Utilization of plant-based protein-polyphenol complexes to form and stabilize emulsions: Pea proteins and grape seed proanthocyanidins

Multispectral analysis and molecular simulation of quinoa protein-tannic acid interactions: Conformational changes and functional properties

This study used multispectral analysis and molecular simulation to investigate the mechanisms of non-covalent interactions between quinoa protein isolate (QPI) and tannic acid (TA), and its effects on protein conformation. The formation of the QPI-TA complex was confirmed by increased turbidity, polyphenol binding capacity, and UV-visible absorbance. The addition of TA decreased α-helices while increasing β-sheets and random coils, resulting in a looser, more disordered protein structure of QPI. Thermodynamic analysis and molecular docking results indicated that the predominant interactions between QPI and TA are hydrophobic interactions and hydrogen bonds. Molecular dynamics simulations confirmed that the binding sites of TA and QPI were tightly associated, thereby maintaining conformational stability. Additionally, the non-covalent modification by TA significantly enhanced the emulsifying and foaming capacities of QPI. This study provides a theoretical foundation for the application of QPI-polyphenol complexes in the production of emulsified foods.

Three physical modifications enhanced the binding interactions of Cyperus esculentus protein with proanthocyanidins and physicochemical properties of complexes: The contribution of non-covalent interactions

This study investigated non-covalent interactions between unmodified/modified (ball-milling, BMP; high pressure homogenization, HPHP; cold plasma, CPP) Cyperus esculentus protein (CEP) and proanthocyanidins (PA and PB2) to evaluate structure, functionalities and potential in emulsions. The PA and PB2 addition significantly increased the turbidity and ζ-potential of CEP samples, as confirmed by aggregations observed via atomic force microscopy, validating the formation of protein-proanthocyanidin complexes. Fluorescence quenching and isothermal titration calorimetry revealed that procyanidins caused CEP sample static quenching, with CEP-proanthocyanidins binding affinity order as CPP > HPHP>BMP > CEP. The CEP-proanthocyanidins involve non-covalent interactions, driven by hydrogen bonding and electrostatic interactions, without altering CEP sample spectral bands and secondary structures, but enhancing thermal stabilities, antioxidant activities, and emulsifying properties. Then, the CPP-PA stabilized emulsion droplet size decreased with aqueous phase pH increasing, contrary to ζ-potential values. Conclusively, these findings illustrated that the modified CEP-proanthocyanidin complexes as a promising strategy for addressing these challenges and stabilizing emulsion.

Non-covalent interaction of rice protein and polyphenols: The effects on their emulsions

In this study, we investigated the non-covalent interaction mechanism between rice protein (RP) and three polyphenols with different concentrations (ferulic acid FA, gallic acid GA, and tannic acid TA) and their effects on the structure and emulsion stability of the proteins. Hydrophobic forces dominated the binding of RP to the polyphenols, and the reaction was heat-absorbing. The three polyphenols are bound to RP in the form of static quenching to form a non-covalent complex, and during the binding process, the RP provides one binding site. RP-polyphenol complexes, particularly RP-GA, enhanced ABTS scavenging and FRAP reduction. Polyphenols improved RP emulsion oxidative stability, inhibiting lipid oxidation and enhancing emulsion rheology and interfacial structure. RP-GA was most effective, maintaining low POV. These findings support the potential applications of RP-polyphenol noncovalent complexes in food processing.

Preparation and characterization of camellia oil body-based oleogels loaded with (-)-epigallocatechin-3-gallate (EGCG)

Growing concern for healthy diets is driving researchers to developed novel solid lipids to reduce the intake of saturated and trans fatty acids. In this study, a novel edible oleogel loaded with EGCG was prepared using camellia oil body emulsion as template under alkaline condition (pH 9.0) and the effect of EGCG concentration (10-150 μM) on the structure and physicochemical properties of the oleogels were investigated. The oil holding capacity, textural strength, and thixotropy recovery of the oleogel were enhanced by increasing EGCG concentration from 10 to 100 μM. Meanwhile, a decreasing trend was found in them at a higher EGCG concentration (150 μM). Besides, the lipid oxidative and thermal stability of the oleogel were significantly improved when EGCG were present. Microscopic observation and LF-NMR results demonstrated that OBs were directionally arranged during the freeze-drying process, forming a continuous gel network. The addition of EGCG improved the continuity of the gel structure and restricted the mobility of oil droplets, especially at an EGCG concentration of 100 μM. Front-face fluorescence spectroscopy, FTIR, and SDS-PAGE results demonstrated that EGCG acts as a bridging agent, inducing intermolecular cross-linking of oil body interfacial proteins, resulting in a significant increase in protein molecular weight, accompanied by notable reductions in α-helix and β-sheet structures, as well as fluorescence quenching. This cross-linking facilitates the aggregation of OBs, improves the anti-destruction ability of OB film, and enhances the structural continuity of COB-based oleogels. This study provides valuable insights into the use of natural OBs and water-soluble antioxidants for creating edible oleogels.

Fabrication of tannins and oat protein non-covalent complexes: Effect on the structure and in vitro digestion properties of oat proteins

This study explored the non-covalent interactions between oat protein isolate (OPI) and two tannic compounds-proanthocyanidins (PA) and tannic acid (TA)-and examined their impact on the structural and digestive properties of oat proteins. The combination of OPI with tannic compounds formed granular complexes with particle sizes ranging from 126 to 240 nm and zeta potentials between -35 and -44 mV. Compared to OPI alone, the α-helix and β-turn contents decreased, while the β-sheet and random coil contents increased in both OPI-tannin complexes. Fluorescence spectra analysis indicated that hydrogen bonding was the main interaction force in OPI-PA complexes, while OPI and TA were primarily bound by hydrophobic interactions. The simulated digestion analysis showed that the protein digestibility was delayed in the OPI-tannin complexes, likely due to the inhibition of digestive enzyme activity by tannic compounds, which slowed OPI digestibility. Additionally, the oxidation resistance of the OPI-tannin complexes significantly improved after in vitro digestion, indicating that the non-covalent complexes provided superior protection for the tannic compounds. These findings offer theoretical support for the design and utilization of oat- and tannin-rich foods.

Functional, structural, and rheological properties of the complexes containing sunflower petal extract with dairy and plant-based proteins

This study aims to investigate the impact of sunflower petal extract (SFE) on the functional and structural properties of sodium caseinate and chickpea proteins. For this purpose, 3.5 % of sodium caseinate solution and 3.5 % of protein extracted from chickpea powder were prepared in phosphate buffer (pH = 7). SFE was used at different concentrations, from 1 to 3 % in different protein solutions and functional, structural and rheological properties were measured. The results revealed that complexation of SFE with different proteins can enhance the antioxidant, foaming properties, solubility, emulsion activity, emulsion stability, viscoelastic behavior, and can decrease surface hydrophobicity. FTIR and docking results showed that the most bonding type was non-covalent bonds. Major phenolic compounds containing heliannone A, B, and kaempferol had strong affinity with sodium caseinate, and then chickpea protein. Therefore, the results demonstrated that SFE and its complexes had appropriate emulsifying properties that reduces interfacial tension in the water/oil interface.

Tailoring ternary complexes of lactoferrin, EGCG, and α-lactalbumin by assembly sequence strategies: Structural characterization, assembly mechanism, and emulsification elucidation

Three distinct ternary complexes (TC-M1, TC-M2, and TC-M3) based on lactoferrin (LF), (-)-epigallocatechin-3-gallate (EGCG), and α-lactalbumin (ALA) were prepared by varying the assembly sequence and EGCG concentrations (ranging from 0 to 2.0 mM). Structural characterization was performed using various spectroscopic techniques, while the assembly mechanisms were investigated through ITC and molecular docking. These ternary complexes were further evaluated as stabilizers in Pickering emulsions. Nephelometry and DLS analysis showed that TC-M1 exhibited the highest turbidity and largest particle size, followed by TC-M2 and TC-M3. FT-IR and fluorescence spectroscopy revealed strong binding between EGCG and both ALA and LF, enhancing the hydrophilicity and extending structure of proteins. ITC and molecular docking studies indicated spontaneous interactions primarily driven by hydrogen bonding and hydrophobic forces, with LF (Ka1 = 1.9 × 105 M-1) and ALA (Ka1 = 3.6 × 104 M-1) binding approximately 3.3 and 2.9 EGCG molecules, respectively. Pickering emulsions formed by these complexes demonstrated superior emulsification properties, with TC-M1 showing the smallest CI (10.09 % ± 0.19 %), particle size (1 to 2 μm), and higher MVI (1.2) and EI (2.5) at 2.0 mM EGCG, outperforming TC-M2 and TC-M3 in stability. Overall, the assembly sequence of LF, ALA, and EGCG, along with EGCG concentration, lays the foundation for designing protein-polyphenol-protein ternary complexes, offering enhanced stability and functionality for diverse EGCG delivery applications.

Effects of polyphenols from Tasmannia lanceolata on structural, emulsifying, and antioxidant properties of pea protein

The effects of polyphenols from Tasmanian pepper (Tasmannia Lanceolata) leaf and berry on the functional properties of pea protein were investigated in flaxseed oil-in-water emulsions. Phenolic acids and flavonols in Tasmanian pepper leaf with smaller molecular weights led to stronger non-covalent interactions with pea protein, while anthocyanins from Tasmanian pepper berry induced protein aggregation under acidic condition and co-existed with proteins in neutral and alkaline conditions. The total phenolic content was significantly increased with incorporation of polyphenols from Tasmanian pepper leaf (334.94-445.92 μg/mL) and berry (72.89-153.03 μg/mL) to pea protein (4.19-15.59 μg/mL). The oxidative stability of emulsions at pH 3 and 7 was enhanced, reducing TBARS value from 1.54 to 2.68 mg MDA/kg in pea protein to 0.56-0.85 mg MDA/kg after 2 weeks storage. These findings illustrated the distinct interactions between pea protein and different polyphenols from Tasmanian pepper leaf and berry to enhance the antioxidant capacity of pea protein.

Characterization of pea protein-different types of glycoside flavonoid complex interactions and functional properties

Flavonoids offer various health benefits due to their chemical properties and non-covalent interactions with food nutrients. Despite extensive research on flavonoid-protein interactions, the effects of flavonoid glycosides on pea protein (PP) remained unclear. This study explored the non-covalent interactions of luteolin (Lu), isoorientin (Iso), and cynaroside (Cyn) with PP using molecular docking and multi-spectral techniques. Results showed that Lu interacted with PP mainly through hydrophobic forces, while Iso and Cyn interacted predominantly via hydrogen bonding. At 298 K, the binding affinity of flavonoids to PP was ranked as Lu (16.98 × 104 M-1) > Iso (7.41 × 104 M-1) > Cyn (6.31 × 104 M-1). Circular dichroism analysis showed that flavonoid glycosides loosened the protein structure by inducing a change in the secondary structure of PP from an α-helix to a random coil. This resulted in improved foaming, emulsification, and antioxidant properties of PP. This study provided insights into flavonoid-protein interactions and their potential applications in functional protein foods.

Advanced characterization of fish skin gelatin-proanthocyanidins covalent and non-covalent composite emulsions for benzyl isothiocyanate delivery

This research endeavored to engineer robust delivery matrices for bioactives, specifically benzyl isothiocyanate (BITC), by harnessing the synergistic covalent and non-covalent interactions between fish skin gelatin (FSG) and proanthocyanidins (PC) to synthesize novel composite emulsions. The objective was to delineate the influence of these molecular interactions on the emulsion's structural integrity and stability, which are pivotal for the efficacious encapsulation and controlled release of BITC. Employing a suite of analytical techniques, including Fourier transform infrared spectroscopy (FTIR), fluorescence spectroscopy, and contact angle measurements, the study delineated the predominant molecular forces at play within the FSG-PC complex, identifying electrostatic and hydrophobic interactions as the cornerstones of this interaction. An assessment of the emulsions' physicochemical properties, encompassing chromaticity, antioxidant efficacy, microstructural attributes, particle dimensions, zeta potential, and BITC retention, was undertaken to discern the optimal encapsulation strategy. The data unequivocally indicated that emulsions enriched with 0.06 wt% PC, in non-covalent synergy with FSG, afforded the most pronounced stability and retention of BITC. This work paves the way for future studies and the translational application of FSG-PC composite emulsions in the realm of bioactive substance delivery, offering a promising avenue for innovation in pharmaceutical and nutraceutical formulations.

Recent advances in the plant protein-polyphenol interactions for the stabilization of emulsions

Proteins from plant sources including legumes, cereals and oilseeds are gaining attention due to their suitability for sustainable production, functionality, and positive consumer perception. On the other hand, polyphenols (PPs) are receiving considerable attention as natural ingredients in the human diet due to their potent antioxidant and anti-inflammatory properties. Recent studies indicate that the emulsifying properties of plant proteins (PLPs) can be improved after modification through covalent and/or non-covalent interactions with PPs due to the changes in the conformation and/or the surface chemistry of the proteins. Complexes formed between PLPs-PPs can serve as innovative ingredients for developing novel food products with modified textural properties. Also, Pickering emulsions, multiple emulsions, multilayer emulsions, nanoemulsions, and high internal phase emulsions can be stabilized by such systems to deliver bioactive compounds. This paper reviews the most recent research on the PLP-PP interactions and their role in the stabilization of various emulsion-based systems. A special emphasis is given to modifying the structure and functionality of PLPs and PPs. The challenges and opportunities of applying PLP-PP interactions in emulsion-based systems are also highlighted.

Health effects of synthetic additives and the substitution potential of plant-based additives

The growth of the world population and the rapid industrialization of food have led to food producers' increased reliance on food additives. While food additives offer numerous conveniences and advantages in food applications, the potential risks associated with synthetic additives remain a significant concern. This report examines the current status of safety assessment and toxicity studies of common synthetic additives, including flavorings (sweeteners and flavor enhancers), colorants, preservatives (antimicrobials and antioxidants), and emulsifiers. The report also examines recent advances in promising plant-based alternative additives in terms of active ingredients, sensory properties, potential health benefits, food application challenges, and their related technologies (edible coatings/films and nanoencapsulation technologies), providing valuable references and insights for the sustainable development of food additives.

Design and fabrication of plant-based milk fat globule mimetics: Flaxseed oil droplets coated with potato, soy, or pea protein

An increasing number of plant-based milk products are appearing on the market as substitutes for dairy milk. These products are becoming more popular due to growing consumers concerns about environmental, health, or ethical issues linked to dairy milk. Typically, plant-based milks are produced using top-down approaches that involve mechanical disruption of plant tissues. In this study, we examined the possibility of using a bottom-up approach to mimic the structural and physicochemical properties of milk fat globules (MFGs) in homogenized milk. Plant-based MFGs (PB-MFGs) were prepared using flaxseed oil as an omega-3 fatty acid rich oil phase, and potato, soy, or pea protein as emulsifiers to create the interfacial membranes. PB-MFGs were prepared with the same oil content (10 %) but different protein contents (0.5, 1, 1.5, and 2 %). The mean particle diameters (d4,3 and d3,2) of the three types of PB-MFGs were slightly smaller than those of dairy MFGs, while their surface charges were somewhat more negative under neutral conditions. There was no significant difference in the shear viscosity of PB-MFGs and MFGs. In terms of stability, PB-MFGs prepared with potato protein exhibited the smallest particle size change after 30 days of storage. Moreover, the pH stability of these PB-MFGs was closest to that of dairy MFGs. Our results provide valuable insights into the design and development of plant-based milks with more dairy-like properties, which may increase their more widespread acceptance and application.

Investigating the effect of whey protein isolate:proanthocyanidin complex ratio on the stability and antioxidant capacity of Pickering emulsions

Whey protein isolate (WPI) has the potential to be a Pickering stabilizer, but its applications in emulsions are restricted due to its structural susceptibility to external environments. Proanthocyanidin (PAC) is a natural antioxidant polyphenol that can improve protein properties and enhance the stability and longevity of emulsions. In the current work, PACs were employed to bind WPIs, forming a complex to stabilize Pickering emulsion. Fluorescence spectroscopy, infrared spectroscopy, confocal microscopy, quartz crystal microbalance with dissipation monitoring (QCM-D), and antioxidant stability of the emulsion were performed to characterize the structural changes of the protein/polyphenol complexes and their effects on the interfacial properties and stability of the emulsion. Results indicated that PACs and WPIs might bind through hydrogen bonding and hydrophobic interactions, effectively increasing the hydrophilicity of the complexes. QCM-D and emulsion stability showed that adsorption at the oil-water interface of the complexes was the largest, and the stability of the Pickering emulsion was optimal when the concentration ratio of PAC to WPI exceeded 1:1. The antioxidant properties of Pickering emulsions were positively correlated with the addition of PACs. These findings demonstrated that PACs could improve the properties of WPIs and enhance the stability and antioxidant properties of WPI Pickering emulsions.

Colloidal and interfacial properties of spray dried pulse protein-blueberry polyphenol particles in model dispersion systems

The phytochemical composition and physicochemical attributes of polyphenol-enriched protein particle ingredients produced with pulse proteins (e.g. chickpea protein, pea protein, and a chickpea-pea protein blend) and polyphenols recovered from wild blueberry pomace were investigated for colloidal and interfacial properties. Anthocyanins were the major polyphenol fraction (27.74-36.47 mg C3G/g) of these polyphenol-rich particles (44.95-62.08 mg GAE/g). Dispersions of pea protein-polyphenol particles showed a superior phase stability before and after heat treatment compared to the chickpea pea protein-polyphenol system. This observation was independent of the added amount of NaCl in the dispersion. In general, at quasi equilibrium state, pulse protein-polyphenol particles and parental pulse protein ingredients showed similar oil-water interfacial tension. However, pea protein-polyphenol particles demonstrated a reduced diffusion-driven oil-water interfacial adsorption rate constant compared to the parental pea protein ingredient. Overall, the obtained results suggest application potential of pea protein-polyphenol particles as a functional food/beverage ingredient.

High internal phase emulsion stabilized by soy protein isolate-Rutin complex: Rheological properties, bioaccessibility and in vitro release kinetics

High internal phase emulsions (HIPEs) are promising carrier materials for encapsulating and delivering hydrophobic bioactive compounds. By strategically adjusting the composition, particle size, or charge of HIPEs, it is possible to enhance both their stability and the bioaccessibility of hydrophobic polyphenols encapsulated within them. In this study, different soy protein isolate (SPI)-rutin (SPI-R) complexes (formed under various preheating temperatures) were used to stabilize HIPEs, while the particle size, and charge of HIPEs was further adjusted through different homogenization rates. The results demonstrated that an optimal preheating temperature of 70 °C for the complex and a homogenization rate of 15,000 rpm for HIPEs enhanced the stability of the entire emulsion system by producing more uniform and smaller droplet distribution with improved rheological properties. Furthermore, in vitro digestion experiments showed that HIPEs stabilized by the SPI-R complexes (HSR) at optimal homogenization rate had better loading efficiency (98.68 %) and bioaccessibility compared to other groups. Additionally, fitting results from release kinetics confirmed that rutin encapsulated by HSR could achieve sustained release effect. Overall, these findings suggest that HSR has great potential as an effective vehicle for delivering hydrophobic bioactive compounds like rutin within the food industry.

Establishing a novel covalent complex of wheat gluten with tea polyphenols: Structure, digestion, and action mechanism

Plant-based proteins represent a more sustainable alternative, the approaches to modify and enhance their functionality and application are focused on. Covalent interaction could significantly modify the structure and function properties of protein. This study investigated the effects of covalent interaction between wheat gluten and tea polyphenols on the structure, aggregation, stability, and digestive properties of their covalent complex, as well as the possible action mechanism. The results showed that tea polyphenols could interact with gluten via covalent bonds (CN and/or CS), while tea polyphenols also acted as a bridge connecting gluten molecules, thus making covalent complex to show the larger particle sizes. This covalent interaction significantly changed the secondary structure, tertiary structure, and surface hydrophobicity of gluten. Moreover, covalent complex exhibited the high polyphenols bioaccessibility during in vitro digestion. The peptide bonds of covalent complex were mainly broken in gastric digestion, while the covalent bonds between tea polyphenols and gluten were completely destroyed in intestinal digestion. In addition, their digestates exhibited excellent antioxidant capability. All results suggest that wheat gluten have potential to prepare functional carrier for transporting active compounds and protecting them during digestion.

The Effect of Dihydromyricetin (DMY) on the Mechanism of Soy Protein Isolate/Inulin/Dihydromyricetin Interaction: Structural, Interfacial, and Functional Properties

The combination of proteins with polysaccharides and polyphenols is expected to improve their physicochemical and functional properties. In this study, a novel plant-based antioxidant emulsifier was formed by soybean protein isolate (SPI), inulin (INU), and dihydromyricetin (DMY). Based on the binary system of SPI/INU, we focused on exploring the effect of the DMY concentration (0.5 mg/mL~2.5 mg/mL) on the formation and properties of the ternary complex. The structure, interaction mechanism, and interfacial and functional properties of the ternary complex were investigated. The results indicate that compared to the SPI/INU binary complex, the SPI/INU/DMY ternary complex had a significant decrease in particle size (~100 nm) and a slight decrease in absolute zeta potential. The SPI/INU binary complex with DMY mainly interacted by hydrogen bonding and hydrophobic interactions. Due to the incorporation of DMY, the structure of SI was denser and more flexible. The ternary complex exhibited an ideal three-phase contact angle and demonstrated better foaming and antioxidant ability. Additionally, compared to SPI/INU, the ternary complex had a significant improvement in EAI. These results provide a strategy for polyphenols to modify the structure, interfacial properties, and functions of protein/polysaccharide complexes. This provides a potential reference for the preparation of more ternary complexes with excellent emulsifying and antioxidant properties for application in emulsions.

Alleviation effect of lutein Pickering emulsion formed by casein-dextran conjugates through Maillard reaction against blue light retinal degeneration

With the increasing prevalence of electronic devices, awareness of the risks linked to blue light exposure has significantly heightened. Lutein, a powerful antioxidant, safeguards eye tissue by filtering blue light, while supplementation with docosahexaenoic acid (DHA) enhances retinal function. Adequate intake of these nutrients can help reduce the potential damage from prolonged blue light exposure. The protective effects of lutein and algal oil stabilized with Pickering emulsion were investigated using casein-dextran (CD) conjugates via Maillard reaction. Microstructural analysis revealed a three-dimensional network structure surrounding oil droplets formed by CD conjugates. With the increase of the oil phase ratio from 55 % to 80 %, the average size of Pickering emulsion droplets decreased. Pickering emulsion demonstrated higher viscoelasticity, excellent recovery, thixotropy, and good thermal stability as the oil phase ratio increased. The retention of lutein in CD-75 % Pickering emulsions showed significant improvement under various conditions. Simulated gastrointestinal digestion demonstrated that CD-75 % Pickering emulsions effectively enhanced the lutein bioaccessibility from 19.97 % to 48.99 %. In vivo experiments showed that lutein-loaded Pickering emulsion could effectively relieve blue light-induced retinal degeneration in mice. These findings suggested that Pickering emulsion can serve as a delivery system to protect lutein, offering a nutritional intervention to mitigate blue light-induced retinal degeneration.

Effect of non-covalent binding of tannins to sodium caseinate on the stability of high-internal-phase fish oil emulsions

In this study, we designed the noncovalent binding of sodium caseinate (SC) to tannic acid (TA) to stabilize high internal phase emulsions (HIPEs) used as fish oil delivery systems. Hydrogen bonding was the dominant binding force, followed by weak hydrophobic interaction and weak van der Waals forces, as demonstrated by FTIR, fluorescence spectroscopy, and molecular docking experiments, with a binding constant of 3.25 × 106, a binding site of 1.2, and a static quenching of the binding. Increasing SC:TA from SC to 2:1 decreased the particle size from 107.37 ± 10.66 to 76.07 ± 2.77 nm and the zeta potential from -6.99 ± 2.71 to -22 ± 2.42 mV. TA increased the interfacial tension of SC, decreased the surface hydrophobicity from 1.3 × 104 to 1.6 × 103 and improved the oxidation resistance of SC. The particle size of high internal phase emulsions stabilized by complexes with different mass ratios (SC:TA from 1:0 to 2:1) increased from 4.9 ± 0.02 to 12.9 μm, the potential increased from -32.37 ± 2.7 to -35.07 ± 2.58 mV, and the instability index decreased from 0.75 to 0.02. Thicker interfacial layers could be observed by laser confocal microscopy, and an increase in the storage modulus indicated a formation of a stronger gel network. SC:TA of 1:0 showed emulsion breakage after 14 d of storage at room temperature. SC:TA of 2:1 showed the lowest degree of oil-water separation after freeze-thaw treatment. Especially, the most stable high endo-phase emulsion (at SC:TA of 2:1) prepared at each mass ratio was selected for further stability exploration. The emulsion particle size increased only from 15.63 ± 0.06 to 22.27 ± 0.35 μm at salt ion concentrations of 50-200 mM and to 249.33 ± 31.79 μm at 300 mM. The instability index and storage modulus of the high endo-phase emulsions increased gradually with increasing salt ion concentrations. At different heating temperatures (55-85 °C), the instability index of the high internal phase emulsion gradually decreased and the storage modulus gradually increased. Meanwhile, at 50 °C for 15 d of accelerated oxidation, the content of hydroperoxide decreased from 53.32 ± 0.18 to 37.48 ± 0.77 nmol/g, about 29.7 %, and the thiobarbituric acid value decreased from 1.06 × 103 to 0.8 × 103, about 24.5 %, in the high endo-phase emulsions prepared by 2:1 SC:TA compared to the fish oils, and the SC-stabilized high endo-phase only emulsion broke at the sixth day of oxidation. From the above findings, it was concluded that the high internal phase emulsion prepared with SC:TA of 2:1 can be used as a good delivery system for fish oil.

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.

Young apple polyphenols confer excellent physical and oxidative stabilities to soy protein emulsions for effective β-carotene encapsulation and delivery

Protein emulsions' poor physical and oxidative stabilities restrict their use in functional foods. Soy protein isolate (SPI) emulsions' physical stability was enhanced by adding young apple polyphenols (YAP) in this study, but decreased when YAP was 0.12%. YAP binding prefolded SPI's structure, which promotes efficient SPI stacking at the interface. YAP also improved SPI emulsions' oxidation resistance in a dose-dependent manner. SPI-YAP interaction promoted more YAP adsorption (>80%) at the interface, which increased emulsions' antioxidant capacities twofold. Furthermore, over 90% of unsaturated fatty acids were preserved, and the oxidation of lipid-SPI-β-carotene appeared to be reduced as YAP increased. In addition, SPI-YAP emulsions were effective in encapsulating and safeguarding β-carotene during emulsion storage and in vitro digestion, leading to a delayed and maximum release of β-carotene. This study improves the understanding of polyphenols inhibition on lipid-protein oxidation through interface strengthening and broadens the potential applications of YAP and SPI in functional foods.

Thermal stability, antioxidant activity and bioavailability of pea protein-naringin Pickering emulsion for enhanced delivery applications

After successfully addressing to mitigate bitterness of naringin through construction Pickering emulsion using pea protein (PP) and naringin (NG) in our previous study, we now probed thermal stability, antioxidant efficacy, and bioavailability. FTIR analysis and UV-vis spectroscopy indicated predominant interactions between PP and NG were hydrogen and hydrophobic bonds. TGA and DSC analyses demonstrated that PP-NG complexes exhibited superior heat-resistance compared to pure PP and NG. Thermal stability assessments indicated a significant retention of NG in the PP-NG Pickering emulsion than the control NG across varied temperatures (4 °C, 25 °C, 37 °C, and 65 °C). Moreover, the antioxidant activity of PP-NG emulsion was dependent on the concentration of NG, as evidenced by DPPH and ABTS free radicals scavenging abilities, ferric reducing power, and lipid peroxidation resistance. Additionally, PP-NG Pickering emulsion exhibited substantially high bioavailability (92.01 ± 3.91%). These results suggest a promising avenue for the application of NG with improved characteristics.

Fabrication, characterization and application of Pickering emulsion gels stabilized by defatted grape seed powder

The feasibility of defatted grape seed powder (DGSP) stabilizing Pickering emulsion gels as butter substitute was investigated. The Pickering emulsion gel was constructed using DGSP through high-speed homogenization, and the effects of particle concentration (c) and oil-phase (Medium chain triglyceride) volume fraction (φ) on its structure and properties were investigated. Its application as a butter substitute was also evaluated. The results showed that DGSP had various particle shapes, a wide particle size distribution (3-130 μm), and a three-phase contact angle of 128.9 ± 2.3°. The O/W Pickering emulsion gels with φ ≥ 60% could be obtained at c ≥ 2%. The droplet diameter was negatively correlated with c and positively correlated with φ, while the gel strength was positively related to c and φ. The resulting emulsion gel demonstrated solid-like viscoelastic behavior and pseudoplasticity, and had the potential to serve as a butter substitute. The results can promote the application of grape seeds in food.

Protecting meat color: The interplay of betanin red and myoglobin through antioxidation and coloration

Myoglobin (Mb) responsible for meat color is easily oxidized resulting in meat discoloration. Here, betanin red (BR), as a natural pigment and antioxidant, was chosen for enhancing redness and inhibiting oxidation. Multiple spectroscopies, isothermal titration calorimetry and molecular docking demonstrated that BR changed the microenvironment of heme group and amino acid residues of Mb, inhibited the oxidation of oxymyoglobin. The main interaction force was hydrogen bond and one variable binding site provided a continuous protective barrier to realize antioxidation. The combination of antioxidation with the inherent red color of BR offered dual color protection effect on processed beef with the addition amount of 0.2 % BR. BR treatment enhanced the redness by 25.59 ∼ 53.24 % and the sensory acceptance by 4.89 ∼ 14.24 %, and decreased the lipid oxidation by 0.58 ∼ 15.92 %. This study paves a theoretical basis for the application of BR and its structural analogues in meat color protection and other quality improvement.

Effect of epigallocatechin-3-gallate modification on the structure and emulsion stability of rice bran protein in the presence of soybean protein isolate

For improving the emulsion stability of rice bran protein (RBP), RBP was modified by different concentrations of epigallocatechin-3-gallate (EGCG) in the presence of soybean protein isolate (SPI), and RBP-EGCG-SPI conjugate was prepared by alkaline pH-shifting. The results showed that the addition of EGCG led to an increase in the bound phenol content and the flexibility of the secondary structure, a decrease in the free sulfhydryl and disulfide bond content of the RBP-EGCG-SPI conjugate. EGCG covalently bound to RBP and SPI through non-disulfide bonds. When the concentration of EGCG was 10 % (w/v), the emulsifying activity index and emulsion stability index of conjugate reached the maximum value (36.61 m2/g and 255.61 min, respectively), and the conjugate had the best emulsion stability. However, an EGCG concentration above 10 % (w/v) negatively affected the emulsion stability, with increasing particle size due to protein aggregation. Summarily, the modification of EGCG improved the emulsion stability of conjugate by regulating the spatial structure of RBP-EGCG-SPI conjugate. The work provided an important guide to further improve the emulsion stability of RBP.

Fabrication and characterization of soy protein isolation-ferulic acid antioxidant hydrogels

BACKGROUND

Soy protein gel products are prone to direct oxidation by reactive oxygen during processing and transportation, thus reducing their functional properties and nutritional values. A covalent complex was prepared with soy protein isolate (SPI) and ferulic acid (FA) catalyzed by laccase (LC). The complex was further treated with microbial transglutaminase (TGase) to form hydrogels. The structural changes of the covalent complex (SPI-FA) and the properties and antioxidant stability of hydrogel were investigated.

RESULTS

The SPI-FA complexes were demonstrated to be covalently bound by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and they had the least hydrophobic and free sulfhydryl groups at a 1.0 mg mL-1 FA concentration. The α-helix of complexes increased from 11.50% to 27.39%, and random coil dropped from 26.06% to 14.44%. The addition of FA caused SPI fluorescence quenching and redshift. The hydrogel was formed after the complex was induced with TGase, and its hardness and water holding capacity was increased by 50.61% and 26.21%, respectively. Scanning electron microscopy showed that a layered and ordered gel structure was formed. After in vitro digestion, the complex hydrogels maintained stable antioxidant activity, and the free radical scavenging rates of DPPH and ABTS reached 87.65% and 84.45%, respectively.

CONCLUSION

SPI-FA covalent complexes were prepared under laccase catalysis, and complex hydrogels were formed by TGase. Hydrogels have stable antioxidant activity, which provides application prospects for the antioxidant development of food. © 2023 Society of Chemical Industry.

Phycocyanin/tannic acid complex nanoparticles as Pickering stabilizer with synergistic interfacial antioxidant properties

This study reported a type of phycocyanin (PC)-tannic acid (TA) complex nanoparticles (NPs) fabricated by simply mixing PC with TA at appropriate mass ratios. The assembly of PC-TA NPs was driven by secondary forces involving hydrophobic interactions and hydrogen bonding. PC-TA NPs promoted formations of Pickering emulsions with an oil volume fraction (φ) of 0.1-0.8. The interfacial antioxidant ability of PC-TA NPs was evaluated by comparing the contents of hydroperoxides, malonaldehyde, and hexanal due to lipid oxidation. The results showed that PC-TA NPs retarded lipid oxidation more efficiently than did PC, TA, tween 20, or tween 80, which suggested the synergistic antioxidant action of PC and TA. Besides, the PC-TA NPs stabilized high internal phase emulsion facilitated a higher retention of β-carotene under UV irradiation. Altogether, our findings demonstrate that the modification of PC by TA represents a strategy to fabricate PC-TA NPs with enhanced emulsification and antioxidant efficiency.

Investigation of peanut allergen-procyanidin non-covalent interactions: Impact on protein structure and in vitro allergenicity

Interactions between plant polyphenols and food allergens may be a new way to alleviate food allergies. The non-covalent interactions between the major allergen from peanut (Ara h 2) with procyanidin dimer (PA2) were therefore characterized using spectroscopic, thermodynamic, and molecular simulation analyses. The main interaction between the Ara h 2 and PA2 was hydrogen bonding. PA2 statically quenched the intrinsic fluorescence intensity and altered the conformation of the Ara h 2, leading to a more disordered polypeptide structure with a lower surface hydrophobicity. In addition, the in vitro allergenicity of the Ara h 2-PA2 complex was investigated using enzyme-linked immunosorbent assay (ELISA) kits. The immunoglobulin E (IgE) binding capacity of Ara h 2, as well as the release of allergenic cytokines, decreased after interacting with PA2. When the ratio of Ara h 2-to-PA2 was 1:50, the IgE binding capacity was reduced by around 43 %. This study provides valuable insights into the non-covalent interactions between Ara h 2 and PA2, as well as the potential mechanism of action of the anti-allergic reaction caused by binding of the polyphenols to the allergens.

Controlled oxidation and digestion of Pickering emulsions stabilized by quinoa protein and (-)-epigallocatechin-3-gallate (EGCG) hybrid particles

In this study, we prepared Pickering emulsions stabilized by quinoa protein isolate (QPI) and (-)-epigallocatechin-3-gallate (EGCG) non-covalent hybrid particles using ultrasonic emulsification technique and demonstrated lipid oxidation and in vitro digestion process of Pickering emulsions. The interaction forces between QPI and EGCG were characterized using fluorescence spectroscopy, isothermal titration calorimetry, and Fourier transform infrared spectroscopy. Results indicated that the non-covalent QPI/EGCG hybrid particles were formed mainly via hydrophobic interactions, hydrogen bonds, and electrostatic interactions at pH 5. Then, the QPI/EGCG non-covalent hybrid particles were applied to modify the Pickering emulsion with ultrasonic homogenization. The rheological experimental results showed that the energy storage modulus (G') was higher than the loss modulus (G″), indicating that the emulsion had solid-like properties. As a physical barrier, interfacial layer fabricated by antioxidant QPI/EGCG hybrid particles limited lipid oxidation at 60 °C for 15 days. At 37 °C, the QPI/EGCG hybrid particles stabilized Pickering emulsions with robust antioxidant interfacial structure limited the lipid digestion under simulated gastrointestinal tract (gastric, small intestine phases). Thus, EGCG and quinoa proteins were more resistant to free radical oxidation and gastrointestinal digestion with the assistance of ultrasound. It provides a basis for better development of food and drug delivery systems by fully utilizing the antioxidant properties of plant polyphenols.

Applications of Plant Bioactive Compounds as Replacers of Synthetic Additives in the Food Industry

According to the Codex Alimentarius, a food additive is any substance that is incorporated into a food solely for technological or organoleptic purposes during the production of that food. Food additives can be of synthetic or natural origin. Several scientific evidence (in vitro studies and epidemiological studies like the controversial Southampton study published in 2007) have pointed out that several synthetic additives may lead to health issues for consumers. In that sense, the actual consumer searches for "Clean Label" foods with ingredient lists clean of coded additives, which are rejected by the actual consumer, highlighting the need to distinguish synthetic and natural codded additives from the ingredient lists. However, this natural approach must focus on an integrated vision of the replacement of chemical substances from the food ingredients, food contact materials (packaging), and their application on the final product. Hence, natural plant alternatives are hereby presented, analyzing their potential success in replacing common synthetic emulsifiers, colorants, flavorings, inhibitors of quality-degrading enzymes, antimicrobials, and antioxidants. In addition, the need for a complete absence of chemical additive migration to the food is approached through the use of plant-origin bioactive compounds (e.g., plant essential oils) incorporated in active packaging.

Recent advances in pulse protein conjugation and complexation with polyphenols: an emerging approach to improve protein functionality and health benefits

Pulses have attracted much attention in the food industry due to their low cost, high yield, and high protein content, which promises to be excellent alternative protein sources. Recently, techniques for covalent and noncovalent binding of pulse proteins to polyphenols are expected to solve the problem of their poor protein functional properties. Additionally, these conjugates and complexes also show several health benefits. This review summarizes the formation of conjugates and complexes between pulse proteins and polyphenols through covalent and noncovalent binding and the impact of this structural change on protein functionalities and potential health benefits. Recent studies show that pulse protein functionalities can be influenced by polyphenol dose. This is mainly the case for adverse effects on solubility and enhancement in emulsifying capacity. Also, the conjugates/complexes exhibit antioxidant activity and can alter protein digestibility. The antioxidant activity of polyphenols could be retained after binding to proteins, while the effect on digestibility depends on the type or dosage of polyphenols. Considering the link between polyphenols and their potential health benefits, pulse polyphenols would be a good choice for producing the conjugates/complexes due to their low cost and proven potential benefits. Further studies on the structure-function-health benefits relationship of pulse protein-polyphenol conjugates and complexes are still required, as well as the validation of their application as functional foods in the food industry.

Plant-Based Protein-Phenolic Interactions: Effect on different matrices and in vitro gastrointestinal digestion

This review summarizes the literature on the interaction between plant-based proteins and phenolics. The structure of the phenolic compound, the plant source of proteins, matrix properties (pH, temperature), and interaction mechanism (covalent and non-covalent) change the secondary structure, ζ-potential, surface hydrophobicity, and thermal stability of proteins as well as their functional properties including solubility, foaming, and emulsifying properties. Studies indicated that the foaming and emulsifying properties may be affected either positively or negatively according to the type and concentration of the phenolic compound. Protein digestibility, on the other hand, differs depending on (1) the phenolic concentration, (2) whether the food matrix is ​​solid or liquid, and (3) the state of the food-whether it is heat-treated or prepared as a mixture without heat treatment in the presence of phenolics. This review comprehensively covers the effects of protein-phenolic interactions on the structure and properties of proteins, including functional properties and digestibility both in model systems and real food matrix.

Pickering emulsions prepared using zein-sugarcane leaves polyphenol covalent crosslinking nanoparticles via ultrasonication: Capacities in storage stability, lipid oxidation, in vitro digestion and safety evaluation

This study firstly used sugarcane leaf polyphenols (SGLp) to modify zein to form covalent nanoparticles (SGLpZ) and used SGLpZ as an emulsifier to stabilize pickering emulsions (SZP) via ultrasonic method. The results showed that the addition of SGLp could alter the physicochemical properties of zein, including improving increasing the hydrophilicity of zein and the antioxidant properties of zein (three basic antioxidant activities test in vitro). SGLpZ could be able to form a dense film on the surface of the pickering emulsions which inhibited lipid oxidation as the concentration of SGLp increased at 4 ℃ for 20 days, thus stabilizing pickering emulsions (SZP). Further assessment of storage stability of pickering emulsions stabilized by SGLp was evaluated via measuring the free fatty acids (FFA) release in vitro gastrointestinal digestion. The results showed that the FFA release of SZP decreased from 20.61 ± 0.10% to 16.14 ± 0.69%. In addition, SGLp gave SZP a yellow color, which inspired that SZP could be used in the food industry to make yellow-colored functional foods. Finally, the safety of SZP initially assessed by in-vitro hemocompatibility and cytotoxicity (MTT) assays. In conclusion, our fingdings were beneficial for the further design and development of SGLp in food fields and enabled the development a new type in functional protein-plant polyphenols food pickering emulsions.

Molecular mechanisms affecting the stability of high internal phase emulsions of zein-soy isoflavone complexes fabricated with ultrasound-assisted dynamic high-pressure microfluidization

In this study, zein-soy isoflavone complex (ZSI) emulsifiers were fabricated using ultrasound-assisted dynamic high-pressure micro fluidization to stabilise highinternal phase pickering emulsions. Ultrasound-assisted dynamic high-pressure micro-fluidization enhanced surface hydrophobicity, zeta potential, and soy isoflavone binding capacity, while it decreased particle size, especially during ultrasound and subsequent microfluidization. The treated ZSI could produce small droplet clusters and gel-like structures, with excellent viscoelasticity, thixotropy and creaming stability owing to their neutral contact angles. Ultrasound and subsequent micro fluidization treatment of the ZSI complexes were highly effective in preventing droplet flocculation and coalescence after long-term storage or centrifugation due to their higher surface load, thicker multi-layer interfacial structure, and stronger electronic repulsion between the oil droplets. This study provides insights and extends our current knowledge of how non-thermal technology affects the interfacial distribution of plant based particles and the physical stability of emulsions.

Preparation, Characterization and Antioxidant Activity of Glycosylated Whey Protein Isolate/Proanthocyanidin Compounds

A glycosylated protein/procyanidin complex was prepared by self-assembly of glycosylated whey protein isolate and proanthocyanidins (PCs). The complex was characterized through endogenous fluorescence spectroscopy, polyacrylamide gel electrophoresis, Fourier infrared spectroscopy, oil-water interfacial tension, and transmission electron microscopy. The results showed that the degree of protein aggregation could be regulated by controlling the added amount of procyanidin, and the main interaction force between glycosylated protein and PCs was hydrogen bonding or hydrophobic interaction. The optimal binding ratio of protein:PCs was 1:1 (w/w), and the solution pH was 6.0. The resulting glycosylated protein/PC compounds had a particle size of about 119 nm. They exhibited excellent antioxidant and free radical-scavenging abilities. Moreover, the thermal denaturation temperature rose to 113.33 °C. Confocal laser scanning microscopy (CLSM) images show that the emulsion maintains a thick interface layer and improves oxidation resistance with the addition of PCs, increasing the application potential in the functional food industry.

Integral Valorization of Grape Pomace for Antioxidant Pickering Emulsions

Full harnessing of grape pomace (GP) agricultural waste for the preparation of antioxidant Pickering emulsions is presented herein. Bacterial cellulose (BC) and polyphenolic extract (GPPE) were both prepared from GP. Rod-like BC nanocrystals up to 1.5 µm in length and 5-30 nm in width were obtained through enzymatic hydrolysis (EH). The GPPE obtained through ultrasound-assisted hydroalcoholic solvent extraction presented excellent antioxidant properties assessed using DPPH, ABTS and TPC assays. The BCNC-GPPE complex formation improved the colloidal stability of BCNC aqueous dispersions by decreasing the Z potential value up to -35 mV and prolonged the antioxidant half-life of GPPE up to 2.5 times. The antioxidant activity of the complex was demonstrated by the decrease in conjugate diene (CD) formation in olive oil-in-water emulsions, whereas the measured emulsification ratio (ER) and droplet mean size of hexadecane-in-water emulsions confirmed the physical stability improvement in all cases. The synergistic effect between nanocellulose and GPPE resulted in promising novel emulsions with prolonged physical and oxidative stability.

Effect of ultrasound treatment on interactions of whey protein isolate with rutin

Rutin is a biologically active polyphenol, but its poor water solubility and low bioavailability limit its application to the food industry. We investigated the effect of ultrasound treatment on the properties of rutin (R) and whey protein isolate (WPI) using spectral and physicochemical analysis. The results revealed that there was covalent interaction between whey protein isolate with rutin, and the binding degree of whey isolate protein with rutin increased with ultrasound treatment. Additionally, solubility and surface hydrophobicity of WPI-R complex improved with ultrasonic treatment, and a maximum solubility of 81.9 % at 300 W ultrasonic power. The ultrasound treatment caused the complex to develop a more ordered secondary structure, resulting in a three-dimensional network structure with small and uniform pore sizes. This research could provide a theoretical reference for studying protein-polyphenol interactions and their applications in food delivery systems.

Investigation of bovine β-lactoglobulin-procyanidin complexes interactions and its utilization in O/W emulsion

Procyanidins are bioactive polyphenols that have a strong affinity to proteins. Beta-lactoglobulin (BLG) is widely used as an emulsifier in the food and other industries. This study evaluated the interaction between BLG and A-type procyanidin dimer (PA2) using the spectroscopic, thermodynamic, and molecular simulation. PA2 decreased the transmissivity and quenched the intrinsic fluorescence of BLG, suggesting that the two molecules formed a complex. The binding of PA2 reduced the surface hydrophobicity and altered the conformation of BLG with increasing the random coil regions. Thermodynamic and isothermal titration calorimetry analyses suggested that the main driving force of PA2-BLG interaction was hydrophobic attraction. Molecular docking simulations were used to identify the main interaction sites and forces in the BLG-PA2 complexes, which again indicated that hydrophobic interactions dominated. In addition, the influence of PA2 on the ability of BLG to form and stabilize O/W emulsions was analyzed. Emulsions formulated using BLG-PA2 complexes contained relatively small droplets (D_4,3 ≈ 0.7 μm) and high surface potentials (absolute value >50 mV). Compared to BLG alone, BLG-PA2 complexes improved the storage stability of the emulsions. This study provides valuable new insights into the formation, properties, and application of protein-polyphenol complexes as functional ingredients in foods.

High-temperature glycosylation modifies the molecular structure of ovalbumin to improve the freeze-thaw stability of its high internal phase emulsion

In this study, ovalbumins (OVAs) were glycosylated with fructo-oligosaccharide (FO) at different temperatures (80 °C, 100 °C, 120 °C, and 140 °C) and durations (1 h and 2 h) via wet-heating. The glycosylated OVAs (GOVAs) were characterized by the degree of glycosylation (DG), particle size, zeta potentials, and structural changes. GOVAs-stabilized high-internal-phase emulsions (HIPEs) were then prepared to compare their macro- and microstructure and freeze-thaw stability. The results showed that the DG of GOVAs increased with the increase in glycosylation temperature and the protein structure unfolded with it. Glycosylation decreased the particle size, zeta potential, and α-helical structures and increased the β-sheets and surface hydrophobicity (H₀) of GOVAs compared with unmodified OVAs. Moreover, GOVAs-stabilized HIPEs exhibited smaller particle sizes, zeta potentials, agglomeration indexes, oil loss rates, and freezing points and higher viscoelasticity, centrifugal stabilities, flocculation indexes, and freeze-thaw stabilities. Notably, HIPEs prepared by GOVAs (glycosylated higher than 120 °C) showed the least changes in macro- and microscopic appearances after freeze-thawing. These findings will provide a novel method for improving and broadening the functionalities of OVAs and potentially develop HIPEs with enhanced freeze-thaw stabilities.

Novel Colloidal Food Ingredients: Protein Complexes and Conjugates

Food proteins, polysaccharides, and polyphenols are natural ingredients with different functional attributes. For instance, many proteins are good emulsifiers and gelling agents, many polysaccharides are good thickening and stabilizing agents, and many polyphenols are good antioxidants and antimicrobials. These three kinds of ingredients can be combined into protein, polysaccharide, and/or polyphenol conjugates or complexes using covalent or noncovalent interactions to create novel multifunctional colloidal ingredients with new or improved properties. In this review, the formation, functionality, and potential applications of protein conjugates and complexes are discussed. In particular, the utilization of these colloidal ingredients to stabilize emulsions, control lipid digestion, encapsulate bioactive ingredients, modify textures, and form films is highlighted. Finally, future research needs in this area are briefly proposed. The rational design of protein complexes and conjugates may lead to the development of new functional ingredients that can be used to create more nutritious, sustainable, and healthy foods.

Interaction between Chinese quince fruit proanthocyanidins and bovine serum albumin: Antioxidant activity, thermal stability and heterocyclic amine inhibition

Heterocyclic amines (HCAs) are carcinogenic and mutagenic substances produced in fried meat. Adding natural antioxidants (e.g., proanthocyanidins (PAs)) is a common method to reduce HCAs; however, the interaction between the PAs and protein can affect the inhibitory efficacy of PAs on the formation of HCAs. In this study, two PAs (F1 and F2) with different degrees of polymerization (DP) were extracted from Chinese quince fruits. These were combined with bovine serum albumin (BSA). The thermal stability, antioxidant capacity and HCAs inhibition of all four (F1, F2, F1-BSA, F2-BSA) were compared. The results showed that F1 and F2 interact with BSA to form complexes. Circular dichroism spectra indicate that complexes had fewer α-helices and more β-sheets, β-turns and random coils than BSA. Molecular docking studies indicated that hydrogen bonds and hydrophobic interactions are the forces holding the complexes together. The thermal stabilities of F1 and, particularly, F2 were stronger than those of F1-BSA and F2-BSA. Interestingly, F1-BSA and F2-BSA showed increased antioxidant activity with increasing temperature. F1-BSA's and F2-BSA's HCAs inhibition was stronger than F1 and F2, reaching 72.06 % and 76.3 %, respectively, for norharman. This suggests that PAs can be used as natural antioxidants for reducing the HCAs in fried foods.

Construction of high internal phase Pickering emulsions using cold plasma modified soy protein isolate-proanthocyanidin complex

Protein-based high internal phase Pickering emulsions (HIPPEs) feature numerous multi-functionalities and widespread applications. However, the direct use of native proteins for the constructions of HIPPEs is limited since it is fragile under various conditions. Here, cold plasma was used to modify soy protein isolates (SPI) to improve their surficial properties. Meanwhile, proanthocyanidins (PA) were applied to interact with cold plasma-treated SPI to form complex. Furthermore, the well-prepared SPI-PA complex was used to construct novel HIPPEs. Results showed cold plasma treatment significantly improved the functionalities of SPI, which were confirmed by surface hydrophobicity (H₀ ＜ 500), sulfhydryl (SH) groups and spectral analysis. Further, the emulsification and oxidation resistance of cold plasma treated SPI were enhanced after forming complex with PA. Soybean oils can be stabilized by SPI-PA complexes to form HIPPEs with a lipid oxidation inhibition rate of ＞ 65%, creaming index (CI) ＞ 80%, excellent rheological properties and better stability compared with conventional emulsion systems. Overall, this SPI-PA complexes provides a unique approach to improve the emulsification and oxidation resistance to engineer HIPPEs with versatile applications.

A review of the structure, function, and application of plant-based protein-phenolic conjugates and complexes

Interactions between plant-based proteins (PP) and phenolic compounds (PC) occur naturally in many food products. Recently, special attention has been paid to the fabrication of PP-PC conjugates or complexes in model systems with a focus on their effects on their structure, functionality, and health benefits. Conjugates are held together by covalent bonds, whereas complexes are held together by noncovalent ones. This review highlights the nature of protein-phenolic interactions involving PP. The interactions of these PC with the PP in model systems are discussed, as well as their impact on the structural, functional, and health-promoting properties of PP. The PP in conjugates and complexes tend to be more unfolded than in their native state, which often improves their functional attributes. PP-PC conjugates and complexes often exhibit improved in vitro digestibility, antioxidant activity, and potential allergy-reducing activities. Consequently, they may be used as antioxidant emulsifiers, edible film additives, nanoparticles, and hydrogels in the food industry. However, studies focusing on the application of PP-PC conjugates and complexes in real foods are still scarce. Further research is therefore required to determine the structure-function relationships of PP-PC conjugates and complexes that may influence their application as functional ingredients in the food industry.

Impacts of Proanthocyanidin Binding on Conformational and Functional Properties of Decolorized Highland Barley Protein

The impacts of interaction between proanthocyanidin (PC) and decolorized highland barley protein (DHBP) at pH 7 and 9 on the functional and conformational changes in DHBP were investigated. It was shown that PC strongly quenched the intrinsic fluorescence of DHBP primarily through static quenching. PC and DHBP were mainly bound by hydrophobic interactions. Additionally, free sulfhydryl groups and surface hydrophobicity obviously decreased in DHBP after combining with PC. The zeta potential of DHBP-PC complexes at pH 7 increased significantly. A change in the structure of DHBP was caused by interactions with PC, resulting in an increase in the number of β-sheets, a decrease in the number of α-helixes, and a spectral shift in the amide Ⅱ band. Furthermore, the presence of PC enhanced the foaming properties and antioxidant activity of DHBP. Overall, this study suggests that DHBP-PC complexes at pH 7 could be designed as a stable additive, and illustrates the potential applications of DHBP-PC complexes in the food industry.