In this work, we present gel-in-gel water-in-oil (W/O) high internal phase emulsions (HIPEs) that feature high stability by structuring both phases of the emulsion. Compared to significant advances ...made in oil-in-water (O/W) HIPEs, W/O HIPEs are extremely unstable and difficult to generate without introducing high concentrations of surfactants. Another main challenge is the low viscosity of both water and oil phases which promotes the instability of W/O HIPEs. Here, we demonstrate ultrastable W/O HIPEs that feature biphasic structuring, in which hydrogels are dispersed in oleogels, and self-forming, low-concentration interfacial Pickering crystals provide added stability. These W/O HIPEs exhibit high tolerance toward pH shock and destabilizing environments. In addition, this novel ultrastable gel-in-gel W/O HIPE is sustainable and made solely with natural ingredients without the addition of any synthetic stabilizers. By applying phase structuring within the HIPEs through the addition of various carrageenans and beeswax as structurants, we can increase the emulsion’s stability and viscoelastic rheological properties. The performance of these gel-in-gel W/O HIPEs holds promise for a wide range of applications. As a proof of concept, we demonstrated herein the application as a gelled delivery system that enables the co-delivery of hydrophilic and hydrophobic materials at maximized loads, demonstrating high resistance to gastrointestinal pHs and a controlled-release profile.
Low concentrations of gelatin (0.02–0.20 wt%) were applied to regulate the surface and interface properties of CNC (0.50 wt%) by forming CNC/G complexes. As gelatin concentration increased from 0 to ...0.20 wt%, the potential value of CNC/G gradually changed from −44.50 to −17.93 mV. Additionally, various gelatin concentrations led to micromorphology changes of CNC/G complexes, with the formation of particle interconnection at gelatin concentration of 0.10 wt%, followed by network structure and enhanced aggregation at gelatin concentration of 0.15 and 0.20 wt% respectively. The water contact angle (25.91°-80.23°) and interface adsorption capacity of CNC/G were improved due to hydrophobic group exposure of gelatin. When gelatin concentration exceeded 0.10 % at a fixed oil phase volume fraction (75 %), a high internal phase emulsion (HIPE) stabilized by CNC/G can be formed with a good storage stability. The rheological and microstructure results of HIPE confirmed that low gelatin concentration can assist CNC to form stable emulsion structure. Especially, the auxiliary stabilization mechanism of various gelatin concentration was different. CNC/G-0.10 % and CNC/G-0.15 % stabilized HIPE mainly depended on the enhanced interface adsorption and network structure, while CNC/G-0.20 % stabilized HIPE mainly relied on enhanced interface adsorption/accumulation due to weak electrostatic repulsion and aggregate granular morphology of CNC/G-0.20 %.
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•Gelatin and CNC were complexed via hydrogen bonding and electrostatic interaction.•Low gelatin concentration affected the surface and interface properties of CNC.•High internal phase emulsion (HIPE) was prepared by a one-step emulsification.•Low gelatin concentration (0.1 % ∼ 0.2 %) can assist CNC (0.5 %) to stabilize HIPE.•Gelatin content can adjust the interface adsorption and network formation of CNC.
In the present work, sodium alginate-based complex (flaxseed protein-sodium alginate) electrostatic complexes (FP-AG) were fabricated, acting as an effective emulsifier for the first time to ...stabilize Pickering high internal phase emulsions (HIPE). Interactions between FP and AG were evaluated by isothermal titration calorimeter and quartz crystal microbalance with dissipation monitoring. These results suggested that electrostatic interactions played a dominant role in FP-AG complexation, and stronger interactions between FP and AG occurred under acidic conditions, forming more viscoelastic layers. FP-AG complexes at pH 4.0 (FP-AG4) exhibited appropriate wettability (87.9°). HIPEs were prepared using FP-AG4 (HIPE-C), contrasted with FP at pH 8.0 (HIPE-P) as a control. Rheological results suggested that HIPE-C exhibited shear-thinning behavior (extrusion), high thixotropy (recovery), and high viscoelasticity (self-supporting), which possessed a great potential for 3D printing. Moreover, 3D printing and the stability of curcumin of HIPE were explored simultaneously for the first time. These results showed that HIPE-C exhibited outstanding printability and printing models presented smooth surfaces, regular shapes, and distinct resolution. HIPE-C showed a better protection for curcumin against ultraviolet and thermal treatments than HIPE-P. FP-AG complexes could be used as an effective HIPE stabilizer and novel edible ink with good 3D printability in food industry.
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•FP-AG complexes could act as an effective emulsifier to stabilize HIPE.•Electrostatic interactions played a dominant role in FP-AG complexation.•Addition of AG could strengthen HIPE’s network structure and mechanical strength.•HIPE-C showed outstanding extrudability and printability during 3D printing.•HIPE-C significantly protected Cur from degradation against UV and heat treatments.
High internal phase emulsion (HIPE) presents an attractive approach for fabricating porous materials, however, most of which require external energy input (e.g., heat, UV) to solidify soft colloid ...templates into robust polymeric skeleton structures. Herein, a ketone-group-containing ambient-condition curable (ACC) copolymer was prepared in order to create a polyHIPE system based on the keto-hydrazide chemistry. Tailored design is made possible by the adaptable construction feature of ACC copolymer, and its amphiphilic properties significantly expand the selection of water-in-oil (W/O) HIPE stabilizers. By utilizing the unmodified ZnO nanoparticles as stabilizers and anti-shrinkage agents based on ionic crosslinking, and employing the ACC copolymer solution as the continuous phase, we streamlined the stabilization modification step, removed the need for purifying polyHIPE, and established a rapid, straightforward, and cost-effective polyHIPE preparation protocol. Results demonstrated that the obtained polyHIPEs exhibit ideal pore structures, with densities as low as 0.046 g/cm³ and porosities exceeding 90%, exhibiting remarkable stability, 3D printing feasibility, and the capacity for crosslinking under ambient circumstances. By using Soxhlet extraction, the gel content of polyHIPEs was found to be 65.5%, and mechanical characteristics were assessed up to 1.9 MPa. The technique’s successful 20-fold scaled-up HIPE production further confirms it as a promising and straightforward approach for large-scale, energy-saving, and environmentally friendly manufacture of self-curable HIPEs.
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•Ambient-condition curable copolymer was developed from emulsion polymerization.•Water-in-Oil HIPE could be spontaneously crosslinked at room temperature.•The HIPE generated is 3D printable which hold the structure stability.•The scaled-up experiment of ambient-condition curable HIPE has been demonstrated.
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Hypothesis: Constructing a segregated network in electrically conductive polymer composites (ECPCs) is an effective method to lower the electrical percolation threshold. The ...segregated network structure can be formed naturally via polymerizing Pickering high internal phase emulsions (HIPEs) because solid particles are assembled at water-oil interfaces. However, most Pickering stabilizers show poor electrical conductivity. In this work, we propose a facile method to prepare lightweight ECPCs with well-controlled segregated structure via Ti3C2Tx-stabilized HIPE templating.
Experiments: Hydrophilic Ti3C2Tx flakes are delicately hydrophobized with a double-chain cation surfactant. The morphology of Ti3C2Tx flakes is investigated by transmission electron microscopy (TEM) and atom force microscopy (AFM). The surface properties of modified Ti3C2Tx are characterized by zeta potential and water contact angle tests. The stability of Ti3C2Tx-stabilized emulsions, and the structure of prepared ECPCs are systematically investigated.
Findings: Surface modified Ti3C2Tx flakes are used to stabilize water-in-oil (w/o) HIPEs for the first time. After the polymerization of continuous oil phase, ECPCs are successfully prepared with closed-cell porous structure. The pore size and size distribution of porous composites can be tailored by varying the content of Ti3C2Tx flakes. The Ti3C2Tx flakes are mainly immobilized at the water–oil interface and eventually form the segregated network in composites. Combining the unique segregated network and the outstanding metallic conductivity of Ti3C2Tx, the prepared porous polymer composites exhibit good conductivity even with ultralow Ti3C2Tx content of 0.016 vol%.
Zein is a widely used plant protein, but its application is limited by its poor water solubility under neutral conditions. In this work, we present an approach to develop a water-soluble zein-gum ...arabic (GA) complex and to explore its application in stabilizing lemon oil-in-water emulsions. As a simple, inexpensive and rapid method, sonication was used to accelerate the glycation reaction between zein and GA. The grafting degree of zein and GA was highest when the sonication power was 400 W and the treatment time was 25 min. SDS-PAGE and 1H NMR confirmed the formation of covalent bonds between zein and GA. The water-dispersibility, antioxidant activity, and thermal stability of zein-GA conjugates were better than those of native zein. The conjugates were used to form stable high internal phase emulsions (HIPEs) containing 80% v/v oil, which had relatively small mean droplet diameter (<10 μm). The HIPEs were semi-solids that exhibited strong shear-thinning behavior. After encapsulation in the HIPEs, the chemical degradation of lemon oil when exposed to UV-light and heat was significantly reduced. This study shows that the functional performance of zein can be extended by covalently linking it to GA using a combination of sonication and heat.
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•Sonication promoted the Maillard reaction between zein and gum arabic (GA).•Zein−GA conjugates exhibited better water solubility and emulsifying properties than zein.•Stable high internal phase emulsions (HIPEs) were formed using zein-GA conjugates.•The HIPEs were semi-solids with strong shear thinning characteristics.•The light and thermal stability of lemon oil was improved by encapsulation in these HIPEs.
We have explored a controllable approach to produce polysaccharide-based high internal phase emulsions (HIPEs) without the use of any surfactants, synthetic particles, or synthesis of Pickering ...emulsions. This strategy required only the centrifugation of ultrasonication-produced shell cross-linked polysaccharide microspheres, and simultaneously provided facile control over the properties of HIPEs. By this means, the strong viscoelastic HIPEs with high oil volume fraction (up to 85.6%) can be stabilized solely by 0.5 wt% polysaccharide. We can further strengthen the HIPEs by generating an additional complex shell through the electrostatic deposition of non-cross-linked polysaccharides back on the cross-linked microsphere surface. Using β-carotene as a model hydrophobic bioactive, these HIPEs stabilized by cross-linking/electrostatic deposition of polysaccharides featured high encapsulation efficiency, oxidation stability, and pH/redox dual stimuli-responsive release. Further development of this strategy could exhibit a great potential to construct tunable HIPEs with desired functionalities for smart delivery and oral adsorption of hydrophobic food active ingredients.
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•An ultrasonication/centrifugation combined strategy is used for HIPE production.•HIPEs are stabilized by cross-linking/electrostatic deposition of polysaccharides.•The properties of HIPEs can be precisely tuned with desired functionalities.•The HIPEs feature pH and redox dual stimuli-responsive release.
The present work aimed to fabricate food-grade Pickering emulsions stabilized by heteroprotein complexes formed by ovotransferrin (OVT) and lysozyme (LYS) as lipid-based nutraceutical delivery ...vehicles. The heteroprotein complexation, as confirmed by turbidity titrations, was proved to be an effective means to prepare food-grade particles. Multiple parameters such as particle size, zeta potential and dispersion stability were characterized in screening for proper OVT–LYS particles as Pickering stabilizers. OVT–LYS particles with OVT/LYS ratio of 8:1 at pH 9.3 met all requirements of eligible Pickering stabilizers such as intermediate wettability. Titrations in the presence of sodium chloride demonstrated that primary driving force of OVT–LYS particle formation was electrostatic attraction. Afterwards, food-grade Pickering emulsions were fabricated using OVT–LYS particles. Visual observation indicated that Pickering emulsions stabilized by OVT–LYS particles at various particle concentrations and oil fractions were stable during one-month storage at room temperature, and OVT–LYS particles could stabilize high internal phase Pickering emulsions at oil fraction of 0.75. Rheological measurements revealed that viscosity and gel-like structures of Pickering emulsions were dependent on particle concentration and oil fraction. When compared with the extent of lipolysis (32.1%) in bulk oil, the extent of lipolysis (71.5%) in OVT–LYS particle-stabilized Pickering emulsion was increased by 39.4%. Curcumin bioaccessibility was increased from 16.1% to 38.3% after encapsulation of curcumin into OVT–LYS particle-stabilized Pickering emulsion. Such improved bioaccessibility demonstrated that OVT–LYS particle-stabilized Pickering emulsion was an effective delivery vehicle for curcumin.
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•Heteroprotein complex formation of ovotransferrin (OVT) and lysozyme (LYS) was confirmed.•OVT–LYS particles could stabilize high internal phase Pickering emulsions.•Food-grade Pickering emulsions stabilized by OVT–LYS particles had superior storage stability.•Pickering emulsions stabilized by OVT–LYS particles had higher extent of lipolysis than bulk oil.•Pickering emulsions stabilized by OVT–LYS particles could improve bioaccessibility of curcumin.
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