Effects of microwave on the structural and emulsifying properties and interfacial properties of oxidized soybean protein aggregates.

This research explored microwave treatment impact on the structuro-functional aspects of oxidized soy protein aggregates (OSPI). Data showed that oxidative treatment promoted the formation of high molecular weight aggregates through hydrophobic interactions, thereby disrupting the structure of natural soy protein isolates (SPI). Microwave treatment for an appropriate time (≤30 s) caused the molecular structure of OSPI to open up and reduction in molecular weight and disulfide bond content, while absolute zeta potential increased. These modifications increased emulsifying capacity of OSPI, as well as the interfacial adsorption of protein. Longer microwave treatment times (>30 s) caused OSPI to exhibit a tendency to aggregate in TEM and CLSM images. It indicated the appropriate microwave electromagnetic field effect and microwave heating effect could coordinatively regulate soy protein functional properties by modifying their aggregation behavior. The results provided new ideas for reducing resource waste, and further expanding soy protein application in the food industry.

Impacts of Industrial Modification on the Structure and Gel Features of Soy Protein Isolate and its Composite Gel with Myofibrillar Protein.

Native soy protein isolate (N-SPI) has a low denaturation point and low solubility, limiting its industrial application. The influence of different industrial modification methods (heat (H), alkaline (A), glycosylation (G), and oxidation (O)) on the structure of SPI, the properties of the gel, and the gel properties of soy protein isolate (SPI) in myofibril protein (MP) was evaluated. The study found that four industrial modifications did not influence the subunit composition of SPI. However, the four industrial modifications altered SPI's secondary structure and disulfide bond conformation content. A-SPI exhibits the highest surface hydrophobicity and I850/830 ratio but the lowest thermal stability. G-SPI exhibits the highest disulfide bond content and the best gel properties. Compared with MP gel, the addition of H-SPI, A-SPI, G-SPI, and O-SPI components significantly improved the properties of the gel. Additionally, MP-ASPI gel exhibits the best properties and microstructure. Overall, the four industrial modification effects may impact SPI's structure and gel properties in different ways. A-SPI could be a potential functionality-enhanced soy protein ingredient in comminuted meat products. The present study results will provide a theoretical basis for the industrialized production of SPI.

Study on the Structure, Function, and Interface Characteristics of Soybean Protein Isolate by Industrial Phosphorylation.

The impacts of industrial phosphorylation on the structural changes, microstructure, functional, and rheological features of soybean protein isolate (SPI) were spotlighted. The findings implied that the spatial structure and functional features of the SPI changed significantly after treatment with the two phosphates. Sodium hexametaphosphate (SHMP) promoted aggregation of SPI with a larger particle size; sodium tripolyphosphate (STP) modified SPI with smaller particle size. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) results showed insignificant alterations in the structure of SPI subunits. Fourier transform infrared (FTIR) and endogenous fluorescence noted a decline in α-helix quantity, an amplification in ß-fold quantity, and an increase in protein stretching and disorder, indicating that phosphorylation treatment fluctuated the spatial structure of the SPI. Functional characterization studies showed that the solubility and emulsion properties of the SPI increased to varying degrees after phosphorylation, with a maximum solubility of 94.64% for SHMP-SPI and 97.09% for STP-SPI. Emulsifying activity index (EAI) and emulsifying steadiness index (ESI) results for STP-SPI were better than those for SHMP-SPI. Rheological results showed that the modulus of G' and G″ increased and the emulsion exhibited significant elastic behavior. This affords a theoretical core for expanding the industrial production applications of soybean isolates in the food and various industries.

The temporal evolution mechanism of structure and function of oxidized soy protein aggregates.

The emulsifying activity of soy protein would decrease after long-term storage, which caused huge economic losses to food processing plants. This study explored the temporal evolution mechanism of oxidation on the structure and function of soy protein aggregates, which would improve the application of soy protein in food industry. Decreased α-helix and increased random coil were observed at the initial oxidation stage (0-4 h), which induced increases in hydrophobicity and disulfide bond content. In addition, emulsibility increased significantly. However, when the oxidation time extended to 6-12 h, the soluble aggregates transformed into insoluble aggregates with large particle size, low solubility, and molecular flexibility. Surface hydrophobicity and emulsifying activity were reduced, resulting in bridging flocculation of emulsion droplets. Mutual transformation between components is affected by factors that include spatial conformation and intermolecular forces, which eventually lead to functional changes in the protein molecules.

Effects of γ-Irradiation on Structure and Functional Properties of Pea Fiber.

In this study, pea residue reserve insoluble diet fiber (hereinafter referred to as pea fiber) was used as a raw material. The effects of γ-irradiation doses (0, 0.5, 1, 2, 3, and 5 kGy) on the structural properties (main composition, particle size and specific surface area, scanning electron microscope (SEM) microstructure, Fourier transform infrared spectroscopy, and X-ray diffraction) and functional properties (oil-holding capacity, swelling and water-holding capacity, and adsorption properties) of pea fiber were explored. The results show that, when the γ-irradiation dose was 2 kGy, compared with the untreated sample, the contents of cellulose, hemicellulose and lignin in pea fiber decreased by 1.34 ± 0.42%, 2.56 ± 0.03% and 2.02 ± 0.05%, respectively, and the volume particle size of pea fiber decreased by 17.43 ± 2.35 µm. The specific surface area increased by 23.70 ± 2.24 m2/kg and the crystallinity decreased by 7.65%. Pore and irregular particles appeared on the microstructure surface of the pea fiber treated with γ-irradiation. The results of the infrared spectrum showed that the hemicellulose and lignin in pea fiber were destroyed by γ-irradiation. These results indicate that γ-irradiation can significantly affect the structural properties of pea fiber. When the γ-irradiation dose was 2 kGy, the highest oil-holding capacity, swelling capacity and water-holding capacity of pea fiber were 8.12 ± 0.12 g/g, 19.75 ± 0.37 mL/g and 8.35 ± 0.18 g/g, respectively, and the adsorption capacities of sodium nitre, cholesterol and glucose were also the strongest. These results indicate that the functional properties of pea fiber are improved by γ-irradiation. In this study, γ-irradiation technology was used as pretreatment to provide a theoretical basis for the application of pea fiber in food processing.