Influence of polysaccharides on the physicochemical properties of lactoferrin–polyphenol conjugates coated β-carotene emulsions

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.

Emulsification properties of ovalbumin-fucoidan (OVA-FUC) binary complexes

The poor thermal stability and emulsifying properties of ovalbumin (OVA) limit its functional performance, but these limitations may be overcome by forming binary complexes. We prepared binary complexes of OVA and fucoidan (FUC) through electrostatic self-assembly and investigated the emulsifying properties of the complex by measuring the particle size, interfacial membrane thickness, zeta potential, and stability of the emulsion prepared with camellia oil and the complex. The OVA-FUC emulsions have a thicker interfacial membrane, lower mobility, higher viscosity, and better stability compared with the OVA emulsions. The emulsion prepared with 1.5 % OVA-FUC remained stable and homogeneous during storage. They tended to become unstable with freeze-thaw, but the oil encapsulated did not leak after coalescence occurred. With the addition of Ca2+, the OVA-FUC emulsion will be converted into a gel state. These findings indicate that OVA-FUC binary complexes can be used to prepare high-performance emulsions with great potential for development.

Effect of Milk Protein-Polyphenol Conjugate on the Regulation of GLP-1 Hormone

Modern functional foods are designed to provide health benefits beyond basic nutrition. They are enriched with bioactive ingredients like probiotics, vitamins, minerals, and antioxidants. These foods support overall health, enhance immune function, and help prevent chronic diseases. Milk proteins and tea are known to influence satiety and regulate body weight. Studies have shown that green tea polyphenols, namely, (-)-epigallocatechin gallate (EGCG), and whey proteins, predominantly lactoferrin (LF) from milk, play a role in regulating satiety. This study aims to investigate the effect of conjugating EGCG with apo-lactoferrin (Apo-LF) and assessing these effects on satiety through monitoring glucagon-like peptide-1 (GLP-1) regulation in a human colon (NCI-H716) cell line. Apo-LF-EGCG conjugates were synthesized and characterized in terms of structural and functional properties. The effect on GLP-1 regulation was assessed by real-time quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA) to monitor gene and protein expressions, respectively. The results revealed that the protein-polyphenol interaction occurs through the complex formation of hydrogen bonds at the O-H and carbonyl groups of EGCG. The conjugates also showed a significant up-regulation of gene and protein expression levels of GLP-1 while also preventing EGCG from degradation, thereby preserving its antioxidant properties. The Apo-LF-EGCG conjugates increase satiety via increasing GLP-1 secretion in human colon cells while simultaneously retaining the antioxidant properties of EGCG. Therefore, these conjugates show potential for use as dietary supplements to enhance satiety.

Remarkable Enhancement of Antioxidant Activity of the Ovalbumin-EGCG Conjugate through a Novel Preceding Selective Protection Grafting Strategy

Conventional radical grafting of proteins with catechins consumed the most antioxidant-active hydroxyls during grafting, thus failing to effectively retain antioxidant activity in conjugates. In this study, a novel strategy of selective protection of the most reactive hydroxyls before grafting was developed to preserve the most reactive hydroxyls and effectively retain antioxidant activity in conjugates. Selective protection of the most reactive hydroxyls of (-)-epigallocatechin-3-gallate (EGCG) was successfully realized in a yield of 87% applying trimethyl orthopropionate and catalytic calcium triflate at 40 °C. The novel ovalbumin (OVA)-EGCG conjugate with 93% grafting ratio was prepared by radical grafting with the selectively protected EGCG and subsequent deprotection. Substantially enhanced antioxidant performance of the novel OVA-EGCG conjugate in liposomes was unveiled with notably reduced curcumin degradation and leakage. The strategy and approaches developed in this study will be valuable to effectively improve the antioxidant activities of protein-catechin grafting conjugates.

The structural and functional properties of hemp protein isolate-epigallocatechin-3-gallate biopolymer covalent complex during heating

BACKGROUND

It is well known that hemp proteins have the disadvantages of poor solubility and poor emulsification. To improve these shortcomings, an alkali covalent cross-linking method was used to prepare hemp protein isolate-epigallocatechin-3-gallate biopolymer (HPI-EGCG) and the effects of different heat treatment conditions on the structure and emulsifying properties of the HPI-EGCG covalent complex were studied.

RESULTS

The secondary and tertiary structures, solubility, and emulsification ability of the HPI-EGCG complexes were evaluated using particle size, zeta potential, circular dichroism (CD), and fluorescence spectroscopy indices. The results showed that the absolute value of zeta potential of HPI-EGCG covalent complex was the largest, 18.6 mV, and the maximum binding amount of HPI to EGCG was 29.18 μmol g-1 . Under heat treatment at 25-35 °C, the α-helix content was reduced from 1.87% to 0%, and the β-helix content was reduced from 82.79% to 0% after the covalent binding of HPI and EGCG. The solubility and emulsification properties of the HPI-EGCG covalent complexes were improved significantly, and the emulsification activity index (EAI) and emulsion stability index (ESI) were increased by 2.77-fold and 1.21-fold, respectively.

CONCLUSION

A new HPI-EGCG covalent complex was developed in this study to provide a theoretical basis for the application of HPI-EGCG in food industry. © 2023 Society of Chemical Industry.

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.

Insight into the composite assembly process, nanofibril structure and stability of undenatured type II collagen in the presence of different types of nanocelluloses

Four types of nanocelluloses (CNs), including cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), cationic etherified nanocellulose (CCNF) and TEMPO-oxidized nanocellulose (TOCNF), were incorporated into the assembly process of undenatured type II collagen (UC-II). In the presence of CNs, the kinetics of UC-II composite assembly slightly fluctuated and the magnitude of UC-II assembly increased (from 59.93 to 66.83-85.06 %). CNC and CNF disrupted the triple helix structure of UC-II while CCNF and TOCNF had weak impact on it. Hydrogen bonding and hydrophobic interactions were dominant driving forces of UC-II/CNs, and electrostatic interactions were also involved in the fabrication of UC-II/CCNF and UC-II/TOCNF. UC-II/CNs exhibited distinct nanostructures due to the differences in shape, level, and surface group of CNs. CCNF and TOCNF contributed to the enhanced physical stability due to the increased surface charge. In addition, the thermal stability and rheological properties of UC-II/CNs were also improved. The composite assembly process, nanofibril structure and stability of UC-II in the presence of different types and levels of CNs, which was useful to develop the novel composite nanofibrils for the application in functional foods.

Characterization and utilization of soy protein isolate-(-)-epigallocatechin gallate-maltose ternary conjugate as an emulsifier for nanoemulsions: Enhanced physicochemical stability of the β-carotene nanoemulsion

In this study, a ternary conjugate was prepared by covalent bonding of protein, polysaccharide, and polyphenol via ultrasound and the Maillard reaction. Subsequently, the β-carotene nanoemulsion was prepared with the soy protein isolate-(-)-epigallocatechin gallate-maltose (SPI-EGCG-maltose) conjugate as the emulsifiers via ultrasound. The SPI-EGCG-maltose conjugate showed superior solubility, emulsification and foaming properties at 4 h reaction time. Meanwhile, the retention rates of β-carotene in the nanoemulsion after 30 d of storage, 8 h of light, and 55 °C of heat were >60%, >75%, and >60%, respectively. Furthermore, ultrasound treatment at 500 W for 10 min produced an inhibitory effect on the degradation of β-carotene. This study indicates that the nanoemulsion based on the ternary conjugate can effectively inhibit the β-carotene degradation by the external environment and prevent the oxidation and degradation of β-carotene in the nanoemulsion.

Maillard induced glycation of β-casein for enhanced stability of the self-assembly micelles against acidic and calcium environment

Bovine β-casein (β-CN) has attracted increasingly interest as biocompatible nanocarrier for hydrophobic flavonoid due to its self-assembly ability to form micelles. This paper reported Maillard induced glycation reaction of β-CN using dextran in order to improve stability of naringenin-loaded β-CN micelles under acidic and high calcium environments. Our results showed that solubility of β-CN-graft-dextran was remarkable increased at acidic pH and the conjugation with 20 kDa dextran had the highest level of graft degree. Glycation restrained β-CN from aggregating around pH 5.0 where was close to the isoelectric point, forming spherical micelles with irregular and rough surfaces, which were significantly larger than the micelles at pH 7.0. β-CN-graft-dextran also overcame destabilization of the micelles induced by excess calcium and had no impact on the chelating ability of calcium. These findings appeared to be promising for future applications of modified β-CN-graft-dextran based on Maillard reaction as fairly stable nanocarrier under extreme condition.

Hemp (Cannabis sativa L.) Seed Protein-EGCG Conjugates: Covalent Bonding and Functional Research

In order to make HPI have a wide application prospect in the food industry, we used EGCG to modify HPI. In this study, we prepared different concentrations (1, 2, 3, 4, and 5 mM) of (-)-epigallocatechin gallate (EGCG) covalently linked to HPI and use methods such as particle size analysis, circular dichroism (CD), and three-dimensional fluorescence spectroscopy to study the changes in the structure and functional properties of HPI after being covalently combined with EGCG. The particle size data indicated that the covalent HPI-EGCG complex was larger than native HPI, and the particle size was mainly distributed at about 200 μm. CD and three-dimensional fluorescence spectroscopy analyses showed that the conformation of the protein was changed by conjugation with EGCG. The β-sheet content decreased from 82.79% to 66.67% after EGCG bound to the protein, and the hydrophobic groups inside the protein were exposed, which increased the hydrophobicity of the protein and changed its conformation. After HPI and 1 mM of EGCG were covalently bonded, the solubility and emulsifying properties of the covalent complex were improved compared with native HPI. These results indicated that HPI-EGCG conjugates can be added in some foods.

Effect of glycosylation with sugar beet pectin on the interfacial behaviour and emulsifying ability of coconut protein

The aim of the present study was to investigate the effect of glycosylation with sugar beet pectin (SBP) on the interfacial behaviour and emulsifying ability of coconut protein (CP). The physical stabilities of the emulsions were predicted by transmission variation, droplet distribution and zeta potentials. The results showed that SBP-CP-stabilized emulsions showed better stability during centrifugation than those stabilized by CP because SBP-CP reduced the degree of variation in the CP transmission profile. The adsorption kinetics of all emulsifiers at the oil-water interface were determined to investigate the relationship between the interfacial behaviour and emulsion stability. The presence of SBP considerably reduced the adsorption rate of CP (0.698 mN/m/s^1/2) and hampered the development of a highly viscoelastic network at the oil-water interface. The values of the dilatational elastic modulus (E_d = 19.477 mN/m) and dilatational viscous modulus (E = 19.719 mN/m) were approximately equal, indicating that the adsorption process was mainly dominated by elastic behaviour. Additionally, the SBP-CP interaction enhanced the dilatational property of the CP-absorbed layer.

Development of astaxanthin-loaded layer-by-layer emulsions: physicochemical properties and improvement of LPS-induced neuroinflammation in mice

Astaxanthin (AST) has been shown to have neuroprotective effects; however, its bioavailability in vivo is low due to its hydrophobic properties. In this study, lactoferrin (LF) was prepared by heat-treatment at different temperatures, and on this basis, a layer-by-layer self-assembly method was used to construct double-layer emulsions with LF as the inner layer and polysaccharide (beet pectin, BP or carboxymethyl chitosan, CMCS) as the outer layer. Then AST was encapsulated in the emulsions and their physiochemical properties and function were investigated. The results indicated that high temperature heated LF (95 °C) showed a more stable structure than the lower temperature one, and the exposed internal nonpolar groups of LF could give the emulsion an enhanced stability. The rheology results showed that compared with CMCS, the double-layer emulsion formed by BP had a higher viscosity. In addition, the 95 °C LF-AST-BP emulsion showed the best stability among all the bilayer emulsions. The best emulsion was then used as a model drug to investigate its effects on lipopolysaccharide (LPS)-induced neuroinflammation and learning-memory loss in C57BL/6J mice. Through animal behavioral experiments, it was found that dietary supplementation with the AST emulsion could effectively improve the brain cognitive and learning memory impairment caused by inflammation. Transmission electron microscopy, mRNA and western blotting results also illustrated that the AST emulsion could alleviate neuroinflammation caused by LPS. This study provides a feasible scheme for exploring an AST loaded system and may be suitable for food and drug applications.

Application of Advanced Emulsion Technology in the Food Industry: A Review and Critical Evaluation

The food industry is one of the major users of emulsion technology, as many food products exist in an emulsified form, including many dressings, sauces, spreads, dips, creams, and beverages. Recently, there has been an interest in improving the healthiness, sustainability, and safety of foods in an attempt to address some of the negative effects associated with the modern food supply, such as rising chronic diseases, environmental damage, and food safety concerns. Advanced emulsion technologies can be used to address many of these concerns. In this review article, recent studies on the development and utilization of these advanced technologies are critically assessed, including nanoemulsions, high internal phase emulsions (HIPEs), Pickering emulsions, multilayer emulsions, solid lipid nanoparticles (SLNs), multiple emulsions, and emulgels. A brief description of each type of emulsion is given, then their formation and properties are described, and finally their potential applications in the food industry are presented. Special emphasis is given to the utilization of these advanced technologies for the delivery of bioactive compounds.

Preparation of Pickering emulsion gels based on κ-carrageenan and covalent crosslinking with EDC: Gelation mechanism and bioaccessibility of curcumin

Pickering emulsions stabilized by zein/carboxymethyl dextrin nanoparticles were added to the κ-carrageenan-based gel matrix to prepare emulsion gels via EDC - induced covalent crosslinking. Texture, WHC and freeze-thaw stability of the emulsion gels increased after crosslinking. The Confocal laser scanning microscope and SEM suggested that droplet clusters could be observed in gel with higher concentration of emulsion. The rheological measurements indicated that the viscosity and gel-like structure were relied on crosslinking agent and emulsion concentration. The photothermal stability of curcumin was significantly enhanced after crosslinking. In addition, in vitro digestion study suggested that the bioaccessibility of curcumin in emulsion gel crosslinked was lower compared to emulsion gel without crosslinking agent. These studies might facilitate the preparation of emulsion gels with excellent stability for bioactive compounds delivery in food and pharmaceutical applications.

Fate of β-Carotene within Loaded Delivery Systems in Food: State of Knowledge

Nanotechnology has opened new opportunities for delivering bioactive agents. Their physiochemical characteristics, i.e., small size, high surface area, unique composition, biocompatibility and biodegradability, make these nanomaterials an attractive tool for β-carotene delivery. Delivering β-carotene through nanoparticles does not only improve its bioavailability/bioaccumulation in target tissues, but also lessens its sensitivity against environmental factors during processing. Regardless of these benefits, nanocarriers have some limitations, such as variations in sensory quality, modification of the food matrix, increasing costs, as well as limited consumer acceptance and regulatory challenges. This research area has rapidly evolved, with a plethora of innovative nanoengineered materials now being in use, including micelles, nano/microemulsions, liposomes, niosomes, solidlipid nanoparticles, nanostructured lipids and nanostructured carriers. These nanodelivery systems make conventional delivery systems appear archaic and promise better solubilization, protection during processing, improved shelf-life, higher bioavailability as well as controlled and targeted release. This review provides information on the state of knowledge on β-carotene nanodelivery systems adopted for developing functional foods, depicting their classifications, compositions, preparation methods, challenges, release and absorption of β-carotene in the gastrointestinal tract (GIT) and possible risks and future prospects.

Gliadin Nanoparticles Pickering Emulgels for β-Carotene Delivery: Effect of Particle Concentration on the Stability and Bioaccessibility

β-carotene is a promising natural active ingredient for optimum human health. However, the insolubility in water, low oral bioavailability, and instability in oxygen, heat, and light are key factors to limit its application as incorporation into functional foods. Therefore, gliadin nanoparticles (GNPs) Pickering emulgels were chosen as food-grade β-carotene delivery systems. The objectives of the present study were to investigate the influence of GNPs concentration on the rheological properties, stability, and simulated gastrointestinal fate of β-carotene of Pickering emulgels. The formulations of Pickering emulgels at low GNPs concentration had better fluidity, whereas at high GNPs concentration, they had stronger gel structures. Furthermore, the thermal stability of β-carotene loaded in Pickering emulgels after two pasteurization treatments was significantly improved with the increase of GNPs concentration. The Pickering emulgels stabilized with higher GNPs concentration could improve the protection and bioaccessibility of β-carotene after different storage conditions. This study demonstrated the tremendous potential of GNPs Pickering emulgels to carry β-carotene.

Enhanced Physicochemical Stability of β-Carotene Emulsions Stabilized by β-Lactoglobulin-Ferulic Acid-Chitosan Ternary Conjugate

The purpose of the present work is to fabricate emulsions with excellent stability to deliver β-carotene using a novel biomacromolecule. β-Lactoglobulin-ferulic acid-chitosan ternary conjugate (BFCC), which was synthesized based on the carbodiimide-mediated coupling reaction and laccase induction, was confirmed by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (¹H NMR) spectra. Also, BFCC was used to stabilize β-carotene emulsions. The results indicated that the concentration of BFCC affected the physical stability of β-carotene emulsions. Compared with the emulsions stabilized by β-lactoglobulin (β-LG), chitosan-ferulic acid conjugate (CFC), and β-LG-CFC mixture (BFCM), the emulsion stabilized by BFCC exhibited better stability under various environmental stresses. Moreover, the emulsion stabilized by BFCC had higher β-carotene retention during storage at 25 and 55 °C or under ultraviolet (UV) light exposure. The knowledge acquired in the current research offered an effective way to develop novel biomacromolecular emulsifiers and could find potential in fabricating delivery systems for bioactive compounds with markedly enhanced physiochemical properties.

Impact on stabilization of ionic gum emulsions by natural and thermally modified Chironji gum

Ionic gums like acacia and tragacanth are known for their emulsifying properties but lower viscosity limits its use. This study explores the effects of natural chironji gum and its thermally modified form on the emulsifying properties of acacia and tragacanth. Formulations of chironji gum (CG) O/W emulsion FA1-FA4 were prepared with acacia and FT1-FT4 with tragacanth respectively. Heat treated gums(CGTs) were obtained by heating CG at 110 °C for time intervals 24 h, 48 h and 96 h. Similarly formulations FHA1-FHA12 and FHT1-FHT12 were prepared with acacia and tragacanth replacing CG with heat treated gums. Heat treated gum formulations showed better stabilizing properties than natural CG emulsions. The FA1-FA4 and FT1-FT4 formulations had droplet size in the range of 9.77-26.55 μm and zeta potential ranging from -14.8 mV to -23.2 mV. In contrast, the droplet size and zeta potential of FHA1-FHA12 and FHT1-FHT12 were in range of 1.42-17.5 μm and -17.2 mV to -40.6 mV respectively signifying improved stabilizing capacity of CGT gums. The droplet size and zeta potential of these formulations remained stable even after 7 days of storage at room temperature with no visible phase separation of the formulation observed for more than a month.

The Improvement of Nanoemulsion Stability and Antioxidation via Protein-Chlorogenic Acid-Dextran Conjugates as Emulsifiers

In this experiment, the peanut protein isolate (PPI), soybean protein isolate (SPI), rice bran protein isolate (RBPI), and whey protein isolate (WPI) were modified by linking chlorogenic acid covalently and linking dextran by Maillard reaction to prepare protein-chlorogenic acid-dextran (PCD) conjugates. As for structures, conformational changes of conjugates were determined by Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE), Fourier transform infrared (FT-IR), and fluorescence measurements. The molecular weights of PCD conjugates became larger, the structure became disorder, and the amino acid residues inside the protein were exposed to the polar environment when compared to protein-chlorogenic acid (PC) and native proteins (NPs). As for properties, the interfacial tension reduced and antioxidant activity of PCD conjugates enhanced in varying degrees. Based on this, PCD conjugates were used as emulsifiers in order to investigate the properties of nanoemulsions and compared with PC conjugates and NPs. The mean droplet diameters (MDD) results showed that the nanoemulsions that were stabilized by PCD conjugates had the smallest particle sizes and exhibited uniformly dispersed spherical shapes. The storage and oxidative stabilities of PCD conjugates were also significantly improved. In comparison, nanoemulsion that was stabilized by PPI-chlorogenic acid-dextran conjugate had the smallest particle size and optimal stability among four protein stabilized nanoemulsions.

Molecular mechanisms of selenium-biofortified soybean protein and polyphenol conjugates in protecting mouse skin damaged by UV-B

Selenium-biofortified crops are a quality functional food resource because of their anti-tumor and anti-cancer properties. In the present study, the conjugates of selenium-biofortified soybean protein and polyphenols were prepared and evaluated by alkali-induced synthesis and in vitro antioxidant tests. Moreover, the antioxidant mechanisms of protecting mice skin damaged by UV-B were studied. The results showed that the antioxidant activity of the conjugate between 7S globulin from selenium-enriched soybean (Se-7S) and EGCG (Se-7S-EGCG) was significantly higher (P < 0.05) than that of Se-7S-GA. Structural characterizations implied that the polymerization of polyphenols with amino acid residues occurred. Se-7S-EGCG inhibited the apoptosis of epidermal cells induced by UV-B. The overexpression of phosphorylated proteins in the MAPK signaling pathway, the activation of related inflammatory factors, and the boost in the MMPs were reversed by Se-7S-EGCG. Overall, this research provides a theoretical and experimental basis for the application of protein and polyphenol conjugates in food and medicine fields.

Effect of Fructus Mori. bioactive polysaccharide conjugation on improving functional and antioxidant activity of whey protein

Whey protein with high biological and technological values is an excellent source of nutrition. However, the limited functional properties prevent its widespread applications in food industry. In this study, the whey protein functionality was improved via glycation with mulberry fruit polysaccharide by Maillard reaction. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile and free amino groups determination confirmed the glycation occurred between whey protein and mulberry fruit polysaccharide. The emulsion capacity and stability of the conjugates were 1.40-fold and 1.52-fold higher than that of whey protein. The conjugates also exhibited remarkably improved antioxidant activity. The fish oil emulsion coated by conjugates demonstrated smaller droplet size, better storage and oxidative stability than that stabilized by whey protein. The findings would be of vital importance for updated understanding of the modification in emulsifying properties of proteins by glycation with natural bioactive polysaccharides as well as for the development of healthy foods.

Recent advances in phenolic-protein conjugates: synthesis, characterization, biological activities and potential applications

Proteins and phenolic compounds are two types of food ingredients with distinct functionalities. In the past decade, many attempts have been made to conjugate phenolic compounds with proteins through covalent linkages. Four types of conjugation reactions including alkaline, free radical mediated grafting, enzyme catalyzed grafting and chemical coupling methods are frequently used to synthesize phenolic-protein conjugates. The synthesized phenolic-protein conjugates can be well characterized by several different instrumental methods, such as UV spectroscopy, Fourier transform infrared spectroscopy, fluorescence spectroscopy, circular dichroism, mass spectroscopy, sodium dodecyl sulfate polyacrylamide gel electrophoresis and differential scanning calorimetry. Importantly, phenolic-protein conjugates exhibit improved biological properties (e.g. antioxidant, anticancer and antimicrobial activities) as compared with native proteins. Moreover, the applications of native proteins can be greatly widened by conjugation with phenolic compounds. Phenolic-protein conjugates have been developed as antioxidant emulsions for nutraceutical delivery, edible films for food packaging, stabilizers for metal nanoparticles, and hydrogels and nanoparticles for controlled drug release. In this review, recent advances in the synthesis, characterization, biological properties and potential applications of phenolic-protein conjugates were summarized.

Core-Shell Biopolymer Nanoparticles for Co-Delivery of Curcumin and Piperine: Sequential Electrostatic Deposition of Hyaluronic Acid and Chitosan Shells on the Zein Core

Curcumin and piperine are natural nutraceuticals that exhibit synergistic biological activities, but have different polarities, which can make their encapsulation within a single delivery system challenging. In this study, the two bioactive components were encapsulated within core-shell nanoparticles formed by a combination of antisolvent precipitation and layer-by-layer deposition. Initially, strongly hydrophobic curcumin (log P = 4.12) was embedded in the hydrophobic core of zein-hyaluronic acid nanoparticles using the antisolvent precipitation method. Then, the weakly hydrophobic piperine (log P = 2.78) was adsorbed to the outer biopolymer shell of these nanoparticles. Finally, the nutraceutical-loaded particles were coated with a layer of chitosan by the electrostatic deposition method. The surface charge and coating thickness depended on the number of adsorbed layers and the nature of the outer layer, being negative for hyaluronic acid and positive for chitosan. Low-, medium-, and high-molecular weight chitosan were utilized to modify the surface properties. Chitosan with a low-molecular weight was selected to fabricate the core-shell nanoparticles because it produced small highly charged cationic particles (d = 599 nm; ζ = +38.1 mV). The encapsulation efficiency and loading capacities were 90.4 and 5.7% for curcumin, and 86.4 and 5.4% for piperine, respectively. The core-shell nanoparticles protected the nutraceuticals from chemical degradation during light exposure, thermal processing, and storage for 2 months. Moreover, the nanoparticles were able to control the release of the bioactive components in simulated gastrointestinal conditions. Our results should facilitate the development of more effective nanodelivery systems for nutraceuticals that exhibit synergistic activities, but have different molecular characteristics.

Novel Bilayer Emulsions Costabilized by Zein Colloidal Particles and Propylene Glycol Alginate. 2. Influence of Environmental Stresses on Stability and Rheological Properties

Novel bilayer emulsions co-stabilized by zein colloidal particles (ZCPs) and propylene glycol alginate (PGA) were designed to overcome some limitations of conventional emulsions or Pickering emulsions. The bilayer emulsions of various concentrations of PGA (0.01-1.50%, w/v) and different incorporation sequences of ZCPs and PGA (ZCPs/PGA and PGA/ZCPs) were fabricated using the layer by layer (LBL) electrostatic deposition technique. Influence of environmental stresses (pH 2.5-8.5; temperature 60-80 °C ; ionic strength 0-100 mM NaCl) was focused on the stability and rheological properties of the novel bilayer emulsions. In comparison to the Pickering emulsion stabilized by ZCPs alone, bilayer emulsions exhibited improved stability and unique rheological characteristics under environmental stresses. The microstructure of well-defined spheres existing a branchlike network was observed in bilayer emulsions by TEM. A comprehensive evaluation was made of the physical characteristics and stimuli-responsive behavior of bilayer emulsions. The result provided meaningful information for understanding the changing mechanism of rheology of bilayer emulsions under environmental stresses.

Impact of Interfacial Composition on Emulsion Digestion Using In Vitro and In Vivo Models

This study explored the influence of different emulsification layers as mono- and bilayers on lipid digestion by using in vitro and in vivo digestion methods. The monolayer emulsion of rapeseed oil contained whey proteins and the bilayer emulsion, whey proteins and carboxymethyl cellulose. The in vitro digestion using human gastrointestinal enzymes showed that the lipid digestion as free fatty acids was slowed down in the bilayer emulsion compared with the monolayer. Droplet size was still low in the gastric phase and pseudoplasticity was well preserved (even though viscosity decreased) during in vitro gastrointestinal digestion. The in vivo studies confirmed a lower fat bioavailability from bilayer emulsions by a reduction in the triglyceride level in the blood of rats, fed by the bilayer emulsion. The results clearly showed that lipid digestion was slower in the bilayer emulsion than in the monolayer. These results provide bio-relevant information about the behavior of emulsions upon digestion. PRACTICAL APPLICATION: The layer-by-layer production approach that was presented here allows the preparation of emulsions with slower fat bioavailability. Such behavior of the bilayer emulsion made it interesting for the formulation of food products with low fat bioavailability.