Double Emulsions Stabilized by Food Biopolymers

Controllable one-step double emulsion formation via phase inversion

Double emulsions, the simplest form of multiple emulsion, have been intensively utilized in various industries as well as in fundamental research. A variety of strategies to effectively form double emulsions have been developed, but no simple yet controlled and scalable technique has been achieved yet. Herein, we examine the mechanism of the entire process of double emulsion formation by phase inversion, and we propose a universal one-step strategy for the formation of an oil/water/oil double emulsion using oil soluble polymers and hydrophobic silica nanoparticles. We demonstrate that this new approach enables control of both the fraction and the number of inner small droplets; even high internal phase double emulsions could be achieved.

The Influence of Chemically Modified Potato Maltodextrins on Stability and Rheological Properties of Model Oil-in-Water Emulsions

The aim of this study was to determine the effect of the maltodextrins prepared from chemically modified starches (crosslinked, stabilized, crosslinked and stabilized) on the stability and rheological properties of model oil-in-water (o/w) emulsions. Based on the obtained results, it was concluded that emulsion stability depended on hydrolysates dextrose equivalent (DE) value. Maltodextrin with the lowest degree of depolymerization effectively stabilized the dispersed system, and the effectiveness of this action depended on the maltodextrin type and concentration. Addition of distarch phosphate-based maltodextrin stabilized emulsion at the lowest applied concentration, and the least effective was maltodextrin prepared from acetylated starch. Emulsions stabilized by maltodextrins (DE 6) prepared from distarch phosphate and acetylated distarch adipate showed the predominance of the elastic properties over the viscous ones. Only emulsion stabilized by maltodextrin prepared from distarch phosphate (E1412) revealed the properties of strong gel. Additionally, the decrease in emulsions G′ and G″ moduli values, combined with an increase in the value of DE maltodextrins, was observed.

In vitro digestion behavior of water-in-oil-in-water emulsions with gelled oil-water inner phases

Double emulsions may be able to protect and release in a controlled manner bioactive compounds during digestion of food matrices. It was hypothesized that the physical state and solid content in the inner phases of water-in-oil-in-water (W₁/O/W₂) emulsions may affect the overall stability and the release behavior of bioactives during in vitro digestion. Therefore, hydrophobic (phytosterols or Vitamin D₃) and hydrophilic (Vitamin B₁₂) molecules were incorporated in double emulsions prepared either with a liquid (soybean oil - SO) or oil-fat gel (soybean oil+trimyristin - STO) lipid phase and liquid internal aqueous phase. In addition, the impact of a gelled inner aqueous phase was studied, using high methoxyl pectin. W₁/O/W₂ emulsions were prepared with polyglycerol polyricinoleate (PGPR) and sodium caseinate as emulsifiers. After the 30min in vitro gastric stage, all double emulsions showed no significant change in size. Lipid crystals were visible in the STO emulsions. Fat crystallization, and the formation of an oil fat gel, led to coalescence of the inner aqueous droplets. The inner aqueous droplets were no longer visible by confocal microscopy after the initial stages of 2h in vitro duodenal digestion. Fat crystals and droplets of non-spherical shape were also noted in the STO double emulsions up to 25min of in vitro duodenal stage. Overall, the STO emulsions had a higher extent of free fatty acid release and consequent bioactive transfer compared to the SO emulsions. The presence of the medium chain fatty acids (from trimyristin), in addition to the surface-to-core distribution of the hydrophobic bioactives within the oil droplet were key factors in lipid digestibility and bioactive release. The STO and SO samples did not differ in terms of the release of the hydrophilic molecule, vitamin B₁₂, over time. On the other hand, there was a significant increase in the stability of the inner water phase, after gastric digestion, when this phase was gelled with high methoxyl pectin. This work demonstrated that the physical properties of the different internal phases of W₁/O/W₂ influenced lipid digestion and bioactive transfer kinetics during in vitro digestion.

Multiple Water-in-Oil-in-Water Emulsion Gels Based on Self-Assembled Saponin Fibrillar Network for Photosensitive Cargo Protection

A gelled multiple water-in-oil-in-water (W₁/O/W₂) emulsion was successfully developed by the unique combination of emulsifying and gelation properties of natural glycyrrhizic acid (GA) nanofibrils, assembling into a fibrillar hydrogel network in the continuous phase. The multiple emulsion gels had relatively homogeneous size distribution, high yield (85.6-92.5%), and superior storage stability. The multilayer interfacial fibril shell and the GA fibrillar hydrogel in bulk can effectively protect the double emulsion droplets against flocculation, creaming, and coalescence, thus contributing to the multiple emulsion stability. Particularly, the highly viscoelastic bulk hydrogel had a high storage modulus, which was found to be able to strongly prevent the osmotic-driven water diffusion from the internal water droplets to the external water phase. We show that these multicompartmentalized emulsion gels can be used to encapsulate and protect photosensitive water-soluble cargos by loading them into the internal water droplets. These stable multiple emulsion gels based on natural, sustainable saponin nanofibrils have potential applications in the food, pharmaceutical, and personal care industries.

Complex Emulsions by Extracting Water from Homogeneous Solutions Comprised of Aqueous Three-Phase Systems

Multiple emulsions can be obtained by binary and ternary liquid phase separation. And the use of the aqueous two-phase system provides a simple route to prepare water-in-water-in-oil (W/W/O) or water-in-water-in-water (W/W/W) multiple emulsions. It is thus expected that we can fabricate more complex emulsions by using an aqueous three-phase system. Herein, we present a simple and versatile method to generate complex emulsions based on phase separation in homogeneous droplets made up of aqueous three-phase system: poly(ethylene glycol) (PEG), poly(vinyl alcohol) (PVA) and dextran (DEX) through extracting water from droplets. We examine the formation process and the effect of mass ratio of each two components in the three phase system. Emulsion droplets with five types of morphologies, i.e., binary-core/shell, core/shell-single phase Janus, ellipsoid Janus, multicore-in-matrix and single core-double shell morphologies can be formed, depending on the mass ratio of each two components and modification of PEG with Fe₃O₄ nanoparticles. We observe transition of core/shell-single phase Janus to binary-core/shell and single core-double shell to core/shell-single phase Janus geometry with prolongation of extracting time, and obtain the geometry map for the formation of different shaped droplets. Due to different affinities of PEG, PVA and DEX to certain materials, we functionalize each compartment in the complex emulsion droplets, and apply the resulting droplet for glucose sensing and the construction of antibody-mediated targeting drug delivery. This emulsion generation method is simple and the choice for the component of the aqueous three-phase system is broad, which can be further extended to generate complex emulsions from aqueous multiphase systems.

Egg white powder-stabilised multiple (water-in-olive oil-in-water) emulsions as beef fat replacers in model system meat emulsions

BACKGROUND

Today, multiple emulsions are believed to have a considerable application potential in food industry. We aimed to investigate physical, chemical and textural quality characteristics of model system meat emulsions (MSME) in which beef fat (C) was totally replaced by 10% (E-10), 20% (E-20) or 30% (E-30) multiple emulsions (W₁ /O/W₂ ) prepared with olive oil and egg white powder (EWP).

RESULTS

Incorporation of W₁ /O/W₂ emulsion resulted in reduced fat (from 11.54% to 4.01%), increased protein content (from 13.66% to 14.74%), and modified fatty acid composition, significantly increasing mono- and polyunsaturated fatty acid content and decreasing saturated fatty acid content. E-20 and E-30 samples had lower jelly and fat separation (5.77% and 5.25%) compared to C and E-10 (9.67% and 8.55%). W₁ /O/W₂ emulsion treatments had higher water-holding capacity (93.96-94.35%) than C samples (91.84%), and also showed the desired storage stability over time. Emulsion stability results showed that E-20 and E-30 samples had lower total expressible fluid (14.05% and 14.53%) and lower total expressible fat (5.06% and 5.33%) compared to C samples (19.13% and 6.09%). Increased concentrations of W₁ /O/W₂ emulsions led to alterations in colour and texture parameters. TBA values of samples were lower in W₁ /O/W₂ emulsion treatments than control treatment during 60 days of storage.

CONCLUSIONS

Our results indicated that multiple emulsions prepared with olive oil and EWP had promising impacts on reducing fat, modifying the lipid composition and developing both technologically and oxidatively stable meat systems. These are the first findings concerning beef matrix fat replacement with multiple emulsions stabilised by EWP. © 2016 Society of Chemical Industry.

The effects of biomacromolecules on the physical stability of W/O/W emulsions

The effect of bovine serum albumin (BSA), whey protein isolate (WPI), whey protein hydrolysate (WPH), sodium caseinate (SC), carboxymethylcellulose sodium (CMC), fish gelatin (FG), high methoxyl apple pectin (HMAP), low methoxyl apple pectin (LMAP), gum Arabic (GA), ι-carrageenan (CGN), and hydroxypropyl chitosan (HPCTS) on physical stability of internal or external aqueous phase of water-in-oil-in-water (W/O/W) emulsions was evaluated. WPI and CGN in the internal aqueous phase, and GA, HPCTS, and CMC in the external phase reduced the size of emulsion droplets. BSA, WPI, SC, FG, CGN, and HPCTS improved the dilution stability of W/O/W emulsions, but HMAP had a negative effect. BSA, WPI, SC, FG, LMAP, GA, CGN, HPCTS, or CMC significantly improved the thermal stability of W/O/W emulsions. Results also indicated that the addition of CGN (1.0%), HMAP (1.0%), WPH (1.0%), or HPCTS (1.0%) in internal aqueous phase significantly increased the viscosity of emulsions, however, addition to the external aqueous phase had insignificant effects. A protein-knockout experiment confirmed that proteins as biomacromolecules, were the key factor in improving physical stability of emulsions.

Single, Janus, and Cerberus emulsions from the vibrational emulsification of oils with significant mutual solubility

Single, Janus, and Cerberus emulsions are prepared in one system consisting of three oils: silicone (SO), fluorocarbon (FO) and ethoxylated trimethylolpropane triacrylate (ETPTA) with mutual solubility. An aqueous solution of Pluronic F127, which is an poly(ethylene oxide)/poly(propylene oxide) co-polymer of average composition EO₉₇PO₆₈EO₉₇, was employed as the continuous phase. The three-dimensional phase diagram of the oils was determined, and different oil compositions within the various regions of the phase diagram were emulsified by one-step vortex mixing with an F127 aqueous solution. The result showed single, Janus, and Cerberus emulsions within the different regions of the phase diagram; i.e. the emulsions reflected the equilibrium system. The topology of the Cerberus droplets is to an overwhelming extent linear-singlet and exclusively lobe order of EF/FO/SF. Since the results indicate a significant effect of the equilibrium interfacial tensions on the drop topology, thermodynamic calculations were made using the experimentally determined interfacial tensions. The results, as expected, show that the Cerberus emulsions are thermodynamically preferred over separate drops of the individual oils. In addition, the calculations demonstrate that the order of lobes within a drop is thermodynamically favored.

Physicochemical properties and encapsulation of silicon in double emulsions for healthier food applications

This article analyses the potential use of double emulsions as silicon delivery systems with reference to the influence of the composition of the inner aqueous phase (W₁, containing NaCl and sodium caseinate or gelatin) on silicon encapsulation and physicochemical properties of food-grade W₁/O/W₂. Irrespective of W₁, DEs initially showed a well-defined monomodal distribution, with the widest range registering in the sample with gelatin. All samples developed a bimodal distribution during storage (3 ± 2 °C). Heating increased the range of droplet size distribution. DEs exhibited high physical stability (creaming), decreasing over storage; this behaviour was generally unaffected by W₁ composition, which maintained similar stability (95-96%) at the end of storage. Viscosity was generally unaffected by formulation, storage time or heating treatment. Si encapsulation efficiency (72.4 and 78.3%) was not affected by W₁ composition, while Si encapsulation stability was generally unaffected by either storage or heating. These DEs can be used as potential ingredient (with lower fat content, better fatty acid profile and with the potential Si health benefits) for the development of healthier foods including meat products.

Biocompatible Stimuli-Responsive W/O/W Multiple Emulsions Prepared by One-Step Mixing with a Single Diblock Copolymer Emulsifier

Multiple water-in-oil-in-water (W/O/W) emulsions are promising materials in designing carriers of hydrophilic molecules or drug delivery systems, provided stability issues are solved and biocompatible chemicals can be used. In this work, we designed a biocompatible amphiphilic copolymer, poly(dimethylsiloxane)-b-poly(2-(dimethylamino)ethyl methacrylate) (PDMS-b-PDMAEMA), that can stabilize emulsions made with various biocompatible oils. The hydrophilic/hydrophobic properties of the copolymer can be adjusted using both pH and ionic strength stimuli. Consequently, the making of O/W (oil in water), W/O (water in oil), and W/O/W emulsions can be achieved by sweeping the pH and ionic strength. Of importance, W/O/W emulsions are formulated over a large pH and ionic strength domain in a one-step emulsification process via transitional phase inversion and are stable for several months. Cryo-TEM and interfacial tension studies show that the formation of these W/O/W emulsions is likely to be correlated to the interfacial film curvature and microemulsion morphology.

Colorimetry Technique as a Tool for Determining Release Kinetics and Mass Transfer Parameters of Anthocyanins Encapsulated in W1/O/W2 Double Emulsions

Anthocyanin extract (AE) was encapsulated in W1/O/W2 double emulsions and colorimetry technique using the CIE L*a*b* system was used to determine the release kinetics. Parameters a* and b* better correlated the variations in color of emulsions due to the release of AE into the external phase. Chroma value (C*) was used for tracking these color variations and to determine the release kinetics. The emulsions showed high stability, droplet sizes didn’t change after 30 days of storage (D4,3=4.74±0.12 μm), and 2.7 % AE was released to the external phase after this time. The possible release mechanism of AE from the internal phase of the emulsion is diffusion controlled with good accordance to Fick’s first law (R2=0.9938) with a diffusion coefficient of 7.15×10−8 cm2/d.

Quantification of Spontaneous W/O Emulsification and its Impact on the Swelling Kinetics of Multiple W/O/W Emulsions

An osmotic imbalance between the two water phases of multiple water-in-oil-in-water (W1/O/W2) emulsions results in either emulsion swelling or shrinking due to water migration across the oil layer. Controlled mass transport is not only of importance for emulsion stability but also allows transient emulsion thickening or the controlled release of encapsulated substances, such as nutriments or simply salt. Our prior work has shown that mass transport follows two sequential stages. In the first stage, the oil-phase structure is changed in a way that allows rapid, osmotically driven water transport in the second, osmotically dominated stage. These structural changes in the oil layer are strongly facilitated by the spontaneous formation of tiny water droplets in the oil phase, induced by the oil-soluble surfactant, i.e., polyglycerol polyricinoleate (PGPR). This study provides a simple method based on microscopy image analysis, allowing a detailed investigation of spontaneous W/O emulsification. It quantitatively describes the volume of droplets generated and the rate of droplet creation. Moreover, it describes the effect of spontaneous W/O emulsification on the swelling kinetics of microfluidic processed W1/O/W2 emulsions. Two different concentration regimes of the oil-soluble surfactant are identified: below a critical concentration the overall water transport rate increases, and above a critical concentration water transport stagnates because of maximized structure formation.