Improving the biological activity, functional properties, and emulsion stability of soybean meal hydrolysate via covalent conjugation with polyphenol

Effect of 4-methylbenzoquinone concentration on its covalent conjugates with β-lactoglobulin: Structural and functional properties

This study examined the effect of quinone concentration on covalent interaction between β-lactoglobulin (β-Lg) and 4-methylbenzoquinone (4MBQ). β-Lg-4MBQ-0.2, β-Lg-4MBQ-0.4, and β-Lg-4MBQ-0.8 were prepared at 1:2, 1:1, and 2:1 M ratio of 4MBQ to β-Lg thiols, respectively. β-Lg-4MBQ-0.8 had the highest polyphenol content (19.04 ± 0.17 mg/g) and the lowest free sulfhydryl (17.12 ± 0.18 μmol/g) and amino group (181.28 ± 5.37 μmol/g) contents. Compared to β-Lg, β-Lg-4MBQ conjugates showed reduced α-helix (0.82-1.26 %) and increased β-sheet (1.17-1.50 %) content. β-Lg-4MBQ-0.8 and β-Lg-4MBQ-0.4 exhibited higher surface hydrophobicity and emulsifying properties than β-Lg-4MBQ-0.2 and β-Lg. Antioxidant activity (DPPH and ABTS scavenging) followed: β-Lg-4MBQ-0.8 (46.75 ± 0.17 % and 50.97 ± 0.51 %) > β-Lg-4MBQ-0.4 (39.50 ± 0.27 % and 46.63 ± 0.59 %) > β-Lg-4MBQ-0.2 (33.35 ± 0.71 % and 43.00 ± 0.39 %) > β-Lg (31.50 ± 0.56 % and 36.25 ± 0.90 %). β-Carotene emulsions stabilized by β-Lg-4MBQ-0.4 exhibited the highest stability. These findings provide insights into developing antioxidant emulsifiers.

Effects of polysaccharides on the structure, functionality, emulsion stability and rheological properties of soybean meal hydrolysate-proanthocyanidin complexes

In this study, the structure, functionality, physicochemical property, emulsion storage stability, and rheological properties of soybean meal hydrolysate-proanthocyanidin (SMH-PC) conjugates in ternary complex with glucan, sodium alginate, or soybean polysaccharides were investigated. Following complexing, the proteins unfolded and their disordered structures positively promoted the emulsifying properties of ternary complexes. The SMH-PC-glucan complex showed the best antioxidant activity and the highest emulsifying activity index (94.11 m2·g-1) and stability index (378.09 min). Moreover, the SMH-PC-glucan complex emulsion exhibited the best emulsion stability, including the smallest particle size and good storage stability. These findings demonstrate the potential of using modified SMHs as emulsifiers to increase the value of soybean meal.

Dynamic covalent interactions between baicalin and soybean protein: Effect of the baicalin on structure, antioxidant properties, and emulsion stability of soybean protein conjugate

To improve the emulsion properties of soybean protein isolate (SPI), the effect of baicalin (BC) concentrations on the structure, antioxidant properties, and emulsion stability of SPI-BC conjugates were investigated. Structure analysis revealed that BC induced structural depolymerization and unfolding of SPI through the formation of covalent bonds (CN and CS), increasing hydrophilicity, stabilizing the interface, and enabling the formation of smaller oil droplets. The increase in zeta potential of SPI-BC conjugates enhanced electrostatic repulsion between droplets, preventing aggregation, while the strengthened interfacial protein network improved viscosity, shear stress, and thixotropic recovery, thereby significantly stabilizing the emulsion structure. The addition of 0.4 mg/mL BC exhibited the optimal emulsification performance, increasing emulsion stability by 35.4 %. Moreover, SPI-BC emulsions demonstrated enhanced stability against various environmental stressors (storage, heating, pH, ionic strength, and oxidation). These findings confirmed that BC covalent modification enhanced the structural properties of SPI and improved the stability of protein-based emulsions through structural regulation. This study provides new insights into the potential of BC in improving SPI functionality.

Controlled hydrolysis and EGCG conjugation enhance the ADH/ALDH activation activity of chia seed meal protein hydrolysates: Fabrication and structural characterization

This study examines the effects of hydrolysis duration (20-100 min using flavourzyme) and EGCG conjugation on the structure and bioactivity of chia seed meal protein hydrolysates (CSPH) through multi-spectroscopic techniques and physicochemical property evaluation. Subsequently, the activation effects of EGCG-conjugated peptides on alcohol metabolism-related enzymes were further analyzed through the integration of peptidomics, bioinformatics, and computational chemistry. It was found that with the extension of hydrolysis time, the thermal stability of CSPH diminishes, its rigid structure becomes more flexible, and its crystallinity decreases (by up to 27.19 %). Meanwhile, the activation effects on alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) activity were significantly enhanced (P < 0.05). CSPH hydrolyzed for 60 min demonstrated the highest binding affinity for EGCG, primarily driven by hydrophobic interactions and hydrogen bonds. The CSPH-EGCG conjugate exhibited enhanced physicochemical properties and significantly elevated activation of ADH and ALDH, with ADH activation rising from 22.66 % to 95.56 % and ALDH activation from 9.45 % to 30.93 %, compared to unmodified CSPH. Seven active peptides were identified from PE-60 by peptidomics and bioinformatics. Computer docking optimized selected three optimal peptides (IPW, FPIH, and IYP). Two-dimensional and three-dimensional interaction analyses showed that these peptides bind to EGCG, ADH, and ALDH via hydrogen bonds, hydrophobic interactions, and salt bridges. These findings highlight the potential of controlled hydrolysis with flavourzyme and EGCG incorporation to enhance CSPH's properties and bioactivities and offer insights into the practical applications of CSPH and its EGCG complexes in food processing and therapeutic systems.

Investigating binding mechanism between coconut globulin and tannic acid mediated by atmospheric cold plasma: Protein structure and stability

Physical methods present promising avenues for inducing covalent modifications of proteins by polyphenols, circumventing the safety and sustainability issues associated with traditional approaches. This study sought to enhance the physicochemical properties of coconut globulin (CG) by facilitating covalent cross-linking with tannic acid (TA) through atmospheric cold plasma (ACP). The ACP treatment effectively transitioned the interaction between CG and TA from non-covalent to covalent in a voltage-dependent manner at pH 6.0, resulting in structural modifications of CG. The treatment with TA enhanced the spherical structure of CG, with a reduction in particle size from 474 to 384 nm. This size reduction was further amplified by the exposure of charged groups induced by ACP treatment. Consequently, the solubility, surface hydrophobicity, and viscosity of ACP-treated CG-TA increased, leading to an elevated denaturation temperature and enhanced physical stability. These results suggest a viable approach to improving the suboptimal physicochemical properties of plant proteins.

Fabrication and characterization of curcumin-encapsulated composite nanoparticles based on soybean protein isolate hydrolysate/soybean polysaccharides: Interaction mechanism, stability and controlled release properties

This study developed a stable nanoparticle (CUR-SPIH/SSPS) using soybean protein isolate hydrolysate (SPIH) and soybean polysaccharides (SPSS) to protect curcumin (CUR) from degradation during storage and exposure to light and heat conditions, achieving controlled release. The SPIH to SPSS mass ratio of 5:1 gave the CUR-SPIH/SPSS nanoparticles with the highest CUR encapsulation efficiency (95.60 ± 3.00 %) and the strongest antioxidant capacity (90.26 ± 2.42 % and 66.78 ± 1.89 % for ABTS•+ and DPPH radical scavenging ability, respectively), and CUR was successfully encapsulated within the CUR-SPIH/SPSS as evidenced by X-ray diffraction. FTIR and fluorescence spectroscopy analysis confirmed that the interactions in CUR-SPIH/SPSS are primarily driven by electrostatic, hydrogen bonding, and hydrophobic interactions. Moreover, the CUR-SPIH/SPSS nanoparticles significantly enhanced CUR's thermal and UV light stability. The UV degradation kinetics showed that the half-life of CUR-SPIH/SPSS (247.55 min) was 1.61 times longer than that of free CUR (154.03 min). The release rate of CUR incorporated into CUR-SPIH/SPSS was significantly delayed during in vitro gastrointestinal digestion. This study introduces an innovative nanoparticle strategy for the stable delivery of lipophilic compounds.

Preparation of oil-in-water emulsions stabilized by faba bean protein-grape leaf polyphenol conjugates: pH-, salt-, heat-, and freeze-thaw-stability

BACKGROUND

Plant proteins are being increasingly utilized as functional ingredients in foods because of their potential health, sustainability, and environmental benefits. However, their functionality is often worse than the synthetic or animal-derived ingredients they are meant to replace. The functional performance of plant proteins can be improved by conjugating them with polyphenols. In this study, the formation and stability of oil-in-water emulsions prepared using faba bean protein-grape leaf polyphenol (FP-GLP) conjugates as emulsifiers. Initially, FP-GLP conjugates were formed using an ultrasound-assisted alkali treatment. Then, corn oil-in-water emulsions were prepared using high-intensity sonication (60% amplitude, 10 min) and the impacts of conjugate concentration, pH, ionic strength, freezing-thawing, and heating on their physicochemical properties and stability were determined.

RESULTS

Microscopy and light scattering analysis showed that oil-in-water emulsions containing small oil droplets could be formed at conjugate concentrations of 2% and higher. The addition of salt reduced the electrostatic repulsion between the droplets, which increased their susceptibility to aggregation. Indeed, appreciable droplet aggregation was observed at ≥ 50 mmol/L sodium chloride. The freeze-thaw stability of emulsions prepared with protein-polyphenol conjugates was better than those prepared using the proteins alone. In addition, the emulsions stabilized by the conjugates had a higher viscosity than those prepared by proteins alone.

CONCLUSION

This study showed that FP-GLP conjugates are effective plant-based emulsifiers for forming and stabilizing oil-in-water emulsions. Indeed, emulsions formed using these conjugates showed improved resistance to pH changes, heating, freezing, and salt addition. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Novel a-linolenic acid emulsions stabilized by octenyl succinylated starch -soy protein-epigallocatechin-3-gallate complexes: Characterization and antioxidant analysis

In this study, octenyl succinylated starch (OSAS)-soy protein (SP)-epigallocatechin-3-gallate (EGCG) complexes were designed to enhance the physical and oxidative stability of α-linolenic acid emulsions. Formations of OSAS-SP-EGCG complexes were confirmed via particle size, ξ-potential, together with fourier transform infrared (FTIR). A mixing ratio of 1:2 for OSAS to SP-EGCG resulted in ternary complexes with the highest contact angle (59.69°), indicating the hydrophobicity. Furthermore, the characteristics of α-linolenic acid emulsions (oil phase volume fractions (φ) of 10% and 20%) stabilized by OSAS-SP-EGCG complexes were investigated, including particle size, ξ-potential, emulsion stability, oxidative stability, and microstructure. These results revealed exceptional physical stability together with enhanced oxidative stability for these emulsions. Particularly, emulsions utilizing complexes having a 1:2 OSAS to SP-EGCG ratio exhibited superior emulsion stability. These findings provide theoretical support to the development of emulsions containing high levels of α-linolenic acid and for the broader application of α-linolenic acid in food products.

Recovery of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) from water using foam fractionation with whey soy protein

Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are persistent anthropogenic chemicals that are widely distributed in the environment and pose significant risks to human health. Foam fractionation has emerged as a promising method to recover PFOS/PFOA from water. However, PFOS/PFOA concentrations in wastewater are often inadequate to generate stable foams due to their high critical micelle concentrations and the addition of a cosurfactant is necessary. In this study, we developed whey soy protein (WSP) as a green frother and collector derived from soybean meal (SBM), which is an abundant and cost-effective agro-industrial residue. WSP exhibited excellent foaming properties across a wide pH range and demonstrated strong collection capabilities that enhanced the recovery of PFOS/PFOA. The mechanism underlying this collection ability was elucidated through various methods, revealing the involvement of electrostatic attraction, hydrophobic interaction, and hydrogen bonding. Furthermore, we designed a double plate internal to improve the enrichment of PFOS/PFOA by approximately 2.3 times while reducing water recovery. Under suitable conditions (WSP concentration: 300 mg/L, pH: 6.0, air flowrate: 300 mL/min), we achieved high recovery percentages of 94-98% and enrichment ratios of 7.5-12.8 for PFOS/PFOA concentrations ranging from 5 to 20 mg/L. This foam fractionation process holds great promise for the treatment of PFOS/PFOA and other per- and polyfluoroalkyl substances.

Alcalase-hydrolyzed insoluble soybean meal hydrolysate aggregates: Structure, bioactivity, function properties, and influences on the stability of oil-in-water emulsions

We studied the influences of hydrolysis time on the structure, functional properties, and emulsion stability of insoluble soybean meal hydrolysate aggregates (ISMHAs). We assume that the ISMHAs produced by soybean meal can be used as emulsifiers to prepare stable emulsions. The molecular weights of these ISMHAs were below 53 kDa. After hydrolysis, a decrease in α-helices and an increase in random coils indicated that the soybean meal proteins were unfolding. Moreover, the fluorescence intensity, UV absorption, and surface hydrophobicity of ISMHAs increased. These results would contribute to their antioxidant activity and functional properties. Additionally, the 90-min ISMHA sample exhibited the highest ABTS+• scavenging activity (80.02 ± 4.55 %), foaming stability (52.92 ± 8.06 %), and emulsifying properties (emulsifying activity index of 97.09 m2/g; emulsifying stability index of 371.47 min). The 90-min ISMHA emulsion exhibited the smallest particle size and excellent storage stability. Soybean meal peptide by-product emulsifier has potential for sustainable application.

Egg White Protein-Proanthocyanin Complexes Stabilized Emulsions: Investigation of Physical Stability, Digestion Kinetics, and Free Fatty Acid Release Dynamics

Egg white proteins pose notable limitations in emulsion applications due to their inadequate wettability and interfacial instability. Polyphenol-driven alterations in proteins serve as an effective strategy for optimizing their properties. Herein, covalent and non-covalent complexes of egg white proteins-proanthocyanins were synthesized. The analysis of structural alterations, amino acid side chains and wettability was performed. The superior wettability (80.00° ± 2.23°) and rigid structure (2.95 GPa) of covalent complexes established favorable conditions for their utilization in emulsions. Furthermore, stability evaluation, digestion kinetics, free fatty acid (FFA) release kinetics, and correlation analysis were explored to unravel the impact of covalent and non-covalent modification on emulsion stability, dynamic digestion process, and interlinkages. Emulsion stabilized by covalent complex exhibited exceptional stabilization properties, and FFA release kinetics followed both first-order and Korsmeyer-Peppas models. This study offers valuable insights into the application of complexes of proteins-polyphenols in emulsion systems and introduces an innovative approach for analyzing the dynamics of the emulsion digestion process.

The biological activity, functionality, and emulsion stability of soybean meal hydrolysate-proanthocyanidin conjugates

The use of by-product hydrolysates as functional ingredients in food production is becoming more widespread. We hypothesized that the covalent binding of proanthocyanidin (PC) to soybean meal hydrolysates (SMHs) will improve the biological activity and function of the SMHs. Accordingly, we investigated the structure, antioxidant activity, and emulsion stability of SMHs after covalent conjugation with different concentrations of PC. An increase in PC addition resulted in the development of more high-molecular-weight SMHs-PC conjugates (40 kDa). The observed increase in the random coil content indicated that greater unfolding and disordered structure formation occurred with increasing PC addition. In addition, the fluorescence intensity and surface hydrophobicity of the SMHs increased, suggesting the presence of free amino acids, which likely contributed to the antioxidant activity and emulsifying properties of the SMHs. Addition of 3.0 mg/mL PC gave the SMHs-PC conjugates the highest antioxidant activity (ABTS+ and DPPH radical scavenging capacities of 89.08 ± 0.47 and 40.90 ± 1.53%, respectively) and emulsifying activity index (79.13 ± 2.80 m2/g), which may be attributed to protein unfolding and maximization of the polyphenol content when PC was covalently bound to the SMHs. Moreover, the SMHs-PC emulsion with 2.0 mg/mL PC showed the smallest particle size and highest viscosity, presenting promising potential as an emulsifier with high biological activity in food.

Interaction and binding mechanism of ovalbumin with cereal phenolic acids: improved structure, antioxidant activity, emulsifying and digestion properties for potential targeted delivery systems

Ovalbumin (OVA) has been considered as a nutrient carrier for bioactive, which has high nutrition value and multiple properties. Recently, proteins-phenolic acids composite delivery systems have received widespread attention. Therefore, this research aimed to investigate the interaction between OVA and cereal phenolic acids (CPA) to establish delivery systems for bioactive. Spectroscopy results have found that CPA generated complexes with OVA, causing the microenvironment changes of OVA. Ferulic acid (FA), p-coumaric acid (CA), vanillic acid (VA), syringic acid (SY), sinapic acid (SI), and protocatechuic acid (PA) not only quenched the intrinsic fluorescence of OVA, but also altered protein microenvironment. Further investigation showed these complexes were formed by static quenching mode, while hydrogen bond and hydrophobic interaction were dominant binding forces. Meanwhile, the interaction decreased α-helix contents and increased β-sheet contents, leading to conformational changes in OVA. Besides, OVA/CPA complexes displayed an increase in hydrophobicity with a reduce in free-SH. After combination with FA, SY, CA, VA, SI, PA, it was found that all formed complexes had superior solubility, emulsifying and antioxidant activities than native OVA. Among them, OVA-PA exhibited the highest emulsifying activity index and emulsion stability index values (36.4 ± 0.39 m2/g and 60.4 ± 0.94 min) and stronger antioxidant activities. Finally, the combination with phenolic acids further improved the digestion efficiency in vitro of OVA. The OVA-CPA complexes showed improved properties for excellent delivery systems. Overall, OVA-CPA complexes could be a good carrier for bioactive, which provided valuable avenues in target delivery system application.

The influence of protein oxidation on structure, pepsin diffusion, and in vitro gastric digestion of SPI emulsion

The stability behaviors of oxidized SPI emulsions under in vitro gastric conditions and the effects of pepsin diffusion on the proteolysis of emulsions were investigated using a static gastric model and the fluorescence recovery after photobleaching method. Results showed that protein oxidation increased the particle size of droplets and decreased the viscoelasticity of the interfacial layer. Compared to the control group (82.81 m²/s), the pepsin diffusivity decreased to 68.52 m²/s (7LA + LOX group) due to the space hindrance of oil droplets. After gastric digestion, protein hydrolysates were re-absorbed on the oil-water interface and formed a thick layer, thereby decreasing the size of oil droplets and reducing the contents of free amino acids in gastric digesta. The protein oxidation may affect the adsorption of interfacial proteins and alter the distribution of droplets, decreasing pepsin diffusion and ultimately impairing the emulsion gastric digestion. And this should be considered in the design of emulsion as the controllable delivery system.