Emulsifying properties of a ferulic acid-grafted curdlan conjugate and its contribution to the chemical stability of β-carotene

Improving the prebiotic activity and oxidative stability of carboxymethyl curdlan - quercetin conjugates stabilized Pickering emulsions for the colonic targeting delivery of curcumin

The carboxymethyl curdlan-quercetin conjugate (CMCD-QUE) was synthesized to stabilize curcumin (CUR) -loaded Pickering emulsions. The physicochemical properties, antioxidant activity, and prebiotic activity of CMCD-QUE were investigated. The effects of different concentrations of CMCD-QUE on CUR-loaded emulsions were also explored. CMCD-QUE exhibited excellent antioxidant activity throughout in vitro simulated gastrointestinal digestion. The particle size and electrostatic repulsion of CMCD-QUE gradually increased with rising pH, indicating that CMCD-QUE was pH-responsive. CMCD-QUE exhibited prebiotic activity and specifically promoted the enrichment of Akkermansia. The droplet size of the CMCD-QUE stabilized emulsions became smaller and more uniform as the carrier concentration increased. A concentration of 5% CMCD-QUE could be stably adsorbed at the oil-water interface of the emulsion, which exhibited a maximum encapsulated efficiency (95.85%) of CUR. CMCD-QUE showed excellent antioxidant capacity, pH responsiveness, and prebiotic activity, making it a promising multifunctional emulsifier for colon-targeted delivery of functional ingredients.

Two-ways regulation of the emulsion gel properties of curdlan by dry ball milling treatment and their relationships with the microstructures, emulsification characteristics and gel properties of ball milled curdlan

Ball milling treatment could affect the microstructures, improve the emulsification properties of curdlan (CL) and regulate the emulsion gel properties of CL based emulsion gel in two-ways. With increasing ball milling time (1 h-8 h), the particle size first decreased and then increased, the relative crystallinity decreased, and the contact angle increased. Ball milled curdlan (BMCL)-6 h showed the best emulsifying property and stability, which was the combined effects of decreased particle size and increased hydrophobic property. Ball milling 1 h and 2 h significantly improved the hardness and chewiness of CL-based emulsion gels, while, ball milling 4 h-8 h could make the emulsion gels much softer and ice cream-like. When the emulsion gels were heated twice consecutively, the visual appearance and texture properties did not change significantly, indicating the excellent thermal stability of these emulsion gels. The BMCL based emulsion gel with adjustable gel properties and good thermal stability has a wide range of uses in the food system.

Construction and digestive characterization of emulsions stabilized with octenyl succinic anhydride-modified curdlan

To expand the scope of application of the insoluble polysaccharide curdlan (CUR), this study modified CUR with octenyl succinic anhydride (OSA) and evaluated the performance of the emulsion formed from the modified CUR derivative. Fourier transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffraction analysis showed that properties such as the molecular structure, crystallinity, and hydrophobicity of the OSA-modified CUR (COSA) changed significantly compared with those of the original CUR, indicating that the hydroxyl group of CUR was successfully replaced by OSA. Subsequently, a stable oil-in-water emulsion system of COSA loaded with curcumin was established. The stability of the emulsions was evaluated by analyzing their microstructure, rheological properties, and curcumin retention. The digestion characteristics of the emulsions were evaluated by in vitro simulated digestion experiments, and the COSA emulsion had higher stability and was better able to improve the chemical stability of curcumin compared to CUR. The OSA grafting resulted in emulsions with higher curcumin release rates and antioxidant capacities. These results indicate that COSA has the potential to be used as an encapsulating material for lipophilic nutrient emulsions and provides theoretical support for expanding the applications of chemically modified CUR derivatives.

Potato starch/naringenin complexes for high-stability Pickering emulsions: Structure, properties, and emulsion stabilization mechanism

In this study, potato starch (PS)/naringenin (NAR) complex was prepared, and its properties and emulsification behavior were evaluated. The experimental results demonstrated that NAR successfully formed a complex with PS molecules through hydrogen bonds and other non-covalent interactions. The emulsifying capacity (ROV) of PS/NAR complex with 16 % composite ratio was 0.9999, which was higher than PS (ROV = 0.3329) (p < 0.05). Based on particle property analysis and molecular dynamics simulation, the mechanism of improving the emulsification performance might be the action of the benzene ring of NAR and intermolecular hydrogen bonding. In addition, the stability of the Pickering emulsions with PS/NAR complexes as emulgators was significantly improved. The emulsifying and rheological behavior of starch-based Pickering emulsions could be adjusted by changing the proportion of the complexes. Results demonstrated that the PS/NAR complexes might be a prospective stabilizer of Pickering emulsions based on starch material and might expand the use of PS in edible products.

Pickering emulsions stabilized by ternary complexes involving curcumin-modified zein and polysaccharides with different charge amounts for encapsulating β-carotene

In this research, zein was modified with curcumin to obtain covalent and non-covalent complexes. They were further covered with polysaccharides (gum arabic or gum karaya) possessing different surface charge amounts to obtain ternary nanoparticles for preparing novel antioxidant Pickering emulsions. The addition of curcumin to the zein-polysaccharide system significantly retarded the UV degradation of the encapsulated β-carotene (maximum retention ∼ 97%) and effectively inhibited the lipid oxidation of the emulsions. In vitro gastrointestinal digestion assays showed that gum karaya significantly delayed the release of free fatty acids, thereby improving the bioaccessibility of β-carotene (the highest bioavailability ∼ 38%). By comparing the performance of the complex particles, the weakly charged polysaccharides were superior to the highly charged ones, while zein-curcumin covalent binding was superior to non-covalent binding in the above experiments. This study provides innovative perspectives on the use of novel Pickering emulsions to provide ideal protection and bioavailability of lipophilic nutraceuticals.

Free Radical-Mediated Grafting of Natural Polysaccharides Such as Chitosan, Starch, Inulin, and Pectin with Some Polyphenols: Synthesis, Structural Characterization, Bioactivities, and Applications-A Review

Polyphenols and polysaccharides are very important natural products with special physicochemical properties and extensive biological activities. Recently, polyphenol-polysaccharide conjugates have been synthesized to overcome the limitations of polysaccharides and broaden their application range. Grafted copolymers are produced through chemical coupling, enzyme-mediated, and free radical-mediated methods, among which the free radical-induced grafting reaction is the most cost-effective, ecofriendly, safe, and plausible approach. Here, we review the grafting reactions of polysaccharides mediated by free radicals with various bioactive polyphenols, such as gallic acid (GA), ferulic acid (FA), and catechins. A detailed introduction of the methods and their mechanisms for free radical-mediated grafting is given. Structural characterization methods of the graft products, including thin-layer chromatography (TLC), ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR) analysis, and X-ray diffraction (XRD) are introduced. Furthermore, the biological properties of polyphenol-polysaccharide conjugates are also presented, including antioxidant, antibacterial, antidiabetic, and neuroprotection activities, etc. Moreover, the potential applications of polyphenol-polysaccharide conjugates are described. Finally, the challenges and research prospects of graft products are summarized.

Determination of the Emulsion Stabilization Mechanisms of Quaternized Glucan of Curdlan via Rheological and Interfacial Characterization

Interfacial-active quaternized glucan of curdlan (QCD) with different degrees of substitution (DS) was prepared and used as stabilizers of oil-in-water (O/W) emulsions at different concentrations. The adsorption behavior of QCDs, rheology of bulk emulsions and interfacial films, emulsion morphology, and stability were investigated. The emulsifying capacity of QCD was essentially related to the viscoelastic features of the interfacial film and the continuous phase and the electrostatic repulsion among oil droplets. QCD molecules with different DS form structurally different interfacial films. The high-DS QCD formed a viscously predominant interfacial film with certain hydrophobicity, whereas the low-DS QCD molecules formed an elastically predominant film characterized by hydrogen bonds among adsorbed chains. The structuralization of low-DS QCD molecules through physical cross-linking in bulk and interfacial films at high concentrations was conducive to emulsion stability. Excess QCD chains in the bulk formed a weak gel-like network, further hindering the movement of droplets in the emulsions. Relevant emulsification and stability mechanisms were proposed. Finally, the stability of curcumin encapsulated in O/W emulsions was evaluated.

Emulsifying properties and bioavailability of clove essential oil Pickering emulsions stabilized by octadecylaminated carboxymethyl curdlan

In the present study, clove essential oil (CEO) Pickering emulsions were stabilized by octadecylamine-modified carboxymethyl curdlan (CMCD-ODA) at different pH values. The droplet size and negatively charged zeta potential of the CMCD-ODA emulsions decreased as the pH increased from 3.0 to 11.0. Rheology results indicated that the CMCD-ODA polymer/emulsion prepared at pH 5.0 showed higher apparent viscosity and viscoelasticity than other pH conditions, which might prevent droplets from flocculating. The Pickering emulsions obtained at pH 5.0 were spherical droplets with a uniform size distribution and a mean diameter of 9.54 μm, and they exhibited excellent stability during 28 days of storage. The morphological structures of the emulsions investigated by confocal laser scanning microscopy and scanning electron microscopy indicated that the CMCD-ODA Pickering emulsion obtained at pH 5.0 was stabilized by loading amphiphilic CMCD-ODA polymer around the spherical oil droplets and forming a weak gel network structure. The CEO-loaded CMCD-ODA emulsions had higher antioxidant capacity than free CEO after 28 days of storage at pH 5.0. Given the good emulsion stability, antioxidant activity, and great antibacterial effect, the CEO-loaded carboxymethyl curdlan Pickering emulsion has promising applications in food, cosmetic, and biomedicine industries.

Kinetic Study of Encapsulated β-Carotene Degradation in Aqueous Environments: A Review

The provitamin A activity of β-carotene is of primary interest to address one of the world's major malnutrition concerns. β carotene is a fat-soluble compound and its bioavailability from natural sources is very poor. Hence, studies have been focused on the development of specific core/shell micro- or nano-structures that encapsulate β-carotene in order to allow its dispersion in liquid systems and improve its bioavailability. One key objective when developing these structures is also to accomplish β-carotene stability. The aim of this review is to collect kinetic data (rate constants, activation energy) on the degradation of encapsulated β-carotene in order to derive knowledge on the possibility for these systems to be scaled-up to the industrial production of functional foods. Results showed that most of the nano- and micro-structures designed for β-carotene encapsulation and dispersion in the water phase provide better protection with respect to a natural matrix, such as carrot juice, increasing the β-carotene half-life from about 30 d to more than 100 d at room temperature. One promising approach to increase β-carotene stability was found to be the use of wall material, surfactants, or co-encapsulated compounds with antioxidant activity. Moreover, a successful approach was the design of structures, where the core is partially or fully solidified; alternatively, either the core or the interface or the outer phase are gelled. The data collected could serve as a basis for the rational design of structures for β-carotene encapsulation, where new ingredients, especially the extraordinary natural array of hydrocolloids, are applied.

Polyphenol-Polysaccharide Complex: Preparation, Characterization and Potential Utilization in Food and Health

Polysaccharides and polyphenols coexist in many plant-based food products. Polyphenol-polysaccharide interactions may affect the physicochemical, functional, and physiological properties, such as digestibility, bioavailability, and stability, of plant-based foods. In this review, the interactions (physically or covalently linked) between the selected polysaccharides and polyphenols are summarized. The preparation and structural characterization of the polyphenol-polysaccharide conjugates, their structural-interaction relationships, and the effects of the interactions on functional and physiological properties of the polyphenol and polysaccharide molecules are reviewed. Moreover, potential applications of polyphenol-polysaccharide conjugates are discussed. This review aids in a comprehensive understanding of the synthetic strategy, beneficial bioactivity, and potential application of polyphenol-polysaccharide complexes. Expected final online publication date for the Annual Review of Food Science and Technology, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Recent Advances in Biological Activity, New Formulations and Prodrugs of Ferulic Acid

Trans-ferulic acid (FA) is a derivative of 4-hydroxycinnamic acid, which is found in many food products, fruits and beverages. It has scientifically proven antioxidant, anti-inflammatory and antibacterial properties. However, its low ability to permeate through biological barriers (e.g., the blood-brain barrier, BBB), its low bioavailability and its fast elimination from the gastrointestinal tract after oral administration limit its clinical use, e.g., for the treatment of neurodegenerative diseases, such as Alzheimer's disease. Therefore, new nanotechnological approaches are developed in order to regulate intracellular transport of ferulic acid. The objective of this review is to summarize the last decade's research on biological properties of ferulic acid and innovative ways of its delivery, supporting pharmacological therapy.

A review presenting production, characterization, and applications of biopolymer curdlan in food and pharmaceutical sectors

Curdlan is an exopolysaccharide, specifically a homopolysaccharide, with a high molecular weight that is made up entirely of monomeric glucose molecules connected by β-1,3-glycosidic bonds. Curdlan was first isolated in 1962 by Harada and his colleagues from Alcaligenes faecalis var myxogenes 10C3. Microbial synthesis of this curdlan is mainly associated with soil bacteria. Preliminary screening of curdlan-producing microorganisms is done on aniline blue media. The aniline blue positive microorganisms are subjected to submerged fermentation for the production of curdlan. To improve the yield of curdlan produced, various optimization techniques are employed such as Plackett–Burman, response surface methodology, and others. Curdlan can be characterized by its morphology, gel strength, its infrared, and magnetic resonances among many other characteristics. Due to its distinctive physicochemical and rheological properties, it has gained immense popularity in the food, biomedical, and pharmaceutical sectors. However, curdlan’s functionality can be improved by chemically modifying curdlan to obtain grafted curdlan, hydrogels, and nanocomposites which are discussed in detail herewith. Curdlan was authorized to be used in the food industry by the United States Food and Drug Administration in 1996 and also in 1989 in Taiwan, Japan, and Korea. Over the years, many patents using curdlan have also been filed from different parts of the world. This review provides information about its structure, biosynthesis, production strategies, optimization, characterization, applications, and patents.

Graphic abstract

Construction and characterization of antioxidative ferulic acid-grafted carboxylic curdlan conjugates and their contributions on β-carotene storage stability

Grafting copolymerization of phenolic acids onto polysaccharides is an important strategy to improve their biological activities. In this study, ferulic acid (FA)-grafted carboxylic curdlan conjugates, namely, Cur-8-g-FA, Cur-24-g-FA, and Cur-48-g-FA, were synthesized by free radical-induced grafting. Results showed that FA was covalently grafted onto carboxylic curdlans via ester bonds. The grafting ratios of Cur-8-g-FA, Cur-24-g-FA, and Cur-48-g-FA were 223.03 ± 12.63, 115.63 ± 5.96, and 152.30 ± 4.57 mg FA/g, respectively, which were related with the carboxylate contents, molecular weights, and chain conformations of carboxylic curdlans. Compared with carboxylic curdlans, the FA-grafted carboxylic curdlan conjugates had lower thermal stability, molecular weight, and rheological property and looser surface morphology but had more prominent antioxidant benefits in vitro, which were proportional to their grafting ratios. Moreover, good storage stability against chemical degradation was exhibited by the β-carotene in Pickering emulsions stabilized by Cur-8-g-FA with a high grafting ratio and molecular weight.