Surface Of Oil Droplets Research Articles

Pickering emulsion gels stabilized by novel complex particles of high-pressure-induced WPI gel and chitosan: Fabrication, characterization and encapsulation

In this paper, WPI-chitosan complex particles (WCCPs) were prepared as a novel Pickering stabilizer based on high hydrostatic pressure (HHP). The mean particle size of WCCPs was larger than that of pure WPI gel particles (WGPs), and the zeta potential reversed from negative to positive, showing that chitosan molecules were adsorbed on the surface of WGPs. The three-phase contact angle (θo/w) of WGPs was about 120.7° while after addition of chitosan that of WCCPs can reach to 88.9°, indicating that WCCPs could be effective emulsifiers for Pickering emulsions. Rheological measurement demonstrated the formation of Pickering emulsion gels stabilized by WCCPs. The particle concentration of WCCPs affected the droplet size and creaming index of the Pickering emulsion gels significantly. Additionally, the emulsion gels strengthened as increasing the particle concentration of WCCPs. The interfacial structure of the Pickering emulsion gels was observed through the confocal laser scanning microscope images which showed that WCCPs coated densely on the surface of oil droplets performing like a compact barrier against coalescence. The effects of environmental stresses, including ionic strengths, pH and thermal treatment, were also evaluated. Lycopene was encapsulated in the WCCPs-stabilized Pickering emulsion gels and its stability during storage and in vitro release under simulated digestion were measured. Overall, these results showed that WCCPs were suitable for stabilizing Pickering emulsion gels and had the potential as a delivery system for bioactive compounds.

One-Step Dynamic Imine Chemistry for Preparation of Chitosan-Stabilized Emulsions Using a Natural Aldehyde: Acid Trigger Mechanism and Regulation and Gastric Delivery.

Chitosan is a polysaccharide widely used as a structuring agent in foods and other materials because of its positive charge (amino groups). At present, however, it is difficult to form and stabilize emulsions using chitosan due to its high hydrophilicity. In this study, oil-in-water emulsions were prepared using a one-pot green-chemistry method. The chitosan and aldehyde molecules were in situ interfacially conjugated during homogenization, which promoted the adsorption of chitosan onto the oil droplet surfaces where they created a protective coating. The universality of this method was verified by using chitosan with different molecular weights and four kinds of natural aldehydes [cinnamaldehyde (CA), citral (CT), citronella (CN), and vanillin (VL)]. Chitosan with higher molecular weight facilitated the formation of emulsions. By harnessing the dynamic covalent nature of imine bonds, chitosan emulsions with an imine link display dynamic behavior with acid-catalyzed hydrolysis. The aldehyde structure could control the pH point of trigger for breakdown of emulsions, which was 1.0, 3.0, 4.0, and 4.0 for CA emulsion, CT emulsion, CN emulsion, and VL emulsion, respectively. At pH 6.5, aldehyde helped to decrease the interfacial tension of chitosan to about 10 mN/m, while this value would increase if the pH decreased by adding acid during the measurement. Chemical kinetics studies indicated that the hydrophobicity and conjugation effect of the aldehyde together determined the trigger points and properties of the emulsion. Finally, we used the optimized emulsions to encapsulate and control the release of curcumin. The gastric release behavior of the curcumin depended on aldehyde structure: VL > CN > CT ≈ CA. Hence, a tailor-made trigger release emulsion system can be achieved by rational selection and design of aldehyde structure to control hydrophobicity and conjugation effect of aldehydes.

Effect of atmospheric cold plasma on structure, interfacial and emulsifying properties of Grass pea (Lathyrus sativus L.) protein isolate

Structure and emulsifying properties of Grass pea (Lathyrus sativus) protein isolate (GPPI) were investigated as function of cold plasma treatment at two voltages (9.4 and 18.6 kVpp) and treatment times (30s and 60s). Optical emission spectroscopy was used to characterize the nature of air DBD-cold plasma. The content of carbonyl group, Di-tyrosine cross-link and free sulfhydryl, secondary and tertiary structures, SDS-PAGE, surface charge, surface hydrophobicity and solubility of GPPI were characterized. Results from the optical emission showed that the density of charged and reactive species were greatly dependent on the voltage applied and increased at the higher voltage. With increasing the treatment time and voltage, the content of carbonyl groups, disulfide bonds, Di-tyrosine cross-link and also surface charge in GPPI increased, which in turn led to a decrease in the absorption rate of protein into the water-oil interface. However, higher efficiency of etching and oxidation rate at 18.6 kVpp after 60s of treatment, increased the dissociation of globulins, and thus the absorption rate of protein into interface increased. Plasma treatment resulted in the formation of more orderly secondary structures such as α and β structures. The loss of tertiary structure in the treated GPPIs at 9.4 kVpp increased the ability of GPPI in lowering the interfacial tension at oil-water interface. Whereas, more compact tertiary structure, higher ordered secondary structure and dissociation of globulins in the treated GPPI at 18.6 kVpp for 60s led to the formation of an interfacial layer with higher interfacial tension value. Compared to native GPPI, oil-droplets size of stabilized-emulsions with treated GPPI at 9.4 kVpp were bigger, indicating that these proteins were not able to form a strong interfacial film around the oil-droplets and prevent them from flocculation within the homogenizer. Whereas, in the emulsion stabilized with treated GPPIs at 18.6 kVpp for 60, the superior protein absorption and formation of dens and elastic interfacial film around oil droplets led to the formation of uniform small droplets with good stability against creaming. Overall, our results indicated that cold plasma treatment had positive effect on the interfacial and emulsifying properties of GPPI in terms of thermodynamic stability of protein on interface, globulin dissociation, and increase in oil-droplet surface electrical charge.

Displacement mechanism of polymeric surfactant in chemical cold flooding for heavy oil based on microscopic visualization experiments

In order to study the microscopic oil displacement mechanism of polymeric surfactant in chemical cold flooding for heavy oil, the indoor microscopic visualization displacement experiments were carried out. The flooding experiment of heavy oil was conducted by using water, osmotic modified oil displacing agent (a kind of polymeric surfactant) and water-in-oil emulsion (obtained by mixing polymeric surfactant and heavy oil) as displacing phases to study the mechanism of polymeric surfactant to enhance oil recovery in heavy oil reservoir. The experimental results show that the polymeric surfactant can increase the viscosity of the water phase, reduce the water-oil mobility ratio, expand the swept area, and there is no obvious fingering phenomenon which occurs during water flooding. The polymeric surfactant has the surfactant characteristics which can reduce the interfacial tension between oil and water to promote the formation of oil droplets with smaller droplet diameter. And the interfacial film composed of polymeric surfactant molecules will be formed on the surface of oil droplets to prevent the coalescence of oil droplets and improve the flow ability of oil phase. The water-in-oil emulsion can be miscible with the oil in heavy oil displacement process, and thus sweeps the areas such as the dead pores which cannot be swept by water and polymeric surfactant flooding, which increases the sweep efficiency to a certain extent. Cited as : Xu, F., Chen, Q., Ma, M., Wang, Y., Yu, F., Li, J. Displacement mechanism of polymeric surfactant in chemical cold flooding for heavy oil based on microscopic visualization experiments. Advances in Geo-Energy Research, 2020, 4(1): 77-85, doi: 10.26804/ager.2020.01.07

Antioxidative pectin from hawthorn wine pomace stabilizes and protects Pickering emulsions via forming zein-pectin gel-like shell structure

The development of natural and biodegradable polymer nanoparticles as Pickering emulsion stabilizers has attracted increasing interest. In this study, antioxidative pectin from hawthorn wine pomace (HP) was first produced. HP and zein-nanoparticles (ZPs) were used to fabricate zein-HP composite nanoparticles (ZHPs) via hydrogen bonding and electrostatic interaction. The ZHP composite at the HP-ZP ratio of 1:1 (w/w) exhibited near-neutral wettability (92.9o ± 1.01), thereby being used for stabilizing Pickering emulsion (ZHPEs). CLSM and cryo-SEM showed the anchoring of ZHPs onto the surface of oil droplets and the gel-like network structure in the continuous-phase. ZHPEs at 0.5–0.7 (v/v) oil fractions were pseudoplastic fluids with elastic-solid characteristics. ZHPEs with 0.6 and 0.7 (v/v) oil fractions showed excellent thermal stability 20–60 °C. The antioxidant capacity of HP helped protect the Pickering emulsion against its lipid oxidation. Therefore, antioxidative polysaccharides could stabilize Pickering emulsions as particle shell-materials while offering protection on lipid components against oxidation. This study has demonstrated the sustainable utilization of food waste for producing value-added products.

Oil-mineral flocculation and settling velocity in saline water

Cohesive particles in aquatic systems can play an important role in determining the fate of spilled oil via the generation of Oil-Mineral Aggregates (OMAs). Series of laboratory experiments have been conducted aiming at filling the knowledge gap regarding how cohesive clay particles influence the accumulation of petroleum through forming different aggregate structures and their resulting settling velocity. OMAs have been successfully created in a stirring jar with artificial sea-water, crude oil and two types of most common cohesive minerals, Kaolinite and Bentonite clay. With the magnetic stirrer adjusted to 490 rpm to provide a high level homogeneous flow turbulence (Turbulence dissipation ε estimated to be about 0.02 m2⋅s−3), droplet OMAs and flake/solid OMAs were obtained in oil-Kaolinite sample and oil-Bentonite sample, respectively. Kaolinite clay with relatively low flocculation rate (Rf = 0.13 min−1) tends to physically attach around the surface of oil droplets. With the lower density of oil, these oil-Kaolinite droplet OMAs generally show lower settling velocity comparing to pure mineral Kaolinite flocs. Differently, Bentonite clay with higher flocculation rate (Rf = 0.66 min−1) produces more porous flocs that can absorb or be absorbed by the oil and form compact flake/solid OMAs with higher density and settling velocity than pure Bentonite flocs. In the mixed Kaolinite-Bentonite sample (1:1 in weight), oil is observed to preferably interacting with Bentonite and increase settling velocity especially in larger floc size classes.

Fabrication of recyclable multi-responsive magnetic nanoparticles for emulsified oil-water separation

In order to promote the convenience and environmental friendliness of recycling process for the magnetic nanoparticles (MNPs) used in emulsified oil-water separation, a series of recyclable multi-responsive MNPs were successfully fabricated via grafting triple sensitive copolymers onto the silica coated ferroferric oxide (Fe3O4@SiO2) nanoparticles. It was found that the performance of fabricated MNPs was significantly influenced by three environmental parameters, namely pH value, temperature and ionic strength (IS) of water. The synthesized MNPs tended to assemble at oil droplet surface at a temperature less than lower critical solution temperature (LCST), lower pH level or higher IS, thereby facilitating removal of emulsified oil from water phase under external magnetic field. On the contrary, these MNPs could also reversibly desorb form oil droplet surface at a temperature higher than LCST, higher pH level or lower IS. Accordingly, the spent MNPs could be easily regenerated by just regulating solution temperature, pH or IS, rather than by washing with organic solvent, thereby minimizing the risks of secondary pollution. Recycling experiment showed that the well-designed MNPs could be reused up to five cycles without showing remarkable decline in separation efficiency. It’s noteworthy that the MNPs exhibited superior separation efficiency at high IS, which is typically encountered for real saline oily water system, thereby spent MNPs could be easily recycled by merely using deionized water due to the dramatical decrease of IS during their rinsing process, suggesting its applicability for practical use. It is expected that the development of this multi-responsive and recyclable MNPs can potentially offer a promising, facile, cost-efficient and eco-friendly route for the emulsified oily wastewater treatment.

Pickering emulsion gels stabilized by high hydrostatic pressure-induced whey protein isolate gel particles: Characterization and encapsulation of curcumin

In this study, whey protein isolate (WPI) gel particles were fabricated via high hydrostatic pressure (HHP) treatment and homogenization and the potential of using the particles as food-grade stabilizers to form Pickering emulsions and emulsion gels were studied. The result showed that pH had a significant effect on the properties of WPI gel particles. In the pH range near the isoelectric point (pI) (around pH 5.0), the particles exhibited spherical structure with larger size. The droplet size, creaming stability, microstructure and rheological properties of the Pickering emulsions stabilized by the WPI gel particles were influenced by pH and ionic strength, particle concentration and oil fraction. Pickering emulsion gels were formed from the Pickering emulsions stabilized by the particles at pH 5.0 after storage for 3 days at room temperature (25 °C). Confocal laser scanning microscopy (CLSM) demonstrated that the WPI gel particles formed a densely packed particle layer on the surface of oil droplet, suggesting the potential of these particles as Pickering emulsion stabilizers. Besides, the Pickering emulsion gels had the highest loading efficiency of curcumin and best stability against light degradation.

Fabrication and characterization of oil-in-water emulsions stabilized by macadamia protein isolate/chitosan hydrochloride composite polymers

To utilize macadamia protein isolate (MPI) from macadamia oil production waste, the emulsifying capacity of macadamia protein isolate (MPI) was investigated. MPI-chitosan hydrochloride (CHC) composite polymer (MCCP) was designed and fabricated using a two-step pH cycling method. The particle size, zeta potential, and stability of MCCPs with different CHC-to-MPI ratios were examined. MCCP fabricated with 20% CHC-to-MPI ratio was selected for emulsion preparation based on its particle size. MCCP stabilized emulsions better than either MPI alone or MPI mixed with CHC. Confocal laser scanning microscopy images proved that MCCP formed a layer on the surface of oil droplets. The surface loading and microstructure of the emulsion suggested that MCCPs stabilize the emulsion through a percolating network structure. The stability of the emulsions increased with increased MCCP concentration and oil fraction. Higher viscosity was also observed with higher MCCP concentration and oil fraction. The stability of the emulsion was then evaluated under different pH values and ionic strengths. Overall, this study successfully fabricated the composite polymers with MPI and CHC, and emulsions stabilized by the composite polymers. It provided a potential application of MPI in novel foods for individuals with vegetarian or Kosher requirements.

Self-assembly of mono- and poly-dispersed nanoparticles on emulsion droplets: antagonistic vs. synergistic effects as a function of particle size.

In this work, using Dissipative Particle Dynamics simulations, we provide fundamental insights into the self-assembly of nanoparticles (NPs) on droplet surfaces in an oil-in-water emulsion. We highlight the effect of particle size on the arrangement of NPs for different interparticle interactions. NPs of two different sizes were considered. In general, when the NP-NP interaction is changed from repulsive to attractive, a transition in the NP arrangement occurs from weekly-connected networks to clusters of NPs separated by particle-free domains. When NP-NP interactions are strongly attractive, NPs yield small 3D aggregates on the droplet surface. These arrangements seem to agree with experimental observations reported in the literature. In addition, our simulations suggest that small NPs are able to diffuse more easily on the droplet surface, which leads to prompt self-organisation, while large NPs are more likely to form metastable structures, perhaps because of slow mobility and strong adsorption to the interface. Our analysis suggests that thermal fluctuations could provide the activation energy for the small NPs to escape local minima in the free energy landscape. The results obtained for systems containing NPs of two sizes provide evidence of size segregation on the droplet surface, which could be useful when NP self-assemblies are used, for example, to template supra-molecular materials. However, analysis of the simulated trajectories suggests that the results depend strongly on the initial configuration, as the larger NPs seem to impose barriers for the small NPs to adsorb and diffuse on the droplet surface.

Hybrid shell microcapsules containing isophorone diisocyanate with high thermal and chemical stability for autonomous self‐healing of epoxy coatings

ABSTRACTSilica‐polyurea/polyuretane hybrid shell microcapsules (MCs) loaded with isophorone diisocyanate (IPDI) with long shelf‐life and high thermal and chemical stability are prepared via emulsification followed by interfacial polymerization at the surface of oil droplets of the oil‐in‐water emulsion. The resultant MCs are aimed at self‐healing performance in epoxy coatings. A commercially available, highly reactive polyisocyanate named tris(p‐isocyanatophenyl) thiophosphate is successfully employed as shell forming agent, while triethoxyoctylsilane and hexadecyltrimethoxysilane (HDMS) are tested as “latent” active hydrogen sources. The resulting MCs display core–shell morphology, spherical shape with diameter of 5–20 μm, shell thickness ca. 1–2 μm, and an IPDI core fraction of 69 and 65 wt %, when HDMS and triethoxyoctylsilane are employed, respectively. MCs exhibit an increased thermal stability, comparing with pure IPDI, which makes them robust enough to resist the thermal cycles involved in the coating's preparation. Stability of MCs inside specific solvents and chemicals, their chemical composition and shelf‐life as well as effect of MCs on the epoxy curing are evaluated by Fourier transformed infrared spectroscopy. MCs, remarkably, show excellent environment stability and a long shelf‐life of more than 3.5 months. Their addition to an epoxy formulation is found to heal damaged zones in the epoxy coating, as shown by scanning electron microscopy and electrochemical impedance spectroscopy. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48751.

Autonomous self-healing in epoxy coatings provided by high efficiency isophorone diisocyanate (IPDI) microcapsules for protection of carbon steel

This work aims at investigating the self-healing ability of epoxy coatings, modified with microcapsules containing highly reactive isocyanate in their core. Highly efficient, thermally and chemically stable isophorone diisocyanate microcapsules were prepared via emulsification followed by interfacial polymerization at the surface of oil droplets of the oil-in-water (O/W) emulsion. The microcapsules were incorporated into an epoxy coating to protect carbon steel from corrosion. Scanning Electron Microscopy (SEM) was used to assess the microcapsules̕ and coating morphology. The physico-chemical characterization of the microcapsules was studied by Fourier Transformed Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). Electrochemical Impedance Spectroscopy (EIS) was employed to evaluate the protective performance of coated steel samples and results confirmed that the barrier properties of modified coatings increased over time. The self-healing ability was studied via Localized Impedance Spectroscopy (LEIS), Scanning Vibrating Electrode Technique (SVET) and Scanning Ion-Selective Electrode Techniques (SIET) on coated steel samples containing artificial defects. This comprehensive study confirmed the ability of the capsules to heal damaged areas in the coating and to mitigate corrosion thanks to the formation of a protective polymeric barrier layer.

Effects of water‐soluble soybean polysaccharide on rheological properties, stability and lipid digestibility of oil‐in‐water emulsion during in vitro gastrointestinal digestion

SummaryWater‐soluble soybean polysaccharide (SSPS) is a naturally occurring emulsifier. SSPS was used as the sole emulsifier to stabilize an oil‐in‐water (O/W) emulsion. The effects were investigated of different SSPS concentrations (3–20% (w/w)) on the lipid digestibility, rheological properties and stability of O/W emulsions during in vitro digestion model. The droplet size of the emulsions tended to increase during the oral phase because the emulsions were unstable and droplets coalesced, except with a SSPS concentration of 20% (w/w). The presence of SSPS markedly reduced the free fatty acid (FFA) content after its stabilized O/W emulsion passed through in vitro gastrointestinal digestion. The amount of FFA significantly decreased as the concentration of SSPS increased due to SSPS stabilization film on oil droplet surface and high viscous system. SSPS may be an attractive alternative ingredient to control the lipid digestibility of emulsions for various food products.

Emulsion stabilization mechanism of combination of esterified maltodextrin and Tween 80 in oil-in-water emulsions.

Esterified maltodextrins (EMs) were prepared using enzyme-catalyzed reaction of maltodextrin (DE of 16 and 9) and palmitic acid. The emulsion stabilization mechanism was investigated of a combination of Tween 80 and EM in oil-in-water emulsion to determine interfacial tension, ζ-potential, non-adsorbed Tween 80 in centrifuged-serum of emulsion, and fluoresced microstructure. The interfacial tension and non-adsorbed Tween 80 content of combination of Tween 80 and EM-stabilized oil-in-water emulsions were closed to those of sole Tween 80-stabilized emulsion. The ζ-potential of sole Tween 80-stabilzed emulsion had a small positive charge but ζ-potential changed to small negative charge as EM was added into Tween 80-stabilzed emulsion. Fluorescence microstructure confirmed that EM was adsorbed on oil droplet surface, stabilized by Tween 80. The mechanism of emulsion stabilization may conclude that Tween 80 was mainly adsorbed at oil surface and EM may interact with Tween 80 to form a double stabilization layer without competitive replacement.

Multi-functional magnetic bacteria as efficient and economical Pickering emulsifiers for encapsulation and removal of oil from water

HypothesisEffective removal of oil pollutants from the surface of water is important in oil-polluted environments. Since living microorganisms can be used as particle-stabilizers for oil emulsification, magnet-responsive oil-degrading bacteria (M-Bacteria) are expected to integrate three intriguing properties, such as Pickering emulsification, magnet-responsiveness and bioactivity. Hence, by acting as an efficient Pickering emulsifier to encapsulate oil pollutants, it should be possible to eliminate oil from water under the application of an external magnetic field. ExperimentsOil-degrading bacteria, Brevibacillus parabrev, were successfully coated with a shell of magnetic Fe3O4 nanoparticles using polycations. The morphology and physicochemical characteristics of M-Bacteria were characterized by various techniques. A systematic study on Pickering emulsification of M-Bacteria and the removal of five types of oils were performed. Specific adsorption of M-Bacteria at the oil droplet surface was observed through optical, fluorescence, and scanning electronic microscopy images. The biodegradation process of oil was monitored using gas chromatography. FindingsEco-friendly M-Bacteria not only acts as an effective particle emulsifier to realize encapsulation and magnetic separation of oil contaminants but also shows a strong ability for further conversion of oil. This is the first report of oil removal via Pickering emulsification of living bacterial cells, which shows the potential of bacterial cells as functional colloidal materials in treating oily wastewater.

Probing the interaction mechanism between oil droplets with asphaltenes and solid surfaces using AFM

Wetting phenomena of oil/water/solid systems are fundamentally governed by the stability of confined water film and interaction mechanism between oil droplet and solid surface in water. Herein, droplet probe AFM was used to quantify the surface forces of model oil droplets including toluene and heptol in presence of interfacial asphaltenes interacting with mica surfaces of varied hydrophobicity in different water environments. It was found that adsorption of asphalenes at oil/water interface could result in the enhanced electrical double layer (EDL) repulsion at low salinity while strengthen the steric repulsion at high salinity, both of which contributed to a more stable water film between oil droplets and mica surfaces, inhibiting oil droplet attachment. Addition of heptane strengthened the repulsive EDL force and steric hindrance since more asphaltenes were adsorbed onto the interface. For hydrophobized mica surface, the attractive hydrophobic interaction could overcome steric hindrance due to interfacially adsorbed asphaltenes, thereby inducing strong attachment and adhesion of oil droplet. Our results demonstrate the nanomechanical mechanism underlying the interactions between oil droplets and solid surfaces in presence of interfacial materials, which can further explain the wetting of oil/water/solid systems in many engineering applications such as oil fouling and corrosion, and oil/water separation.

Oil detachment by modified nanoparticles: A molecular dynamics simulation study

Stripping residual oil adsorbed on reservoir surface is essential for enhanced oil recovery (EOR). Abundant experimental and modelling have investigations identified the superior EOR capability of Janus nanoparticle. However, the tortuous synthesis procedure and expensive cost heavily limit its large-scale application. In this work, adopting molecular dynamics simulation, three kind of modified nanoparticles grafted with hydrophilic chains (NP1), hydrophobic chains (NP2), and mixed hydrophilic and hydrophobic chains (NP3), were designed to detach adsorbed oil droplet on silica surface. These modified nanoparticles could be prepared via conveniently chemical modification. The equilibrium adsorption configuration and dynamic displacing process were investigated. Simulations indicate that the grafted nanoparticles could promote the oil droplet detachment, and the NP3 gives optimal EOR capability. Furthermore, the interaction between oil droplet and silica surface, oil/water interfacial activity, and coherent energy of oil droplet, were analyzed to reveal the underlying EOR mechanism of grafted nanoparticles. This work provides one kind of modified nanoparticle (NP3) for the development of high-performance EOR agent.

Design of a biodegradable carrier for the application of controller bacteria on air–water interfaces

The formulation of a biodegradable carrier which effectively concentrates microorganisms on air-water interfaces is proposed. This avoids the dispersion of bacteria into the bulk liquid phase and at the same time prevents their sedimentation. This formulation can be used in biocontrol and bioremediation treatments where the target is at the position of the air-water interface, as in the case of the treatment of rice diseases caused by Sclerotium oryzae and Rhizoctonia complex. The carrier is an oil-in-water (O/W) emulsion which contains lecithin and chitosan in both phases at different proportions. In a stable formulation, bacteria that are adsorbed onto the surface of oil droplets are carried with them and flowed upward to the air-water interface, due to buoyancy forces. When using the biodegradable carrier, it is possible to recover at least 15-fold more bacteria from the air-water interface than in the case of using the aqueous formulation. The emulsion O/W is applied to the surface by dripping, resulting in a homogeneous two-dimensional film distribution. With this application device, the number of bacteria at the air-water interface is significantly increased. © 2019 Society of Chemical Industry.

Stability of emulsion stabilized by low-concentration soybean protein isolate: Effects of insoluble soybean fiber

Effects of insoluble soybean fiber (ISF) on the emulsion properties stabilized by soybean protein isolate (SPI, 0.40 wt%) and the stability of emulsions exposed to environmental conditions (pH and NaCl) were studied in this paper. As ISF increased (0–0.40 wt%), higher ζ-potential and smaller d4,3 of suspended SPI/ISF complexes were observed in aqueous system, which might be due to the interactions between SPI and ISF and the formation of SPI/ISF complexes. The ζ-potential of emulsions continuously decreased, the d4,3 firstly decreased and then increased while surface protein content (PA) and concentrations (Γ), viscosity as well as storage modulus (G′) continuously increased, which might be related to the low concentration of SPI, the SPI/ISF interactions and excessive unadsorbed ISF molecules in the continuous phase. The emulsions exhibited better resistance to pH and salt with increasing ISF while ISF also had a positive effect on the storage stability. All the results indicated that ISF could promote the stability of SPI emulsion, which was most likely ascribed to the electrostatic interactions, the gel-like network structure and the function of ISF as emulsifier and thickener, facilitating adsorption of protein onto the oil droplet surface and enhancing the interfacial protective coating. In summary, the ISF has a great potential to be applied in the emulsion system containing low-concentration protein, thus lowering the addition of protein and endowing the nutritional value of insoluble dietary fiber.

Continuous synthesis of plate-like silica microparticles using microfluidics

The synthesis of plate-like silica particles, which are of importance for a variety of applications, are mainly based on the widely adopted method of the sol-gel reaction of silicon alkoxides in traditional batch-wise instrumentation. In this study, continuous-flow synthesis of amorphous plate-like silica particles is reported through combining droplet-based microfluidics and the sol-gel reaction of tetraethyl orthosilicate. The reaction was conducted at the surface of oil droplets, comprising tetraethyl orthosilicate (TEOS), suspended in acidic (HCl) water, resulting in silica particles on the surface of the droplets, leaving the device with outlet flow. The synthesized particles had plate-like structure with thickness less than 1 μm and microscale in two other dimensions. The influences of experimental parameters (TEOS and HCl concentrations and the flow rate of aqueous phase) on the silica production rate were examined. With increase in the TEOS and HCl concentrations, the production rate increases monotonically. With increase in the flow rate of aqueous phase, the production rate increases up to a specific flow rate. Beyond the flow rate, the production rate decreases with increase in the flow rate. A phenomenological model is proposed to address the production rate using the droplet-based microfluidic system. In addition, response surface methodology (RSM) was used to statistically model and optimize the production rate. At optimum values for the experimental parameters, the experimentally measured production rate was considerably comparable to that predicted by RSM.