Search

This study investigated the changes in the structure and properties of soybean protein after hydrolysis using two types of hybrid nanoflowers (alcalase@Cu3(PO4)2•3H2O (ACHNs) and dispase@Cu3(PO4)2•3H2O (DCHNs)) and examined the basic properties and oxidative stability of hydrolyzed soybean protein emulsions. The formations of the two hybrid nanoflowers were first determined using a scanning electron microscope, transmission electron microscope, and Fourier infrared spectroscopy. The structure and functional properties of soybean protein treated with hybrid nanoflowers were then characterized. The results indicated that the degree of hydrolysis (DH) of the ACHNs hydrolysates was higher than that of the DCHNs for an identical reaction time. Soybean protein hydrolysates treated with two hybrid nanoflowers showed different fluorescence and circular dichroism spectra. The solubility of the hydrolysates was significantly higher (p < 0.05) than that of the soybean protein (SPI) at all pH values tested (2.0–10.0)*: at the same pH value, the maximum solubility of ACHNs hydrolysates and DCHNs hydrolysates was increased by 46.2% and 42.2%, respectively. In addition, the ACHNs hydrolysates showed the highest antioxidant activity (DPPH IC50 = 0.553 ± 0.009 mg/mL, ABTS IC50 = 0.219 ± 0.019 mg/mL, and Fe2+ chelating activity IC50 = 40.947 ± 3.685 μg/mL). The emulsifying activity index of ACHNs and DCHNs hydrolysates reached its maximum after hydrolysis for 120 min at 61.38 ± 0.025 m2/g and 54.73 ± 0.75 m2/g, respectively. It was concluded that the two hydrolysates have better solubility and antioxidant properties, which provides a theoretical basis for SPI product development. More importantly, the basic properties and oxidative stability of the soybean-protein-hydrolysates oil-in-water emulsions were improved. These results show the importance of proteins hydrolyzed by hybrid nanoflowers as emulsifiers and antioxidants in the food and pharmaceutical industry. [ABSTRACT FROM AUTHOR]

A soy protein isolate-gallic acid (SPI-GA) complex was synthesized, mediated using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide. Different amounts of Fe3+ were then added to the SPI-GA complex to produce hydrogels (SPA@Fe) containing metal-phenolic network without heating the protein. Spectral analysis revealed that these hydrogels contained multiple modes of cross-linking, such as Schiff bases, hydrogen bonds, and coordination bonds. Coordination bonds formed between GA and Fe3+ mainly had a coordination number of three, and they changed the structure of the protein. Furthermore, these coordination bonds also endowed SPA@Fe with a more compact crosslinked network, thus improving the hydrogel's textural characteristics, thermal stability, storage modulus, and glucose adsorption capacity. The SPA@Fe hydrogel exhibited the best performance when the molar ratio of GA to Fe3+ was 1, with the thermal stability, hardness, springiness, and glucose adsorption capacity being 3.9, 1.84, 1.22, and 1.93 times higher than those of the SPI-GA hydrogel, respectively. Moreover, in-vitro digestion tests showed that SPA@Fe could control the release of loaded curcumin, had good capacity for adsorbing bile salt, and showed delayed degradation. This hydrogel system may offer a safe and feasible way to deliver bioactive substances such as curcumin. [Display omitted] • Metal-phenolic networks (MPN) was prepared by chelating GA and Fe. • MPN is used as a green cross-linking agent for SPI to obtain hydrogels. • The composite hydrogels are thermally stable with excellent mechanical properties. • Adjustment of the hydrogel characteristics allows the controlled release of curcumin. [ABSTRACT FROM AUTHOR]

• The effect of ultrasound combined with L-histidine on protein was investigated. • The structures of SPI were changed by ultrasound combined with L-His. • L-His has different effects on protein function at different strengths. • Ultrasound combined with L-His improved the emulsifying properties of SPI. Herein, the effects of ultrasound-assisted L-histidine (L-His) on the physicochemical properties and conformation of soybean protein isolate (SPI) were investigated. Particle size, zeta potential, turbidity, and solubility were used to evaluate protein aggregation, and the relationship between structural and functional changes of the proteins was characterized using spectral analysis, surface hydrophobicity, emulsification, and antioxidant properties. After ultrasound-assisted L-His treatment, SPI exhibited a smaller particle size, higher solubility, and more homogeneous micromorphology owing to the decrease in alpha-helix content and subsequent increases in zeta potential and active sulfhydryl content. In addition, spectral analysis showed that L-His and SPI could form a complex, which changed the microenvironment of the amino acid residues in SPI, thus improving its emulsification and antioxidant properties. At the concentration of L-His was 0.3 % w/w, the nanocomplex had a smaller particle size (140.03 nm), higher ζ-potential (–23.63 mV), and higher emulsification stability (22.48 min). [ABSTRACT FROM AUTHOR]

• Alkaline-treated soybean protein isolate (SPI) had better functional properties. • The affinity of treated SPI and (−)-epigallocatechin-3-gallate (EGCG) were enhanced. • Antioxidant activity and EGCG bioaccessibility were improved. Polyphenols are readily affected by environmental factors, such as heat and light, which cause them to degrade; however, the functional properties of polyphenols can be protected by complexing them with proteins. In this study, we investigate the effects of acid and alkali treatments on the functional properties of soybean protein isolate (SPI) and interactions between the treated protein and (−)-epigallocatechin-3-gallate (EGCG). The results show that alkali treatment (pH 12–7) affects the structure and functional performance of the protein more significantly than acid treatment (pH 2–7) because the protein structure unfolds, resulting in improved solubility, surface hydrophobicity, and emulsification. In addition, because alkali treatment can change the structure of a protein more than acid treatment, its structure loosens. The interactions between alkali-treated proteins and EGCG were also found to be stronger than those of acid-treated proteins and the control protein, and EGCG binds to a protein through van der Waals forces and hydrophobic interactions; these interactions protect EGCG from degradation, ensuring that its antioxidant properties are maintained and its bioavailability rate is improved. [ABSTRACT FROM AUTHOR]

The use of enzyme-assisted aqueous extraction to extract soybean oil will produce soy protein hydrolysates (SPH) that have good antioxidant properties but are bitter and hygroscopic. To microencapsulate these hydrolysates, soy protein isolate/maltodextrin mixtures were used as the carrier. The effects of spray-drying and freeze-drying on the bitterness, hygroscopicity, and antioxidant properties were compared. The properties of different dried samples were compared using solubility, hygroscopicity, moisture content, water activity, flowability, and glass transition temperature (Tg). The results showed that the spray-drying was more effective than freeze-drying. Hygroscopicity was reduced to 18.2 g/100 g, and the Tg value was raised to 80.8°C. The morphology was analyzed using scanning electron microscopy, and the antioxidant properties of the samples were measured using the ABTS˙+ radical scavenging activity. The results showed that spray-dried SPH had more carrier masking, which weakened bitterness, reduced moisture absorption, and had no significant negative impact on its oxidation resistance, solubility, and flowability, and spray-drying after carrier encapsulation of SPH improved the recovery rate. [ABSTRACT FROM AUTHOR]

In this study, oil-in-water emulsions were co-stabilized by a soy protein isolate-(−)-epigallocatechin gallate (SPI-EGCG) conjugate, tea saponin (TS), and hexadecyltrimethylammonium bromide (CTAB) (0.01–1.00%, w/v), and the influence of the mixed SPI-EGCG-conjugate–surfactant interface on the physical stability and protein–lipid co-oxidation properties of each emulsions was investigated. Our results demonstrated that TS exhibits a better emulsifying ability than CTAB by significantly reducing interfacial tension; this emulsion contained the smallest particles at a TS concentration of 1.0% (w/v). In addition, the interfacial protein content revealed the existence of synergistic (CTAB) and competitive (TS) adsorption between the protein and surfactant. The presence of TS displaced protein molecules at the interface and inhibited protein oxidation, which reveals that proteins adsorbed at the oil–water interface are more sensitive to oxidation than unadsorbed proteins. The degrees of protein and lipid oxidation were enhanced in the presence of CTAB. Furthermore, the addition of TS delayed lipid oxidation; this phenomenon was most pronounced at a TS concentration of 1.0% (w/v). Our results indicate that combining SPI-EGCG conjugates with TS provides an optimal design for the development of nutritionally fortified products with longer shelf lives. [Display omitted] • Effects of the surfactant concentration and type on the emulsions were investigated. • TS gave the best emulsification ability and effective interfacial tension reduction. • The co-oxidation of proteins and lipids occurred depending on the protein location. [ABSTRACT FROM AUTHOR]

• Various interfacial structures were observed in the emulsions. • The SPs–TS mixtures displayed synergistic effects in interfacial tension decays. • TS as the outer layer improved the oxidative stability of the emulsion. • TS not only fills the interfacial gaps but also adsorbs on the particle surfaces. • TS inhibited the release of free fatty acids during emulsion digestion. Herein, the effects of the concentration (0.1%–1.0%, w/v) and addition sequence of tea saponin (TS) on the physical stability, oxidative stability, rheological properties, and in vitro digestion of the emulsions stabilized by heat-induced soy protein isolate nanoparticles (SPs) were investigated. The results revealed that the concentration and addition sequence of TS have significant impact on the microstructure, stability, rheological properties, and in vitro digestion of the emulsions. TS was shown to not only fill the interfacial gaps but also adsorb on the particle surfaces, contributing to interfacial wettability. With increasing TS concentration, interfacial tension decay is clearly observed. Further, TS endows the droplets with electrostatic repulsion and steric resistance, preventing their flocculation, coalescence, and oxidation. Finally, in vitro digestion experiments demonstrated that the presence of TS delayed the lipid digestion of the emulsions. [ABSTRACT FROM AUTHOR]

The structure and physicochemical properties of a protein have significant effects on its molecular flexibility. Herein, different flexible protein molecules are obtained after ultrasound treatment at different power conditions (0, 200, 400, and 600 W), and the structural and functional changes in the soybean protein isolate (SPI) are determined. The correlation between flexibility (F), surface hydrophobicity (H 0), and emulsifying properties is established. It is demonstrated that ultrasound decreases the α -helical content and increases the β -sheet content of the SPI, thereby increasing its flexibility and sulfhydryl content, and unfolding its tertiary structure. The SPI affords the best solubility, turbidity, surface hydrophobicity, emulsifying activity (EA), and emulsifying stability (ES) when subjected to an ultrasound power of 400 W. The correlation coefficients between flexibility and emulsification performance (0.938 (F:EA) and 0.958 (F:ES)) are significantly higher than those between the surface hydrophobicity and emulsification performance (0.772 (H 0 :EA) and 0.883 (H 0 :ES)). Therefore, the conformational flexibility of SPI, rather than its surface hydrophobicity, determines its emulsification properties. These findings provide a theoretical basis for understanding the emulsification mechanism of ultrasound-modified proteins, which is important in the food industry. • Ultrasound treatment changes the structure and functional properties of the protein. • Effect of flexibility and surface hydrophobicity on emulsifying ability are compared. • The emulsifying properties of protein are determined by flexibility. [ABSTRACT FROM AUTHOR]

Phosphatidylcholine-soybean protein isolate (PC-SPI) nanoemulsions were prepared by ultrasonication. The effects of preparation conditions (SPI and PC addition, ultrasonic power and time) on the structural properties of the nanoemulsions and their storage stability were investigated. The results showed that the most optimal adsorption capacity and adsorption tightness at the oil–water interface under optimal conditions (1.5% SPI, 0.20% PC, 500 W ultrasonic power and 9 min ultrasonic time) were exhibited by the SPI-PC conjugate, which demonstrated that this nanoemulsions can be categorized as a high-quality emulsion suitable for research. To test its stability, and the high-quality nanoemulsion of β-carotene was stored. After degradation of the nanoemulsions during storage, β-carotene was released. The β-carotene retention rate of the high-quality emulsion was maintained above 86% at different temperatures in the absence of light for up to 30 days. This study provides new information for the development of transport and stability systems for nanoemulsions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Covalently conjugated SPI-EGCG microgel particles were used to stabilize HIPPEs. • EGCG addition improved the functional properties of β-carotene-loaded HIPPEs. • Thick particle layer and gel network jointly promoted the stability of HIPPEs. • Encapsulation of β-carotene enhanced the chemical stability and bioaccessibility. In the current study, soy protein isolate (SPI) and epigallocatechin-3-gallate (EGCG) covalent composite microgel particles with antioxidant capacity were prepared and the particles was used as β-carotene-loaded high internal phase Pickering emulsions (HIPPEs) stabilizers. The covalent binding of SPI-EGCG altered the structures of the SPI through an unfolding of the polypeptide chain. Moreover, compared to HIPPEs stabilized by SPI alone, HIPPEs stabilized by SPI-EGCG microgel particles showed smaller particle size, higher apparent viscosity, and better stability. Microstructure of the fabricated HIPPEs results revealed that SPI-EGCG covalent conjugates promoted the formation of a thick and dense protective layer on the surfaces of oil droplets. Furthermore, β-carotene-loaded HIPPEs stabilized by SPI-2% EGCG microgel particles exhibited a higher retention rate after 42 days of storage and better bioaccessibility (86.64 ± 0.27% and 54.43 ± 0.50%, respectively) compared to HIPPEs stabilized by SPI (75.80 ± 0.49% and 38.31 ± 0.93%, respectively). The current study illustrated that the design of HIPPEs stabilized with protein–polyphenol composite particles were of great importance for the delivery of lipophilic bioactive compounds. [ABSTRACT FROM AUTHOR]