Stable Pickering Emulsions Research Articles

Development and Characterization of Pickering Emulsion Stabilized by Walnut Protein Isolate Nanoparticles.

This study was conducted to prepare walnut protein isolate nanoparticles (nano-WalPI) by pH-cycling, combined with the ultrasound method, to investigate the impact of various nano-WalPI concentrations (0.5~2.5%) and oil volume fractions (20~70%) on the stability of Pickering emulsion, and to improve the comprehensive utilization of walnut residue. The nano-WalPI was uniform in size (average size of 108 nm) with good emulsification properties (emulsifying activity index and stability index of 32.79 m2/g and 1423.94 min, respectively), and it could form a stable O/W-type Pickering emulsion. When the nano-WalPI concentration was 2.0% and the oil volume fraction was 60%, the best stability of Pickering emulsions was achieved with an average size of 3.33 μm, and an elastic weak gel network structure with good thermal stability and storage stability was formed. In addition, the emulsion creaming index value of the Pickering emulsion was 4.67% after 15 days of storage. This study provides unique ideas and a practical framework for the development and application of stabilizers for food-grade Pickering emulsions.

Preparation and characterisation of linalool oil-in-water starch-based Pickering emulsions and the effects of the addition of cellulose nanocrystals on their stability

Creaming could be generated during storage of the starch-based Pickering emulsions. And cellulose nanocrystals in the solution are usually dispersed by relatively strong mechanical force, otherwise they may appear in the form of aggregates. In this work, we investigated the effects of cellulose nanocrystals on the stability of the starch-based Pickering emulsions. Results showed that the stability of Pickering emulsions was significantly improved by adding cellulose nanocrystals. Cellulose nanocrystals increased the viscosity, electrostatic repulsion and steric hindrance of the emulsions, which delayed the movement of droplets and obstructed the contact between droplets. This study provides new insights into the preparation and stabilisation of starch-based Pickering emulsions.

Citrus derived Pickering emulsion stabilized by insoluble citrus dietary fiber modified by ultra-high pressure

To make the most of citrus residues, Pickering emulsions containing bergamot oil and medium chain triglyceride were formulated using insoluble citrus dietary fiber (ICDF) particles from citrus residues after pectin and essential oil were extracted. The ICDF particles were treated using ultra-high pressure (UHP, 100, 200, 300, 400, 500 and 600 MPa) to improve their emulsifying properties. UHP did not affect the composition of ICDFs. The treatments at 100 and 200 MPa decreased the ICDF particle size and promoted interfacial adsorption and network formation in the continuous phase, improving the emulsifying property and stability of the Pickering emulsion. This study would lay a foundation for the preparation of stable Pickering emulsions using citrus fibers and the comprehensive utilization of citrus residues.

Fabrication of glycerol functionalized silica nanoparticles via pickering emulsion for durable, superhydrophobic fabrics

Stable oil-in-water Pickering emulsions were successfully developed via the simplest approach: amine-terminated polydimethylsiloxane with very high viscosity and low surface free energy was encapsulated by glycerol functionalized silica NPs using a rotor-stator device. The factors affecting the Pickering emulsions performance were investigated. At a certain process (silica NPs concentration: 3 wt%, Oil/water ratio: 1:20, emulsifying speed: 15,000 rpm, emulsifying time: 5 min), it gave smaller and more stable emulsions. Then the Pickering emulsion was applied on plain weave cotton and polyester fabrics through conventional pad-dry-cure method. The coated substrates showed superhydrophobicity and maintained good water-repellency even after 30 standard laundering cycles, which are attributed to the synergistic effect of low surface free energy composite and hierarchical roughness. By contrast, fabrics coated with classical emulsifiers stabilizing Pickering emulsion adopting the same recipes were quickly wetted by liquid droplets.

Evaluation of alginate hydrogel stabilized Pickering emulsion liquid membrane for methylene blue extraction from aqueous solutions

In this work, the potential of an alginate hydrogel stabilized Pickering emulsion liquid membrane (PELM) for methylene blue (MB) extraction from aqueous solution was investigated. The waste cooking oil (WCO) was used as a green diluent, aliquat 336 was used as a carrier, and potassium hydroxide (KOH) was used as a stripping agent to synthesize PELM. The use of WCO replaces the hazardous and ecologically harmful petroleum-based organic solvents that are frequently employed in PELM production. The MB removal was maximum at internal phase concentration 1:5, initial external feed phase concentration 5 ppm, emulsifier concentration 1% (w/w), carrier concentration 20% (w/w) and O/A ratio 1:1. The mechanism of MB extraction by PELM was elucidated. The maximum extraction efficiency was 91.58% at optimum condition. The kinetic study revealed that the MB extraction by PELM followed a zero-order reaction. Furthermore, thermodynamic analysis indicated that the extraction process was both endothermic and spontaneous in nature. Overall, the findings of this study demonstrate the potential of PELM as a promising technique for the extraction of MB from aqueous solutions using alginate hydrogel as an eco-friendly and sustainable materials.

Phase Diagram of Pickering Emulsions Stabilized by Cellulose Nanocrystals.

Cellulose is a promising renewable and biocompatible biopolymer for stabilizing Pickering emulsions (PEs). In the present study, PEs were produced by low-frequency ultrasounds with cellulose nanocrystals (CNCs) and caprylic/capric triglycerides. Phase diagrams allowed to understand mechanisms of formation and long-term stabilization of PEs. Emulsion type, continuous phase viscosity, and yield of oil incorporation were studied after PEs formation. Droplet size, oil release, and stability were measured weekly up to 56 days of storage. Results showed that oil mass fraction above 70% w/w led to unstable W/O PEs. Lower oil mass fraction formed O/W PEs of stability depending on CNC content and oil mass fraction. Droplet size stability increased with CNCs/oil ratio. A very low CNCs/oil ratio led to phase separation and oil release. High CNC content stabilized oil droplets surface, increased aqueous phase viscosity, and prevented creaming. Highly stable PEs were produced for CNC content above 3% (w/w) and oil mass fraction below 50% (w/w). Mechanisms for PEs formation and stabilization were proposed for various CNC contents and oil mass fractions.

Enzymatically produced nanocellulose as emulsifier for Pickering emulsion

With the increasing demand for label-friendly emulsion products, chemical treatments and the addition of non-natural ingredients are inadvisable in food, cosmetic, and pharmaceutical sectors. The current research proposed a green development strategy from nanocellulose production to emulsion preparation, i.e., enzymatically prepared nanocellulose (ENC) for stabilizing O/W Pickering emulsions. Benefiting from a mild enzymatic reaction, ENC inherently had low Zeta potential and oil/water interfacial tension, facilitating the formation of stable Pickering emulsions. Biphasic fluorescence staining, emulsion polymerization, and rheology were employed to investigate the emulsification characteristics of ENC, establishing the interfacial adsorption behavior and concentration-dependent phase behavior of ENC-stabilized Pickering emulsions. Importantly, due to strong particle-particle and interface-particle interactions dominated by van der Waals forces and hydrogen bonding, ENC-stabilized Pickering emulsions exhibited excellent stability under different temperatures, pH values, NaCl concentrations, and centrifugation. This work provides a green pathway for the development of nanocellulose-based Pickering emulsions.

Production of cellulose nanocrystals from tomato pomace as a food waste and their application for stabilizing of Pickering emulsions

This study aimed to purify cellulose from tomato pomace and investigate properties of obtained cellulose nanocrystals (CNC) and their application for stabilization of Pickering emulsion. The tomato pomace was treated under alkaline and bleaching to produce purified cellulose and cellulose nanocrystals were then extracted by acid hydrolysis at different temperatures and times. The best CNC were obtained under acid hydrolysis at 45 °C and 30 min with crystallinity of 79%. Analysis of FTIR, TGA, and DSC was used to investigate the chemical and thermal properties of cellulose nanocrystals. TEM images showed spherical particles with average diameter of 104 ± 10 nm. To test the emulsifying ability of CNC, different concentrations of nanocrystals were applied to stabilize an oil in water Pickering emulsion. By increased the CNCs concentration, stability of the emulsions to physical stress, heat, and storage time increased. The results of this study showed that cellulose nanocrystals as an environmentally friendly material can be extracted from a food waste and have the ability to stabilize oil in water emulsions.

Acetalized starch-based nanoparticles stabilized acid-sensitive Pickering emulsion as a potential antitumor drug carrier

Pickering emulsions are attracting increased attention owing to their therapeutic applications. However, the slow-release property of Pickering emulsions and the in vivo solid particle accumulation caused by the solid particle stabilizer film limit their applications in therapeutic delivery. In this study, drug-loaded, acid-sensitive Pickering emulsions were prepared using acetal-modified starch-based nanoparticles as stabilizers. The acetalized starch-based nanoparticles (Ace-SNPs) not only act as a solid-particle emulsifier to stabilize Pickering emulsions but also exhibit acid sensitivity and degradability, conducive to the destabilization of Pickering emulsions to release the drug and reduce the effect of particle accumulation in an acidic therapeutic environment. In vitro drug release profiles show that 50 % of curcumin was released in 12 h in an acidic medium (pH 5.4), whereas only 14 % of curcumin was released in 12 h at higher pH (7.4), indicating that the Ace-SNP stabilized Pickering emulsion possess good acid-responsive release characteristics in acidic environments. Moreover, acetalized starch-based nanoparticles and their degradation products showed good biocompatibility, and the resulting curcumin-loaded Pickering emulsions exhibited significant anticancer activity. These features suggest that the acetalized starch-based nanoparticle-stabilized Pickering emulsion has the potential for application as an antitumor drug carrier to enhance therapeutic effects.

High internal phase Pickering emulsions stabilized by modified sturgeon myofibrillar protein for quercetin delivery

In this study, the modified sturgeon myofibrillar protein was prepared by the combination of malondialdehyde and ultrasonic induction and used as the emulsifier to form a stable high internal phase Pickering emulsion (HIPPEs) with internal phase up to 75%. The results showed that combined modification reduced the fluorescence intensity, enhanced the surface hydrophobicity, changed the secondary structure, and made the protein particles smooth. The confocal laser scanning microscopy confirmed the formation of a stable HIPPEs. The interfacial tension and rheological properties of protein stabilized HIPPEs were improved by the combined modification and the encapsulation efficiency of quercetin reached 89.32%. In vitro digestion showed that the combined modified protein-stabilized HIPPEs significantly improved the rate of lipid digestion and the bioavailability of quercetin while reducing the degradation of quercetin. The findings indicated that the utilization of modified sturgeon myofibrillar protein to stabilize HIPPEs hold significant promise for various biological applications, owing to its capacity as a carrier for the regulated discharge of bioactive agents.

Optimized hydrophobic magnetic nanoparticles stabilized pickering emulsion for enhanced oil recovery in complex porous media of reservoir

With an extensive application of flooding technologies in oil recovery, traditional emulsion flooding has seen many limits due to its poor stability and easy demulsification. Pursuing a new robust emulsion plays a fundamental role in developing highly effective emulsion flooding technology. In this work, a novel Pickering emulsion with special magnetic nanoparticles Fe3O4@PDA@Si was designed and prepared. To disclose the flooding mechanism from magnetic nanoparticles, the physico-chemical characterization of Fe3O4@PDA@Si was systematically examined. Meanwhile, the flooding property of the constructed Pickering emulsion was evaluated on the basis of certain downhole conditions. The results showed that the synthesis of Fe3O4@PDA@Si nanoparticles was found to have a hydrophobic core-shell structure with a diameter of 30 nm. Pickering emulsions based on Fe3O4@PDA@Si nanoparticles at an oil-to-water ratio of 5:5, 50°C, the water separation rate was only 6% and the droplet diameter of the emulsion was approximately 15 μm in the ultra-depth-of-field microscope image. This demonstrates the excellent stability of Pickering emulsions and improves the problem of easy demulsification. We further discussed the oil displacement mechanism and enhanced oil recovery effect of this type of emulsion. The microscopic flooding experiment demonstrated that profile control of the Pickering emulsion played a more important role in enhanced recovery than emulsification denudation, with the emulsion system increasing oil recovery by 10.18% in the micro model. Core flooding experiments have established that the incremental oil recovery of the Pickering emulsion increases with decreasing core permeability, from 12.36% to 17.39% as permeability drops from 834.86 to 219.34 × 10−3 μm2. This new Pickering emulsion flooding system stabilized by Fe3O4@PDA@Si nanoparticles offers an option for enhanced oil recovery (EOR).

Pickering emulsion stabilized by parasin I and chitosan nanoparticles enhances protection against intestinal microbiota homeostasis by reducing inflammation in peritonitis mice

Although various researches evaluated the stability and drug loading efficiency of chitosan Pickering emulsion, few studies assessed the role and mechanism of emulsions in gut flora homeostasis. Thus, in the basics of our previously published natural and antimicrobial Pickering emulsions, the function of emulsion on the intestinal microbiota and inflammation response was explored in Kunming mice with peritonitis. The results showed that lipid/peptide nanoparticles emulsion (LPNE) and the chitosan peptide-embedded nanoparticles emulsion (CPENE) presented less collagen fiber than parasin I in peritoneal tissue, and CPENE could reduce peritoneal inflammation by decreasing the expression of NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3). The CPENE showed better histological morphology with a smaller fibrosis area in the spleen. Moreover, CPENE, LPNE, and parasin I-conjugated chitosan nanoparticle emulsion (PCNE) groups can increase the abundance of ABC transporters, DNA repair, and recombination proteins, and improve gut microbial. Furthermore, the Pickering emulsion showed a better protection effect on the composition and function of intestinal microbiota by decreasing interleukin-1β secretion and assembly of the inflammasome of NLRP3. These results could provide evidence for intestinal microbiota homeostasis of chitosan Pickering emulsion in inflammation-related diseases.

Nanofluids of Amphiphilic Kaolinite-Based Janus Nanosheets for Enhanced Oil Recovery: The Importance of Stable Emulsion.

To meet the increasing global demand for energy, better recovery of crude oil from reservoirs must be achieved using methods that are economical and environmentally benign. Here, we have developed a nanofluid of amphiphilic clay-based Janus nanosheets via a facile and scalable method that provides potential to enhance oil recovery. With the aid of dimethyl sulfoxide (DMSO) intercalation and ultrasonication, kaolinite was exfoliated into nanosheets (KaolNS) before being grafted with 3-methacryloxypropyl-triemethoxysilane (KH570) on the Alumina Octahedral Sheet at 40 and 70 °C to form amphiphilic Janus nanosheets (i.e., KaolKH@40 and KaolKH@70). The amphiphilicity and Janus nature of the KaolKH nanosheets have been well demonstrated, with distinct wettability obtained on two sides of the nanosheets, and the KaolKH@70 was more amphiphilic than the KaolKH@40. Upon preparing Pickering emulsion in a hydrophilic glass tube, the KaolKH@40 preferentially stabilized emulsions, while the KaolNS and KaolKH@70 tended to form an observable and high-strength elastic planar interfacial film at the oil-water interface as well as films climbing along the tube's surface, which were supposed to be the result of emulsion instability and the strong adherence of Janus nanosheets towards tube's surface. Subsequently, the KaolKH was grafted with poly(N-Isopropylacrylamide) (PNIPAAm), and the prepared thermo-responsive Janus nanosheets demonstrated a reversible transformation between stable emulsion and the observable interfacial films. Finally, when the samples were subjected to core flooding tests, the nanofluid containing 0.01 wt% KaolKH@40 that formed stable emulsions showed an enhanced oil recovery (EOR) rate of 22.37%, outperforming the other nanofluids that formed observable films (an EOR rate ~13%), showcasing the superiority of Pickering emulsions from interfacial films. This work demonstrates that KH-570-modified amphiphilic clay-based Janus nanosheets have the potential to be used to improve oil recovery, especially when it is able to form stable Pickering emulsions.

Properties of Pickering emulsions stabilized by cellulose nanocrystals extracted from litchi peels

The development of Pickering emulsions which are applicable to the food industry still remains challenges due to the limited availability for biocompatible, edible and natural emulsifiers. The purpose of this study was to extract cellulose nanocrystals from litchi peels (LP-CNCs), and evaluate their emulsifying properties. The results showed that the LP-CNCs were needle-like and they possessed high crystallinity (72.34 %) and aspect ratio. When the concentrations of LP-CNCs were >0.7 wt% or the contents of oil were no >0.5, stable Pickering emulsions were obtained. The microstructures of emulsions confirmed that LP-CNCs formed dense interfacial layers on the surface of oil droplets, which functioned as barriers to prevent aggregation and flocculation among droplets. Rheological results showed that the emulsions exhibited typical shear thinning behavior. The elastic of emulsions was dominant, and their gel strength could be enhanced by regulating the contents of emulsifiers or oil. Additionally, the Pickering emulsions stabilized by LP-CNCs showed extremely high pH, ionic strength, and temperature tolerance. This strategy provides an innovative alternative to tackle the dilemma of preparing highly stable Pickering emulsions using natural particles in food products.

High throughput disassembly of cellulose nanoribbons and colloidal stabilization of gel-like Pickering emulsions

We introduce a strategy to disintegrate cellulose microfibrils present in the cell walls of plant fibers. The process includes impregnation and mild oxidation followed by ultrasonication, which loosens the hydrophilic planes of crystalline cellulose while preserving the hydrophobic ones. The resultant molecularly-sized cellulose structures (cellulose ribbons, CR) retain a length of the order of a micron (1.47 ± 0.48 μm, AFM). A very high axial aspect ratio is determined (at least 190), considering the CR height (0.62 ± 0.38 nm, AFM), corresponding to 1–2 cellulose chains, and width (7.64 ± 1.82 nm, TEM). The new molecularly-thin cellulose proposes excellent hydrophilicity and flexibility, enabling a remarkable viscosifying effect when dispersed in aqueous media (shear-thinning, zero shear viscosity of 6.3 × 105 mPa·s). As such, CR suspensions readily develop into gel-like Pickering emulsions in the absence of crosslinking, suitable for direct ink writing at ultra-low solids content.

Heat stability promoted Pickering emulsions stabilized by glidian/sodium caseinate nanoparticles and konjac glucomannan

Pickering emulsions have attracted much attention in the food industry due to their green and non-polluting properties. Effect of konjac glucomannan (KGM) on the heat stability of Pickering emulsions were analyzed by optical microscopy, confocal laser scanning microscope (CLSM), volume mean diameter (d4,3), creaming index (CI) and rheological tests. The results showed that the emulsions without KGM were unstable and delaminated after heat treatment. The d4,3 value of the Pickering emulsion prepared without KGM and 40% oil phase fraction (v/v) was 11.33 ± 0.86 μm at room temperature, while it increased to 35.97 ± 2.00 μm after heat treatment at 100 °C. The Pickering emulsions with KGM concentration of 0.6% and camellia oil content of 60% exhibited desirable particle size and viscoelasticity even after treatment at 100 °C. Therefore, it can be inferred from the results that the increase of KGM concentration and camellia oil content can improve the thermal stability of Pickering emulsion. This study broadens the idea of the processing treatment of Pickering emulsions in food applications and provides a feasible method and theoretical basis for their application in food, pharmaceutical and cosmetic fields.

Effective stabilization of pickering emulsion using a smart material with V-shaped surface structure via controlled polymerization: Its multi-responsive behavior, recyclable process and applications

Poly (2-(dimethylaminoethyl methacrylate)-b-(glycidyl methacrylate)-b-(acrylic acid)) blocks prepared by RAFT polymerization were grafted to the surface of Fe3O4 to obtain four-responsive nanocomposite particles (P(DMAEMA-b-GMA-b-AA)/Fe3O4) with V-shaped surface structure. Subsequently, the structure and properties of the P(DMAEMA-b-GMA-b-AA)/Fe3O4 nanoparticles were characterized by FT-IR, TEM and TGA. Moreover, various factors on P(DMAEMA-b-GMA-b-AA)/Fe3O4 Pickering emulsion stability were investigated including pH, nanoparticle concentration, water–oil ratio and oil phase polarity. Notably, its superiority was demonstrated by the formation of the Pickering emulsion that underwent CO2, temperature, magnetic and pH-induced reversible emulsification/demulsification for at least 10 cycles without obvious performance decay or even morphology changes. It was demonstrated that the emulsification/demulsification mechanisms under the action of temperature, CO2, and temperature might be related to the surface wettability of nanoparticles by measuring zeta potential, interfacial tension and contact angle. Furthermore, the P(DMAEMA-b-GMA-b-AA)/Fe3O4 nanoparticles exhibited environmentally friendly behavior and could be easily recycled and further utilized through magnetic force. They were also found to stabilize diverse real oil phases. Therefore, the developed nanoparticles have significant potential for applications in oily wastewater treatment, oil transfer, and design of crude oil delivery systems.

Graphene nanosheet stabilized Pickering emulsion and its polystyrene nanocomposites

AbstractHigh thermal conductivity and electrical insulation materials are necessary for packaging materials of miniaturized electronic equipment at present. Graphene nanosheets (GNs) have great potential in polymer composites due to its excellent thermal conductivity. However, the ultra‐high conductivity of GNs will reduce the insulation of polymer composites, so that the GN composites have good thermal conductivity and electrical insulation has become the focus of research. Herein, the closed cell polystyrene nanocomposites are polymerized by using a Pickering emulsion route. Based on the exfoliating effect of pristine graphite at the oil–water interface and the amphiphilic properties of GNs during the preparation of emulsion, the resulting graphite can achieve good dispersion in the polystyrene resin. Furthermore, the high heat transfer rate of the resulting graphite makes the temperature of polystyrene resin increase by 60.2°C at room temperature within 1 min. Meanwhile, the high volume electrical resistivity (3.63 × 109 Ω·m) and breakdown strength (33.8 kV·mm−1) confirms the PNGL0.610%/PS composite keep excellent electrical insulation at 10.0 wt% filler loading.

Construction of butyric acid modified porous starch for stabilizing pickering emulsions: Encapsulation of paclitaxel

In this study, butyric acid (BA) modified porous starch (PS) was fabricated to stabilize Pickering emulsions and probe its application for encapsulating paclitaxel. BA modified PS with different degree of substitution (DS) were synthesized by esterification successfully. The structural properties were determined by N2 adsorption, SEM, 1H NMR, FT-IR and XRD analysis, confirming the porosity and ester linkages. Besides, BA-PS was used as stabilizers to produce Pickering emulsions encapsulating paclitaxel. Properties of emulsions, including emulsification index, particle size and microstructure, were evaluated. Findings indicated that emulsions produced by BA-PS with higher DS had the smaller particle size and better stability. After encapsulating paclitaxel, encapsulation efficiency, retention rate and release performance during digestion were further characterized. The results demonstrated that the emulsifying and sustained release capacity were significantly improved using higher substituted BA-PS as stabilizers. As emulsifiers, BA-PS thus has a potential application in food industry.

High-internal phase Pickering emulsion stabilized by crystals of nobiletin: assembly of supramolecular metal-polyphenolic coordination complexes for surface coating.

High internal phase Pickering emulsion has attracted extensive attention due to its unique properties, and has broad application prospects in the food field, such as as a fat replacer, packaging and delivery of nutrients or probiotics, and 3D printing of food. However, efficient and edible high-internal phase Pickering stabilizer is still a persistent challenge for food scientists. Herein, the nobiletin (NOB) was selected as a model substance, the particle physicochemical properties (droplet size, rheological behavior, and transmission profile) showed that supramolecular metal-polyphenolic coordination networks could suppress the ripening and growth of crystals on the oil-water interface. When the ratio of tannic acid (TA) and Fe3+ was 3:1, the crystallization growth of NOB could be effectively inhibited. Due to the reduction of energy steric hindrance in the adsorption process, the resulting NOB-TA3 -Fe3+ 1 (NT3 Fe1 ) nanoparticles had the greatest potential to extend emulsion storage time. This particle could stabilise a high-internal phase emulsion, of which the oil phase was 80%, for at least 30 days and eventually lead to high system viscosity. The findings in this work provided a novel selection of healthy emulsifiers as well as an effective emulsion delivery system for hydrophobic and crystalline nutrients. This article is protected by copyright. All rights reserved.