Encapsulation of orange oil in a spray dried double emulsion

Flow cytometric printing of double emulsions into open droplet arrays

Delivery of double emulsions in air is crucial for their applications in mass spectrometry, bioanalytics, and material synthesis. However, while methods have been developed to generate double emulsions in air, controlled printing of double emulsion droplets has not been achieved yet. In this paper, we present an approach for in-air printing of double emulsions on demand. Our approach pre-encapsulates reagents in an emulsion that is reinjected into the device, and generates double emulsions in a microfluidic printhead with spatially patterned wettability. Our device allows sorting of ejected double emulsion droplets in real-time, allowing deterministic printing of each droplet to be selected with the desired inner cores. Our method provides a general platform for building printed double emulsion droplet arrays of defined composition at scale.

Microencapsulation as a Route for Obtaining Encapsulated Flavors and Fragrances

Microencapsulation methods for active substances, such as fragrance compounds and aromas, have long been of interest to researchers. Fragrance compositions and aromas are added to cosmetics, household, and food products. This is often because the choice of a particular product is dictated by its fragrance. Fragrance compositions and aromas are, therefore, a very important part of the composition of these items. During production, when a fragrance composition or aroma is introduced into a system, unfavorable conditions often exist. High temperatures and strong mixing have a detrimental effect on some fragrance compounds. The environments of selected products, such as high- or low-pH surfactants, all affect the fragrance, often destructively. The simple storage of fragrances where they are exposed to light, oxygen, or heat also has an adverse effect. The solution to most of these problems may be the encapsulation process, namely surrounding small fragrance droplets with an inert coating that protects them from the external environment, whether during storage, transport or application, until they are in the right conditions to release the fragrance. The aim of this article was to present the possible, available and most commonly used methods for obtaining encapsulated fragrances and aromas, which can then be used in various industries. In addition, the advantages and disadvantages of each method were pointed out, so that the selection of the appropriate technology for the production of encapsulated fragrances and aromas will be simpler.

W/o/w multiple emulsions: A novel trend in functional ice cream preparations?

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The possible applications of w/o/w multiple emulsions (MEs) in ice creams are described.

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W/o/w MEs enable the encapsulation of sensitive compounds.

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Fat content is reduced using w/o/w MEs without losing the creaminess of the final products.

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Ice cream is a very suitable matrix for application of Pickering emulsions.

Ice cream is a popular product worldwide. Unfortunatelly, it contains a significant amount of fat. In this review, promising strategies for the use of w/o/w multiple emulsion structures in creams are assessed. W/o/w multiple emulsions (MEs) enable reduction the fat without losing the creamy taste and mouthfeel and also encapsulation of sensitive compounds. The encouraging application and formation of MEs in ice cream mixtures is supported by the use of natural food ingredients, such as fiber, which helps to stabilize the whole system and improves nutritional value. The future trends may be focused on the target stabilizations using Pickering paticles (PPs). The possible advantages, manufacture, evaluation methods, and predicted future prospects of MEs in ice creams are discussed.

Fabrication of Microfluidic Devices for Emulsion Formation by Microstereolithography

Droplet microfluidics—the art and science of forming droplets—has been revolutionary for high-throughput screening, directed evolution, single-cell sequencing, and material design. However, traditional fabrication techniques for microfluidic devices suffer from several disadvantages, including multistep processing, expensive facilities, and limited three-dimensional (3D) design flexibility. High-resolution additive manufacturing—and in particular, projection micro-stereolithography (PµSL)—provides a promising path for overcoming these drawbacks. Similar to polydimethylsiloxane-based microfluidics 20 years ago, 3D printing methods, such as PµSL, have provided a path toward a new era of microfluidic device design. PµSL greatly simplifies the device fabrication process, especially the access to truly 3D geometries, is cost-effective, and it enables multimaterial processing. In this review, we discuss both the basics and recent innovations in PµSL; the material basis with emphasis on custom-made photopolymer formulations; multimaterial 3D printing; and, 3D-printed microfluidic devices for emulsion formation as our focus application. Our goal is to support researchers in setting up their own PµSL system to fabricate tailor-made microfluidics.

Lipids for Taste masking and Taste assessment in pharmaceutical formulations

Pharmaceutical products often have drawbacks of unacceptable taste and palatability which makes it quite difficult for oral administration to some special populations like pediatrics and geriatrics. To curb this issue different approaches like coating, granulation, extrusion, inclusion complexation, ion-exchange resins, etc for taste masking are employed and among them use of lipids have drawn special attention of researchers. Lipids have a lower melting point which is ideal for incorporating drugs in some of these methods like hot-melt extrusion, melt granulation, spray drying/congealing and emulsification. Lipids play a significant role as a barrier to sustain the release of drugs and biocompatible nature of lipids increases their acceptability by the human body. Further, lipids provide vast opportunities of altering pharmacokinetics of the active ingredients by modulating release profiles. In taste sensors, also known as electronic tongue or e-tongue, lipids are used in preparing taste sensing membranes which are subsequently used in preparing taste sensors. Lipid membrane taste sensors have been widely used in assessing taste and palatability of pharmaceutical and food formulations. This review explores applications of lipids in masking the bitter taste in pharmaceutical formulations and significant role of lipids in evaluation of taste and palatability.

Modular microfluidics for double emulsion formation

For many engineering applications such as manipulating two phase flows, generating single and double emulsions, and passively propelling liquids through channels, control over the surface energy of microfluidic channels is essential. In particular, double emulsion formation, which benefits from alternating hydrophobic and hydrophilic sections of channel, represents a challenge in fabricating controlled microfluidic channel surface properties. As double emulsions find further applications in single-cell handling and analysis, straightforward methods for generating them increase in value. Here, we present a method for generating double emulsions in microfluidic channels fabricated from modular fluidic blocks. By using a vapor-phase polymer coating technology-initiated chemical vapor deposition-we are able to fabricate blocks with varying surface properties. Assembling these blocks together then creates step-like changes in surface energy within a microchannel.

The Potential of Combined Emulsification and Spray Drying Techniques for Encapsulation of Polyphenols from Rosemary (Rosmarinus officinalis L.) Leaves

The present study evaluates the potential of encapsulation of polyphenolic antioxidants from rosemary (Rosmarinus officinalis L.) leaves by combining emulsification and spray drying techniques. To stabilize the emulsions and prepare samples suitable for use in dry products, double emulsions encapsulating rosemary polyphenolic extract and containing polyglycerol polyricinoleate (4%), whey protein isolates (2 and 4%) as emulsifiers, and maltodextrins (MDE 10 and 21) as enhancing coatings were subjected to spray drying. The obtained results show insignificant (p>0.05) effect of used maltodextrin type and protein content on mean particle size of double emulsions containing rosemary polyphenols. Morphology analyses showed that double emulsions were successfully prepared, spherical microcapsules were obtained after spray drying of double emulsions and double emulsion form was still preserved after rehydration of spray-dried microcapsules. Regardless of used maltodextrins, significantly (p>0.05) higher encapsulation efficiencies (EE) of total polyphenols (39.57 and 42.83%) in rehydrated samples were achieved when higher protein content (4% whey protein isolate) was used, indicating the major impact of protein content on EE of rosemary polyphenols. Also, using HPLC analysis, rosmarinic and caffeic acids, apigenin and luteolin derivatives were detected among specific polyphenols, where rosmarinic acid had notable encapsulation efficiency ranging from 62.15 to 67.43%. In this way, the obtained microcapsules encapsulating rosemary polyphenols could be easily blended with various dry mixtures, and serve for delivery in different functional products.

Encapsulation of Volatile Compounds in Silk Microparticles

Various techniques have been employed to entrap fragrant oils within microcapsules or microparticles in the food, pharmaceutical, and chemical industries for improved stability and delivery. In the present work we describe the use of silk protein microparticles for encapsulating fragrant oils using ambient processing conditions to form an all-natural biocompatible matrix. These microparticles are stabilized via physical crosslinking, requiring no chemical agents, and are prepared with aqueous and ambient processing conditions using polyvinyl alcohol-silk emulsions. The particles were loaded with fragrant oils via direct immersion of the silk particles within an oil bath. The oil-containing microparticles were coated using alternating silk and polyethylene oxide layers to control the release of the oil from the microspheres. Particle morphology and size, oil loading capacity, release rates as well as silk-oil interactions and coating treatments were characterized. Thermal analysis demonstrated that the silk coatings can be tuned to alter both retention and release profiles of the encapsulated fragrance. These oil containing particles demonstrate the ability to adsorb and controllably release oils, suggesting a range of potential applications including cosmetic and fragrance utility.

Controlled generation of double emulsions in air

This Letter describes the controlled generation of double emulsions in the gas phase, which was carried out using an integrated emitter in a poly(dimethylsiloxane) (PDMS) microfluidic chip. The integrated emitter was formed using a molding approach, in which metal wires with desirable diameters were used as emitter molds. The generation of double emulsions in air was achieved with electrohydrodynamics actuation, which offers controllable force exerting on the double emulsions. We developed this capability for future integration of droplet microfluidics with mass spectrometry (MS), where each aqueous droplet in the microchannel is introduced into the gas phase as a double emulsion for subsequent ionization and MS analysis.

Double emulsions with controlled morphology by microgel scaffolding

Double emulsions are valuable structures that consist of drops nested inside bigger drops; they can be formed with exquisite control through the use of droplet-based microfluidics, allowing their size, composition, and monodispersity to be tailored. However, only little control can be exerted on the morphology of double emulsions in their equilibrium state, because they are deformable and subject to thermal fluctuations. To introduce such control, we use droplet-based microfluidics to form oil-in-water-in-oil double emulsion drops and arrest their shape by loading them with monodisperse microgel particles. These particles push the inner oil drop to the edge of the aqueous shell drop such that the double emulsions adopt a uniform arrested, anisotropic shape. This approach circumvents the need for ultrafast polymerization or geometric confinement to lock such non-spherical and anisotropic droplet morphologies. To demonstrate the utility of this technique, we apply it to synthesize anisotropic and non-spherical polyacrylate-polyacrylamide microparticles with controlled size and shape.

Faster multiple emulsification with drop splitting

Microfluidic devices can form emulsions in which the drops have an intricate, controlled structure; however, a challenge is that the droplets are produced slowly, typically only a few millilitres per hour. Here, we present a simple technique to increase the production rate. Using a large drop maker, we produce large drops at a fast volumetric rate; by splitting these drops several times in a splitting array, we create drops of the desired small size. The advantage of this over forming the small drops directly using a small drop maker is that the drops can be formed at much faster rates. This can be applied to the production of single and multiple emulsions.

Microfluidic melt emulsification for encapsulation and release of actives

A microfluidic melt emulsification method for encapsulation and release of actives is presented. Using a water-in-oil-in-water (W-O-W) double emulsion template, solid capsules can be formed by freezing the middle shell phase. Actives encapsulated inside the solid shell can be controllably and rapidly released by applying a temperature trigger to melt the shell. The choice of the shell materials can be chosen to accommodate the storage and release temperatures specific to the applications. In addition, we have also demonstrated the same concept to encapsulate multiple actives in multicompartment capsules, which are promising as multifunctional capsules and microreactors.

From a bouncing compound drop to a double emulsion

We show that a double emulsion (oil in water in oil) can be created starting from a compound droplet (surfactant solution in oil). The compound drop bounces on a vertically vibrated liquid surface. When the amplitude of the vibration exceeds a threshold value, the oil layer penetrates the water content and leaves a tiny oil droplet within. As this phenomenon occurs at each vigorous impact, the compound drop progressively transforms into a double emulsion. The emulsification threshold, which is observed to depend on the forcing frequency but not on the drop size, is rationalized by investigating the impact of compound drops onto a static liquid surface. The droplet creation occurs when the kinetic energy released at impact is larger than the energy required to deform the compound drop, namely when the Weber number is higher than a given threshold value.

High loading fragrance encapsulation based on a polymer-blend: preparation and release behavior

The six fragrances, camphor, citronellal, eucalyptol, limonene, menthol and 4-tert-butylcyclohexyl acetate, which represent different chemical functionalities, were encapsulated with a polymer-blend of ethylcellulose (EC), hydroxypropyl methylcellulose (HPMC) and poly(vinyl alcohol) (PV(OH)) using solvent displacement (ethanol displaced by water). The process gave >or=40% fragrance loading capacity with >or=80% encapsulation efficiency at the fragrance to polymer weight ratio of 1:1 and at initial polymer concentrations of 2000-16,000 ppm and the obtained fragrance-encapsulated spheres showed hydrodynamic diameters of less than 450 nm. The release profile of the encapsulated fragrances, evaluated by both thermal gravimetric and electronic nose techniques, indicated different release characteristics amongst the six encapsulated fragrances. Limonene showed the fastest release with essentially no retention by the nanoparticles, while eucalyptol and menthol showed the slowest release.

The Fabrication and Progress of Core-Shell Composite Materials

Core-shell materials, in which a layer or multilayer of inorganic or organic material surrounds an inorganic or organic particle core, have been investigated both as a means to improve the stability and surface chemistry of the core particle and as a way of accessing unique physical and chemical properties that are not possible from one material alone. As a result, the fabrication of core-shell particles is attracting a great deal of interest because of their unique properties and potential applicability in catalysis, semiconductors, drug delivery, enzyme immobilization, molecular recognition, chemical sensing, etc. As evidenced by the literature described and discussed in this review, a basic understanding of the mechanism and recent progress in production methods have enabled the fabrication of core-shell particles with unique and tailored properties for various applications in materials science.

Pharmaceutical particle engineering via spray drying

This review covers recent developments in the area of particle engineering via spray drying. The last decade has seen a shift from empirical formulation efforts to an engineering approach based on a better understanding of particle formation in the spray drying process. Microparticles with nanoscale substructures can now be designed and their functionality has contributed significantly to stability and efficacy of the particulate dosage form. The review provides concepts and a theoretical framework for particle design calculations. It reviews experimental research into parameters that influence particle formation. A classification based on dimensionless numbers is presented that can be used to estimate how excipient properties in combination with process parameters influence the morphology of the engineered particles. A wide range of pharmaceutical application examples—low density particles, composite particles, microencapsulation, and glass stabilization—is discussed, with specific emphasis on the underlying particle formation mechanisms and design concepts.

Microdroplet dissolution into a second-phase solvent using a micropipet technique: test of the Epstein-Plesset model for an aniline-water system

The Epstein-Plesset model was originally derived for the dissolution of a single gas bubble in an infinite aqueous solution (Epstein, P. S.; Plesset, M. S. J. Chem. Phys. 1950, 18, 1505-1509). The micropipet manipulation technique was previously shown to test this theory on air microbubbles and air-filled lipid-coated microparticles accurately and appropriately (Duncan, P. B.; Needham, D. Langmuir 2004, 20, 2567-2578). This same theory is now tested to model liquid microdroplet dissolution in a well-defined solution environment. As presented previously for the gas-bubble system, holding a single microparticle at the end of a micropipet was not shown to affect the dissolution profile and allowed isotropic diffusion significantly, a necessary condition for the validation of the theory. Here, an aniline-water system with an initial droplet diameter of 50 microm was used as a model liquid-liquid system. A microdroplet of aniline in an aqueous solution presatureated with aniline at distinct levels was tested, as was the reverse system of a water droplet in an aniline solution. The dissolution lifetime was shown to increase with increasing medium saturation fraction according to the Epstein-Plesset time-dependent theory (including the time required to establish the stationary layer) neglecting interfacial tension. The droplet lifetime can be increased by an order of magnitude (from about 10 to 100 s) by increasing the saturation fraction from 0 to 0.9 and by another order of magnitude by increasing from 0.9 to 0.99. The technique proved to be an accurate and appropriate method to test the dissolution of single liquid microdroplets in a second liquid solution and establishes a systematic experimental and theoretical approach to the investigation of the formation of polymer and other microparticles.

Monodisperse Double Emulsions Generated from a Microcapillary Device

Double emulsions are highly structured fluids consisting of emulsion drops that contain smaller droplets inside. Although double emulsions are potentially of commercial value, traditional fabrication by means of two emulsification steps leads to very ill-controlled structuring. Using a microcapillary device, we fabricated double emulsions that contained a single internal droplet in a core-shell geometry. We show that the droplet size can be quantitatively predicted from the flow profiles of the fluids. The double emulsions were used to generate encapsulation structures by manipulating the properties of the fluid that makes up the shell. The high degree of control afforded by this method and the completely separate fluid streams make this a flexible and promising technique.

Liposomal incorporation of Artemisia arborescens L. essential oil and in vitro antiviral activity

The effect of liposomal inclusion on the in vitro antiherpetic activity of Artemisia arborescens L. essential oil was investigated. In order to study the influence of vesicle structure and composition on the antiviral activity of the vesicle-incorporated oil, multilamellar (MLV) and unilamellar (SUV) positively charged liposomes were prepared by the film method and sonication. Liposomes were obtained from hydrogenated (P90H) and non-hydrogenated (P90) soy phosphatidylcholine. Formulations were examined for their stability for over one year, monitoring the oil leakage from vesicles and the average size distribution. The antiviral activity was studied against Herpes simplex virus type 1 (HSV-1) by a quantitative tetrazolium-based colorimetric method. Results showed that Artemisia essential oil can be incorporated in good amounts in the prepared vesicular dispersions. Stability studies pointed out that vesicle dispersions were very stable for at least six months and neither oil leakage nor vesicle size alteration occurred during this period. After one year of storage oil retention was still good, but vesicle fusion was present. Antiviral assays demonstrated that the liposomal incorporation of A. arborescens essential oil enhanced its in vitro antiherpetic activity especially when vesicles were made with P90H. On the contrary, no significant difference in antiviral activity was observed between the free and SUV-incorporated oil.

A mathematical model of volatile release in mouth from the dispersion of gelled emulsion particles

This paper presents a mathematical model of in-mouth volatile release from gelled emulsion particles dispersed in a continuous aqueous phase. Data based on APCI MS-Breath analysis is presented to demonstrate the effect of particle size, oil content and oil-water partition coefficients. It is shown that in-mouth release of aroma from the dispersion of gelled emulsion particles follows a two-component kinetic equation with fast and slow components. Both the fast and slow rate constants depend on the particle size, oil content and oil water partition coefficient of the aroma. The relative amount of aroma contributing to the fast and slow components also depends on the size of the particles. In order to understand this unexpected behaviour, an analytical model was developed that considers the interplay between the mass transfer of flavour across the interface of the particles and that across the air-liquid interface. Analytical expressions for the two rate constants and the relative ratio of aroma contributing to the fast component have been derived. From this model, three regimes of in-mouth release of aroma from the dispersion of gelled emulsion particles were identified including, the emulsion regime, the transition regime and the gel particle regime. In the emulsion regime, changes in the size of gelled emulsion particles had negligible impact on the overall release. In the transition regime, the release was controlled by the interaction of flavour transfer from the particles with that across the air-water interface. In the gel particle regime, aroma release at long times was governed by the particles and that at short times was governed by the air-water interface, and the two processes were fully decoupled. A simple relationship was derived for the critical size above which the release of aroma from the dispersion of gelled emulsion particles is affected by the size of the particles.

Double emulsions stabilized with hybrids of natural polymers for entrapment and slow release of active matters

The main focus and efforts for the next few years in the area of emulsion technology will be to improve stability and control the release of active matter in double emulsions (3rd World Congress on Emulsions, Lyon, France, September 2002). Almost any possible blends of low-molecular weight emulsifiers, oils, cosolvents and coemulsifiers have been already tested. Biopolymers, synthetic graft and comb co-polymers and polymerizable emulsifiers that impart steric or mechanical stabilization with improved stability and better controlled release were explored. Amphiphilic macromolecules, natural occurring or synthetic, that increase the viscosity of each of the phases, complex with the oil or the emulsifiers and form systems that will behave much like microcapsules, microspheres and/or mesophasic liquid crystals have been mentioned as possible new technologies for improved stability. This review will concentrate only on the most recent findings that can enhance stability of the double emulsions and/or will reduce droplets sizes for potential food applications. The attempts and achievements include: selection of food-grade blends of emulsifiers to enhance emulsion stability at both inner and outer interfaces and use of new polymeric amphiphiles (carriers, complexing agents, natural polymeric emulsifiers) to control and reduce the reverse micellar transport phenomena and to control the addenda transport.