Pickering Stabilization Research Articles

Engineering surfactant-free pickering double emulsions gels with different structures as low-calorie fat analogues: Tunable oral perception, inhibiting lipid digestion, and potent co-delivery for lycopene and epigallocatechin gallate

Structural design has been as a transformative strategy to create clean-label and well-nourished fat-based foods. Herin, surfactant-free, plant-based oil-in-water-in-oil (O/W/O) and water-in-oil-in-water (W/O/W) emulsions gels (EGs) were designed using protein microgels and fat crystals formed in situ, which achieved dual-interface Pickering stabilization. The suitability and difference of O/W/O and W/O/W EGs as fat analogues in maintaining fat texture, inhibiting lipid digestion, target release and bioactivity of co-loading epigallocatechin gallate (EGCG) and lycopene were examined. O/W/O and W/O/W EGs displayed own unique characteristics, and could be tailored to optimize their performance. O/W/O EGs provided smoother oral perception similar to butter. The multi-structure and interface modulation for double EGs achieved inhibiting lipid digestion, fat phase position mainly controlled the digestive process. Co-delivery systems exhibited synchronous release profiles, allowing a more obvious in-time sustained release of lycopene in O/W/O and EGCG in W/O/W EGs. Both co-delivery O/W/O and W/O/W showed anti-inflammatory bioactivity.

Impact of ultrasound process on cassava starch nanoparticles and Pickering emulsions stability

Using green techniques to convert native starches into nanoparticles is an interesting approach to producing stabilizers for Pickering emulsions, aiming at highly stable emulsions in clean label products. Nanoprecipitation was used to prepare the Pickering starch nanoparticles, while ultrasound technique has been used to modulate the size of these nanoparticles at the same time as the emulsion was developed. Thus, the main objective of this study was to evaluate the stabilizing effect of cassava starch nanoparticles (SNP) produced by the nanoprecipitation technique combined with ultrasound treatment carried out in the presence of water and oil (more hydrophobic physicochemical environment), different from previous studies that carry out the mechanical treatment only in the presence of water. The results showed that the increased ultrasound energy input could reduce particle size (117.58 to 55.75 nm) and polydispersity (0.958 to 0.547) in aqueous dispersions. Subsequently, Pickering emulsions stabilized by SNPs showed that increasing emulsification (ultrasonication) time led to smaller droplet sizes and monomodal size distribution. Despite flocculation, long-term ultrasonication (6 and 9 min) caused little variation in the droplet size after 7 days of storage. The cavitation effects favored the interaction between oil droplets through weak attraction forces and particle sharing, favoring the Pickering stabilization against droplet coalescence. Our results show the potential to use only physical modifications to obtain nanoparticles that can produce coalescence-stable emulsions that are environmentally friendly.

Pectin-based cinnamon essential oil Pickering emulsion film with two-sided differential wettability: A major role in the spatial distribution of microdroplets

Pickering emulsions have attracted much attention as a novel emulsifying technology. This research to explore Zein-Citrus pectin nanoparticles stabilized cinnamon essential oil (CEO) Pickering emulsion (ZCCPEs) for constructing Pickering emulsion edible film (PEF). Unlike traditional research, which focuses on antibacterial and antioxidant activities, our research examined the physical properties of PEF, specifically changes in wettability. The results show that PEF has better transparency and tensile strength than the pectin alone direct emulsion film (PAEF), and the spatial distribution of Pickering emulsion droplets gives different wettability on both sides of PEF. The partially hydrophobic upside has important application value in food packaging. At the same time, the PEF is biodegradable and environmentally non-polluting. The edible film loaded with essential oils, developed based on the Pickering stabilization mechanism in this study, possesses several desirable characteristics for potential used as bioactive packaging films in food applications.

Ultra-stable Pickering liquid crystal-in-water emulsions decorated with thermoresponsive soft microgels and their response to aqueous analytes

This work presents an extensive investigation of the Pickering stabilization of liquid crystal (LC)-in-water emulsions using soft nanometer-sized colloidal poly(N-isopropylacrylamide) (PNIPAM) microgel particles and the responsivity of the PNIPAM microgel-stabilized Pickering LC droplet-based assembly towards amphiphilic analytes. The evolution of size and stability of LC droplets with microgel concentration are found to be dependent on the emulsifier-regime. Despite microgel coating, the LC-water interface remains accessible to model analytes such as anionic sodium dodecyl sulfate (SDS) and cationic dodecyltrimethylammonium bromide (DTAB). The analytes can pass through the interfacial pores and/or meshes of porous microgels to induce a bipolar-to-radial ordering transition within the droplets. The dose-response behaviour is largely influenced by the initial microgel concentration, type of analytes and interfacial layer (charge), and the number of droplets exposed to the analytes. The PNIPAM microgel-coated LC droplets notably exhibited enhanced sensitivity under conditions promoting electrostatic attractive interactions between the interfacial microgel layer and analytes. Overall, the results highlight the potential of Pickering LC-in-water emulsions for reliable and quantitative analysis of aqueous analytes, thus opening up new avenues toward the development of droplet-based optical sensors.

Pickering emulsions stabilized by β-Lactoglobulin-Rosmarinic acid-Pectin nanoparticles: Influence of interfacial behavior and rheology performance

Grafting polyphenols and glycosylation are effective means to enhance the wettability and emulsifying properties of natural protein particles. A stable pickering emulsion (PE) with antioxidant properties was prepared using β-Lactoglobulin-Rosmarinic acid-Pectin (β-LG-RA-PC) conjugates as stabilizers in this study. When PC and β-LG-RA with the same mass were covalently combined, the solid protein-based particles exhibited ideal wettability (84.2 ± 0.3°), emulsification performance, and molecular flexibility. PEs with an oil content of 66.7% were successfully prepared using a 10 mg/mL concentration of the complex. The intrinsic reasons for the stabilization of the PE were explored through interfacial tension (from 16.02 mN/m to 12.18 mN/m), adsorption kinetics, interfacial expansion viscoelastic modulus (the tangent of the phase angle was 0.22), microstructure, and rheological properties, revealing that the dense, ideally viscoelastic interface layer formed was the main factor. The electrostatic repulsion between droplets, and the formation of a robust spatial network structure, facilitated PEs’ stability. These studies confirmed the possibility of implementing protein-based particles to yield food-grade PE.

Pickering stabilization of water-in-crude oil emulsions by paraffin wax crystals: Insights from X-ray scattering

Previous studies suggest asphaltenes are active materials at the oil-water interface, affecting the formation and stability of crude oil emulsions. However, even oils of low asphaltene content generate stable emulsions, indicating the involvement of other oil fractions. Due to the role of paraffin waxes as Pickering stabilizers or gel network formers in emulsions from other applications, this study explores their stabilization capacity in water-in-oil (W/O) emulsions and their interaction with other fractions with interfacial activity. The extraction and physicochemical characterization of paraffin waxes from two Brazilian crude oils allowed us to correlate their properties with the emulsification of both crude and model oils. Removal of asphaltenes enhances emulsion stability. Emulsion preparation with crude oils without waxes and asphaltenes demonstrates the participation of other amphiphilic components in emulsion formation, whereas waxes are necessary for their stabilization. Experiments with emulsions formed by a model oil confirmed the combined action of waxes and an amphiphilic material in the formation and stabilization of the interfacial film. However, the combination of waxes and asphaltenes are ineffective. Small-angle X-ray scattering (SAXS) analysis revealed that waxes only form a lamellar structure when highly purified, suggesting Pickering stabilization rather than the formation of a gel network. In conclusion, polar oil fractions other than asphaltene play a crucial role in emulsion formation, whereas paraffin wax provides Pickering stabilization, even beyond the wax appearance temperature (WAT). This study enhances our understanding of the mechanisms governing waxy Brazilian crude oil emulsions.

Control of the Colloidal and Adsorption Behaviors of Chitin Nanocrystals and an Oppositely Charged Surfactant at Solid, Liquid, and Gas Interfaces.

Chitin has a unique hierarchical structure, spanning the macro- and nanoscales, and presents chemical characteristics that make it a suitable component of multiphase systems. Herein, we elucidate the colloidal interactions between partially deacetylated chitin nanocrystals (cationic ChNC) and an anionic surfactant, sodium dodecyl sulfate (SDS). We investigate charge neutralization and association (electrophoretic mobility, surface tensiometry, and quartz crystal microgravimetry) and their role in the stabilization of Pickering emulsions. We find SDS adsorption and association with ChNC under distinctive regimes: At low SDS concentration, submonolayer assemblies form on ChNC, driven by the hydrophobic effect and electrostatic interactions. With the increased SDS concentration, bilayers or patchy bilayers form, followed by adsorbed hemimicelles and micelles. We further suggested the role of hydrophobic effects in the observed colloidal transitions and complex conformations. At the highest SDS concentration tested, charge neutralization and SDS/ChNC flocculation take place. Remarkably, at given concentrations, adsorbed SDS endows the chitin nanoparticles with an effective hydrophobicity that opens the opportunity to achieve tailorable Pickering stabilization. Hence, a facile route is proposed by in situ modification by SDS physisorption, which extends the potential of renewable nanoparticles in the formulation of complex fluids, for instance, those relevant to household and healthcare products.

A deeper insight into the evaluation of water-in-oil amicroemulsion templated samarium sulfide nanospheres: exploring its role in pickering emulsion formulation for photocatalytic dye degradation and synthesis of PANI@Sm2S3 nanocomposites.

This study examines the effectiveness of W/O microemulsion-mediated Sm2S3 nanospheres in pickering emulsion-based crystal violet (CV) dye degradation and PANI@Sm2S3 nanocomposite synthesis. The evaluation of nanospheres inside the core of reverse micelles was performed through DLS, TEM and FESEM analyses. The formation of nanospheres involve two phases: a nucleation phase (5-30 min) and growth phase (30-120 min). Through in situ hydrophobization of negatively charged (with a zeta value of -4.47 mV at neutral pH) Sm2S3 nanoparticles (0.1 wt%) with a suitable amount of a cationic CTAB surfactant, a stable O/W pickering emulsion was developed. 0.1 wt% Sm2S3in situ hydrophobized with 2.7 mM CTAB offered a stable pickering emulsion with a diameter of 23 μm after 1 day of storage. This pickering emulsion improves the local concentration of CV by efficiently encapsulating dye molecules inside the core of emulsion droplets. Therefore, dye molecules get numerous opportunities to interact with the Sm2S3 photocatalyst and efficiently degrade. The pickering emulsion stabilised by 0.1 wt% of Sm2S3 nanoparticles in situ hydrophobized with 2.7 mM of CTAB results in almost 100% degradation. Moreover, using only solid Sm2S3 (having wt% of 0.025 or 0.075) as a pickering stabiliser, new PANI@Sm2S3 spherical nanocomposites were synthesised via pickering emulsion polymerization. The formation of PANI@Sm2S3 composites was identified via UV-vis, IR, and 1H-NMR investigations. The analysis of FESEM images showed that the amount of nanoparticles used in the dispersion (for 0.025 wt%, 35 nm and 0.075 wt%, 29 nm) strongly influences the size and shape of the composites.

Enhanced foamability and stability of aqueous foams through novel pickering fat globules formulated with solid lipid particles

Pickering fat globules (PFGs), known for their remarkable stability via the Pickering effect, eco-friendliness, and ability to carry hydrophobic flavors and nutrients, play a pivotal role in the advancement of food foam systems. This study investigates highly unsaturated and exceptionally stable aqueous foams stabilized by PFGs with interfacial activity. These PFGs are derived from two types of solid lipid particles (SLPs): fully hydrogenated soybean oil with sodium caseinate (FHSO-SC-SLPs-PFGs) and glyceryl stearate citrate (GSC-SLPs-PFGs), which were formulated with varying SLPs concentrations (0.5 wt%, 2.5 wt% and 5 wt%) while coating 10 wt% and 20 wt% oil droplets. Remarkably, 0.5 wt% SLPs could accommodate up to 20 wt% of low-melting-point liquid oil, enhancing the unsaturation of PFGs. GSC-SLPs-PFGs generated foams with overrun values reaching up to 235%, exhibiting stability for at least 40 days. In contrast, foams derived from FHSO-SC-SLPs-PFGs, with the highest overrun value of 145%, remained stable for only 2 h. Compared with FHSO-SC-SLPs-PFGs, GSC-SLPs-PFGs exhibited superior foaming performance and stability attributed to their properties such as smaller particle size, enhanced hydrophilicity, higher apparent viscosity, increased surface potential, and superior surface tension reduction. Furthermore, increasing the concentration of SLPs and/or reducing the oil phase can also improve the properties of SLPs-PFGs, resulting in greater foamability and foam stability. Surface dynamic adsorption, interfacial shear rheology, and microstructural observations revealed robust adsorption of all SLPs-PFGs at the air-liquid interface, indicative of pronounced Pickering stabilization, with GSC-SLPs-PFGs also exhibited three-dimensional network structure. These SLPs-PFGs stabilized foams presented heightened stability and reduced saturated fat content, paving the way for novel and healthier foam-based food products.

Correction to: Banana peel nanocellulose and soy protein hydrolysate complexed colloidal nanoparticles synthesis using ultrasonic interventions: characterization and stable pickering emulsion formation

Correction to: Banana peel nanocellulose and soy protein hydrolysate complexed colloidal nanoparticles synthesis using ultrasonic interventions: characterization and stable pickering emulsion formation

Pickering Emulsion Properties Generated by Nanofibrillated Cellulose Isolated from Oil Palm Fruit Bunch (OPEFB) as a Stabilizer

This study aims to find the optimal nanofibrillated cellulose (NFC) concentration isolated from oil palm empty fruit bunch (OPEFB) particles to form stable pickering emulsions against creaming and coalescence. The emulsification process is based on a combination of homogenizer and ultrasonication. Pickering emulsion was prepared by mixing the dispersed phase (palm oil) and the dispersing phase (NFC concentration of 0.05 - 0.7 w/v%) at the ratio of 10:90. Fresh emulsion has a milky white appearance and is homogeneous. However, some samples' creaming process occurred on the 30th day of storage. Microscopic observations show that the droplets are round with various sizes. Differences in NFC concentrations significantly affect droplet size, zeta potential, rheology, and emulsion stability. Increasing the NCF concentration resulted in smaller droplet sizes, viscosity, zeta potential, and pickering emulsion stability. The emulsion has high stability against coalescence and creaming. NFC at 0.7 w/v% generates an emulsion with the best characteristics and high stability against creaming and coalescence. OPEFB-based NFC has the potential as a pickering emulsion stabilizer particle that can be applied to the food and non-food industries.

Promising application of probiotic microorganisms as Pickering emulsions stabilizers

The purpose of this work was to study the ability of nineteen food-grade microorganisms as Pickering emulsion (PE) stabilizers. Medium-chain triacylglycerol (MCT) oil-in-water (50:50) PEs were fabricated by 10 wt% or 15 wt% of thermally-inactivated yeast, cocci, Bacillus spp. and lactobacilli cells. The characteristics of microorganisms related to “Pickering stabilization” including morphology, surface charge, interfacial tension, and “contact angle” were firstly studied. After that, the cells-stabilized PEs were characterized from both kinetic and thermodynamic viewpoints, microstructure and rheological properties. The interfacial tension and “contact angle” values of various microorganisms ranged from 16.33 to 38.31 mN/m, and from 15° to 106°, respectively. The mean droplet size of PEs ranged from 11.51 to 57.69 µm. Generally, the physical stability of cell-stabilized PEs followed this order: lactobacilli > Bacillus spp. > cocci > yeast. These variations were attributed to the morphology and cell wall composition. Increasing the microorganism concentration significantly increased the physical stability of PEs from a maximum of 12 days at 10 wt% to 35 days at 15 wt% as a result of better interface coverage. Shear-thinning and dominant elastic behaviors were observed in PEs. Physical stability was affected by the free energy of detachment. Therefore, food-grade microorganisms are suggested for stabilizing PEs.

Oleofoams stabilized by monoacylglycerides: Impact of chain length and concentration

Oleofoams are plant oil based whipped systems which have drawn academic and industry attention in recent years. The aim of this study was to determine the effect of fatty acid chain length and monoacylglyceride (MAG) concentration on the performance and structural properties of MAG-based oleofoams. Four different MAGs (monolaurin, monomyrystin, monopalmitin, and monostearin) were studied at three concentration levels (5, 10, and 15 wt%). The fatty acid chain length had a statistically significant impact on the size and shape of crystals formed, while higher MAG concentrations led to higher numbers of crystals in the continuous oil phase. These differences affected the performance and physical properties of the oleofoams: compared to other MAGs, monostearin based oleofoams were harder and exhibited higher values of G′ and G″, had higher overrun and showed better stability. Lastly, through microscopy techniques it was successfully proved that monostearin-based oleofoams are stabilized by both bulk and Pickering stabilization.

General Method to Synthesize Highly Stable Nanoclusters via Pickering-Stabilized Microemulsions

The ability to not only control but also maintain the well-defined size of nanoclusters is key to a scientific understanding as well as their practical application. Here, we report a synthetic protocol to prepare and stabilize nanoclusters of different metals and even metal salts. The approach builds on a Pickering stabilization effect inside a microemulsion system. We prove that the emulsion interface plays a critical role in the formation of nanoclusters, which are encapsulated in situ into a silica matrix. The resulting nanocapsule is characterized by a central cavity and a porous shell composed of a matrix of both silica and nanoclusters. This structure endows the nanoclusters simultaneously with high thermal stability, good biocompatibility, and excellent photostability, making them well suited for fundamental studies and practical applications ranging from materials chemistry, catalysis, and optics to bioimaging.

Pickering water in oil emulsions prepared from biocompatible gliadin/ethyl cellulose complex particles

Water-in-oil (W/O) emulsions have gained interest in many fields, including food, healthcare, pharmaceutical, and agriculture. However, research on Pickering W/O emulsions is limited due to the lack of available stabilizers. This study aimed to demonstrate the development of edible Pickering W/O emulsions using biocompatible and biodegradable gliadin/ethyl cellulose complex particles (GECPs) with neutral hydrophobicity as the stabilizer. The characterizations of GECPs indicated that the particle size, contact angle, and dynamic interfacial tension could be adjusted by varying the gliadin-to-ethyl cellulose (EC) ratio. The investigations of emulsions revealed that the most stable emulsions were obtained when the gliadin-to-EC ratio was 2:1. Moreover, stable emulsions could be prepared at particle concentrations higher than 1.5%. The phase inversion of emulsions from W/O to O/W occurred at 55 wt.% water. Confocal laser scanning microscopy and the theoretical calculations confirmed that GECPs formed multiple interfacial layers and acted as physical barriers against coalescence, thereby contributing to the stability of emulsions for at least 433 days; no reverse inversion occurred after 2.3 years of storage. This study provided a new approach to prepare stable Pickering W/O emulsions from GECPs. This strategy might open interesting avenues in solving the dilemma where Pickering stabilization using edible particles is required. Schematic illustration of preparation for stable Pickering W/O emulsions using biocompatible gliadin/ethyl cellulose complex particles as the particulate emulsifier. • Biocompatible gliadin/ethyl cellulose complex particles (GECPs) were fabricated using simple method. • GECPs were used to generate food-grade W/O Pickering emulsions with a stable period of at least 2.3 years. • The W/O emulsions can contain up to 50 wt.% water phase. • The type of emulsions shifted from W/O to O/W at water fraction higher than 55 wt.%. • Formation of multiple interfacial GECPs layers was confirmed.

Interfacial activity and Pickering stabilization of kraft lignin particles obtained by solvent fractionation

Upgrading lignin particles with controlled morphology and amphiphilicity to investigate the stabilization mechanism in Pickering systems is reported.

Heteroaggregation effects on Pickering stabilization using oppositely charged cellulose nanocrystal and nanochitin

Pickering emulsions are stabilized using complexes of cellulose nanocrystals (CNC) and nanochitin (NCh). The colloidal behavior and heteroaggregation in aqueous media are studied in relation to complex formation and net charge. The complexes are remarkably effective in stabilizing oil-in-water Pickering emulsions under conditions of slightly net positive or negative charges, as determined by the CNC/NCh mass ratio. Close to charge neutrality (CNC/NCh ~5), large heteroaggregates form, resulting in unstable emulsions. By contrast, under net cationic conditions, interfacial arrest of the complexes leads to non-deformable emulsion droplets with high stability (no creaming for 9 months). At given CNC/NCh concentrations, emulsions with up to 50% oil fraction are produced. This study shows how to control emulsion properties beyond consideration of the typical formulation variables, for instance, through adjusting CNC/NCh ratio or charge stoichiometry. We highlight the possibilities that are available for emulsion stabilization by using a combination of polysaccharide nanoparticles.

Synthesizing CNT/MgO nanocomposite to form stable pickering emulsion at high temperature and salinity and its application to improved oil displacement efficiency

In this work CNT/MgO nanocomposites is synthesized to investigate their effect on oil displacement efficiency in porous media. Characterization methods confirmed that the CNT/MgO nanocomposite is synthesized successfully where the MgO nanoparticles covered the CNTs homogenously. The stability of the formed emulsions confirmed that the CNT/MgO nanocomposite form stable emulsions at high temperatures and salinity conditions. It was found that while using this nanocomposite, the interfacial tension (IFT) is reduced significantly. Moreover, the contact angle measurements proved that the synthesized nanoparticle is able to alter the wettability of the porous media from the oil-wet condition to the water-wet condition, which is highly demanded in the EOR application. As a dynamic method to investigate the EOR mechanism of nanofluid injection, microfluidic flooding method is employed to verify the result of static tests and show the potential of the prepared nanocomposites on enhancing the recovery factor. It is observed the investigated nanofluid with a concentration of 0.5 wt%‌ provides a higher recovery factor (about 60%) in comparison to deionized water flooding (about 20 %).

Exploration of stabilization mechanism of polyol-in-oil-in-water quercetin-loaded Pickering double emulsions

The low solubility of quercetin considerably decreases its loading efficiency in traditional water and oil-based emulsion systems, which has limited their applications. To find a solution to this issue, in this investigation, polyol consisting of dipropylene glycol and glycerol as a solvent was used to increase quercetin solubility. It was further incorporated in polyol-in-oil-in-water Pickering double emulsions stabilized by SiO2. The characterization of these Pickering double emulsions was performed by analyses of their microscopic structures, particle sizes, rheology, and storage stability. The rise in the concentration of quercetin from 0 to 0.60 wt% decreased the droplet size of these emulsions and increased their viscoelasticity and storage stability. The microstructure of the emulsions showed the presence of some quercetin on the water-oil interface, suggesting that this bioactive compound might have recrystallized from the internal polyol phase during the preparation and then acted as a particle stabilizer in synergy with SiO2. To test and validate this hypothesis, we examined the Pickering stabilization properties of the recrystallization quercetin and its interaction with SiO2. We found that the recrystallized quercetin interacted with SiO2 through a hydrogen bond and co-stabilized the interface. Additionally, it also served as a thickener that was involved in the development of an intense entangled network structure that connected the droplets, which improved the emulsion stability. These results revealed an effective approach for the preparation of stable Pickering double emulsions with high quercetin loading.

Influence of xanthan gum and gluten on in vitro digestibility and textural properties of rice bread

SummaryStarch digestibility of gluten‐free bread has been expected to be suppressed for the purpose of decreasing glycemic response. The objective of this study was to investigate the effects of adding xanthan gum and gluten on starch and protein digestibility of rice bread prepared using the developed recipe involving pickering stabilization of foams and emulsions. The extent of starch digestion of gluten‐free bread was suppressed by adding 2% xanthan gum from 79.8% to 57.3%. This suppressive effect was diminished by using gluten and that of rice bread containing 2% xanthan gum and 20% gluten was 75.5%. The extent of starch digestion of gluten‐free bread was similar or less than that of bread containing gluten. The gluten‐free bread with 2% xanthan gum had significantly lower loaf volume, porosity, and sticker structure of breadcrumb than the control. The suppressive effects of xanthan gum on starch and protein digestion were mainly dependent on reducing accessibility of the enzyme into the inner structure.