Stable Pickering Emulsions Research Articles

Synergistic stabilization of a menthol Pickering emulsion by zein nanoparticles and starch nanocrystals: Preparation, structural characterization, and functional properties

Synergistic stabilization of a menthol Pickering emulsion by zein nanoparticles and starch nanocrystals: Preparation, structural characterization, and functional properties

Modified Janus silica-based sheets stable stimulus-responsive Pickering emulsion: An excellent recycling platform for tandem reaction

To accommodate the advancement of green chemistry and further enhance hydrogen utilization efficiency and organic compound conversion in reactions, a smart Pickering emulsion stabilized by modified Janus silica particles was successfully prepared for the tandem reaction of ammonia borane hydrolysis and organic hydrogenation reduction. The emulsion has been confirmed to possess high stability and rapid stimulus responsiveness. The high stability and large oil-water interface area of Pickering emulsions, along with their low energy demulsification method, provide an excellent reaction platform and catalyst in situ recovery strategy for tandem reactions. Moreover, the anisotropy of Janus particles facilitates the progression of tandem reactions, mitigating the waste associated with "sacrifice" mechanisms and averting hydrogen loss. Experimental results demonstrate that even when the molar amount of hydrogen released from ammonia borane is comparable to that of organic compounds, organic compounds still achieve a conversion rate of 99 %, with a hydrogen utilization efficiency 3–4 times higher than that of conventional two-phase systems. By simply adjusting the pH, the catalyst can be recovered in situ for the next cycle. Even after 5 cycles, a high conversion rate of organic compounds is maintained.

Dynamic covalent Fe3O4 nanoparticles for dual-responsive Pickering emulsions triggered by pH and magnetism

In this study, we successfully synthesized silica coated Fe3O4 nanoparticles (Fe3O4@SiO2 NPs) and further animated their surface to create amino modified Fe3O4@SiO2 (Fe3O4@SiO2-NH2) NPs. By taking advantage of the pH-responsive dynamic (covalent) imine bond between the hydrophilic Fe3O4@SiO2-NH2 NPs and the hydrophobic cinnamaldehyde molecule (R), we developed dynamic covalent Fe3O4@SiO2 (Fe3O4@SiO2-R) NPs with switching wettability. These NPs were then utilized to form Pickering emulsions, and whose stability and pH/magnetic response were thoroughly investigated. As the NPs concentration in the emulsion increased, the emulsion stability initially improved but then subsequently slightly decreased. Emulsifiers exhibited emulsifying effect on various oil phases, with paraffin oil demonstrating the best effect. By adding Hydrochloric acid to the emulsion, we successfully broke the imine bond at a pH value of 2.8, resulting in demulsification. Applying a magnetic field also achieved demulsification. After five cycles of pH or magnetic response-induced emulsification and demulsification, a stable Pickering emulsion could still be obtained. Stimuli-responsive Pickering emulsions have been extensively studied, but there is limited research on double-responsive Pickering emulsions. This study presents a novel design of Pickering emulsions with pH/magnetic dual responsiveness, offering great potential for oil-water separation applications.

All-natural polysaccharide and protein complex nanoparticles from Clitocybe squamulosa as unique Pickering stabilizers for oil-in-water emulsions

This study aimed to develop novel nanoparticles that can serve as an excellent oil-in-water (O/W) Pickering stabilizer. The polysaccharide-protein complex nanoparticles (PPCNs-20 and PPCNs-40) were prepared at different ultrasonication amplitudes (20 % and 40 %, respectively) from the polysaccharide-protein complexes (PPCs) which were extracted from the residue of Clitocybe squamulose. Compared with PPCs and PPCNs-20, the PPCNs-40 exhibited dispersed blade and rod shape, smaller average size, and larger zeta potential, which indicated significant potential in O/W Pickering emulsion stabilizers. Subsequently, PPCNs-40 stabilized Pickering emulsions were characterized at different concentrations, pHs, and oil phase contents. The average size, micromorphology, rheological properties, and storage stability of the emulsions were improved as the concentration of PPCNs-40, the ratio of the soybean oil phase and pH value increased. Pickering emulsions showed the best stability when the concentration of PPCNs-40 was 3 wt%, and the soybean oil fraction was 30 % under both neutral and alkaline conditions. The emulsions demonstrated shear thinning and gelation behavior. These findings have implications for the use of eco-friendly nanoparticles as stabilizers for Pickering emulsions and provide strategies for increasing the added value of C. squamulosa.

Pickering emulsion co-delivery system: Stimuli-responsive biomineralized particles act as particulate emulsifiers and bioactive carriers

Pickering emulsions provide a promising platform for the efficient delivery of bioactive. However, co-delivery of fragile bioactives with different physicochemical properties for comprehensive effects still faces practical challenges due to the limited protection for bioactives and the lack of stimuli-responsive property for on-demand release. Herein, a stimuli-responsive co-delivery system is developed based on biomineralized particles stabilized Pickering emulsions. In this tailor co-delivery system, hydrophilic bioactive (pepsin) with the fragile structure is encapsulated and immobilized by biomineralization, the obtained biomineralized particles (PPS@CaCO3) are further utilized as emulsifiers to form O/W Pickering emulsions, in which the hydrophobic oxidizable bioactive (curcumin) is stably trapped into the dispersed phase. The results show that two bioactives are successfully co-encapsulated in Pickering emulsions, and benefiting from the protection capacities of biomineralization and Pickering emulsions, the activity of pepsin and curcumin shows a 7.33-fold and 144.83-fold enhancement compared to the free state, respectively. Moreover, In vitro study demonstrates that Pickering emulsions enable to co-release of two bioactives with high activity retention by the acid-induced hydrolyzation of biomineralized particles. This work provides a powerful stimuli-responsive platform for the co-delivery of multiple bioactive compounds, enabling high activity of bioactives for the comprehensive health effects.

Study on the colloidal and emulsifying properties of different whole-component plant-based particles

In this work, nine different plant materials (lettuce, broccoli, shepherd's purse, orange peel, tangerine peel, lemon peel, lotus root, yam, and ginkgo nut) were used to prepare whole-component colloidal particles through the media milling. The colloidal properties and applicability in forming and stabilizing Pickering emulsions were investigated. The results showed that some particles exhibited good interfacial wettability. These particles could spontaneously absorb at the oil-water interface and effectively decrease interfacial tension. Pickering emulsions stabilized by broccoli colloidal particles exhibited better homogeneity and exceptional stability. While others were unstable to creaming/sedimentation. After slight stratification, the Pickering emulsions stabilized by fruit peel colloidal particles formed a solid gel unexpectedly. The Pickering emulsions stabilized by starch-based colloidal particles were rapidly stratified and coalesced during storage. Colloidal particles prepared from green vegetables and fruit peels demonstrated superior emulsifying capabilities than starch-based colloidal particles. This study indicates that broccoli can be a renewable source of whole-component plant-based stabilizers. It will provide valuable information for the exploitation of natural particle stabilizers and expand the application of plant resources in the food industry.

Assembly mechanism of glycosylated soybean protein isolate-chitosan nanocomposite particles and its Pickering emulsion construction for stabilization of Alpinia galanga essential oil: A mechanistic investigation

This study aimed to assess the feasibility of stabilization of Pickering emulsion with glycosylated soybean protein isolate-chitosan (SPI-Dex: CS) nanocomposite particles. The results indicated that the glycosylated modifications induced changes in the micromorphology and molecular structure of SPI, which resulted in a decrease in particle size and hydrophobicity and an increase in zeta potential. The complexation of CS-induced changes in the micromorphology and molecular arrangement of the composite nanoparticles, as well as the binding sites and modification effect, decreased with increased CS ratio. SPI-Dex-CS composite nanoparticles successfully stabilize Pickering emulsions loaded with Alpinia galanga essential oil, in which glycosylation and CS complexation jointly improved the encapsulation efficiency, centrifugal/storage stability, and rheological behavior of emulsions for essential oils. Nanocomposite particle assembly was subjected to electrostatic, hydrogen bonding, and hydrophobic forces, with the optimal performance of emulsions in the SPI-Dex75: CS25 ratio. The study is rewarding for applying polysaccharide-protein-based encapsulation systems in food and packaging applications.

Octenyl succinylation of myofibrillar protein: Structural, physicochemical and emulsifying properties

In this study, different succinylation degree octenyl succinic anhydride modified myofibrillar protein (OSA-modified MP) were prepared through succinylation modification by adding various OSA (1%, 3%, 6%, 11%, 16%, 21% and 26% of the weight of MP) to MP. The structure, physicochemical properties and emulsifying properties of OSA-modified MP were investigated. Results showed that succinylation degree of the modified protein rose from 1.46% to 94.99%. Electrophoresis, fourier transform infrared spectroscopy, intrinsic tryptophan fluorescence emission spectroscopy and scanning electron microscopy demonstrated the structure of MP was changed. As the DS increased, the particle size decreased by the maximum values of 0.24 times, the surface net charge and solubility increased by the minimum values of 2.71 and 13.50 time, respectively. All these results caused emulsifying activity and emulsifying stability to increase by 2.32 and 1.46 times, respectively, indicated that succinylation greatly improved the emulsifying properties of MP. Compared to the native MP, OSA-modified MP was more beneficial to stabilize Pickering emulsion. Thus, succinylation improved the emulsifying properties of MP and effectively expanded the application range of MP in the food industry.

Evolution Kinetics of Stabilizing Pickering Emulsion by Brush-Modified Janus Particles: DPD Simulation and Experimental Insights.

In the present study, we report the evolution of stabilizing Pickering emulsions using brush-modified Janus particles (JPs), utilizing the dissipative particle dynamics (DPD) simulation technique. Our results are subsequently corroborated with experimental findings. Each JP has one-half of the hydrophobic surface, with the other half embedded with hydrophilic polymer brushes grown via atom transfer radical polymerization (ATRP). Our generic simulation model analyzes the chemical kinetics of polymer brush growth on one-half of the initiator-embedded microparticle (MP) surface, resulting in the formation of JP. This involves evaluating monomer conversion and reaction rates. Our results exhibit a substantial influence of the number of JPs, grafted brush density, and brush length on oil-in-water emulsion stability. We studied the evolution kinetics and stability of emulsion formation by analyzing the growth of average domain size and corresponding scaling functions up to a late time limit. This study aims to clarify the connection between the size, quantity, and functionality of JPs and the stability of Pickering emulsions.

Natural product of angelica essential oil developed as a stable Pickering emulsion for joint interface lubrication

Development of high-performance joint injection lubricants has become the focus in the field of osteoarthritis treatment. Herein, natural product of angelica essential oil combined with the graphene oxide were prepared to the stable Pickering emulsion as a biological lubricant. The tribological properties of the Pickering emulsion under different friction conditions were studied. The lubricating mechanism was revealed and the biological activities were evaluated. Results showed that the prepared Pickering emulsion displayed superior lubrication property at the Ti6Al4V biological material interface. The maximum friction reduction and anti-wear abilities of the Pickering emulsion were improved by 36% and 50% compared to water, respectively. This was primarily due to the action of the double-layer lubrication films composed of the graphene oxide and angelica essential oil molecules. It was worth noting that the friction reduction effect of the Pickering emulsion at the natural cartilage interface was higher about 19% than that of HA used in clinic for OA commonly. In addition, the Pickering emulsion also displayed antioxidant activity and cell biocompatibility, showing a good clinical application prospect in the future.

Structural characteristics and emulsifying properties of linear dextrin/eicosapentaenoic acid composites: Effect of the degree of polymerization

This work aimed at building functional emulsions based on the linear dextrins (LDs) emulsion system. The gradient polyethylene glycol (PEG) precipitaion method was used to fractionate LDs into fractions with different degrees of polymerization (DP). A package, and co-precipitation procedure of LDs, and eicosapentaenoic acid (EPA) was used to fabricate LDs-EPA composites. The gas chromatograph, Fourier transform infrared spectroscopy, X-ray diffraction and differential scanning calorimetry analyses affirmed the formation of the LDs-EPA composites. The sizes of these composites were 38.55 nm, 59.14 nm to 80.62 nm, respectively, and they had good amphiphilicity. Compared with LDs, these LDs-EPA composites stabilized Pickering emulsion had higher stability and antioxidant capacity. Their emulsifying ability was positively correlated with the DP values of LDs. Furthermore, the oxidation stability results showed that LDsF10-EPA emulsion had the lowest lipid hydroperoxide (LHs) content, malondioxide (MDA) content and hexal concentration, which were 138.75 mmol kg−1 oil, 15.50 mmol kg−1 oil and 3.83 μmol kg−1 oil, respectively. The study provided a new idea and application values for the application of LDs in emulsion.

Effects of different solid particle sizes on oat protein isolate and pectin particle-stabilized Pickering emulsions and their use as delivery systems

Oat protein isolate (OPI)/high methoxyl pectin (HMP) complexes (OPP) were prepared to stabilized Pickering emulsions and applied as nutraceutical delivery systems. The different mass ratios and pH changed the interactions between OPI and HMP that caused the different size of OPP. Specifically, smaller particle size of OPP (125.7–297.6 nm) were formed when hydrophobic interactions along with electrostatic forces predominant in OPP (OPI:HMP = 3:1, pH 4, 5). Among these particles, OPP-2 could stabilize Pickering emulsion efficiently through formation of dense interfacial film, which exhibited the highest apparent viscosity and the smallest average droplet size (23.39 μm). Moreover, OPP-2 stabilized Pickering emulsions with superior stability not only exhibited higher encapsulation efficiency of 85.63%, but also could control curcumin release in simulated gastrointestinal fluids to improve curcumin's bioaccessibility. These results verified the possibility of OPP to be a Pickering emulsions stabilizer, and also identified its potential to be a stable delivery system for bioactive compounds.

Fabrication, characterization and application of Pickering emulsion gels stabilized by defatted grape seed powder

The feasibility of defatted grape seed powder (DGSP) stabilizing Pickering emulsion gels as butter substitute was investigated. The Pickering emulsion gel was constructed using DGSP through high-speed homogenization, and the effects of particle concentration (c) and oil-phase (Medium chain triglyceride) volume fraction (φ) on its structure and properties were investigated. Its application as a butter substitute was also evaluated. The results showed that DGSP had various particle shapes, a wide particle size distribution (3–130 μm), and a three-phase contact angle of 128.9 ± 2.3°. The O/W Pickering emulsion gels with φ ≥ 60% could be obtained at c ≥ 2%. The droplet diameter was negatively correlated with c and positively correlated with φ, while the gel strength was positively related to c and φ. The resulting emulsion gel demonstrated solid-like viscoelastic behavior and pseudoplasticity, and had the potential to serve as a butter substitute. The results can promote the application of grape seeds in food.

Chitosan-highland barley gliadin complex stabilizes Pickering emulsion

This study aimed to investigate the phase behavior of chitosan (Cs) - highland barley gliadin (HBG) complex and application in stabilizing Pickering emulsion. The turbidity results indicated that the insoluble complex was more likely to form between Cs and HBG at the higher concentration of HBG and NaCl (the optimal concentration ratio (1:40). The results of scanning electron microscope (SEM) and surface tension showed that the insoluble complex formed between Cs and HBG at pH 4.0 had better solubility and surface wettability. The results of isothermal titration calorimetry (ITC) indicated that each molecule of Cs could interact with 1, 2, and 7 HBG molecules under pH 2.5, 3.2, and 4.0, respectively. In addition, the Pickering emulsion stabilized by Cs-HBG complex showed great rheological properties, thermal stability and storage stability under the conditions of pH 4.0, concentration ratio (Cs:HBG) of 1:40, and oil fraction of 50%. These researches would contribute to the better utilization of polysaccharide-hydrophobic protein complex in the food and pharmaceutical fields.

Scalable Jet‐Based Fabrication of PEI‐Hydrogel Particles for CO2 Capture

The capture, regeneration, and conversion of CO2 from ambient air and flue gas streams are critical aspects of mitigating global warming. Solid sorbents for CO2 absorption are very promising as they have high mass transfer areas without energy input and reduce emissions and minimize corrosion as compared to liquid sorbents. However, precisely tunable solid CO2 sorbents are difficult to produce. Here, we demonstrate the high‐throughput production of hydrogel‐based CO2‐absorbing particles via liquid jetting. By wrapping a liquid jet consisting of an aqueous solution of cross‐linkable branched polyethylenimine (PEI) with a layer of suspension containing hydrophobic silica nanoparticles, monodisperse droplets with a silica nanoparticle coating layer was formed in the air. A stable Pickering emulsion containing PEI droplets was obtained after these ejected droplets were collected in a heated oil bath. The droplets turn into mm‐sized particles after thermal curing in the bath. The diameter, PEI content, and silica content of the particles were systematically varied, and their CO2 absorption was measured as a function of time. Steam regeneration of the particles enabled cyclic testing, revealing a CO2 absorption capacity of 6.5 ± 0.5 mol kg−1 solid PEI in pure CO2 environments and 0.7 ± 0.3 mol kg−1 solid PEI for direct air capture. Several thousands of particles were produced per second at a rate of around 0.5 kg per hour, with a single nozzle. This process can be further scaled by parallelization. The complete toolbox for the design, fabrication, testing, and regeneration of functional hydrogel particles provides a powerful route toward novel solid sorbents for regenerative CO2 capture.

Fabricating Pea Protein Micro-Gel-Stabilized Pickering Emulsion as Saturated Fat Replacement in Ice Cream.

Unsaturated fat replacement should be used to reduce the use of saturated fat and trans fatty acids in the diet. In this study, pea protein micro-gels (PPMs) with different structures were prepared by microparticulation at pH 4.0-7.0 and named as PPM (pH 4.0), PPM (pH 4.5), PPM (pH 5.0), PPM (pH 5.5), PPM (pH 6.0), PPM (pH 6.5), and PPM (pH 7.0). Pea protein was used as a control to evaluate the structure and interfacial properties of PPMs by particle size distribution, Fourier transform infrared spectroscopy (FTIR), free sulfhydryl group content, and emulsifying property. PPM (pH 7.0) was suitable for application in O/W emulsion stabilization because of its proper particle size, more flexible structure, high emulsifying activity index (EAI) and emulsifying stability index (ESI). The Pickering emulsion stabilized by PPM (pH 7.0) had a uniform oil droplet distribution and similar rheological properties to cream, so it can be used as a saturated fat replacement in the manufacture of ice cream. Saturated fat was partially replaced at different levels of 0%, 20%, 40%, 60%, 80%, and 100%, which were respectively named as PR0, PR20, PR40, PR60, PR80, and PR100. The rheological properties, physicochemical indexes, and sensory properties of low-saturated fat ice cream show that PPM (pH 7.0)-stabilized emulsion can be used to substitute 60% cream to manufacture low-saturated fat ice cream that has high structural stability and similar melting properties, overrun, and sensory properties to PR0. The article shows that it is feasible to prepare low-saturated fat ice cream with PPM (pH 7.0)-stabilized Pickering emulsion, which can not only maintain the fatty acid profile of the corn oil used, but also possess a solid-like structure. Its application is of positive significance for the development of nutritious and healthy foods and the reduction of chronic disease incidence.

Innovative production of phosphoric acid-hydrolyzed chitin nanocrystals for Pickering emulsion stabilization

Addressing the need for sustainable emulsification methods, this study introduces a novel approach by producing chitin nanocrystals (PA-ChNCs) through solid-state hydrolysis using minimal phosphoric acid. The aim was to assess the capability of PA-ChNCs to stabilize Pickering emulsions. Our investigation revealed a pH-responsive variation in particle size and surface charge of PA-ChNCs, critical for emulsion stability. They varied from 321.5 ± 10.5 nm to 2366.7 ± 171.6 nm and from 33.7 ± 1.2 mV to −19.9 ± 1.4 mV, respectively, when pH increased from 3 to 10. Notable, emulsions with a 50% oil-to-water (O:W) ratio presented larger droplets with increased viscosity, enhancing stability over 30 days significantly. In contrast, higher PA-ChNCs concentrations (2.0 wt%) at pH 10 resulted in smaller droplets and higher viscosity, indicating superior emulsion stability. This research contributes novel insights into eco-friendly emulsifier development, utilizing seafood byproducts and underscoring the use of PA-ChNCs as effective Pickering emulsion stabilizers in food applications.

Probing the stability and quality of the cellulose-based Pickering emulsion containing sesamolin-enriched sesame oil by chemometrics-assisted ATR-FTIR spectroscopy

This study presents the employment of Fourier transform infrared (FTIR) spectroscopy with attenuated total reflection and principal component analysis (PCA) to analyze the stability of a Pickering emulsion stabilized by carboxylated-cellulose nanocrystal (cCNC) comprising sesame oil phases with or without sesamolin. FTIR measurements identified an intermolecular hydrogen bond between the ester group of the triglyceride and the carboxyl group of the cCNC to create the emulsion droplet. The spectral bands from the hydroxyl group vibration (3700–3050 cm−1), carbonyl (1744 cm−1), CO groups of the ester triglyceride and cCNC (1160–998 cm−1) markedly discriminated between stabilized and destabilized emulsions. The PCA of FTIR spectra detected the change of molecular interaction during storage according to creaming, aggregation, and coalescence and changes in physicochemical parameters such as droplet size, refractive index, and zeta potential. Hence, PCA enabled the observation of the destabilization of emulsion in real-time.

Starch modification and its application in Pickering emulsion stabilization: a review

Starch modification and its application in Pickering emulsion stabilization: a review

Bacterial cellulose nanofibrils for the physical and oxidative stability of fish oil-loaded Pickering emulsions

Fish oil, a crucial unsaturated ω-3 unsaturated fatty acid supplement, is susceptible to oxidation. To improve the stability of fish oil, this study produced a fish oil Pickering emulsion via ultrahigh-pressure homogenization pressure (UHPH) using bacterial cellulose nanofibrils (BCNFs) as the water phase. The BCNFs exhibited a high aspect ratio fibril structure with an average diameter size of 12.64 nm. The results of particle size, zeta potential, emulsion properties, and oxidative stability showed that the emulsions with a 4:6 oil-water ratio and 0.15 % BCNFs exhibited excellent oxidative stability and good physical stability. The CLSM and rheological results suggested the BCNFs acted as a stabilizer and thickener, stabilizing the oil-water medium and enhancing the oxidation stability of fish oil Pickering emulsions. The Low-field nuclear magnetic analysis results indicated the emulsion had good physical stability, and water dispersed very well in the emulsion system. Moreover, the emulsions exhibited good stability at pH 6–12 and temperature 4–75 °C. This study provided a promising method for producing fish oil Pickering emulsions and improving the stability of fish oil.