Search

In this study, polyethylene glycol (PEG) and dextran (Dex) were chemically modified to obtain amino-functionalized PEG (PEG-(NH2)2) and oxidized dextran (ODex). They were subsequently reacted via -NH2 and -CHO groups to synthesize a macromolecular Schiff base particle. The structures, morphologies, and thermal properties of the macromolecular Schiff base particle were characterized using Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and thermogravimetry analysis (TGA). The macromolecular Schiff base particle was then employed as a stabilizer to stabilize Dex/PEG water-in-water (W/W) emulsions, and the effects of stabilizer composition, concentration, and dextran oxidation degree on emulsion phase separation and microstructure were investigated. The results from the laser particle size analyzer indicate that the macromolecular Schiff base stabilizers have particle sizes ranging from 100 to 200 nm and exhibit an interpenetrating network structure, as observed in SEM images. A decrease in emulsion droplet size was observed with increasing mass ratio of PEG-(NH2)2 to ODex, ODex oxidation degree, and stabilizer concentration. Rheological analysis showed that the viscosity of W/W emulsions decreased with increasing shear rate. Contact angle measurements indicated that the macromolecular Schiff base stabilizers preferentially interacted with the continuous phase of PEG, thereby promoting emulsion stability. [ABSTRACT FROM AUTHOR]

[Display omitted] The stability of purely aqueous emulsions (W/W) formed by mixing incompatible polymers, can be achieved through the Pickering effect of particles adsorption at the interface. However, there is, as yet, no guideline regarding the chemical nature of the particles to predict whether they will stabilize a particular W/W emulsion. Bis-hydrophilic soft microgels, made of copolymerized poly(N -isopropylacrylamide) (pNIPAM) and dextran (Dex), act as very efficient stabilizers for PEO/Dextran emulsions, because the two polymers have an affinity for each polymer phase. The ratio between both components of the microgels is varied in order to modulate the bis-hydrophilic balance, the content of Dex compared to pNIPAM varying from 0 to 60 wt%. The partition between the two aqueous phases and the adsorption of microgels at the W/W interface is measured by confocal microscopy. The stability of emulsions is assessed via turbidity measurements and microstructural investigations under sedimentation or compression. The adsorption of particles and their partitioning is found to evolve progressively as a function of bis-hydrophilic balance. At room temperature, the stability of the resulting W/W emulsions also depends on the bis-hydrophilic balance with a maximum of stability for the particles containing 50%wt of Dex, for the Dex-in-PEO emulsions, while the PEO-in-Dex become stable above this value. The thermo-responsiveness of the microgels translates into stability inversion of the emulsions below 50 wt% of Dex in the microgels, whereas above 50 wt%, no emulsion is stable. This work paves the way of a guideline to design efficient and responsive W/W stabilizers. [ABSTRACT FROM AUTHOR]

Water-in-water emulsions, which have a very low interfacial tension and a thick interfacial layer, are formed by two thermodynamically incompatible hydrophilic macromolecules in a certain proportion. It has been reported that the system cannot be stabilized by surfactants, but can avoid macroscopic phase separation by gelation of one or two phases. Recently, it has been found that the stability of water-in-water emulsions can be improved by the irreversible adsorption of solid particles at the interface based on the stabilization mechanism of oil-in-water Pickering emulsions. In this review, we summarize recent advances in research on the stabilization of water-in-water emulsions, and focus on the stability of Pickering emulsions stabilized by solid particles and its influential factors, as well as its applications in the food field. It is expected that this review will provide new ideas for food structure design based on the stabilization of water-in-water emulsions.

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] The use of templates in materials chemistry is a well-established approach for producing membrane-bounded hollow spheres used for microencapsulation applications, but also in synthetic biology to assemble artificial cell-like compartments. Sacrificial solid or gel micro-particles, but also liquid-like oil-in-water or water-in-oil emulsion droplets are routinely used as templates to produce capsules. Yet, disruption of the core sacrificial material often requires harsh experimental conditions, such as organic solvents, which limits the use of such approach to encapsulate fragile solutes, including biomolecules. Recently, water-in-water emulsion droplets have emerged as promising alternative templates to produce capsules in solvent-free conditions. These water-in-water droplets result from liquid-liquid phase separation in dilute aqueous polymer or surfactants solutions. Their ease of preparation, the large palette of components they can be assembled from and the lack of harsh solvent or oil used for their production make water-in-water emulsions of practical importance in materials chemistry. Water-in-water droplets can also spontaneously sequester solutes by equilibrium partitioning, which provides a simple strategy to locally accumulate molecules of interest and encapsulate them in capsules after interfacial shell formation. Here, we review recent works that employ water-in-water emulsion droplets to prepare capsules and suggest possible additional applications in materials chemistry. [ABSTRACT FROM AUTHOR]

[Display omitted] Using the platelet-like starch nanocrystals (SNCs) to stabilize emulsions is attractive because as-prepared emulsions have promising applications in cosmetics and food fields. Limited studies mainly focus on the oil- in -water system, and another important system, the water- in -water emulsions stabilized by SNCs, has not yet been unveiled. Two surface modification strategies, crosslinking and acetylation, were applied to tune surface property and aggregation of SNCs, and a common all-aqueous system (dextran/poly(ethylene glycol)) was used here as template. The viscoelasticity and morphology of emulsions were studied in terms of the SNC loadings and polymer ratios. Crosslinking results in aggregation of SNCs, and the particle size increases (from 110 nm to 370 nm) with increased levels of substitution. This favors improving emulsifying ability of particles. Acetylation decreases the particle size (∼90 nm) and weakens the affinity of SNCs to the two aqueous phases, improving the emulsifying efficiency of SNCs. More intriguingly, the two emulsion systems show different phase inversion behaviors. The depletion-stabilization mechanism for the cross-linked SNCs and the diffusion-controlled mechanism for the acetylated SNCs are proposed using the emulsion viscoelasticity as probe. This study makes a comprehensive insight into the regulation of water- in -water emulsion morphology and types with the platelet-like SNCs. [ABSTRACT FROM AUTHOR]

Aqueous multiphase systems have attracted a lot of interest recently espeically due to target applications in the biomedical field, cosmetics, and food. In turn, water‐in‐water Pickering emulsions are investigated frequently. In here, graphitic carbon nitride (g‐CN) stabilized water‐in‐water Pickering emulsions are fabricated via the dextran and poly(ethylene glycol)‐based aqueous two‐phase system. Five different derivatives of g‐CN as the Pickering stabilizer are described and the effect of g‐CN concentration on droplet sizes is investigated. Stable emulsions (up to 16 weeks) are obtained that can be broken on purpose via various approaches, including dilution, surfactant addition, and most notably light irradiation. The novel approach of water‐in‐water emulsion stabilization via g‐CN opens up considerable advances in aqueous multiphase systems and may also introduce photocatalytic properties. [ABSTRACT FROM AUTHOR]

Microstructural, rheological, and textural behaviour of tara gum–bovine sodium caseinate aqueous mixtures and their acid gels were evaluated. Acid gels with different microstructures and texture were obtained. These results can be related to a competition between the protein acid gelation process and the segregative phase separation. Depending on the concentration ratio of both biopolymers, a continuous protein gel network or a water‐in‐water emulsion stabilised by acid gelation was observed. These findings may be used to address the development of new food‐grade gels with different textures and also for the obtention of protein microgels to encapsulate hydrophilic compounds. [ABSTRACT FROM AUTHOR]

Abstract: The fabrication of stable colloidosomes derived from water‐in‐water Pickering‐like emulsions are described that were produced by addition of fluorescent amine‐modified polystyrene latex beads to an aqueous two‐phase system consisting of dextran‐enriched droplets dispersed in a PEG‐enriched continuous phase. Addition of polyacrylic acid followed by carbodiimide‐induced crosslinking with dextran produces hydrogelled droplets capable of reversible swelling and selective molecular uptake and exclusion. Colloidosomes produced specifically in all‐water systems could offer new opportunities in microencapsulation and the bottom‐up construction of synthetic protocells. [ABSTRACT FROM AUTHOR]

The effect of sulfate ester content on type I allomorph cellulose nanoparticles (CNPs) surface was evaluated in water-in-water emulsions with amylopectin (AMP) dispersed in xyloglucan (XG) phase. In addition, effect of cellulose allomorph type II was also verified. From a single source: microcrystalline cellulose (MCC) sulfated CNCs were isolated by sulfuric acid hydrolysis and subsequently sulfate content was modulated on CNPs surface with partial and quasi-total desulfation, keeping a rod-like particle morphology. MCC was solubilized with phosphoric acid and precipitated in water generating type II spherical nanocellulose allomorph. Particles were characterized by AFM, XRD, zeta potential and their surface groups were quantified by conductometric titration. Effect of adding these particles was evaluate at different concentrations in the phase diagram where XG is continuous phase. It was revealed that sulfated CNCs preference interact with XG increasing its viscosity and stabilizing the emulsions regardless their superficial sulfate content. On the other hand, phosphated nanocellulose interacts less with XG allowing it to migrate to XG-AMP interface and partially stabilize emulsions by Pickering effect. [Display omitted] • Cellulose particles with different morphologies and allomorphs were used as Pickering particles. • Sulfated cellulose nanoparticles stabilize emulsions by gelation. • Cellulose particle allomorph II stabilizes w/w emulsions by Pickering effect. • Cellulose allomorph plays an important role in the interactions with xyloglucan. [ABSTRACT FROM AUTHOR]

Most current methods for the preparation of tissue spheroids require complex materials, involve tedious physical steps and are generally not scalable. We report a novel alternative, which is both inexpensive and up-scalable, to produce large quantities of viable human keratinocyte cell clusters (clusteroids). The method is based on a two-phase aqueous system of incompatible polymers forming a stable water-in-water (w/w) emulsion, which enabled us to rapidly fabricate cell clusteroids from HaCaT cells. We used w/w Pickering emulsion from aqueous solutions of the polymers dextran (DEX) and polyethylene oxide (PEO) and a particle stabilizer based on whey protein (WP). The HaCaT cells clearly preferred to distribute into the DEX-rich phase and this property was utilized to encapsulate them in the water-in-water (DEX-in-PEO) emulsion drops then osmotically shrank to compress them into clusters. Prepared formulations of HaCaT keratinocyte clusteroids in alginate hydrogel were grown where the cells percolated to mimic 3D tissue. The HaCaT cell clusteroids grew faster in the alginate film compared to the individual cells formulated in the same matrix. This methodology could potentially be utilised in biomedical applications.

We synthesize colloidal zein particles using the anti-solvent precipitation method and study particle behavior at water-water interfaces. When added to phase-separating aqueous mixtures of fish gelatin and dextran, particles accumulate at the interface. In order to explain the mechanism of particle accumulation at the water-water interface, we investigate how zein particles interact with polymers (i.e. fish gelatin and dextran). We show that both polymers adsorb similarly on particle surface, which can explain why particles form contact angles close to 90°. Moreover, we show that particle accumulation is accompanied by aggregation. Those aggregates are able to arrest the late stage of the demixing process of the emulsion by the formation of a stable particle-rich layer at the water-water interface. This layer is referred as a ‘foam-like layer’ due to its morphology similar to that of a wet (non-drained) foam, and contains droplets of one phase, surrounded by particle-stabilized lamellae of the other phase. [ABSTRACT FROM AUTHOR]

Water-in-water (w/w) emulsions have been recognized for their broad applications in foods, cosmetics, and biomedical engineering. In this work, silica Janus nanosheets (JNs) with polyacrylic acid (PAA) chains grafted on one surface via crushing functional silica foams, and used silica JNs as Pickering stabilizer to produce stable water-in-water (w/w) emulsions from the aqueous two-phase system (ATPS) containing methacrylic acid (MAA) and NaCl are prepared. The interfacial area of w/w emulsions increases linearly with the concentration of silica JNs, and the interfacial coverage of nanosheets is calculated to be about 98%. After polymerizing w/w emulsions prepared from MAA/NaCl ATPS, it is found that silica JNs are entrapped at the interface of w/w emulsions with the smooth PAA-grafted surface located toward MAA-rich phase due to their specific interaction. These results show that functional silica JNs can be used as a promising amphiphilic Pickering stabilizer to produce well-defined w/w emulsions for numerous application fields., (© 2023 Wiley-VCH GmbH.)

The main idea of this paper is that the primordial soup may be modelled by food systems whose structure-property relationship is based on non-specific interactions between denatured biopolymers. According to the proposed hypothesis, polysaccharides were the first biopolymers that decreased concentration of salts in the primordial soup, `compatibilised' and drove the joint evolution of proto-biopolymers. Synthesis of macromolecules within the polysaccharide-rich medium could have resulted in phase separation of the primordial soup and concentration of the polypeptides and nucleic acids in the dispersed phase particles. The concentration of proto-biopolymer mixtures favoured their cross-linking in hybrid supermacromolecules of conjugates. The cross-linking of proto-biopolymers could occur by hydrophobic, electrostatic interactions, H-bonds due to freezing aqueous mixed biopolymer dispersions and/or by covalent bonds due to the Maillard reaction. Cross-linking could have increased the local concentration of chemically different proto-biopolymers, fixed their relative positions and made their interactions reproducible. Attractive-repulsive interactions between cross-linked proto-biopolymer chains could develop pairing of the monomer units, improved chemical stability (against hydrolysis) and led to their mutual catalytic activity and coding. Conjugates could probably evolve to the first self-reproduced entities and then to specialized cellular organelles. Phase separation of the primordial soup with concentration of conjugates in the dispersed particles has probably resulted in proto-cells. [ABSTRACT FROM AUTHOR]

The following hypotheses are the cardinal points of this paper. First, food systems and beverages containing denatured non-specifically interacting biopolymers could model the primordial soup. Second, polysaccharides were the first biopolymers. Third, the joint evolution of proto-biopolymers could start with their cross-linking. Fourth, cross-linked proto-biopolymers, i.e. conjugates, evolved into self-reproducible particles, the proto-cellular organelles. Fifth, the proto-cells resulted from phase separation of the primordial soup with concentration of conjugates in the dispersed particles accompanied by adsorption of lipid containing conjugates between aqueous phases. Sixth, the essential driving trend of life is to maintain homeostasis, i.e. to survive. Finally, polysaccharides are responsible for ecological contacts of living entities, i.e. for nutrition and non-specific universal immunity. [Copyright &y& Elsevier]

We studied the incompatibility between the polysaccharides amylopectin (AMP) and xyloglucan (XG) from tamarind seed and also generated a phase diagram of mixtures of these polymers. We evaluated the effect of XG concentration on the stability of water-in-water emulsions. Using protein particles with varying shapes produced from β-lactoglobulin (microgels and nanofibrils), we measured the stability of AMP and XG emulsions and the particle adsorption at the interface at various pH values. At pH < 5, microgels stabilized the emulsions, while at higher pH values, the interaction between the AMP-rich phase and particles led to the formation of a strong gel phase. Compared to spherical particles used in water-in-water emulsion stabilization, the adsorption of nanofibrils at the interface of AMP with XG occurred at pH 4 and 5 as well as at pH 6 and 7. At the latter pH, AMP droplets were observed in the XG continuous phase for up to 24 h. Image 1 • An amylopectin–xyloglucan phase diagram was constructed. • Protein particles with different morphologies were produced and characterized. • Microgels were able to stabilize AMP–XG emulsions at pH 4.0 by adsorption at the interface of the droplets. • Nanofibrils were adsorbed at droplet interfaces at a higher pH values. [ABSTRACT FROM AUTHOR]

Soy protein isolates (SPI) are capable of forming cold-set gels. This techno-functional property can be affected by the presence of tara gum (TG). Under certain conditions, these SPI/TG systems may also form water-in-water (W/W) emulsions. The aim of this study was to evaluate acid gels formed from soy protein isolates (SPI) and tara gum (TG) aqueous mixtures, and to find the conditions in which the W/W emulsions of SPI droplets dispersed in a TG continuous phase can be stabilized by SPI gelation as a strategy to prevent emulsion destabilization. Cold-set gels of SPI 0.3 g/L at different TG concentrations (0–0.05 g/L) showed different microstructures, a consequence of a different balance between gelation and segregative phase separation processes. SPI gels showed a homogenous and compact microstructure. When TG was present at 0.01 g/L and 0.02 g/L, the protein network was less interconnected, showing coarse-stranded and bicontinuous gels, respectively. At TG > 0.03 g/L, stable W/W emulsions were formed, revealing an abrupt decrease in gel firmness, a significant loss of fracture capacity, and a decrease in the water holding capacity. These findings may be used as a starting point for the application of these gelled systems as thickeners, texture modifiers, and coating materials for delivery of bioactive compounds. • Soy protein isolate/tara gum gels showed substantially different microstructures. • Different cold-set gel microstructures were related to different texture behavior. • The gel firmness decrease occurred along with its water holding capacity. • This study has revealed a simple method for obtaining stable W/W emulsions. [ABSTRACT FROM AUTHOR]