Uniform Oil Droplets Research Articles

Fabrication of high internal phase emulsions (HIPEs) using pea protein isolate-hyaluronic acid-tannic acid complexes: Application of curcumin-loaded HIPEs as edible inks for 3D food printing

Pea protein isolate (PPI)-hyaluronic acid (HA)-tannic acid (TA) ternary complexes were assembled using non-covalent interactions, their potential application in 3D printing and delivery of curcumin were investigated. As the HA-to-TA ratio in the complexes changed from 1:0 to 0:1, the oil-water interfacial tension first decreased and then increased, and the secondary structure of the proteins changed. The composition of the complexes (HA-to-TA ratio) was optimized to produce high internal phase emulsions (HIPEs) containing small uniform oil droplets with good storage and thermal stability. When the HA to TA ratio is 7:1 (P-H7-T1), HIPEs exhibited better viscosity, viscoelasticity, and thixotropy, which contributed to its preferable 3D printing. Moreover, curcumin-loaded HIPEs stabilized by P-H7-T1 showed a high lipid digestibility (≈101%) and curcumin bioaccessibility (≈79%). In summary, the PPI-HA-TA-stabilized HIPEs have good potential to be 3D-printable materials that could be loaded with bioactive components.

An RF Ring Resonator across Fluidic Media for Dielectric Sensing and Air-bubble Detection

Design, fabrication, and characterizations of an RF ring resonator used as a dielectric sensor, air-bubble detector and droplet sizer inside fluidic media are presented. The resonator with a split in its design has been analyzed and optimized using numerical methods and design guidelines are established to select the most sensitive resonance mode. A tube with an inner diameter of 800 µm placed over the 350 µm split is used to bring liquids and test samples. Different types of liquids (Isopropyl alcohol and de-ionized water) are easily distinguished by frequency shifts in the resonance peak. For instance, a 5 MHz frequency shift between air and water is observed. Furthermore, uniform oil droplets (0.6mm and 2.8mm long) were passed through the tube and measured to demonstrate the transient response of the sensor in detecting droplet sizes.

High internal phase emulsions stabilized by pea protein isolate-EGCG-Fe3+ complexes: Encapsulation of β-carotene

Protein complexes have great potential for forming and stabilizing high internal phase emulsions (HIPEs) loaded with bioactive compounds. In this study, we investigated the potential of three types of complexes, namely pea protein isolate (PPI), PPI-epigallocatechin gallate (EGCG) and PPI-EGCG-Fe3+, to form and stabilize HIPEs with a 75% oil phase volume fraction. Initially, the impact of pH and emulsifier type on emulsions performance was investigated. Confocal laser scanning microscopy (CLSM) and particle size analysis showed that all three complexes could form HIPEs that remained stable under acidic and neutral conditions. These emulsions contained uniform oil droplets coated by a layer of the complexes. Notably, the PPI-EGCG-Fe3+ complexes formed HIPEs with the highest thermal and storage stability, which was attributed to the denser and thicker interfacial coatings. These emulsions also protected encapsulated β-carotene from degradation when exposed to light and thermal stress conditions. Furthermore, we measured lipid digestion and β-carotene bioaccessibility in the emulsions using an in vitro digestion model. The PPI-EGCG-Fe3+ stabilized emulsions not only exhibited slow fatty acid release but also enhanced β-carotene bioaccessibility (46.5%) under simulated small intestine conditions. This study demonstrates the potential of using protein-polyphenol-Fe3+ complexes to form and stabilize HIPEs, which may then be used to enhance the bioaccessibility and bioactivity of hydrophobic nutraceuticals.

Replacement of fat with highland barley β-glucan in zein-based cheese: Structural, rheological, and textual properties

Nowadays, few plant-based cheese provides satisfactory viscoelastic property like conventional cheese, promoting the application of zein. Our study prepared zein-based cheese containing different concentrations (0–30 %) of highland barley β-glucan (HBG) as a fat replacer. Increased HBG caused smaller and more uniform oil droplets in zein network. SAXS pattern implied Rg decreased from 0.936 nm to 0.567 nm with increased HBG concentration. The stretchability of Cheddar and Violife cheese was 23.69 cm and 6.72 cm, respectively, while that of zein-based cheese added with HBG was 7.76–16.47 cm. The melting behavior of zein-based cheese did not fully mimic Cheddar cheese, but those of HBG5 and HBG10 were more comparable than Violife cheese. Violife cheese lacked hardness and gumminess compared to Cheddar cheese, while more similarities in textural properties were observed between Cheddar and zein-based cheese added with 10 % HBG. Our results provide opportunities in creating meltable low-fat plant-based cheese.

균일한 에멀젼의 연속 생산을 위해 폴리비닐 알코올로 개질한 동축 정렬 캐필러리 미세유체장치

균일한 에멀젼의 연속 생산을 위해 폴리비닐 알코올로 개질한 동축 정렬 캐필러리 미세유체장치

Consolidating the gelling performance of myofibrillar protein using a novel OSA-modified-starch-stabilized Pickering emulsion filler: Effect of starches with distinct crystalline types

Starch-stabilized Pickering emulsions were employed as a novel particulate filler in myofibrillar protein (MP)-based gels for improving the gelling characteristics. The role of emulsions prepared by native starches (NS) with distinctive crystalline types (i.e., A-type waxy corn starch, B-type potato starch, and C-type pea starch) and their OSA-modified counterparts (A-OS, B-OS, C-OS) in the gelling performance was evaluated and compared with MP-stabilized-emulsion. Compared with MP-emulsion, starch-emulsion caused substantial increases in the gelling properties, notably for OSA-starch emulsions. Herein, A-OS exhibited up to 1.26-, 5.3-, and 2.9-fold increments in storage modulus, gel strength, and water holding capacity relative to pure MP gel, respectively, higher than B-OS and C-OS. Moreover, light microscopy evinced a more compact gel network filled with smaller and uniform oil droplets when A-OS emulsions were incorporated into the gels. The addition of OSA-starch emulsions, especially A-OS emulsion, facilitated the protein conformational conversion from α-helix to β-sheet and caused a marked reduction of free sulfhydryls in the gels; yet, the chemical forces that stabilized the gels altered, where remarkable reinforcements in hydrogen bond and hydrophobic interaction were detected, in support of the construction of splendid MP gels. Hence, OSA-starch emulsions show promise as functional components in meat products.

Individual effects of l‐arginine or l‐lysine on stability of pork or chicken emulsion sausages with partial replacement of porcine backfat by soybean oil

SummaryThe individual effects of l‐arginine or l‐lysine on the physical (cooking loss (CL), total expressible fluid (TEF) and expressible fat (EFAT)) and chemical (thiobarbituric acid‐reactive substances (TBARS), and carbonyl and total sulphhydryl (T‐SH) content) stability of pork or chicken emulsion sausage with partial replacement of porcine backfat by soybean oil were determined. l‐arginine or l‐lysine increased pH but decreased CL, TEF and EFAT. Confocal laser scanning microscopy revealed that supplementation with l‐arginine or l‐lysine caused more regular and uniform oil droplets, for enhanced physical stability of pork or chicken sausage. Subjected to the same treatments, chicken sausage displayed higher physical stability than pork sausage. Overall, chicken sausages treated with l‐arginine or l‐lysine had lower TBARS and carbonyl content but higher T‐SH content than the corresponding control during storage; for pork sausages, l‐arginine or l‐lysine treatment generally resulted in higher TBARS throughout storage, lower carbonyl content during the initial 14 days and higher T‐SH content on days 7 and 14 but lower T‐SH content on days 1 and 21. Generally, l‐arginine/l‐lysine effectively increased the chemical stability of chicken sausage but decreased the chemical stability of pork sausage.

Maximizing the oil content in polysaccharide-based emulsion gels for the development of tissue mimicking phantoms

Formulations based on agar and κ-carrageenan were investigated for the production of emulsion gels applicable as tissue mimicking phantoms. The effects of the polysaccharide matrix, the oil content and the presence of surfactants on the micro-/nanostructure, rheology, and mechanical and dielectric properties were investigated. Results showed a high capacity of the agar to stabilize oil droplets, producing gels with smaller (10−21 μm) and more uniform oil droplets. The addition of surfactants allowed increasing the oil content and reduced the gel strength and stiffness down to 57 % and 34 %, respectively. The permittivity and conductivity of the gels were reduced by increasing the oil content, especially in the agar gels (18.8 and 0.05 S/m, respectively), producing materials with dielectric properties similar to those of low-water content tissues. These results evidence the suitability of these polysaccharides to design a variety of tissue mimicking phantoms with a broad range of mechanical and dielectric properties.

Microfluidic Approach to Generate a Tadpole-Egg-Shaped Alginate Fiber and Its Application in Tissue Engineering.

Herein, we introduce a facile microfluidic technique to produce a hybrid alginate fiber with a tadpole-egg shape. A triple-flow polydimethylsiloxane microfluidic device was constructed to allow the formation of oil droplets inside the alginate stream and was instantaneously gelated with the coaxially adjacent CaCl2. The fiber entrapping the uniform oil droplets was dehydrated, leading to the formation of a distinct tadpole-egg-shaped structure. A series of diverse fiber architectures was fabricated in a controlled manner based on the flow rates of the relevant flows. The tadpole-egg-shaped alginate fibers were employed as building blocks to create a three-dimensional microwell template for cell cultures. First, the tadpole-egg-shaped alginate fibers containing the oil droplets were half-dipped into a melted agarose solution. After the solidification of the agarose gel, the alginate fibers were degraded by an ethylenediaminetetraacetic acid (EDTA) solution to generate the hemispherical microwells. Mesenchymal stem cells (MSCs) were cultured in the microwells to generate spheroids, which were induced into chondrocytes using transforming growth factor-β3. The formed MSC spheroids exhibited a relatively high ratio of cell viability with more than 95% live cells after 14 days of culture. The success of the chondrogenic differentiation was proven based on staining (Safranin O) and the glycosaminoglycan levels. The latter was significantly higher in spheroids that were induced to form chondrocytes compared to those that were not induced after 21 days of differentiation. Second, we investigated the potential of the tadpole-egg-shaped alginate fibers as microcarriers for applications in drug delivery and implantable technologies. It was revealed that the degradation of the Ca-alginate wall of the hybrid fibers to release the oil droplets required an EDTA solution with a concentration of 500 mM for a 15 min period. This result can be used to further develop the tadpole-egg-shaped alginate fibers as uniform microcarriers with multiple compartments.

Can emollients of similar composition be assumed to be therapeutically equivalent: a comparison of skin occlusivity and emulsion microstructure.

IntroductionEmollient therapy is the mainstay for treating skin conditions such as atopic dermatitis and psoriasis. New emollients have been introduced recently and are assumed to be therapeutically interchangeable with the innovator products because, superficially, they appear to have similar compositions. This study compares a) the ex vivo human skin occlusion performance and b) the visual and microscopic properties of Isomol gel (IMG) and Doublebase gel (DBG).Materials and MethodsOcclusion was measured gravimetrically by reduction in cumulative 48-hour evaporative weight loss from ex vivo human skin samples following single applications of the two test emollients and Vaseline®. Skin samples from a single donor were mounted in Franz diffusion cells and then the emollients were spread over the skin surface with an applied dose of approximately 2 mg/cm2. The assemblies (four replicates per treatment) were then accurately weighed at baseline (T0) and again after 5-, 24-, and 48-hour postapplication. The quality of the two emollient gel formulations was compared by visual examination of their film-forming characteristics and by microstructural examination using environmental scanning electron microscopy (ESEM).ResultsOcclusivity of the DBG emollient gel formulation was comparable with Vaseline and substantially better than IMG, with the DBG-treated skin samples losing less than half as much weight as the IMG-treated skin samples over 48 hours and at a much slower rate during the first 5 hours. The film-forming characteristics and microstructure of the gels were also very different. Whereas DBG maintained a smooth, uniform film over 24 hours, the IMG formulation phase-separated. ESEM results showed that the DBG emulsion has a stable structural matrix with uniform oil droplets, whereas for IMG the emulsion system is inhomogeneous with the oil phase coalescing into larger irregular shaped rafts.ConclusionsWe have demonstrated substantial performance differences between two prescribed emollient gels.

Preparation of ruthenium-loaded CNT–TiO2 nanohybrids and their catalytic performance for the selective oxidation of benzyl alcohol

CNT–TiO 2 nanohybrids were synthesized using CNTs as a substrate and isopropyl titanate as a titanium source by a hydrothermal method. The nanohybrids were characterized by SEM and XRD, and their dispersion ability as an emulsion was investigated by optical microscopy. Ruthenium was loaded onto TiO 2 and the nanohybrids by an impregnation method, and their catalytic performance was evaluated by the selective oxidation of benzyl alcohol to benzylaldehyde. The mechanism involved in the reaction was proposed. Results show that the dispersion ability of the CNT–TiO 2 nanohybrids, judged by the numbers of uniform oil droplets in water per unit liquid volume, is better than that of TiO 2 . The catalytic activity and selectivity of the Ru/CNT–TiO 2 for the selective oxidation reactions are higher than for Ru/TiO 2 , indicating that they are closely related to the dispersion ability of the catalysts as emulsions. [New Carbon Materials 2013, 28(4): 289–294]

Influence of homogenisation conditions and drying method on physicochemical properties of dehydrated emulsions containing different solid components

SummaryDehydrated o/w emulsions containing sodium caseinate and lactose (sample 1), and gelatine, sucrose and maltodextrin (DE 10) (sample 2) were used to study the influence of homogenisation conditions – homogenisation pressure (15 and 70 MPa) and number of passes (1 and 2) – and the drying method – spray‐drying vs. freeze‐drying – on physicochemical parameters, including oil microencapsulation efficiency (ME), oil droplet size in reconstituted emulsions, water activity, glass transition temperature, powder bulk density and time for emulsion reconstitution in water. Results showed that small and uniform oil droplets attained with increased homogenisation pressure were not sufficient for high oil encapsulation. The permeability of the solid wall to the extraction solvent appeared to be the dominant factor, and this may increase with homogenisation pressure. With the exception of oil droplet size in sample 1 and ME in sample 2, the drying method exerted larger changes in the physicochemical parameters studied than the homogenisation pressure. For sample 2, significant changes in the ME were not observed between the freeze‐dried and spray‐dried samples, even though a great emulsion destabilisation was observed in the reconstituted emulsion of the latter.

Role of β‐Conglycinin and Glycinin Subunits in the pH‐Shifting‐Induced Structural and Physicochemical Changes of Soy Protein Isolate

Soy β-conglycinin (7S) and glycinin (11S) were incubated up to 4 h in acidic (pH 1.5 to 3.5) or alkaline (pH 10 to 12) solutions to induce protein structural unfolding followed by refolding 1 h at pH 7.0, a process known as pH-shifting. The pH-shifting markedly increased (P < 0.05) emulsifying activity of 11S and to a lesser extent 7S; the former also produced more uniform oil droplets. The emulsifying activity improvements were accompanied by a significant rise in protein surface hydrophobicity, slight loss of the secondary structure (circular dichroism), and substantial dissociation of disulfide-linked basic and acidic 11S subunits. The findings suggested that 11S globulins of soy protein isolate (SPI) were more responsive to pH-shifting treatments than were 7S globulins, and the resulting emulsifying activity enhancements of 11S, in parallel with that of SPI, were indicative of its determinant role in the overall emulsifying properties of pH-shifting-treated SPI. Extreme alkaline (pH 12) and acidic (pH 1.5) medium treatments can significantly modify the structure and enhance the emulsifying properties of both β-conglycinin and glycinin components of SPI. The functionality improvement by the pH processes is more remarkable for the glycinin protein fraction. Therefore, SPI enriched with glycinin seems to be particularly suitable for extreme acidic or alkaline processes to produce surface-active functional ingredients for food applications.

A Comparative Study of SPG Membrane Emulsification in the Presence and Absence of Continuous-Phase Flow

Membrane emulsification using Shirasu porous glass (SPG) membranes is a promising technique for preparing uniformly sized emulsion droplets and has potential applications in many fields. In this study, to gain further insight into droplet formation behavior from SPG membranes in the absence of continuous-phase flow, a comparative investigation of droplet formation behavior with and without water phase flow was carried out in an oil-in-water emulsion system consisting of soybean oil and 1 wt/v % polyoxyethylene(20)sorbitan monooleate (Tween 80) aqueous solution. In the absence of water phase flow, uniformly sized oil droplets with a mean diameter of 9.88 μm and a diameter distribution span of 0.62 were spontaneously formed from the pore openings of an SPG membrane with a mean pore diameter of 3.04 μm. Under these conditions, the various forces acting on a droplet formed at a pore opening were estimated from the dimensionless numbers (Bond, Capillary and Weber numbers). The estimation results indicated that oil-water interfacial tension is the dominating force for the spontaneous droplet detachment, due to the fact that the oil phase distorted by the tortuous pores is transformed into spherical droplets by the interfacial tension. In the presence of water phase flow, uniform oil droplets with a mean diameter of 8.63 μm and a diameter distribution span of 0.43 were detached from the same membrane by the shear force caused by the water phase flow before growing enough at the pore openings. The absence of water phase flow resulted in an increase in the proportion of active pores, compared to the presence of water phase flow. This is because, in the latter case, the oil droplets at the pore openings are deformed by the water phase flow, and thus the effect of steric hindrance between the neighboring droplets becomes greater.

Effects of Channel and Operation Parameters on Emulsion Production Using Oblong Straight-Through Microchannels

Straight-through microchannel (MC) arrays consisting of numerous oblong straight-through holes are promising MC emulsification devices for producing monodisperse emulsions in large droplet-production scales. We investigated the effects of MC dimensions and velocity of a crossflowing continuous phase on the production of soybean oil-in-water emulsions using straight-through MC arrays made of single-crystal silicon. The aspect ratio of oblong MCs with equivalent diameters of 21μm to 22μm significantly af fected droplet generation and the sensitivity of droplet size to continuous-phase velocity. Uniform oil droplets with diameters of about 100μm and coefficients of variation of less than 3% were generated using large oblong MCs with equivalent diameters of 54μm to 55μm. Data analysis demonstrated that oblong MCs with aspect ratios exceeding a threshold of 3 were necessar y to generate uniform oil droplets in a wide range of MC cross-sectional sizes. Moreover, the cross-flow of the continuous phase did not affect the size of the droplets generated using oblong MCs with a large aspect ratio.