A Review of Pickering Emulsions: Perspectives and Applications

Encapsulation of roast beef flavor by soy protein isolate/chitosan complex Pickering emulsions to improve its releasing properties during the processing of plant-based meat analogues

During the production of plant-based meat analogues (PBMA), a significant loss of flavor characteristic compounds in meat-flavor essences could be observed. Pickering emulsion-based encapsulation is an effective method to improve their stability. Therefore, a soy protein isolate (SPI)/chitosan (CS) complex Pickering emulsion was fabricated to encapsulate roast beef flavor (RBF) and further applied in the processing of PBMA. Our results indicated that the network structure of emulsions was dominated by elasticity, while hydrogen and covalent bonding interactions played important roles in the encapsulation process. The release rate of flavor compounds gradually increased with the increase of pH value, glutamine transaminase, NaCl content, heating temperature or heating time, while encapsulation significantly reduced the loss of characteristic aroma compounds. In addition, the releasing characteristics of aroma compounds and textural properties of PBMA were greatly improved by treating with RBF-loaded emulsions. Consequently, the emulsions were promising to improve the flavor quality of PBMA.

Multi-responsive Pickering emulsifiers: a comprehensive study on the emulsification-demulsification behavior of modified chitosan-coated Fe3O4 nanocomposites

The surface characteristics of stimuli-responsive Pickering emulsifiers can be modified by external environmental triggers, making them highly versatile in various applications. In this study, we report three novel organic-inorganic composite structure emulsifiers. These emulsifiers were designed with a core of magnetic Fe3O4 particles, surrounded by a protective silica layer, and coated on the exterior with three distinct types of modified chitosan (CS). Experimental results demonstrate that these emulsifiers can stabilize emulsion systems consisting of liquid paraffin and deionized water at a concentration of 0.5 wt%. The unique properties of the modified CS coatings allowed for the controlled demulsification of two types of emulsions by adjusting the proton concentration. Additionally, these emulsifiers exhibited magnetic-responsive demulsification under the control of an external magnetic field. The findings of this study provide valuable insights into the design and construction of multi-responsive chitosan-based magnetic Pickering emulsifiers with controllable properties.

Deep-Eutectic-Solvent-in-Water Pickering Emulsions Stabilized by Starch Nanoparticles

Deep eutectic solvents (DESs) have received extensive attention in green chemistry because of their ease of preparation, cost-effectiveness, and low toxicity. Pickering emulsions offer advantages such as long-term stability, low toxicity, and environmental friendliness. The oil phase in some Pickering emulsions is composed of solvents, and DESs can serve as a more effective alternative to these solvents. The combination of DESs and Pickering emulsions can improve the applications of green chemistry by reducing the use of harmful chemicals and enhancing sustainability. In this study, a Pickering emulsion consisting of a DES (menthol:octanoic acid = 1:1) in water was prepared and stabilized using starch nanoparticles (SNPs). The emulsion was thoroughly characterized using various techniques, including optical microscopy, transmission microscopy, laser particle size analysis, and rheological measurements. The results demonstrated that the DES-in-water Pickering emulsion stabilized by the SNPs had excellent stability and retained its structural integrity for more than 200 days at room temperature (20 °C). This prolonged stability has significant implications for many applications, particularly in the field of storage and transportation. This Pickering emulsion based on DESs and SNPs is sustainable and stable, and it has great potential to improve green chemistry practices in various fields.

Accelerated full-thickness skin wound tissue regeneration by self-crosslinked chitosan hydrogel films reinforced by oxidized CNC-AgNPs stabilized Pickering emulsion for quercetin delivery

BACKGROUND

The non-toxic self-crosslinked hydrogel films designed from biocompatible materials allow for controlled drug release and have gathered remarkable attention from healthcare professionals as wound dressing materials. Thus, in the current study the chitosan (CS) film is infused with oil-in-water Pickering emulsion (PE) loaded with bioactive compound quercetin (Qu) and stabilized by dialdehyde cellulose nanocrystal-silver nanoparticles (DCNC-AgNPs). The DCNC-AgNPs play a dual role in stabilizing PE and are involved in the self-crosslinking with CS films. Also, this film could combine the advantage of the controlled release and synergistic wound-healing effect of Qu and AgNPs.

RESULTS

The DCNC-AgNPs were synthesized using sodium periodate oxidation of CNC. The DCNC-AgNPs were used to stabilize oil-in-water PE loaded with Qu in its oil phase by high speed homogenization. Stable PEs were prepared by 20% v/v oil: water ratio with maximum encapsulation of Qu in the oil phase. The Qu-loaded PE was then added to CS solution (50% v/v) to prepare self-crosslinked films (CS-PE-Qu). After grafting CS films with PE, the surface and cross-sectional SEM images show an inter-penetrated network within the matrix between DCNC and CS due to the formation of a Schiff base bond between the reactive aldehyde groups of DCNC-AgNPs and amino groups of CS. Further, the addition of glycerol influenced the extensibility, swelling ratio, and drug release of the films. The fabricated CS-PE-Qu films were analyzed for their wound healing and tissue regeneration potential using cell scratch assay and full-thickness excisional skin wound model in mice. The as-fabricated CS-PE-Qu films showed great biocompatibility, increased HaCat cell migration, and promoted collagen synthesis in HDFa cells. In addition, the CS-PE-Qu films exhibited non-hemolysis and improved wound closure rate in mice compared to CS, CS-Qu, and CS-blank PE. The H&E staining of the wounded skin tissue indicated the wounded tissue regeneration in CS-PE-Qu films treated mice.

CONCLUSION

Results obtained here confirm the wound healing benefits of CS-PE-Qu films and project them as promising biocompatible material and well suited for full-thickness wound healing in clinical applications.

Pickering emulsions with high ionic strength resistance stabilized by pea protein isolate-polyglycerol conjugate particles with good biocompatibility

Among various biopolymers, protein particles are widely used for stabilizing Pickering emulsions, yet their emulsifying ability are easily influenced by the ion concentration, pH, and high temperatures. To address these challenges, this study utilized chemical modification to prepare pea protein isolate-polyglycerol (PPI-PG) conjugates by Schiff-base reaction. Compared with other chemical modifications, this method produces conjugate particles with excellent biocompatibility, capable of promoting cell proliferation by up to 177 %. These conjugates showed improved dispersibility, with diffusion coefficients 3.5 times greater than pure PPI, and the isoelectric points shift from pH 4.6 to pH 1.5, which contribute to the pH stability of emulsions (pH 3-9). Additionally, the anisotropic nature of the conjugate particles, with a three-phase contact angle close to 90°, make particles need more energy for detachment from the oil-water interface, leading to good thermal stability of emulsion (80 °C, 48 h). Notably, after conjugation, these particles rely more on PG chains for dispersibility, which are less affected by ions, resulting in emulsions with high ionic strength resistance (3000 mM). Furthermore, the prepared Pickering emulsion demonstrates remarkable antioxidative properties (only a 10 % decrease), indicating widely potential applications in food, cosmetics, and pharmaceutical sectors.

Technological Functionalisation of Microencapsulated Genistein and Daidzein Delivery Systems Soluble in the Stomach and Intestines

Encapsulating antioxidant-rich plant extracts, such as those found in red clover, within microcapsules helps protect them from degradation, thus improving stability, shelf life, and effectiveness. This study aimed to develop a microencapsulation delivery system using chitosan and alginate for microcapsules that dissolve in both the stomach and intestines, with the use of natural and synthetic emulsifiers. The microcapsules were formed using the extrusion method and employing alginate or chitosan as shell-forming material. In this study, all selected emulsifiers formed Pickering (β-CD) and traditional (white mustard extract, polysorbate 80) stable emulsions. Alginate-based emulsions resulted in microemulsions, while chitosan-based emulsions formed macroemulsions, distinguishable by oil droplet size. Although chitosan formulations with higher red clover extract (C1) concentrations showed potential, they exhibited slightly reduced firmness compared to other formulations (C2). Additionally, both alginate and chitosan formulations containing β-CD released bioactive compounds more effectively. The combined use of alginate and chitosan microcapsules in a single pill offers an innovative way to ensure dual solubility in both stomach and intestinal environments, increasing versatility for biomedical and pharmaceutical applications.

Research progress on plant-based protein Pickering particles: Stabilization mechanisms, preparation methods, and application prospects in the food industry

At present, there have been many research articles reporting that plant-based protein Pickering particles from different sources are used to stabilize Pickering emulsions, but the reports of corresponding review articles are still far from sufficient. This study focuses on the research hotspots and related progress on plant-based protein Pickering particles in the past five years. First, the article describes the mechanism by which Pickering emulsions are stabilized by different types of plant-based protein Pickering particles. Then, the extraction, preparation, and modification methods of various plant-based protein Pickering particles are highlighted to provide a reference for the development of greener and more efficient plant-based protein Pickering particles. The article also introduces some of the most promising applications of Pickering emulsions stabilized by plant-based protein Pickering particles in the food field. Finally, the paper also discusses the potential applications and challenges of plant-based protein Pickering particles in the food industry.

Proteinaceous Microsphere-Based Water-in-Oil Pickering Emulsions for Preservation of Chlorella Cells

Microalgae are highly regarded as ideal materials for the creation of liquid biofuels and have substantial potential for growth and utilization. However, traditional storage and culture methods for microalgae are plagued by challenges such as uncontrolled growth, bacterial contamination, and self-shading among algae. These issues severely impede the photosynthetic process and the efficient extraction of biomass energy. This study tackles these problems by utilizing magnetic hydrophobic protein particles to stabilize water-in-oil Pickering emulsions. This allows for the micro-compartment storage and magnetic transfer of algae. Additionally, the successful encapsulation of Chlorella cells in high-internal-phase water-in-oil Pickering emulsions effectively mitigates the settling problem of Chlorella cells in the liquid phase, thereby enabling the potential use of Pickering emulsions for the confined cultivation of microalgae.

Ternary composite degradable plastics based on Alpinia galanga essential oil Pickering emulsion templates: A potential multifunctional active packaging

To reduce the use of petroleum-based plastics and explore multifunctional plastics, this study was conducted to prepare ternary composite plastics by doping Pickering emulsions containing Alpinia galanga essential oil into a polymer network consisting of poly(vinyl alcohol)-acetylated pullulan polysaccharides. Scanning electron microscopy results showed that although incompatible components were present in the composite plastic, compatibility improved with the addition of pullulan polysaccharides, resulting in smooth surfaces and cross-sections, which was consistent with the observation of continuous dark zones and low relative roughness (Ra = 5.51) in Atomic force microscopy. Further, Fourier transform spectroscopy and X-ray diffraction characterization revealed that the composite plastic disrupted the molecular and crystalline structures of the pure PVA, causing the stretching vibration of -OH and the decrease of relative crystallinity. Moreover, this plastic performed optimally at a PVA to pullulan polysaccharide ratio of 75:25, exhibiting good thermal (13.12 J/g) and mechanical properties, low water absorption (70.71 %) and water vapor transmission (1.80 × 10-3 g/m2 s), as well as excellent degradability. In addition, Alpinia galanga essential oil components in the composite plastic provided favorable antioxidant scavenging of DPPH and ABTS and inhibitory effects against Escherichia coli and Staphylococcus aureus. Chicken meat packaging revealed that the plastic maintained sensory parameters such as pH and color by inhibiting the oxidation of proteins and lipids during shelf-life. The findings provide insights into developing innovative, green, multifunctional packaging and broaden the in-depth application of Alpinia galanga essential oil.

Addition of Canna edulis starch and starch nanoparticles to stabilized Pickering emulsions: In vitro digestion and fecal fermentation

Starch nanoparticles (SNPs) were prepared through acid hydrolysis of Canna edulis native starch and modified with octenyl succinic anhydride (OSA) to yield OS-starch and OS-SNPs. These modified particles were used to stabilize curcumin-loaded Pickering emulsions. Effects on gut microbiota during in vitro fecal fermentation were examined. The surface of OS-starch exhibits a porous structure, while OS-SNPs display layered grooves. OSA modification was confirmed by Fourier transform infrared spectroscopy (with peaks at 1728 cm-1 and 1573 cm-1) and proton nuclear magnetic resonance spectra (0.5-2 ppm). The degree of substitution for OS-starch and OS-SNPs is 0.0106 ± 0.0004 and 0.0079 ± 0.0003, respectively. Following modification, the crystallinity decreased from 35.69 ± 0.46 % (native starch) to 30.17 ± 0.70 % (OS-starch), SNPs decreased from 45.87 ± 0.89 % to 43.63 ± 0.64 % (OS-SNPs). Contact angles for OS-starch and OS-SNPs are 77.47 ± 1.78 and 55.57 ± 0.21, respectively. OS-SNPs exhibited superior emulsification properties compared to OS-starch, forming stable Pickering emulsions with pseudoplastic fluid behavior and enhanced curcumin storage protection over 14 days (60.88 ± 4.26 %) with controlled release. Stabilizing Pickering emulsions with OS-starch and OS-SNPs positively affected on gut microbiota and improved the intestinal environment, showing promise for their application in transportation systems and innovative prebiotic food formulations.

Nanoscale Pickering emulsion food preservative films/coatings: Compositions, preparations, influencing factors, and applications

Pickering emulsion (PE) technology effectively addresses the issues of poor compatibility and low retention of hydrophobic active ingredients in food packaging. Nonetheless, it is important to recognize that each stage of the preparation process for PE films/coatings (PEFCs) can significantly influence their functional properties. With the fundamental considerations of environmental friendliness and human safety, this review extensively explores the potential of raw materials for PEFC and introduces the preparation methods of nanoparticles, emulsification technology, and film-forming techniques. The critical factors that impact the performance of PEFC during the preparation process are analyzed to enhance food preservation effectiveness. Moreover, the latest advancements in PE packaging across diverse food applications are summarized, along with prospects for innovative food packaging materials. Finally, the preservation mechanism and application safety have been systematically elucidated. The study revealed that the PEFCs provide structural flexibility, where designable nanoparticles offer unique functional properties for intelligent control over active ingredient release. The selection of the dispersed and continuous phases, along with component proportions, can be customized for specific food characteristics and storage conditions. By employing suitable preparation and emulsification techniques, the stability of the emulsion can be improved, thereby enhancing the effectiveness of the films/coatings in preserving food. Including additional substances broadens the functionality of degradable materials. The PE packaging technology provides a safe and innovative solution for extending the shelf life and enhancing the quality of food products by protecting and releasing active components.

Smart antibacterial nanocellulose packaging film based on pH-stimulate responsive microcapsules synthesized by Pickering emulsion template

Spoilage results in food waste and endangers consumer health, and the smart antibacterial packaging can effectively inhibit bacterial growth and reduce food spoilage. In this study, the smart antibacterial nanocellulose packaging films were developed by adding the pH-stimulated responsive microcapsules into cellulose nanofibril (CNF) film-forming. The microcapsules were synthesized by interfacial polymerization of Pickering emulsion. Carboxylated cellulose nanocrystals as solid particles stabilized the composited oil phase to prepare the oil-in-water Pickering emulsion. The emulsion with the particle concentration of 1.25 wt% and the oil phase mass fraction of 7.5 % processes excellent stability and uniform particle size, was chosen to synthesize microcapsules. The cinnamaldehyde in the film with the addition amount of microcapsules 0.6 g burst released in the first 1 h and then slowly, and the cumulative release at pH 2.0, 4.0, 5.5 and 7.2 was 28.43 μg/cm2, 18.84 μg/cm2, 16.52 μg/cm2 and 12.89 μg/cm2, respectively. The inhibitory rate of film against both E. coli and L. monocytogenes reached 99 % at pH 4.0. The shelf life of pork packed by the film prolonged to nearly 9 d at room temperature. The developed films have the potential to be used in food packaging.

Oil-in-Water Pickering Emulsions Stabilized with Nanostructured Biopolymers: A Venue for Templating Bacterial Cellulose

Pickering emulsions (PEs) differ from conventional emulsions in the use of solid colloidal particles as stabilizing agents instead of traditional amphiphilic molecules. Nanostructured biopolymers (NBs) emerge as a promising alternative for PE stabilization owing to their remarkable biocompatibility, abundant availability, and low cost. To explore this potential, a study is herein presented, in which cellulose nanocrystals (CNCs), both type I and type II allomorphs, and chitin nanocrystals (ChNCs) were used for stabilizing oil-in-water PEs prepared by the use of ultrasound. Sunflower oil was selected as the oil phase as it offers the advantages of being edible, renewable, and inexpensive. By utilizing ζ-potential, static light diffraction, and visual observations, we determined the optimal oil/water ratio for each type of NB to obtain stable emulsions after 14 days. The optimized PEs were used to form bacterial nanocellulose composites through emulsion templating. To our knowledge, this study represents a pioneering work in exploiting oil-in-water PEs for this approach. Additionally, it entails the first utilization of nonmercerized type II CNCs as stabilizers for PEs, while also establishing a direct comparison among the most relevant NBs. The resulting composites exhibited a unique morphology, composed of larger pores compared to standard bacterial nanocellulose aerogels. These findings highlight the notable potential of NBs as stabilizers for PEs and their ability to generate green nanocomposites with tailored properties.

Pickering Emulsion Stabilized by β-Cyclodextrin and Cinnamaldehyde/β-Cyclodextrin Composite

A Pickering emulsion was prepared using β-cyclodextrin (β-CD) and a cinnamaldehyde (CA)/β-CD composite as emulsifiers and corn oil, camellia oil, lard oil, and fish oil as oil phases. It was confirmed that Pickering emulsions prepared with β-CD and CA/β-CD had good storage stability. The rheological experiments showed that all emulsions had G' values higher than G″, thus confirming their gel properties. The results of temperature scanning rheology experiments revealed that the Pickering emulsion prepared with β-CD and CA/β-CD composites had high stability, in the range of 20-65 °C. The chewing properties of Pickering emulsions prepared by β-CD and corn oil, camellia oil, lard, and herring oil were 8.02 ± 0.24 N, 7.94 ± 0.16 N, 36.41 ± 1.25 N, and 5.17 ± 0.13 N, respectively. The chewing properties of Pickering emulsions made with the CA/β-CD composite and corn oil, camellia oil, lard, and herring oil were 2.51 ± 0.05 N, 2.56 ± 0.05 N, 22.67 ± 1.70 N, 3.83 ± 0.29 N, respectively. The texture properties confirmed that the CA/β-CD-composite-stabilized-emulsion had superior palatability. After 28 days at 50 °C, malondialdehyde (MDA) was detected in the emulsion. Compared with the β-CD and CA + β-CD emulsion, the CA/β-CD composite emulsion had the lowest content of MDA (182.23 ± 8.93 nmol/kg). The in vitro digestion results showed that the free fatty acid (FFA) release rates of the CA/β-CD composite emulsion (87.49 ± 3.40%) were higher than those of the β-CD emulsion (74.32 ± 2.11%). This strategy provides ideas for expanding the application range of emulsifier particles and developing food-grade Pickering emulsions with antioxidant capacity.

Nanocrystals in cosmetics and cosmeceuticals by topical delivery

The main issues with local delivery of cosmetics are their high sensitivity and limited drug loading of active pharmaceutical ingredient. Nanocrystal technology offers consumers cutting-edge and effective products and exhibits enormous development potential in the beauty business as a new delivery method to address the issue of low solubility and low permeability of sensitive chemicals. In this review, we described the processes for making NCs, along with the impacts of loading and the uses of different carriers. Among them, nanocrystalline loaded gel and emulsion are widely used and may further improve the stability of the system. Then, we introduced the beauty efficacy of drug NCs from five aspects: anti-inflammation and acne, anti-bacterial, lightening and freckle removal, anti-aging as well as UV protection. Following that, we presented the current scenario about stability and safety. Finally, the challenges and vacancy were discussed along with the potential uses of NCs in the cosmetics industry. This review serves as a resource for the advancement of nanocrystal technology in the cosmetics sector.

Investigation and Characterization of Pickering Emulsion Stabilized by Alkali-Treated Zein (AZ)/Sodium Alginate (SA) Composite Particles

Pickering emulsions stabilized by food-grade colloidal particles have attracted increasing attention in recent years due to their "surfactant-free" nature. In this study, the alkali-treated zein (AZ) was prepared via restricted alkali deamidation and then combined with sodium alginate (SA) in different ratios to obtain AZ/SA composite particles (ZS), which were used to stabilize Pickering emulsion. The degree of deamidation (DD) and degree of hydrolysis (DH) of AZ were 12.74% and 6.58% respectively, indicating the deamidation occurred mainly in glutamine on the side chain of the protein. After the treatment with alkali, AZ particle size decreased significantly. Moreover, the particle size of ZS with different ratios was all less than 80 nm. when the AZ/SA ratio was 2:1(Z2S1) and 3:1(Z3S1), the three-phase contact angle (θ_o/w) were close to 90°, which was favorable for stabilizing the Pickering emulsion. Furthermore, at a high oil phase fraction (75%), Z3S1-stabilized Pickering emulsions showed the best long-term storage stability within 60 days. Confocal laser scanning microscope (CLSM) observations showed that the water-oil interface was wrapped by a dense layer of Z3S1 particles with non-agglomeration between independent oil droplets. At constant particle concentration, the apparent viscosity of the Pickering emulsions stabilized by Z3S1 gradually decreased with increasing oil phase fraction, and the oil-droplet size and the Turbiscan stability index (TSI) also gradually decreased, exhibiting solid-like behavior. This study provides new ideas for the fabrication of food-grade Pickering emulsions and will extend the future applications of zein-based Pickering emulsions as bioactive ingredient delivery systems.