A diffusing wave spectroscopy study of the dynamics of interactions between high methoxyl pectin and sodium caseinate emulsions during acidification

A non-invasive technique, diffusing wave spectroscopy (DWS), and traditional dynamic light scattering (DLS) were used to study the interactions of high methoxyl pectin (HMP) with sodium caseinate-stabilized emulsion droplets. At pH 6.8, the droplet size measured by DLS did not change as a function of HMP concentration (up to 0.3%). However, the droplet diameter measured by DWS kept relatively constant up to 0.07% HMP after which it showed drastic increases. The turbidity parameter 1/l* decreased with HMP concentration and levelled off at 0.07% HMP, indicating that the system underwent reorganization and reached equilibrium at 0.07% HMP. During acidification at pH 5.4, right before the pH of aggregation of control emulsions, all emulsions containing 0.05–0.2% HMP showed an increase of 1/l*. This increase indicated the interaction of HMP with sodium caseinate at the interface. Emulsions containing 0.05 and 0.1% HMP also showed destabilization, and the pH of destabilization depended on the concentration of HMP. Sufficient amounts of HMP (0.2%) stabilized the caseinate-coated oil droplets, and the mean square displacement slope was close to 1 throughout, indicating free diffusion of emulsion droplets.     

Fractional crystallization of oil droplets in O/W emulsions dispersed by Synperonic F127

The aim of this works is to study an oil-in-water emulsion stabilized with a triblock copolymer Synperonic F127 which presents a double size distribution of oil droplets. The emulsions were studied experimentally by means of differential scanning calorimetry (DSC) and dynamic light scattering (DLS). The DSC analysis was carried out focusing on the cooling behavior of the emulsion. The cooling thermograms of the oil-in-water emulsion revealed two crystallization peaks with Gaussian profile; the interesting characteristic is that both peaks are separated in temperature. In accordance to previous works for a single oil dispersed within an aqueous phase, the DSC technique must show a single Gaussian peak of crystallization attributable to a size distribution of droplets. In the present case of emulsions stabilized with 1 g/L of Synperonic F127, the aggregation behavior of triblock as a function of temperature allows to produce an emulsion with a double size droplet distribution. Comparison with emulsions stabilized with 2 and 4 wt% of non-ionic Tween 20 are also presented.     

Preparation characteristics of water-in-oil-in-water multiple emulsions using microchannel emulsification

Microchannel (MC) emulsification is a novel technique for preparing monodispersed emulsions. This study demonstrates preparing water-in-oil-in-water (W/O/W) emulsions using MC emulsification. The W/O/W emulsions were prepared by a two-step emulsification process employing MC emulsification as the second step. We investigated the behavior of internal water droplets penetrating the MCs. Using decane, ethyl oleate, and medium-chain triglyceride (MCT) as oil phases, we observed successful MC emulsification and prepared monodispersed oil droplets that contained small water droplets. MC emulsification was possible using triolein as the oil phase, but polydispersed oil droplets were formed from some of the channels. No leakage of the internal water phase was observed during the MC emulsification process. The internal water droplets penetrated the MC without disruption, even though the internal water droplets were larger than the resulting W/O/W emulsion droplets. The W/O/W emulsion entrapment yield was measured fluorometrically and found to be 91%. The mild action of droplet formation based on spontaneous transformation led to a high entrapment yield during MC emulsification.     

Stabilization of Water‐Soluble Antioxidant in Water‐in‐Oil‐in‐Water Double Emulsions

Abstract

In this study, we are introducing a method that can effectively stabilize antioxidants in water‐in‐oil‐in‐water (W/O/W) double emulsions. Preliminarily, stable W/O/W double emulsions were produced by manipulating the characteristics of internal aqueous phase via two‐stage emulsification, resulting consequently in the formation of fine internal water droplets in the dispersed oil droplets. From conductivity measurements that can determine the elution amount of internal aqueous phase, it was confirmed that the double emulsion stability could be improved by treating the internal aqueous phase with a hydroxypropyl‐beta‐cyclodextrin. In this study, kojic acid, 5‐hydroxy‐2‐(hydroxymethyl)‐4‐pyrone was selected as a model antioxidant. The stabilization of kojic acid was attempted by locating it in the internal water droplets of the stable W/O/W double emulsions. The stability of kojic acid in the double emulsion system could be maintained at 90% for 10 weeks at high temperature. We believe that these stable W/O/W double emulsions could be used meaningfully as a carrier for many unstable antioxidants.     

Characterization of fluorocarbon-in-water emulsions with added triglyceride

Fluorocarbon-in-water emulsions are being explored clinically as synthetic oxygen carriers in general surgery. Stabilizing fluorocarbon emulsions against coarsening is critical in maintaining the biocompatibility of the formulation following intravenous administration. It has been purported that the addition of a small percentage of long-chain triglyceride results in stabilization of fluorocarbon emulsions via formation of a three-phase emulsion. In a three-phase emulsion, the triglyceride forms a layer around the dispersed fluorocarbon, thereby improving the adhesion of the phospholipid surfactant to the dispersed phase. In the present study, we examined the effect of triglyceride addition on the physicochemical characteristics of the resulting complex dispersion. In particular, we examined the particle composition and stability of the dispersed particles using a method which first fractionates (classifies) the different particles prior to sizing (i.e., sedimentation field-flow fractionation). It was determined that the addition of a long-chain triglyceride (soybean oil) results in oil demixing and two distinct populations of emulsion droplets. The presence of the two types of emulsion droplets is not observed via light scattering techniques, since the triglyceride droplets dominate the scattering due to a large difference in the refractive index between the particles and the medium as compared to fluorocarbon droplets. The growth of the fractionated fluorocarbon emulsion droplets was followed over time, and it was found that there was no difference in growth rates with and without added triglyceride. In contrast, addition of medium-chain-triglyceride (MCT) oils results in a single population of emulsion droplets (i.e., a three-phase emulsion). These emulsions are not stable to droplet coalescence, however, as significant penetration of MCT into the phospholipid lipid interfacial layer results in a negative increment in the monolayer spontaneous curvature, thereby favoring water-in-oil emulsions and resulting in destabilization of the emulsion to the effects of terminal heat sterilization or mechanical stress.     

Oil-in-water emulsification induced by ellipsoidal hematite colloids: evidence for hydrolysis-mediated self-assembly

We report on the preparation of a novel type of particle-stabilized oil-in-water emulsions. The emulsification mechanism comprises partial hydrolysis of the oil phase promoted by the alkaline surface of ellipsoidal hematite colloids stabilized by tetramethylammonium hydroxide. This mechanism yields monodisperse oil droplets with embedded single ellipsoidal particles. The emulsions, which are stable for at least several months, can be polymerized by radical initiation, to yield latex-like particles with interesting optical and magnetic properties due to their anisotropic hematite cores. Moreover, we show that complex composite core-shell colloids can be prepared by PMMA growth and silica deposition on polymerized emulsion droplets. Finally, as an example of a possible application for our system, we have measured translational and rotational diffusion coefficients of hematite-stabilized oil droplets by depolarized dynamic light scattering. The latter technique can also be employed to monitor the spontaneous emulsification in time.     

Preparation of calcium alginate nanoparticles using water-in-oil (W/O) nanoemulsions

A procedure for the preparation of calcium alginate nanoparticles in the aqueous phase of water-in-oil (W/O) nanoemulsions was developed. The emulsions were produced from mixtures of the nonionic surfactant tetraethylene glycol monododecyl ether (C(12)E(4)), decane, and aqueous solutions of up to 2 wt % sodium alginate by means of the phase inversion temperature (PIT) emulsification method. This method allows the preparation of finely dispersed emulsions without a large input of mechanical energy. With alginate concentrations of 1-2 wt % in the aqueous phase, emulsions showed good stability against Ostwald ripening and narrow, monomodal distributions of droplets with radii <100 nm. Gelation of the alginate was induced by the addition of aqueous CaCl(2) to the emulsions under stirring, and particles formed were collected using a simple procedure based on extraction of the surfactant on addition of excess oil. The final particles were characterized using cryo-transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS). They were found to be essentially spherical with a homogeneous interior, and their size was similar to that of the initial emulsion droplets. The herein presented "low-energy" method for preparation of biocompatible nanoparticles has the potential to be used in various applications, e.g., for the encapsulation of sensitive biomacromolecules.     

Internally self-assembled submicrometer emulsions stabilized with a charged polymer or with silica particles

Internally self-assembled submicrometer emulsions were stabilized by F127, by the charged diblock copolymer K151, by L300 particles, and by sodium dodecyl sulfate (SDS). The stabilization of all investigated internal phases and the impact of the stabilizer on them are discussed. The use of charged stabilizers results in a highly negative zeta potential of the emulsion droplets, which can be exploited as a means to control their adsorption onto charged surfaces. Small-angle X-ray scattering and dynamic light scattering were used to determine the internal structure and size of the emulsion droplets, respectively.     

Temperature-induced protein release from water-in-oil-in-water double emulsions

A model water-in-oil-in-water (W1/O/W2) double emulsion was prepared by a two-step emulsification procedure and subsequently subjected to temperature changes that caused the oil phase to freeze and thaw while the two aqueous phases remained liquid. Our previous work on individual double-emulsion globules1 demonstrated that crystallizing the oil phase (O) preserves stability, while subsequent thawing triggers coalescence of the droplets of the internal aqueous phase (W1) with the external aqueous phase (W2), termed external coalescence. Activation of this instability mechanism led to instant release of fluorescently tagged bovine serum albumin (fluorescein isothiocyanate (FITC)-BSA) from the W 1 droplets and into W2. These results motivated us to apply the proposed temperature-induced globule-breakage mechanism to bulk double emulsions. As expected, no phase separation of the emulsion occurred if stored at temperatures below 18 degrees C (freezing point of the model oil n-hexadecane), whereas oil thawing readily caused instability. Crucial variables were identified during experimentation, and found to greatly influence the behavior of bulk double emulsions following freeze-thaw cycling. Adjustment of these variables accounted for a more efficient release of the encapsulated protein.     

Nanoemulsions prepared by a two-step low-energy process

A simple low-energy two-step dilution process has been applied in oil/surfactant/water systems with pentaoxyethylene lauryl ether (C12E5), dodecyldimethylammonium bromide, sodium bis(2-ethylhexyl)sulfosuccinate, sodium n-dodecyl sulfate-pentanol, and hexadecyltrimethylammonium bromide-pentanol. Appropriate formulations were chosen for the concentrate to be diluted with water to generate oil-in-water (O/W) emulsions or nanoemulsions. For the system of decane/C12E5/water, bluish, transparent nanoemulsions having droplet radii of the order of 15 nm were formed, only when the initial concentrate was a bicontinuous microemulsion, whereas opaque emulsions were generated if the concentrate began in an emulsion-phase region. Nanoemulsions generated in the system decane/C12E5/water have been investigated both by dynamic light scattering (DLS) and contrast-variation small-angle neutron scattering (SANS). The SANS profiles show that nanodroplets exist as spherical core-shell (decane-C12E5) particles, which suffer essentially no structural change on dilution with water, at least for volume fractions phi down to 0.060. These results suggest that the nanoemulsion droplet structure is mainly controlled by the phase behavior of the initial concentrate and is largely independent of dilution. A discrepancy between apparent nanoemulsion droplet sizes was observed by comparing DLS and SANS data, which is consistent with long-range droplet interactions occurring outside of the SANS sensitivity range. These combined phase behavior, SANS, and DLS results suggest a different reason for the stability/instability of nanoemulsions compared with earlier studies, and here it is proposed that a general mechanism for nanoemulsion formation is homogeneous nucleation of oil droplets during the emulsification.     

Osmotically Driven Formation of Double Emulsions Stabilized by Amphiphilic Block Copolymers

Double emulsions are valuable for the formation of multi‐compartmental structures. A variety of pathways to prepare double emulsions have been developed, but high‐throughput routes to droplets of controlled size and architecture remain scarce. A new single‐step process is introduced for preparation of water‐in‐oil‐in‐water double emulsions by a previously unexplained process of self‐emulsification. We show that the origin of this process is the osmotic stress resulting from the presence of salt impurities within the amphiphilic block copolymers used for emulsion stabilization. Further, we utilize osmotically driven emulsification to tailor the structures of multiple emulsions, which upon solvent evaporation can yield multi‐compartmental capsules or hierarchically structured porous films.     

Differential scanning calorimetry (DSC) in multiple W/O/W emulsions

Multiple water-in-oil-in-water (W/O/W) emulsions offer a huge potential as encapsulation systems in different food, cosmetic, and pharmaceutical applications. Because of their complex structure, however, it is difficult to characterize these systems. Typical measurement techniques to determine the size and stability of the inner water droplets encapsulated in the oil droplets show limitations and inaccuracies. Determining the total amount of water in the inner droplets is most often done by indirect methods to date. We describe an analytical method based on differential scanning calorimetry (DSC) for characterizing the total amount of encapsulated water droplets and their stability in W/O/W multiple emulsions. It uses the possibility to directly determine the latent heat of freezing of water droplets of the same size and composition as in the multiple emulsions. The amount of water in the inner droplets of a W/O/W emulsion can thus be calculated very accurately. It is shown that this method enables furthermore detecting multi-modalities in the size distribution of inner water droplets in W/O/W emulsions. Changes in droplet size distribution of the inner droplets occurring during the second emulsification step of processing or during storage can be detected. DSC thus offers a powerful tool to characterize the structure of multiple W/O/W emulsions.     

Phase transitions and microstructure of emulsion systems prepared with acylglycerols/zinc stearate emulsifier

The emulsification processes, during which acylglycerols/zinc stearate emulsifier, water, and oil phase formed ternary systems, such as water-in-oil (W/O) emulsions, oil-in-water (O/W) dispersions, and unstable oil-water mixtures, were investigated in order to characterize the progressive transformations of the dispersed systems. The type, structure, and phase transitions of the systems were found to be determined by temperature and water phase content. Crystallization of the emulsifier caused the destabilization and subsequent phase inversion of the emulsions studied, at a temperature of 60-61 degrees C. The observed destabilization was temporary and led, at lower temperature, to W/O emulsions, "O/W + O" systems, or O/W dispersions, depending on the water content. Simultaneous emulsification and cooling of 20-50 wt % water systems resulted in the formation of stable W/O emulsions that contained a number of large water droplets with dispersed oil globules inside them ("W/O + O/W/O"). In water-rich systems (60-80 wt % of water), crystallization of the emulsifier was found to influence the formation of crystalline vesicle structures that coexisted, in the external water phase, with globules of crystallized oil phase. Results of calorimetric, rheological, and light scattering experiments, for the O/W dispersions obtained, indicate the possible transition of a monostearoylglycerol-based alpha-crystalline gel phase to a coagel state, in these multicomponent systems.     

Study on the relationship between emulsion stability and droplet dynamics of a spontaneous emulsion for chemical enhanced oil recovery

Spontaneous emulsion (SE) has attracted increasing attention, especially in the development of low-permeability reservoirs (with an average throat radius of 0.1–2?µm) for enhanced oil recovery. In this work, based on multiple light scattering principles, the relationship between emulsion stability and the droplet dynamics of SEs was investigated. The results showed that the synergistic effect of surfactant and polymer was crucial for oil emulsification in brine, since the stability of the emulsion was greatly improved. The emulsion stability and droplet dynamics depend on the temperature, concentration, and type of emulsifier. The optimal combination system had the lowest Turbiscan stability index value, and the emulsion stability time was more than 2000s. The average droplet size was 1.50?µm, and the droplet migration rate was 7.21?mm/h. The stability of the emulsion was resulted from the microscopic droplet dynamics. By reducing the migration rate of the droplets, stability of the emulsion can be obtained. Finally, the stability and droplet dynamics mechanism of the system were explained by using a schematic representation of the various equilibriums in the spontaneous emulsification flooding system.     

pH和光对复合型乳液拓扑结构的调控

Complex emulsions have attracted much attention because of their relevant application in various fields over the past decade. Though complex emulsions with various topologies can be created by adjusting the fraction of selected components during the homogenization processes, it is still a challenge to control the topology of complex emulsion droplets in situ using stimuli-responsive factors such as light, pH, and temperature. In this work, a three-phase complex emulsion of heptane and perfluorohexane (1:1 volume ratio) in an aqueous solution of a fluorosurfactant, F(CF₂)_x(CH₂CH₂O)_yH (Zonyl FS-300), and a synthesized pH and light dual-responsive surfactant, 1-[2-(4-decylphenylazo-phenoxy)-ethyl]-1-diethylenetriamine (C₁₀AZOC₂N₃) (both serving as emulsifiers), was prepared using the temperature-induced phase separation method. The topology of the heptane-perfluorohexane-water (H/F/W) three-phase complex emulsion was highly dependent on the concentration of C₁₀AZOC₂N₃. Light microscopy images showed that phase inversion from H/F/W to F/H/W type double emulsion via Janus emulsion was achieved by gradually increasing the concentration of C₁₀AZOC₂N₃. It was noticed that interfacial tension between heptane and an aqueous solution containing 0.1% Zonyl FS-300 (mass fraction) decreased from 28.2 to 7.4 mN∙m^-1 when the concentration of C₁₀AZOC₂N₃ was increased to 0.1% (mass fraction). The topology of the complex emulsion droplets is primarily determined by three interfacial tensions at the contact line: the H/W interface (γ_H), F/W interface (γ_F), and H/F interface (γ_HF). The reduction in interfacial tension between heptane and water was the major factor that controlled the topological transition of the complex emulsion. First, it decreases the contact angle between the H/W and H/F interfaces (θ_H). Second, it increases the contact angle between the F/W and H/F interfaces (θ_F) simultaneously. Surfactant C₁₀AZOC₂N₃ is responsive to both pH and light, and therefore, it potentially endows the fabricated complex emulsion with the corresponding stimuli-responses. Experimental results confirmed that the morphologies of complex emulsions can be tuned reversibly between Janus emulsion and F/H/W type double emulsion either by pH variation or UV/blue light irradiation. Interfacial tension measurements between heptane and water show that either protonation variation or trans-cis isomerization of C₁₀AZOC₂N₃ caused a decrease of about 5 mN∙m^-1 in interfacial tension, suggesting that the nature of pH- and light-induced morphological changes of complex emulsion droplets is the same as that induced by the changes in the concentration of C₁₀AZOC₂N₃. Correspondingly, a mechanism for the stimuli-responsive morphological change of complex emulsion was proposed based on the reduction of interfacial tension between heptane and aqueous solution interface by changing the configuration of C₁₀AZOC₂N₃ using pH alteration and light irradiation. This work provides a new approach for controlling the morphologies of complex emulsion droplets with an external double stimulus by simply introducing a dual-responsive surfactant.     

One-step inversion process to a Janus emulsion with two mutually insoluble oils

High internal phase ratio (HIPR) aqueous Janus emulsions of two immiscible oils, silicone oil (SO) and a vegetable oil (VO), were prepared using a vibration mixer. The simple HIPR Janus emulsions, (VO + SO)/W, were found at weight fractions of the aqueous phase in excess of 0.3, while at a corresponding fraction of 0.1, a triple emulsion was obtained with the Janus emulsion forming a drop inside the vegetable oil to give a double Janus emulsion, (VO + SO)/W/VO, which in turn formed drops in the silicone oil resulting in a triple Janus emulsion (VO + SO)/W/VO/SO. Increasing the aqueous-phase fraction from 0.1 to 0.3 consequently meant an inversion, of which one intermediate stage was observed: a more complex configuration, e.g., one in which large SO drops with highly distorted VO drops attached were dispersed in a regular aqueous emulsion with spherical Janus (VO + SO) drops. A preliminary investigation was made into the destabilization process of the triple emulsions.     

A one-step process for oil-in-water-in-oil double emulsion formation using a single surfactant

A one-step double emulsification protocol using one surfactant was developed for oil-in-water-in-oil (O(1)/W/O(2)) double emulsions. Two n-alkane oils and three different surfactants were studied, with focus placed on a formulation containing mineral oil, glycerol monoleate (GMO) and deionized water. Phenomenologically, double emulsion formation and stability originate from the combined actions of phase inversion and interfacial charging of the oil/water interface during high shear homogenization. Based on the extent of double emulsion formation and stability, a critical emulsification zone dependent on the weight ratios of GMO to water was identified. Within this critical zone, enhanced O(1)/W/O(2) emulsion formation occurred at higher pH and lower salt concentrations, demonstrating the key role of interfacial charging on double emulsification. Overall, this novel approach provides a novel platform for the development of double emulsions with simple compositions and processing requirements.     

A Three-Step Model for Submicron W/O Emulsion Formation in a Transitional-Phase Inversion Process

A three-step model of the transitional phase inversion (TPI) process for the formation of water-in-oil (W/O) emulsions is presented. Three types of emulsions exist in an emulsification process at different oil–water ratios and hydrophilic–lipophilic balance (HLB). A stable W/O emulsion was obtained using Sorbitan oleate (Span 80) and polyoxyethylenesorbitan monooleate (Tween 80) with a specified HLB and oil volume fraction. Oil was added into water, which contained the water-soluble surfactant, to dissolve the oil-soluble surfactant. This route allowed TPI to occur, and an interesting emulsification process was observed by varying the HLB, which corresponded to the change in the oil–water ratio. Two types of emulsions in the emulsification process were found: transition emulsion 1 (W/O/W high internal phase emulsion) and target emulsion 2 (W/O emulsion with low viscosity). This study describes the changes that occurred in the emulsification process.     

FORMATION OF O/W EMULSIONS BY SURFACTANT PHASE EMULSIFICATION AND THE SOLUTION BEHAVIOR OF NONIONIC SURFACTANT SYSTEM IN THE EMULSIFICATION PROCESS

Surfactant-Phase Emulsification is a very useful method to produce oil-in-water emulsions having fine and uniform droplets. The mechanism of this emulsification method and the effect of hydrophile-lipophile balance (HLB) of the surfactants on the process of this emuisification were investigated by using phase diagrams of nonionic surfactant/hexadecane/water/1,3-butanediol four component systems.

It was shown that the process of this emulsification begins with the formation of isotropic surfactant solution, followed by formation of oil-in-surfactant clear gel emulsion, and finally by formation of oil-in-water emulsion. By using this emulsification technique, fine oil-in-water emulsions were formed without a need for adjusting of HLB.     

Emulsifying potency of new amino acid-type surfactant (II): stable water-in-oil (W/O) emulsions containing 85 wt% inner water phase

The ternary phase diagram for N-[3-lauryloxy-2-hydroxypropyl]-L-arginine L-glutamate (C12HEA-Glu), a new amino acid-type surfactant, /oleic acid (OA)/water system was established. The liquid crystal and gel complex formations between C12HEA-Glu and OA were applied to a preparation of water-in-oil (W/O) emulsions. Stable W/O emulsions containing liquid paraffin (LP) as the oil and a mixture of C12HEA-Glu and OA as the emulsifier were formed. The preparation of stable W/O emulsions containing 85 wt% water phase was also possible, in which water droplets would be polygonally transformed and closely packed, since the maximum percentage of inner phase is 74% assuming uniformly spherical droplets. Water droplets would be taken into the liquid crystalline phase (or the gel complex) and the immovable water droplets would stabilize the W/O emulsion system. The viscosity of emulsions abruptly increased above the 75 wt% water phase (dispersed phase). The stability of W/O emulsions with a lower weight ratio of OA to C12HEA-Glu and a higher ratio of water phase was greater. This unusual phenomenon may be related to the formation of a liquid crystalline phase between C12HEA-Glu and OA, and the stability of the liquid crystal at a lower ratio of oil (continuous phase). W/O and oil-in-water (O/W) emulsions containing LP were selectively prepared using a mixture of C12HEA-Glu and OA since the desirable hydrophile-lipophile balance (HLB) number for the emulsification was obtainable by mixing the two emulsifiers.