Fabrication mechanism and structural characteristics of the ternary aggregates by lactoferrin, pectin, and (-)-epigallocatechin gallate using multispectroscopic methods

Enhancing the emulsion properties and bioavailability of loaded astaxanthin by selecting the reaction sequence of ternary conjugate emulsifiers in nanoemulsions

This study investigated the effects of the conjugate reaction sequences of whey protein concentrate (WPC), epigallocatechin gallate (EGCG) and dextran (DEX) on the structure and emulsion properties of conjugates and the bioaccessibility of astaxanthin (AST). Two types of ternary covalent complexes were synthesised using WPC, EGCG and DEX, which were regarded as emulsifiers of AST nanoemulsions. Results indicated that the WPC-DEX-EGCG conjugate (referred to as 'con') exhibits a darker SDS-PAGE dispersion band and higher contents of α-helix (6%), β-angle (24%) and random coil (32%), resulting in a greater degree of unfolding structure and fluorescence quenching. These findings suggested WPC-DEX-EGCG con had the potential to exhibit better emulsification properties than WPC-EGCG-DEX con. AST encapsulation efficiency (76.22%) and bioavailability (31.89%) also demonstrated the superior performance of the WPC-DEX-EGCG con emulsifier in nanoemulsion delivery systems. These findings indicate that altering reaction sequences changes protein conformation, enhancing the emulsification properties and bioavailability of AST.

Pectin-coated whey protein isolate/zein self-aggregated nanoparticles as curcumin delivery vehicles: Effects of heating, pH, and adding sequence

In this work, pectin was employed as a coating material to fabricate zein/whey protein isolate (WPI)/pectin complex nanoparticles via a pH-adjusted and heat-induced electrostatic adsorption process for potential oral administration applications of curcumin. Factors such as the order of raw material addition, heating temperature and pH, and zein concentration were comprehensively examined. In addition to electrostatic interactions, Fourier transform infrared and fluorescence spectroscopy indicated that hydrophobic interactions and hydrogen bonds were also involved in the development of complex nanoparticles. The complex nanoparticles obtained not only improved the antioxidant activity of curcumin in aqueous phase, but also contributed to its controlled release under gastrointestinal conditions. Our findings revealed that the heating pH and adding sequence of raw materials had a notable impact on the properties of complex nanoparticles, and that pectin coating had an exceptional stabilizing effect on complex nanoparticles under gastrointestinal circumstances. This study provides novel insights and perspectives for the preparation of polysaccharide-protein complex nanoparticles, signifying the potential use of zein/WPI/pectin complex nanoparticles as delivery vehicles in the functional food and pharmaceutical industries.

Construction of protein-, polysaccharide- and polyphenol-based conjugates as delivery systems

Natural polymers, such as polysaccharides and proteins, have been used to prepare several delivery systems owing to their abundance, bioactivity, and biodegradability. They are usually modified or combined with small molecules to form the delivery systems needed to meet different needs in food systems. This paper reviews the interactions of proteins, polysaccharides, and polyphenols in the bulk phase and discusses the design strategies, coupling techniques, and their applications as conjugates in emulsion delivery systems, including traditional, Pickering, multilayer, and high internal-phase emulsions. Furthermore, it explores the prospects of the application of conjugates in food preservation, food development, and nanocarrier development. Currently, there are seven methods for composite delivery systems including the Maillard reaction, carbodiimide cross-linking, alkali treatment, enzymatic cross-linking, free radical induction, genipin cross-linking, and Schiff base chemical cross-linking to prepare binary and ternary conjugates of proteins, polysaccharides, and polyphenols. To design an effective target complex and its delivery system, it is helpful to understand the physicochemical properties of these biomolecules and their interactions in the bulk phase. This review summarizes the knowledge on the interaction of biological complexes in the bulk phase, preparation methods, and the preparation of stable emulsion delivery system.

Covalent modification of (+)-catechin to improve the physicochemical, rheological, and oxidative stability properties of rice bran protein emulsion

The aim of this study is the effects of (+)-catechin (CC) covalent cross-linking (CCCI) (0.05-0.25 %, w/v) on the physicochemical properties, rheological properties, and oxidative stability of rice bran protein (RBP) emulsion. Analysis of particle size, ζ-potential, circular dichroism, fluorescence spectroscopy, surface hydrophobicity, and emulsifying properties demonstrated that a concentration of 0.15 % (w/v) CCCI facilitated protein structure unfolding, resulting in reduced particle size, enhanced electrostatic repulsion, and improved emulsion stability. Moreover, the covalent complexes of RBP-0.15 %CC (w/v) exhibited increased viscosity and shear stress, reflected by the highest G' and G″ values, ultimately enhancing the oxidative stability. Furthermore, analysis using atomic force microscopy and confocal laser scanning microscopy revealed that the RBP-0.15 %CC complexes exhibited the smallest particle size (164 nm) and displayed greater homogeneity. An increase in CC concentration to 0.25 % (w/v) resulted in a higher emulsion aggregation. The emulsions stabilized by CCCI exhibited superior rheological properties and enhanced oxidation stability compared to the control. In conclusion, an appropriate amount of CC can enhance the rheology and oxidation stability of the RBP emulsion, while CCCI treatment holds potential for expanding the utility of RBP in various applications.

Interactions between tea polyphenols and nutrients in food

Tea polyphenols (TPs) are important secondary metabolites in tea and are active in the food and drug industry because of their rich biological activities. In diet and food production, TPs are often in contact with other food nutrients, affecting their respective physicochemical properties and functional activity. Therefore, the interaction between TPs and food nutrients is a very important topic. In this review, we describe the interactions between TPs and food nutrients such as proteins, polysaccharides, and lipids, highlight the forms of their interactions, and discuss the changes in structure, function, and activity resulting from their interactions.

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.

Fabrication and characterization of gelatin-EGCG-pectin ternary complex: formation mechanism, emulsion stability, and structure

BACKGROUND

Protein-polyphenol-polysaccharide ternary complex particles have better emulsion interfacial stability compared to protein-polysaccharide binary complexes. However, knowledge is scarce when it comes to the fabrication of protein-polyphenol-polysaccharide ternary complexes as interfacial stabilizers and the interactions between the three substances. In the present work, ternary complexes were prepared using gelatin, high methoxyl pectin, and epigallocatechin gallate (EGCG) as raw materials. The effect of different influencing factors on the formation process of ternary complexes was investigated by varying different parameters. physicochemical stability, emulsifying properties, and structural characteristics were analyzed.

RESULTS

The ternary complex had a smaller particle size (275 nm) and polydispersity index (0.112) when the mass concentration ratio of gelatin to high methoxyl pectin was 9:1, addition of EGCG was 0.05%, pH value was 3.0, and ionic strength was 10 mmol L^-1 . Meanwhile, the complex had the highest emulsifying stability index (691.75 min) and emulsifying activity index (22.96 m²  g^-1 ). Scanning electron microscopical observation demonstrated that the addition of EGCG promoted the dispersion of ternary complex more uniformly, and effectively reduced the agglomeration phenomenon. The discrepancy in fluorescence intensity suggested that interactions between EGCG and gelatin occurred, which altered the protein spatial conformation of gelatin. Fourier transform infrared spectroscopic analysis elucidated that hydrogen bond interaction was the primary non-covalent interaction between EGCG and gelatin-high methoxyl pectin binary complex.

CONCLUSION

The aforementioned results purposed to provide some theoretical reference and basis for the rational design of stable protein-polyphenol-polysaccharide ternary complexes. © 2022 Society of Chemical Industry.

Impact of Phenolic Acid Derivatives on β-Lactoglobulin Stabilized Oil-Water-Interfaces

The physical stability of protein-based emulsions depends on intra- and intermolecular interactions of the interfacial protein-film. As studied in aqueous systems before, phenolic acid derivatives (PADs) non-covalently or covalently crosslink proteins depending on pH-value and thus, may impact interfacial protein-films. Whether these interactions occur in the same manner at the interface as in water and how they vary the properties of the interfacial protein-film has not been clarified. The present study aimed to investigate the interfacial protein-film viscoelasticity and physical emulsion-stability after non-covalently (pH 6.0) and covalently (pH 9.0) crosslinking depending on PAD-structure. For this purpose, we studied an interfacial β-lactoglobulin film with dilatational rheology after crosslinking with PADs, varying in number of π-electrons and polar substituents. Then, we analyzed the physical emulsion-stability by visual evaluation and particle size distribution. The results indicate that PADs with a high number of π-electrons (rosmarinic acid and chicoric acid) weaken the protein-film due to competing of phenol-protein interactions with protein-protein interactions. This is reflected in a decrease in interfacial elasticity. PADs with an additional polar substituent (verbascoside and cynarine) seem to further weaken the protein film, since the affinity of the PADs to the interface increases, PADs preferentially adsorb and sterically hinder protein-protein interactions. In emulsions at pH 6.0 and thus low electrostatic repulsion, PADs promote bridging-flocculation. Due to higher electrostatic repulsion at pH 9.0, the PADs are sterically hindered to form bridges, even though they are polymeric. Hence, our research enables the control of protein-film viscoelasticity and emulsion-stability depending on the PAD-structure.

Graphical abstract

Effects of different dietary polyphenols on conformational changes and functional properties of protein-polyphenol covalent complexes

In this study, conjugates of whey protein isolate (WPI) and four polyphenols (epigallocatechin gallate [EGCG], quercetin [QC], apigenin [AG], and naringenin [NG]) were prepared through free-radical grafting. The results for polyphenol binding equivalents and content of free amino and sulfhydryl groups as well as those from sodium dodecyl sulfate-polyacrylamide gel electrophoresis confirmed the covalent interaction between WPI and the polyphenols. Fourier transform infrared spectroscopy and fluorescence spectrum analysis identified the potential binding sites of the complexes and determined changes in the protein structure. The particle size distribution and scanning electron microscopy data demonstrated increases in conjugate particle sizes and surface changes in the complexes. The conjugation process significantly increased the polyphenols' antioxidant properties and thermal stabilities, whereas surface hydrophobicity was substantially reduced. WPI-EGCG had the best functional properties, followed by WPI-QC, WPI-AG, and WPI-NG.

Improved stabilization of coix seed oil in a nanocage-coating framework based on gliadin-carboxymethyl chitosan-Ca2

Coix seed oil (CSO) is easily suffered functional-loss by oxidation and hydrothermal-treatment. The environmental stable nanocage-coating-CSO particles (OGC-Ca) by the frameworks consist of gliadins, carboxymethyl chitosan (CMCS) and Ca²⁺ were investigated. Results showed Ca²⁺ was the key controller for fabricating this nanocage-coating-frameworks, bridging macromolecule-chains with electrostatic interaction and hydrogen bonds, detected by FTIR, CD, DSC and XRD. SEM displayed new-formed velvet-like twigs after cross-linking CMCS to gliadins. Ca²⁺ assisted the nanocage-coating by significant down-sizing conversion OGC to OGC-Ca with consumption of twigs. OGC-Ca displayed a good stability towards heat (60-80 °C, 0-80 min), pH (3-8), NaCl (0-0.5 mM), storage (4/25 °C, 12 days), and a reduce of the pre-oxidation value of CSO in water and the improved controlled release of CSO in simulated GI tract. It illustrated GC-Ca frameworks would be a suitable delivery carrier for the CSO like pharmaceuticals and nutraceuticals for the food or medical use.

Characterization, spectroscopic and crystallographic analyses of β-lactoglobulin and docosahexaenoic acid nanocomplexes

In this work, we investigated the interaction of docosahexaenoic acid (DHA) with β-lactoglobulin (β-Lg) using spectroscopic and crystallographic methods. The fluorescence results showed that DHA formed complexes with β-Lg with a binding constant of 4.13 × 10⁴ M^-1. The secondary structure of β-Lg was not significantly (p > 0.05) changed after binding with DHA. Dynamic light scattering showed the particle size of β-Lg-DHA complexes was about 5 nm, the same as that of β-Lg alone. The turbidity of DHA in aqueous solution decreased after binding with β-Lg. The crystallographic results showed that DHA was bound at one site in the calyx of β-Lg and that the aliphatic chain was hidden inside the hydrophobic β-barrel while the carboxyl group was located at the calyx entrance. These findings indicate that β-Lg can act as an effective nanocarrier for DHA.

Structures, fabrication mechanisms, and emulsifying properties of self-assembled and spray-dried ternary complexes based on lactoferrin, oat β-glucan and curcumin: A comparison study

Protein-polyphenol-polysaccharide non-covalent ternary complexes possess many unique structural and functional properties. However, rare work is available to fabricate the neutral polysaccharide-based ternary complexes. Herein, the ternary complexes composed of lactoferrin (LF), oat β-glucan (OG), and curcumin (Cur) with three binding sequences were successfully developed through self-assembly technique and spray drying technique, respectively. Spray drying could enhance the extent of the intermolecular associations among LF, OG, and Cur, leading to the formation of ternary complexes with smaller particle sizes and lower turbidities. Cur can be loaded in LF-OG complexes to form an amorphous complex through the intermolecular interactions (mainly hydrophobic interactions and hydrogen bonding). The ternary complexes can be used as potential emulsifiers to stabilize oil-in-water Pickering emulsions. The emulsifying capacity (to enhance physical stability) of the complexes was in the order as follows: the spray-dried ternary complexes > the spray-dried LF-OG complexes > the self-assembled ternary complexes > the self-assembled LF-OG complexes. The structural and functional properties (e.g., emulsifying property) of OG-based ternary complexes can be controlled by adjusting the binding sequences. These results will broaden our current understanding of protein-polyphenol-polysaccharide ternary complexes and provide more applications of OG in food, cosmetics, and pharmaceutical industries.

Improving emulsion stability based on ovalbumin-carboxymethyl cellulose complexes with thermal treatment near ovalbumin isoelectric point

Ovalbumin (OVA) is an important protein emulsifier. However, it is unstable near the isoelectric point pH, which limits its applications in the food industry. Polysaccharides may be explored to tackle this challenge by improving its pH-dependent instability. In this work, carboxymethyl cellulose (CMC) was used as a model polysaccharide to mix with OVA near its isoelectric point (pH 4.7) with subsequent mild heating at 60 °C for 30 min. The molecular interactions between OVA and CMC were comprehensively studied via a series of characterizations, including turbidity, zeta potential, intrinsic fluorescence, surface hydrophobicity, circular dichroism (CD) spectra and Fourier transform infrared spectroscopy (FTIR). The droplet sizes of the emulsions prepared by OVA-CMC were measured to analyze emulsifying property and stability. The results indicated that free OVA was easily aggregated due to loss of surface charges, while complexing with CMC significantly inhibited OVA aggregation before and after heating owing to the strong electrostatic repulsion. In addition, OVA exposed more hydrophobic clusters after heating, which resulted in the growth of surface hydrophobicity. Altogether, the heated OVA-CMC complexes presented the best emulsifying property and stability. Our study demonstrated that complexing OVA with CMC not only greatly improved its physicochemical properties but also significantly enhanced its functionality as a food-grade emulsifying agent, expanding its applications in the food industry, as development of emulsion-based acidic food products.

Activity of catechins and their applications

Background

Catechins, which are polyphenol compounds found in many plants and are an important component of tea leaves, are strong anti-oxidants.

Research

Many studies seek to enhance the effects of catechins on the human body and boost their protective power against UV radiation. There are many examples of the positive anti-microbial, anti-viral, anti-inflammatory, anti-allergenic, and anti-cancer effects of catechins. Catechins increase the penetration and absorption of healthy functional foods and bio cosmetics into the body and the skin, thus improving their utility. High value-added anti-oxidant substances have been extracted from food and plant sludge, and experiments have shown that catechins are safe when applied to the human body. The stability of catechins is very important for their absorption into the human body and the effectiveness of their anti-oxidant properties.

Conclusion

Continued research on the strong anti-oxidant effects of catechins is expected to result in many advances in the food, cosmetics, and pharmaceutical industries.

Novel Bilayer Emulsions Costabilized by Zein Colloidal Particles and Propylene Glycol Alginate, Part 1: Fabrication and Characterization

In this study, both zein colloidal particles (ZCPs) and propylene glycol alginate (PGA) were simultaneously applied to prepare novel bilayer emulsions using the method of layer-by-layer (LBL) electrostatic deposition. The effects of different concentrations of PGA as well as incorporating sequences of ZCPs and PGA on physical stability and microstructure of bilayer emulsions were investigated. Furthermore, optical microscopy as well as confocal laser scanning microscopy (CLSM) showed that the oil droplets presented uniform spheres and a compact network appeared in bilayer emulsion. Compared to the Pickering emulsion stabilized by ZCPs alone, novel bilayer emulsions exhibited simultaneous and long-term stability against creaming, coalescence, and Ostwald ripening due to the unique interface framework of a particle-polysaccharide hierarchical structure. Novel bilayer emulsions synergistically stabilized by colloidal particles and biopolymers were designed by using interfacial engineering, and a promising pathway was found to produce stable bilayer emulsions for the delivery of bioactive compounds.

Physicochemical stability and antioxidant activity of soy protein/pectin/tea polyphenol ternary nanoparticles obtained by photocatalysis

The ternary nanoparticles were fabricated by soy protein, pectin and tea polyphenol through photocatalysis. The particulate characteristics, including particle size, polydispersity index, and zeta potential were monitored for ternary nanoparticles formed under different photocatalysis time. Photocatalysis was favorable to form ternary nanoparticles with moderate particle size (310-370 nm), uniform distribution, spherical shape, and improved antioxidant activity. It was found that the fluorescence intensity of soy protein decreased with the increase in photocatalysis time in the ternary nanoparticles. Far-UV circular dichroism results indicated that increasing photocatalysis time could alter the secondary structure of soy protein with an increase in the proportion of β-sheet and β-turn structure at the cost of unordered coil and α-helix structure. According to FT-IR results, photocatalysis time could also modulate the conjugation between pectin and soy protein. In addition, photocatalysis could increase the binding affinities among the components, leading to better environmental stability of the ternary nanoparticles. The ternary nanoparticles in this study could be used as a good alternative to understand and consequently improve the physicochemical stability in food, pharmaceutical, and cosmetic matrices.

Nano- and micro-particles for delivery of catechins: Physical and biological performance

Catechins, present in many fruits and vegetables, have many health benefits, but they are prone to degradation. Nano- and micro-particle systems have been used to stabilise catechins when exposed to adverse environments and to improve their bioavailability after ingestion. This review discusses the inherent properties of various catechins, the design of delivery formulations and the properties of catechin-loaded nano- and micro-particles. The protection afforded to catechins during exposure to harsh environmental conditions and gastrointestinal tract transit is reviewed. The bioavailability and efficacy of encapsulated catechins, as assessed by various in vitro and in vivo conditions, are discussed. Bioavailability based on uptake in the upper gut alone underestimates the bioavailability as polyphenols. The caveats with interpretation of bioavailability based on various tests are discussed, when taking into consideration the pathways of catechin metabolism including the role of the gut microflora. However, taken together, the weight of the evidence suggests that there are potentially improved health benefits with the use of appropriately designed nano- and micro-particles for delivery of catechins. Further systematic studies on the metabolism and physiological effects of encapsulated catechins in vivo and clinical trials are needed to validate the bioefficacy of the encapsulated catechins.

Development of a soy protein isolate–carrageenan–quercetagetin non-covalent complex for the stabilization of β-carotene emulsions

The current study investigated the application of a soy protein isolate (SPI), κ-carrageenan (CG) and quercetagetin (Qut) non-covalent complex in stabilizing β-carotene emulsions.

Binding behaviors and structural characteristics of ternary complexes of β-lactoglobulin, curcumin, and fatty acids

This study clarified the interaction mechanism and structural characteristics of ternary complexes of β-lactoglobulin, curcumin, and fatty acids.

Utilization of interfacial engineering to improve physicochemical stability of β-carotene emulsions: Multilayer coatings formed using protein and protein-polyphenol conjugates

The impact of lactoferrin (LF)-chlorogenic acid (CA) and (-)-Epigallocatechin-3-gallate (EGCG) conjugates on the physicochemical properties of β-carotene emulsions was investigated. Formation of lactoferrin-polyphenol conjugates, which was confirmed by SDS-PAGE, caused changes in the structure and nature of lactoferrin. Based on layer-by-layer electrostatic deposition, β-carotene bilayer emulsions were prepared by lactoferrin and lactoferrin-polyphenol conjugates at pH 7.0. The physicochemical properties of primary and secondary emulsions were evaluated and the results suggested that LF-polyphenol conjugates-stabilized primary and secondary emulsions exhibited better emulsifying properties and improved physical stability of β-carotene bilayer emulsions under freeze-thaw, ionic strength and thermal treatments. In addition, the lactoferrin-polyphenol conjugates could effectively enhance chemical stability of β-carotene in oil-in-water emulsions against heat treatment and ultraviolet light exposure, and the least degradation of β-carotene occurred in LF-EGCG conjugate-stabilized primary emulsion. The interfacial engineering technology utilized in this study may lead to the formation of emulsions with improved physicochemical and functional performance.