Thermoresponsive starch-based particle-stabilized Pickering high internal phase emulsions as nutraceutical containers for controlled release

Advanced treatment and reuse of dye wastewater using thermo-irreversible on/off switch starch with disruption of dissolution/precipitation dynamic equilibrium

The development of irreversible on/off switching materials is a potential strategy for unidirectional capture and encapsulation of pollutants, preventing the pollutant leakage problem resulting from the reversible dissolution of flocculants. Herein, a thermo-irreversible on/off switch starch (TISS) is prepared through modifying starch by etherification grafting glycidyl phenyl ether and 2,4-bis(dimethylamino)-6-chloro-[1,3,5]-triazine. It breaks the dissolution/precipitation dynamic equilibrium across heating-cooling cycles by thermal-induced irreversible coil-to-globule self-assembly of polymer chains, resulting in a 50-fold decrease in polymer solubility. Particularly, TISS shows a superior double-locking effect on pollutants and flocculants through its unique irreversible conformation memory capability, leading to a high-quality reuse water. 99.9 % of reactive brilliant red dye and 97.9 % of TISS remain fixed within sludge flocs even after prolonged immersion in cold water at 24 °C for 60 days. Furthermore, direct recycling and reuse of dye-bath energy can be realized through the isothermal flocculation and dyeing method, showing a 75 % decrease in energy consumption after three cycles compared to traditional dyeing techniques. This work presents a novel approach to constructing an irreversible pollutant delivery system using thermo-irreversible on/off switch starch, addressing the problems of high energy dissipation and water quality fluctuations during wastewater treatment.

Structure, characterization, and application of a novel thermoreversible emulsion gel fabricated by citrate agar

A novel thermoreversible emulsion gel was successfully prepared with citrate agar (CA) as the sole emulsifier. Compared with native agar gel emulsion, CA gel emulsion (CAGE) formed a stable emulsion gel when the CA concentration was increased to 1.25 % (w/w). Results of time-temperature scanning experiments showed that the emulsion gel rapidly transformed into liquid emulsion when heated to 40-50 °C and then solidified into emulsion gel after cooling to the critical temperature of solidification. The emulsion gel had stable sol-gel transformation ability after seven cycles repeated heating-cooling treatment (HCT) at 85 °C and 4 °C. However, the stability of emulsion gels gradually decreased because of the large-droplet formation during heating, which affected the CA molecular-reconfiguration network structure in cooling. The conjunction analysis of microstructure and properties of the emulsion gel indicated that its stability depended primarily on the spatial repulsion and electrostatic repulsion provided by CA gel, and the main factor driving thermal reversibility was the temperature-responsive gelation performance of CA. The retention of quercetin was >90.23 % after seven HCTs because CAGEG enhanced the homogeneity and stability of the droplets.

Enhanced stability and biocompatibility of HIPEs stabilized by cyclodextrin-metal organic frameworks with inclusion of resveratrol and soy protein isolate for β-carotene delivery

High internal phase Pickering emulsions (HIPEs) constitute a significant research domain within colloid interface chemistry, addressing the demand for robust emulsion systems across various applications. An innovative nanoparticle, synthesized from a cyclodextrin metal-organic framework encapsulated with a composite of resveratrol and soy isolate protein (RCS), was employed to fortify a high internal phase emulsion. The emulsion's three-dimensional printing capabilities, alongside the encapsulated delivery efficacy for β-carotene, were thoroughly examined. Cyclodextrin metal-organic frameworks (CD-MOFs), facilitated by cellulose nanofibrils, were synthesized to yield particles at the nanoscale, maintaining a remarkable 97.67 % cellular viability at an elevated concentration of 1000 μg/ml. The RCS nanoparticles demonstrated thermal stability and antioxidant capacities surpassing those of CD-MOF. The integration of soybean isolate protein augmented both the hydrophobicity (from 21.95 ± 0.64° to 59.15 ± 0.78°) and the interfacial tension (from 14.36 ± 0.46 mN/m to 5.34 ± 0.81 mN/m) of the CD-MOF encapsulated with resveratrol, thereby enhancing the RCS nanoparticles' adsorption at the oil-water interface with greater stability. The durability of the RCS-stabilized high internal phase emulsions was contingent upon the RCS concentration. Emulsions stabilized with 5 wt%-RCS exhibited optimal physical and chemical robustness, demonstrating superior performance in emulsion 3D printing and β-carotene encapsulation delivery. This investigation furnishes a novel perspective on the amalgamation of food customization and precision nutrition.

New Approach for Preparation of Porous Polymers with Reversible Pore Structures for a Highly Safe Smart Supercapacitor

Porous polymers have many industrial applications, but their pore structures (open or closed) are usually fixed during polymerization. In this study, polymers with reversible and controllable pore structures, namely, thermosensitive porous hydrogels with regulated volume phase transition temperature, were prepared using a Pickering high-internal-phase emulsion as the template. Upon heating, the hydrogels transformed not only in their wettability (between hydrophilicity and hydrophobicity with water contact angles of 21.8 and 100.9°) but also their pore structure (between open through-holes and closed holes with pore throat sizes of 15.58 and 0 μm, respectively) in a short time (<10 s). When the hydrogel was used as a separator in smart supercapacitors (SCs), this behavior effectively limited the path of electrolyte migration, reducing the chance of conflagration accidents. Moreover, by utilizing the highly reversible pore structures and wettability of the porous hydrogel, reversible charging and discharging were restored after the system cooled down. This work not only provides great guidance for preparing porous polymers with reversible pore structures but also paves the way for designing smart SCs with enhanced safety.

A review of high internal phase Pickering emulsions: Stabilization, rheology, and 3D printing application

High internal phase Pickering emulsion (HIPPE) is renowned for its exceptionally high-volume fraction of internal phase, leading to flocculated yet deformed emulsion droplets and unique rheological behaviors such as shear-thinning property, viscoelasticity, and thixotropic recovery. Alongside the inherent features of regular emulsion systems, such as large interfacial area and well-mixture of two immiscible liquids, the HIPPEs have been emerging as building blocks to construct three-dimensional (3D) scaffolds with customized structures and programmable functions using an extrusion-based 3D printing technique, making 3D-printed HIPPE-based scaffolds attract widespread interest from various fields such as food science, biotechnology, environmental science, and energy transfer. Herein, the recent advances in preparing suitable HIPPEs as 3D printing inks for various applied fields are reviewed. This work begins with the stabilization mechanism of HIPPEs, followed by introducing the origin of their distinctive rheological behaviors and strategies to adjust the rheological behaviors to prepare more eligible HIPPEs as printing inks. Then, the compatibility between extrusion-based 3D printing and HIPPEs as building blocks was discussed, followed by a summary of the potential applications using 3D-printed HIPPE-based scaffolds. Finally, limitations and future perspectives on preparing HIPPE-based materials using extrusion-based 3D printing were presented.

Encapsulation of ferulic acid in high internal phase Pickering emulsions stabilized using nonenyl succinic anhydride (NSA) and octenyl succinic anhydride (OSA) modified quinoa and maize starch nanoparticles

High internal phase Pickering emulsions (HIPPEs) stabilized using modified starch nanoparticles (SNPs) were studied as a delivery system for ferulic acid (FA). The quinoa (Q, 153 nm) and maize (M, 221 nm) SNPs were prepared by sono-precipitation and modified with nonenyl succinic anhydride (NSA) and octenyl succinic acid (OSA). The FA-encapsulated HIPPEs obtained showed neither coalescence nor Ostwald ripening, as reflected by emulsion index and droplet size measurements. Confocal laser scanning microscopy revealed FA entrapped droplets surrounded by the SNPs layer. The rheological measurements confirmed strong network formation and long-term stability. In vitro studies (pH 7.4, 96 h) showed sustained release of FA from the gel network. After 15 days, the encapsulation efficiencies for HIPPEs stabilized with both NSA and OSA modified QSNPs and MSNPs were close to 99%. The results showed that FA could be feasibly encapsulated in HIPPEs stabilized using modified SNPs.

Development, application and future trends of starch-based delivery systems for nutraceuticals: A review

As a natural biopolymer, starch is ideally adapted as an encapsulant material for nutraceutical delivery systems due to its unique nature of extensive sources, versatility and high biocompatibility. This review offers an outline of recent advances in the development of starch-based delivery systems. The structure and functional properties of starch in encapsulating and delivering bioactive ingredients are first introduced. Structural modification of starch improves the functionalities and extends the applications of starch in novel delivery systems. Then, various nutraceutical delivery systems are systematically summarized, which include porous starch, starch particle, amylose inclusion complex, cyclodextrin, gel, edible film and emulsion. Next, the delivery process of nutraceuticals is discussed in two parts: digestion and release. Intestinal digestion plays an important role during the whole digestion process of starch-based delivery systems. Moreover, controlled release of bioactives can be achieved by porous starch, starch-bioactive complexation and core-shell structure. Finally, the challenges of the existing starch-based delivery systems are deliberated, and the directions for future research are pointed out. Composite delivery carriers, co-delivery, intelligent delivery, delivery in real food systems, and reuse of agricultural wastes may be the research trends for starch-based delivery systems in the future.

Biopolymer-based pickering high internal phase emulsions: Intrinsic composition of matrix components, fundamental characteristics and perspective

Pickering HIPEs have received tremendous attention in recent years due to their superior stability and unique solid-like and rheological properties. Biopolymer-based colloidal particles derived from proteins, polysaccharides and polyphenols have been demonstrated to be safety stabilizers for the construction of Pickering HIPEs, which can meet the demands of consumers for "all-natural" products and provide "clean-label" foods. Furthermore, the functionality of these biopolymers can be further extended by forming composite, conjugated and multi-component colloidal particles, which can be used to modulate the properties of the interfacial layer, thereby adjusting the performance and stability of Pickering HIPEs. In this review, the factors affecting the interfacial behavior and adsorption characteristics of colloidal particles are discussed. The intrinsic composition of matrix components and fundamental characteristics of Pickering HIPEs are emphatically summarized, and the emerging applications of Pickering HIPEs in the food industry are reviewed. Inspired by these findings, future perspectives concerning this field are also put forward, including (1) the exploration of the interactions between biopolymers used to produce Pickering HIPEs and target food ingredients, and the influence of the added biopolymers on the flavor and mouthfeel of the products, (2) the investigation of the digestion properties of Pickering HIPEs under oral administration, and (3) the fabrication of stimulus-responsive or transparent Pickering HIPEs. This review will give a reference for exploring more natural biopolymers for Pickering HIPEs application development.

Formulation and stabilization of high internal phase emulsions: Stabilization by cellulose nanocrystals and gelatinized soluble starch

In this work, high internal phase emulsions (HIPEs) stabilized by naturally derived cellulose nanocrystals (CNC) and gelatinized soluble starch (GSS) were fabricated to stabilize oregano essential oil (OEO) in the absence of surfactant. The physical properties, microstructures, rheological properties, and storage stability of HIPEs were investigated by adjusting CNC contents (0.2, 0.3, 0.4 and 0.5 wt%) and starch concentration (4.5 wt%). The results revealed that CNC-GSS stabilized HIPEs exhibited good storage stability within one month and the smallest droplets size at a CNC concentration of 0.4 wt%. The emulsion volume fractions of 0.2, 0.3, 0.4 and 0.5 wt% CNC-GSS stabilized HIPEs after centrifugation reached 77.58, 82.05, 94.22, and 91.41 %, respectively. The effect of native CNC and GSS were analyzed to understand the stability mechanisms of HIPEs. The results revealed that CNC could be used as an effective stabilizer and emulsifier to fabricate the stable and gel-like HIPEs with tunable microstructure and rheological properties.

Protein-Based High Internal Phase Pickering Emulsions: A Review of Their Fabrication, Composition and Future Perspectives in the Food Industry

Protein-based high internal phase Pickering emulsions (HIPEs) are emulsions using protein particles as a stabilizer in which the volume fraction of the dispersed phase exceeds 74%. Stabilizers are irreversibly adsorbed at the interface of the oil phase and water phase to maintain the droplet structure. Protein-based HIPEs have shown great potential for a variety of fields, including foods, due to the wide range of materials, simple preparation, and good biocompatibility. This review introduces the preparation routes of protein-based HIPEs and summarizes and classifies the preparation methods of protein stabilizers according to their formation mechanism. Further outlined are the types and properties of protein stabilizers used in the present studies, the composition of the oil phase, the encapsulating substances, and the properties of the constituted protein-based HIPEs. Finally, future development of protein-based HIPEs was explored, such as the development of protein-based stabilizers, the improvement of emulsification technology, and the quality control of stabilizers and protein-based HIPEs.

Research Progress of Food-Grade High Internal Phase Pickering Emulsions and Their Application in 3D Printing

High internal phase Pickering emulsion (HIPPE) is a type of emulsion stabilized by solid particles irreversibly adsorbed on an interfacial film, and the volume fraction of the dispersed phase (Φ) is larger than the maximum packing volume fraction (Φ_max). Proteins, polysaccharides, and their composite particles can be used as good particle stabilizers. The contact angle can most intuitively demonstrate the hydrophilicity and hydrophobicity of the particles and also determines the type of emulsions (O/W or W/O type). Particles' three-phase contact angles can be adjusted to about 90° by compounding or modification, which is more conducive to emulsion stability. As a shear thinning pseudoplastic fluid, HIPPE can be extruded smoothly through 3D printer nozzles, and its high storage modulus can support the structure of printed products. There is huge potential for future applications in 3D printing of food. This work reviewed the biomacromolecules that can be used to stabilize food-grade HIPPE, the stabilization mechanism of the emulsions, and the research progress of food 3D printing to provide a reference for the development of advanced food products based on HIPPE.

Engineering Emulsion Gels as Functional Colloids Emphasizing Food Applications: A Review

Gels are functional materials with well-defined structures (three-dimensional networks) assembled from the dispersed colloids, and capable of containing a large amount of water, oil, or air (by replacing the liquid within the gel pores), known as a hydrogel, oleogel, and aerogel, respectively. An emulsion gel is a gelled matrix filled with emulsion dispersion in which at least one phase, either continuous phase or dispersed phase forms spatial networks leading to the formation of a semisolid texture. Recently, the interest in the application of gels as functional colloids has attracted great attention in the food industry due to their tunable morphology and microstructure, promising physicochemical, mechanical, and functional properties, and superior stability, as well as controlled release, features for the encapsulated bioactive compounds. This article covers recent research progress on functional colloids (emulsion gels), including their fabrication, classification (protein-, polysaccharide-, and mixed emulsion gels), and properties specifically those related to the gel-body interactions (texture perception, digestion, and absorption), and industrial applications. The emerging applications, including encapsulation and controlled release, texture design and modification, fat replacement, and probiotics delivery are summarized. A summary of future perspectives to promote emulsion gels' use as functional colloids and delivery systems for scouting potential new applications in the food industry is also proposed. Emulsion gels are promising colloids being used to tailor breakdown behavior and sensory perception of food, as well as for the processing, transportation, and targeted release of food additives, functional ingredients, and bioactive substances with flexibility in designing structural and functional parameters.

Fabrication of food-grade Pickering high internal phase emulsions (HIPEs) stabilized by a dihydromyricetin and lysozyme mixture

This study evaluated the feasibility of fabricating food-grade HIPEs using a dihydromyricetin and lysozyme mixture. The effects of the oil phase volume fraction (φ), composition (lysozyme:dihydromyricetin, k), and addition amount (w) of the mixture on the formation and properties of the HIPEs were analyzed. Then, the interactions of dihydromyricetin and lysozyme were investigated. The results indicated that when w was 0.4%, HIPEs with φ value of 90% could be obtained. Furthermore, the k also affected the microstructure, mechanical properties, oil oxidation, and lutein protection ability of the HIPEs. However, the presence of dihydromyricetin did not affect lysozyme activity. Both isothermal titration calorimetry and molecular simulations proved that they did not form a typical host-guest complex. But, dihydromyricetin could absorb on the lysozyme surface. Therefore, we speculated that lysozyme and dihydromyricetin particles could overlap and form a 3D network structure to stabilize the HIPEs, which was consistent with the microstructure observations.

High internal phase emulsions stabilized by native and heat-treated lactoferrin-carboxymethyl chitosan complexes: Comparison of molecular and granular emulsifiers

While the high internal phase emulsions (HIPEs) have been formed by food-grade biopolymers and granules have been widely reported, it is not known which components are more effective. In this work, we first used heat-treated lactoferrin (LF)-carboxymethyl chitosan (CMCTS) granules and native LF-CMCTS physical mixtures as emulsifiers to form HIPEs. The results showed that the interfacial behavior and emulsifying properties of the two complexes were controlled by the ratio of LF-CMCTS and the optimal ratio of LF to CMCTS was 1:1. Heated LF-CMCTS granules anchored to the water-oil interface and formed an elastic shell to stabilize HIPEs, while unheated LF-CMCTS complexes formed a thick film layer to stabilize HIPEs. Both HIPEs could act as delivery systems loaded with curcumin, and they showed better protection of curcumin than Tween-80 under light. This study provides a new basis for the design of LF-based HIPEs systems loaded with lipophilic food functional ingredients.

Temperature-responsive Pickering high internal phase emulsions for recyclable efficient interfacial biocatalysis

The field of biocatalysis is expanding owing to the increasing demand for efficient low-cost green chemical processes. However, a feasible strategy for achieving product separation, enzyme recovery, and high catalytic efficiency in biocatalysis remains elusive. Herein, we present thermoresponsive Pickering high internal phase emulsions (HIPEs) as controllable scaffolds for efficient biocatalysis; these HIPEs demonstrate a transition between emulsification and demulsification depending on temperature. Ultra-high-surface-area Pickering HIPEs were stabilized by Candida antarctica lipase B immobilized on starch particles modified with butyl glycidyl ether and glycidyl trimethyl ammonium chloride, thus simplifying the separation and reuse processes and significantly improving the catalytic efficiency. In addition, the switching temperature can be precisely tuned by adjusting the degree of substitution of the modified starches to meet the temperature demands of various enzymes. We believe that this system provides a green platform for various interfacial biocatalytic processes of industrial interest.

The thermoresponsive Pickering high internal phase emulsions stabilized by starch particles as controllable scaffolds for efficient biocatalysis, which simplified the separation and reuse processes and significantly improved the catalytic efficiency.

High internal phase Pickering emulsions stabilized by a cod protein-chitosan nanocomplex for astaxanthin delivery

High internal phase Pickering emulsions (HIPPEs) stabilized by a food protein have attracted widespread attention. In this study, a novel cod protein-chitosan nanocomplex was prepared through electrostatic interactions and used as a particle emulsifier to stabilize the oil-water interface. The application of the cod protein-chitosan nanocomplex was demonstrated in the formation of stable HIPPEs with an internal phase as high as 84%. The influence of the system composition on the stability, microstructure and rheology of the HIPPEs was determined. The HIPPEs stabilized by the cod protein-chitosan nanocomplex formed a compact three-dimensional network structure, which gave the emulsion a higher storage modulus, viscoelasticity and good thixotropy. Interestingly, the chemical stability of astaxanthin was significantly improved by the developed HIPPEs. The bioavailability of astaxanthin in the HIPPEs stabilized by the nanocomplexes of 2.0% (w/w) cod protein and 0.1% (w/w) chitosan reached 49%. In summary, these results demonstrated that the food-grade cod protein-chitosan nanocomplex had potential in the development of HIPPEs, which could be used as carriers for hydrophobic bioactive compound delivery.

Polysaccharide-Based Nanoparticles as Pickering Emulsifiers in Emulsion Formulations and Heterogenous Polymerization Systems

Bio-based Pickering emulsifiers are a nontoxic alternative to surfactants in emulsion formulations and heterogenous polymerizations. Recent demand for biocompatible and sustainable formulations has accelerated academic interest in polysaccharide-based nanoparticles as Pickering emulsifiers. Despite the environmental advantages, the inherent hydrophilicity of polysaccharides and their nanoparticles limits efficiency and application range. Modification of the polysaccharide surface is often required in the development of ultrastable, functional, and water-in-oil (W/O) systems. Complex surface modification calls into question the sustainability of polysaccharide-based nanoparticles and is identified as a significant barrier to commercialization. This review summarizes the use of nanocelluloses, -starches, and -chitins as Pickering emulsifiers, highlights trends and best practices in surface modification, and provides recommendations to expedite commercialization.

pH-Responsive Pickering high internal phase emulsions stabilized by Waterborne polyurethane

HYPOTHESIS

Waterborne polyurethane (WPU) is a common colloidal dispersion that can aggregate in the aqueous phase to form nanoparticles with hydrophobic polyurethane chains as the core and hydrophilic ionic groups as the shell. Considering their structure and pH-responsive functional groups, WPU nanoparticles could be ideal particulate emulsifiers for preparing pH-responsive Pickering high internal phase emulsions (HIPEs).

EXPERIMENTS

A series of anionic WPU with different content of 2,2-bis(hydroxymethyl)propionic acid (DMPA) side chains were synthesized via a polyaddition reaction. The DMPA content, size, ζ-potential, and interfacial behaviors of WPU were then investigated. Furthermore, the effects of particle concentration, internal phase fraction (ϕ), oil type, and pH values on the Pickering HIPEs' morphology, stability, and rheological behaviors were systematically studied. Finally, we demonstrated the emulsification-demulsification process of WPU-stabilized Pickering HIPEs and discussed its mechanism.

FINDINGS

Oil-in-water (O/W) Pickering HIPEs with tailored morphology and excellent pH-responsiveness were prepared from anionic WPU nanoparticles. The WPU concentration, ϕ, and oil type had a large impact on the formation and mean droplet size of the WPU-stabilized emulsions. Rheology analysis demonstrated that the strictly limited movement of droplets endowed the WPU-stabilized HIPEs with high stability, shear sensitivity, and excellent thixotropic recovery. By simply changing the aqueous-phase pH value, the WPU-stabilized HIPEs could undergo more than ten emulsification-demulsification cycles, as the physical and interfacial properties of WPU nanoparticles were pH-dependent. The excellent performance of the WPU-stabilized pH-responsive Pickering HIPEs exhibited their potential practical applications, such as for oil transportation and recovery, emulsion polymerization, and heterogeneous catalysis.

Recent Innovations in Emulsion Science and Technology for Food Applications

Emulsion technology has been used for decades in the food industry to create a diverse range of products, including homogenized milk, creams, dips, dressings, sauces, desserts, and toppings. Recently, however, there have been important advances in emulsion science that are leading to new approaches to improving food quality and functionality. This article provides an overview of a number of these advanced emulsion technologies, including Pickering emulsions, high internal phase emulsions (HIPEs), nanoemulsions, and multiple emulsions. Pickering emulsions are stabilized by particle-based emulsifiers, which may be synthetic or natural, rather than conventional molecular emulsifiers. HIPEs are emulsions where the concentration of the disperse phase exceeds the close packing limit (usually >74%), which leads to novel textural properties and high resistance to gravitational separation. Nanoemulsions contain very small droplets (typically d < 200 nm), which leads to useful functional attributes, such as high optical clarity, resistance to gravitational separation and aggregation, rapid digestion, and high bioavailability. Multiple emulsions contain droplets that have smaller immiscible droplets inside them, which can be used for reduced-calorie, encapsulation, and delivery purposes. This new generation of advanced emulsions may lead to food and beverage products with improved quality, health, and sustainability.

Fabrication of food-grade Pickering high internal phase emulsions stabilized by the mixture of β-cyclodextrin and sugar beet pectin

Food-grade Pickering high internal phase emulsions (HIPEs) stabilized by a mixture of β-cyclodextrin (β-CD) and sugar beet pectin (SBP) were fabricated for the first time. The factors affecting the microstructures, mechanical properties, and stabilities of the Pickering HIPEs were systematically investigated. The corresponding hybrid particles were also separated and characterized to reveal the formation mechanism. The results indicated that the mixture could induce the formation of HIPEs with an oil phase volume fraction (φ) of 75% using a one-step high-speed shearing process at room temperature. The composition (the mass ratio of β-CD to SBP, R_c/s) and concentration (W) of the mixture had significant effects on the formation and properties of HIPEs. When W ≥ 1.0% and R_c/s = 2:2 or 3:1, HIPEs had smaller oil droplets, higher gel strengths, better centrifugation stabilities and lutein protection effects. The spectral analysis suggested that SBP could adhere to the surface of β-CD particles to form hybrid particles during the homogenization. Compared with native β-CD particles, these hybrid particles had higher ζ-potential absolute values, and the SBP could also increase the viscosity of the aqueous phase, which contributed to the formation and properties of these HIPEs.