding mechanism between Mog-V and SPIs was explored through multi-spectroscopy, particle size, zeta potential, and computational simulation. The results of the multi-spectroscopic experiments indicated that Mog-V enhanced the fluorescence of 7S/11S protein in a static mode. The binding affinity of 7S-Mog-V was greater compared with 11S-Mog-V. Particle size and zeta potential analysis revealed that the interaction could promote aggregation of 7S/11S protein with different stability. Furthermore, computational simulations further confirmed that Mog-V could interact with the 7S/11S protein in different ways. This research provides a theoretical foundation for the development and application of SPI to improve the flavor of Mog-V, opening a new avenue for further expanding the market demand for Mog-V.

Biomimetic androgen receptor-based AIE biosensor for detecting bisphenol analogues: An integrating in silico topological analysis, molecular docking, and experimental validation study

Bisphenol analogues are the typical class of endocrine disrupting chemicals (EDCs) that interfere with binding of endogenous hormones to androgen receptor (AR). With the expansion of industrial activities and the intensification of environmental pollution, an increasing array of bisphenol analogues is being released into the environment and food chain. This highlights the urgency to develop sensitive methods for the detection of bisphenol analogues. Here, we propose a biomimetic AR-based biosensor platform for detecting bisphenol analogues (BPF, TBBPA, and TBBPS) by binding with Aggregation-Induced Emission (AIE) probes. Following a comparison of the PROSS and ABACUS methods, biomimetic AR was designed using the ABACUS approach and subsequently expressed in vitro via the E. coli expression system. Through molecular docking and the observation of fluorescence changes upon binding with biomimetic AR, BS-46006 was selected as the AIE probe for the biosensor. The biomimetic AR-based biosensor showed sensitive detections of BPF, TBBPA, and TBBPS within a range of 0-50 mM. To further elucidate the multi-residue recognition mechanism, molecular orbitals, Electron Localization Function (ELF), and Localized Orbital Locator (LOL) were systematically calculated in this study. Lowest unoccupied molecular orbital and highest occupied molecular orbital indicated the energy gap of BPF, TBBPA, and TBBPS, which correspond to 0.12812, 0.19689, and 0.18711 eV, respectively. ELF and LOL offered clearer perspective through heat maps to visually represent the electron delocalization in BPF, TBBPA, and TBBPS. The matrix effect analysis suggested that the responses of bisphenol analogues in soil matrices could be effectively mitigated through sample pretreatment. The analysis of spiked soil samples showed the acceptable recoveries ranged from 91 % to 105 %. Additionally, the biomimetic AR-based AIE biosensor, which combines multi-residue detection with Tolerable Daily Intakes, shows great promise for the risk assessment of bisphenol analogues. This research may present a viable approach for the analysis of environmental pollutants.

Supercritical CO2 Treatment to Modify Techno-Functional Properties of Proteins Extracted from Tomato Seeds

Tomato seeds are a rich source of protein that can be utilized for various industrial food purposes. This study delves into the effects of using supercritical CO2 (scCO2) on the structure and techno-functional properties of proteins extracted from defatted tomato seeds. The defatted meal was obtained using hexane (TSMH) and scCO2 (TSMC), and proteins were extracted using water (PEWH and PEWC) and saline solution (PESH and PESC). The results showed that scCO2 treatment significantly improved the techno-functional properties of protein extracts, such as oil-holding capacity and foaming capacity (especially for PEWC). Moreover, emulsifying capacity and stability were enhanced for PEWC and PESC, ranging between 4.8 and 46.7% and 11.3 and 96.3%, respectively. This was made possible by the changes in helix structure content induced by scCO2 treatment, which increased for PEWC (5.2%) and decreased for PESC (8.0%). Additionally, 2D electrophoresis revealed that scCO2 hydrolyzed alkaline proteins in the extracts. These findings demonstrate the potential of scCO2 treatment in producing modified proteins for food applications.

ε-Polylysine and soybean protein isolate form nanoscale to microscale electrostatic complexes in solution: properties, interactions and as antimicrobial edible coatings on citrus

A feasible approach to enhance the antimicrobial efficacy of ε-polylysine (PL) in applications is to form delivery complexes with delicate structures and good dispersion properties. This work aims to study the multiscale structures, properties and interactions, and edible coating applications of the electrostatic complex formed by PL and soy protein isolate (SPI). When the mass ratio of SPI to PL (SE) was between 5 and 15, especially 11, microscale solid-liquid phase separation occurred in the system due to the small absolute zeta potential. When the SE was in the range of 15-20, the system formed a stable nanoscale suspension, the average particle size and zeta potential were 191 nm and -20 mV, respectively. The physicochemical properties of the complexes were investigated including the colloidal properties, spectroscopy and interactions analysis, viscosity, contact angle, and antimicrobial activities against Escherichia coli, Staphylococcus aureus, and Penicillium expansum. Finally, the in vivo application on citrus demonstrated that the nanoscale PL/SPI electrostatic complex (SE = 20) as functional coatings has both barrier and antimicrobial activities. The study provides a novel application strategy for PL and nanoscale electrostatic complexes as postharvest coatings.

Soy Protein Isolate Interacted with Acrylamide to Reduce the Release of Acrylamide in the In Vitro Digestion Model

Acrylamide (AA), a common carcinogen, has been found in many dietary products.. This study aimed to explore the interaction of soybean protein isolate (SPI) with AA and further research the different effects of SPI on the AA release due to interactions in the in vitro digestion model. Analysis of variance was used to analyze the data. The results suggested that AA could bind with SPI in vitro, leading to the variation in SPI structure. The intrinsic fluorescence of SPI was quenched by AA via static quenching. The non-covalent (van der Waals forces and hydrogen bonding) and covalent bonds were the main interaction forces between SPI and AA. Furthermore, the release of AA significantly decreased due to its interaction with SPI under simulated gastrointestinal conditions. SPI had different effects on the AA release rate after different treatments. The thermal (80, 85, 90, and 95 °C for either 10 or 20 min) and ultrasound (200, 300, and 400 W for either 15, 30, or 60 min) treatments of SPI were useful in reducing the release of AA. However, the high pressure-homogenized (30, 60, 90, and 120 MPa once, twice, or thrice) treatments of SPI were unfavorable for reducing the release of AA.

Study on the binding behavior and functional properties of soybean protein isolate and β-carotene

This study focused on the non-covalent interaction between soybean protein isolate (SPI) and β-carotene (BC). The conformational changes of SPI with β-carotene in varying proportions (BC/SPI: 2%, 4%, 6%, 8%, and 10%) were investigated by multi-spectroscopy and molecular docking. Results showed that the quenching mode is static quenching and binding affinity increased with temperature. The stoichiometry was 1:1, indicating there was only one binding site in SPI. The binding was based on entropy and primarily driven by hydrophobic interactions and its binding constant was in the order of 104 L⋅mol–1. The addition of the β-carotene affected the secondary structure of SPI resulting in an increase in α-Helix and a decrease in random coil and β-turn content, indicating protein aggregated and hydrophobic interactions occurred. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) verified that no new larger molecular weight substance was formed and no covalent interaction existed. Molecular docking corroborated that electrostatic and hydrophobic interactions were both involved in the formation of complexes, where hydrophobic interaction was the dominant one. Moreover, β-carotene improved 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, foaming capacity, and emulsifying stability of SPI. These findings provide useful information about the interaction mechanism of SPI and β-carotene, which contributes to the further development and application of SPI products rich in β-carotene in the food industry.

Soy Protein Isolate/Sodium Alginate Microparticles under Different pH Conditions: Formation Mechanism and Physicochemical Properties

The effects of sodium alginate (SA) and pH value on the formation, structural properties, microscopic morphology, and physicochemical properties of soybean protein isolate (SPI)/SA microparticles were investigated. The results of ζ-potential and free sulfhydryl (SH) content showed electrostatic interactions between SPI and SA, which promoted the conversion of free SH into disulfide bonds within the protein. The surface hydrophobicity, fluorescence spectra, and Fourier transform infrared spectroscopy data suggested that the secondary structure and microenvironment of the internal hydrophobic groups of the protein in the SPI/SA microparticles were changed. Compared with SPI microparticles, the surface of SPI/SA microparticles was smoother, the degree of collapse was reduced, and the thermal stability was improved. In addition, under the condition of pH 9.0, the average particle size of SPI/SA microparticles was only 15.92 ± 0.66 μm, and the distribution was uniform. Rheological tests indicated that SA significantly increased the apparent viscosity of SPI/SA microparticles at pH 9.0. The maximum protein solubility (67.32%), foaming ability (91.53 ± 1.12%), and emulsion activity (200.29 ± 3.38 m²/g) of SPI/SA microparticles occurred at pH 9.0. The application of SPI/SA microparticles as ingredients in high-protein foods is expected to be of great significance in the food industry.

Partial Removal of Phenolics Coupled with Alkaline pH Shift Improves Canola Protein Interfacial Properties and Emulsion in In Vitro Digestibility

The effect of polyphenol removal (“dephenol”) combined with an alkaline pH shift treatment on the O/W interfacial and emulsifying properties of canola seed protein isolate (CPI) was investigated. Canola seed flour was subjected to solvent extraction to remove phenolic compounds, from which prepared CPI was exposed to a pH₁₂ shift to modify the protein structure. Dephenoled CPI had a light color when compared with an intense dark color for the control CPI. Up to 53% of phenolics were removed from the CPI after the extraction with 70% ethanol. Dephenoled CPI showed a partially unfolded structure and increased surface hydrophobicity and solubility. The particle size increased slightly, indicating that soluble protein aggregates formed after the phenol removal. The pH₁₂ shift induced further unfolding and decreased protein particle size. Dephenoled CPI had a reduced β subunit content but an enrichment of disulfide-linked oligopeptides. Dephenol improved the interfacial rheology and emulsifying properties of CPI. Although phenol removal did not promote peptic digestion and lipolysis, it facilitated tryptic disruption of the emulsion particles due to enhanced proteolysis. In summary, dephenol accentuated the effect of the pH shift to improve the overall emulsifying properties of CPI and emulsion in in vitro digestion.