Medium Internal Phase Emulsions Research Articles

Fat analogue emulsions stabilized by peanut protein microgel particles: microscale and nanoscale structure and stabilization process analysis.

Biopolymer-based microgels are being regarded increasingly as promising building blocks in food applications. This study aimed to clarify the evolution process of the network for fat analogue emulsions stabilized by peanut protein isolate (PPI) microgel particles. It also investigated the interfacial structure and characteristics of emulsions (50% oil phase, w/w) stabilized by microgels under different pH conditions. There was an increasing interfacial adsorption capacity for PPI microgels over time (from 85.26% to the maximum of 89.78% at 24 h of storage) due to the aggregation of microgels around droplets and the development of cross-linking microgel chains between adjacent interfaces. The increased β-sheet content (from 35.51% to 41.12%) of adsorbed microgels indicated unfolding and the enhanced aggregation of microgels, which led to stronger droplet interaction. The network evolution observed with different microscopes clarified the transition to a self-supporting emulsion. The uneven adsorption of large microgel aggregates at the oil-water interface promoted larger and deformed droplets, so more fat-like medium internal phase emulsion stabilized by PPI microgel could be obtained by adjusting the microgel pH to 4.5. The interfacial membranes observed by scanning electron microscopy were thicker and coarser at pH 3.0 and 4.5 than those at pH 7.0 and 9.0. The adsorption of PPI microgel aggregates enhanced the structural strength and improved emulsion stability. This work could form a basis for further studies relating physical properties to the design of plant protein-based fat analogues. © 2024 Society of Chemical Industry.

Replacement of milk fat by rapeseed oil stabilised emulsion in commercial yogurt

The incorporation of lipid droplets and further characterization of matrices within dairy products may be possible using such adjacent particles as protein complexes/lipids. Among the range of varied emulsions and their functionalities, great attention has recently focused on the fabrication of high internal phase types. Feasibly, stable alternatives structured with health-beneficial lipids like those derived from plants could replace saturated fatty acids. As a fat replacement strategy, the fate of incorporated HIPE would require some adjustments either with storage stability and/or structural feat for the food matrix. Therefore, the replacement of milk fat by rapeseed oil stabilised emulsion in commercial yogurt was investigated. This involved 25%, 50% and 75% rapeseed oil respectively assigned as low (LIPE), medium (MIPE), and high internal phase emulsion (HIPE). Specifically, emulsions were examined by droplet size, encapsulation, pH, zeta potential, phase separation, and rheology. The fat free yogurt supplemented by HIPE were examined by droplet size, zeta potential, pH, color, sensory, texture and microbiological aspects against positive (regular milk fat) and negative (fat free) yogurt controls. Results showed increasing rapeseed oil contents would form smaller droplet-like emulsions. Within the yogurt matrix however, incorporating HIPE would seemingly reduce oil droplet size without much compromise to bacterial viability, sensory, or texture. Overall, this simple method of lipid alternation shows promise in dairy products.

Semisolid medium internal phase emulsions stabilized by dendritic-like mushroom cellulose nanofibrils: Concentration effect and stabilization mechanism

Emulsions with reduced fat and natural stabilizers are currently prevalent. Herein, semisolid emulsions with an oil phase of 50 % were successfully prepared using cellulose nanofibrils from mushroom stipes as stabilizers. Cellulose nanofibrils obtained by high-pressure homogenization were dendritic-like and possessed a contact angle of 70.50 ± 0.41°. The rheological properties and stability of emulsions increased significantly as nanocellulose concentrations increased from 5 to 20 mg/mL, while nanocellulose at 25–30 mg/mL significantly reduced the storage stability and anti-lipid oxidation ability of emulsions. The microstructure of semisolid emulsions demonstrated that nanocellulose fibers at 20 mg/mL could stabilize emulsions by forming compact interfacial films around droplets and creating intensive bridging networks between neighboring droplets, while nanofibers at concentrations over 20 mg/mL easily clustered in the aqueous phase, making the droplets more susceptible to aggregation and demulsification. The results demonstrate that cellulose nanofibrils from mushroom byproducts have the potential to stabilize semisolid food-grade emulsions.

Tuning the rheological and tribological properties to simulate oral processing of novel high internal phase oleogel-in-water emulsions

The current study reported novel oil-in-water high internal phase emulsions (HIPEs) stabilized by oleogel and a protein. Effects of ethyl cellulose (EC, oleogelator) and oil fraction on the microstructures, stability, linear/non-linear rheological, and tribological properties of the emulsions were investigated. CLSM and Cryo-SEM observations indicated that the increase of oil and EC content contributed to a smaller size (from 13.3 to 8.17 μm) and tighter packing of the droplets. EC was distributed inside the oil droplets and tended to move towards the interface. Gelation of the oil phase allowed the emulsions with higher physical stability against centrifugation. Compared to medium internal phase emulsions (60 wt% oil), HIPEs (75 wt% oil) were more sensitive to shearing. Small amplitude oscillation shearing analysis revealed that the inclusion of EC led to stiffer (higher moduli), stronger (higher critical stress), and more brittle (lower critical strain) properties of the emulsions. Large amplitude oscillation shearing tests showed that the emulsions with higher oil content presented weaker strain overshoot behaviors, while HIPEs with EC showed strain thinning characteristics. Lissajous-Bowditch curves further revealed that HIPEs were more sensitive to large deformation. Emulsions without EC showed higher structural elasticity and were more resistant to large deformations, while emulsions with EC exhibited higher nonlinear responses. Tribology tests suggested that the addition of EC contributed to higher friction coefficients of emulsions in mixed and hydrodynamic lubrication regions. The information obtained would be helpful in understanding the oral behavior of concentrated emulsions and designing functional food.

Preparation and Characterization of Nifedipine-Loaded Dry Medium Internal-Phase Emulsions (Dry MIPEs) to Improve Cellular Permeability.

A nifedipine (NP) dry emulsion was fabricated by the adsorption of medium internal-phase emulsions (MIPEs). Simple homogenizers were first used to mix conventional liquid MIPEs, and then a microfluidizer was used to reduce the resulting emulsions’ droplet sizes. The dry MIPEs (solid) were produced by adsorbing the emulsions onto solid carriers with a high surface area. The dry MIPEs were diluted in a simulated gastric fluid under gentle agitation to form emulsions. The diluted dry MIPEs were divided into three groups based on an NP content of 0.3%, 0.5%, and 0.7%, with sizes of 5026–5404 nm, 2583–3233 nm, and 1318–1618 nm in diameter, respectively. Powder X-ray diffraction (PXRD) measurements and differential scanning calorimetry (DSC) were used to characterize the physical properties of the dry MIPEs. The samples contained 0.5% or 0.7% drug, 2–4% surfactant, and 8–16% oil (5RH2/8, 7RH2/8, and 7RH4/16) and showed the characteristic peak for NP. No NP peak was observed in formulations with 0.3% NP and any oil-phase content (3RH2/8, 3RH4/16, and 3RH8/32). The formulations with 0.5% drug, 4–8% surfactant, 16–32% oil (5RH4/16 and 5RH8/32) and those with 0.7% drug, 8% surfactant, and 32% oil (7RH8/32) also did not show the peak for NP. These findings demonstrated that microfluidization improved the solubility of NP in the formulations. The subsequent drug dissolution results were consistent with the DSC thermogram and PXRD pattern results. 3RH2/8, 3RH4/16, 3RH8/32, 5RH4/16, 5RH8/32, and 7RH8/32 were completely dissolved and showed higher dissolved NP amounts than 5RH2/8, 7RH2/8, 7RH4/16, and NP powder. The lowest mean dissolution time was for 7RH8/32 (13.31 ± 0.87 min). Caco-2 cells were used to determine drug uptake, and 7RH8/32 showed the maximum intracellular uptake (10.89%). After storage under accelerated and normal conditions (3 and 6 months), the selected formulations remained stable. The developed formulations can be used to improve NP solubility and absorption.

One‐pot route to hyperbranched polyethylenimine‐dictated open cellular monolith as effective and charge‐selective adsorbent

AbstractThis study shows a one‐pot route to open cellular and functional monoliths. An oil‐in‐water high or medium internal phase emulsion readily forms by dropping oil into a dispersion of microcrystalline cellulose (MC) in aqueous branched polyethylenimine (PEI) solution. Crosslinking of PEI followed by removing the volatile yields an open cellular monolith. The key point of this strategy is that PEI can act as an emulsifier at high pH and simultaneously as reactants and finally as absorbing component. Results show that the rigid MC skeleton is fully covered by the flexible PEI network. The active amine content of the monolith reaches up to 3.3 mmol NH per g monolith. The open‐cellular structure stems from volume contraction. The porous monolith can sequester trace anionic dyes in water with an absorbing capacity up to 440 mg g−1 monolith, whereas the adsorption is highly charge‐selective. The monolith is pH‐recyclable and facilely separable from water.

An approach for the scalable production of macroporous polymer beads

A tubular co-flow reactor to produce macroporous polymer beads by polymerization of medium and high internal phase emulsion (M/HIPE) templates was developed. This reactor allows for improved production rates compared to tubing based microfluidic devices. Water-in-oil (W/O) M/HIPEs, containing methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) monomers in the continuous phase, were injected into a re-circulating carrier phase. The continuous phase of the emulsion droplets was UV polymerized in situ, resulting in polyM/HIPE beads. The emulsion composition was adjusted to produce poly(MMA-co-EGDMA) porous polymer beads with a protective crust and an interconnected internal pore structure. HCl loaded beads were produced by adding the active ingredient into the dispersed emulsion phase, leading to HCl encapsulation in the porous structure of the beads after polymerization. Even after exposure to ambient conditions for 24 h, 60% of the HCl remained in the beads, indicating good encapsulation efficiencies. Thus, it is possible to use such macroporous beads as delivery vehicles.

Permeable emulsion-templated porous polyepoxides

Porous polyepoxides are attractive materials for a range of applications. Liquid foam precursors can be net-shaped by moulding. We report preparation of permeable polyepoxide, Araldite®2020, foams with porosities in the range of 45–60% from surfactant-stabilised W/O medium internal phase emulsion templates. Alteration of internal phase volume ratio and surfactant concentration were used to tailor the properties of the resulting polyMIPEs. These polyepoxide foams had elastic moduli in the range of 60–200 MPa and compression strengths between 2 and 6.5 MPa with permeabilities up to 200 mD. The theoretical average molecular weight between crosslinks was 534 g mol−1, while the foams had 500 ± 50 g mol−1. Swelling tests confirmed the excellent chemical stability of the porous epoxy. However, the swelling ratio depended on the polarity of the solvents used. It decreased with decreasing solvent polarity.

A rheological investigation of oil-in-water Pickering emulsions stabilized by cellulose nanocrystals

HypothesisHigh and medium internal phase Pickering emulsions stabilized with cellulose nanocrystals (CNCs) exhibited very different performance compared to their peers stabilized with a surfactant. In this paper, we ascribed the difference to the formation of hydrogen bonding and van der Waals interactions between the CNC nanoparticles on adjacent oil droplets. ExperimentsRheological properties of CNC-stabilized oil-in-water medium internal phase emulsions (MIPEs, oil content = 65% v/v) and high internal phase emulsions (HIPEs, oil content = 80% v/v) were comprehensively characterized using both oscillatory and rotational tests. FindingsIt was found that in the MIPEs, the van der Waals and hydrogen bonding interactions dominate the emulsion properties, whereas the compact structure of oil droplets plays a more important role in the HIPEs. CNC concentration in the aqueous phase also affects the emulsion properties, especially for the HIPEs, and the results can be correlated to the stabilization mechanisms we previously reported. The information from these tests provides a much-needed guidance for the practical application of CNC-stabilized emulsions.

3D Printable and Sub‐Micrometer Porous Polymeric Monoliths with Shape Reconfiguration Ability by Miniemulsion Templating

AbstractPorous monoliths prepared by high internal phase emulsion (HIPE) templating have received various attentions in the fields of catalysis, separation, and tissue engineering. However, the application of the monoliths from HIPE is limited by their poor mechanical performance and the difficulty of fabricating hierarchically porous structures. Additive manufacturing is an emerging technique that achieves high design freedom by depositing materials layer‐by‐layer. This work designs medium internal phase emulsion (MIPE) ink with the concept of miniemulsion to prepare 3D printable porous polymeric monoliths with sub‐micrometer pores. High shear energy is used to reduce the droplet size of the internal phase and jam the emulsion ink. The jammed MIPE ink shows prominent shear‐thinning behavior and appropriate elastic modulus for direct ink writing (DIW). After printing, the external phase composed of stearyl acrylate and hexanediol diacrylate can be cured by photopolymerization to produce poly(MIPE) with interconnected pores in the size of several hundred nanometers. The printed poly(MIPE) demonstrates high mechanical strength and can be reprogrammed into complex geometries difficult for the common DIW processes. The proposed technique provides a new route to fabricate hierarchically porous monoliths with a drastic change of pore dimension, high mechanical strength, and tunable shape reconfiguration.

Development of porous material via chitosan-based Pickering medium internal phase emulsion for efficient adsorption of Rb+, Cs+ and Sr2+

The radioactive Rb+, Cs+ and Sr2+ have serious threat for the aquatic life and human health, its removal has been granted increasing concern. Hence the adsorbent with excellent adsorption performance and favourable reusability is strongly demanded. This work prepared a novel porous polymer of chitosan-g-polyacrylamide (CTS-g-PAM) by grafting the acrylamide (AM) onto the chitosan (CTS) with sufficient pore structure via an eco-friendly surfactant-free (corn oil)-in-water Pickering medium internal phase emulsion (O/W Pickering MIPE), solely stabilized by CTS. Interestingly, its pore structure could be tuned by varying the emulsion character via changing the molecular weight and concentration of CTS, as well as the pH values. Due to the abundant –COO− and −NH2 functional groups in the porous material of CTS-g-PAM, the high adsorption capacities of 195.43, 237.44 and 185.63 mg/g for Rb+, Cs+ and Sr2+ could be reached within 40, 30 and 20 min, respectively. Moreover, the CTS-g-PAM had excellent regeneration ability and reusability. Herein, we provided a feasible and low-cost pathway for preparation of the porous adsorbent with tunable porous structure for adsorption and separation application.

Improvement of O/W emulsion performance by adjusting the interaction between gelatin and bacterial cellulose nanofibrils

This study was designed to improve the stability of medium internal phase emulsion by adjusting the electrostatic interaction between gelatin (GLT) and TEMPO-oxidized bacterial cellulose nanofibrils (TOBC). The influences of polysaccharide-protein ratio (1:10, 1:5, and 1:2.5) and pH (3.0, 4.7, 7.0, and 11.0) on the emulsion properties were investigated. The droplet size of TOBC/GLT-stabilized emulsion was increased with the TOBC proportion increasing at pH 3.0–11.0. Additionally, emulsion had a larger droplet size at pH 4.7 (the electrical equivalence point pH of mixtures). However, the addition of TOBC significantly improved the emulsion stability. The emulsions prepared with TOBC/GLT mixtures (mixing ratio of 1:2.5) at pH 3.0–7.0 were stable without creaming during the storage. It was because the formation of nanofibrils network impeded the droplet mobility, and the emulsion viscosity and viscoelastic modulus were increased with the addition of TOBC. These findings were meaningful to modulate the physical properties of emulsions.

One‐Pot Fabrication of Hierarchically Bicontinuous Polystyrene Monoliths with Homogeneous Skeletons and Glycopolymer Surfaces

Inside cover: Article number 2100154 by Jian-Bo Qu and co-workers, a bicontinuous medium internal phase emulsion templating method is used to fabricate hierarchically bicontinuous polystyrene monoliths with homogeneous skeletons and glycopolymer surfaces. The monoliths combine the advantages of polysaccharides and polystyrene supports, which are promising in high-speed protein chromatography, catalysis, and biomedical applications after further derivatization.

One-Pot Fabrication of Hierarchically Bicontinuous Polystyrene Monoliths with Homogeneous Skeletons and Glycopolymer Surfaces.

The hierarchically bicontinuous polystyrene monoliths (HBPMs) with homogeneous skeletons and glycopolymer surfaces are fabricated for the first time based on the medium internal phase emulsion (MIPE) templating method via activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP). The synergistic self-assembly of amphiphilic diblock glycopolymer (ADG) and Pluronic F127 (PF127) at the oil/water interface via hydrogen bonding interaction contributes to the formation of bicontinuous MIPE with deformed neighboring water droplets, resulting in the highly interconnected HBPM after polymerization. There is a bimodal pore size distribution in the HBPM, that is, through pores (150-5000nm) and mesopores (10-150nm). The HBPMs as prepared show excellent biocompatibility, homogeneous skeletons, strong mechanical strength, and high bed permeability, overcoming the practical limitations of the second generation of polystyrene (PS) monoliths. Glycoprotein concanavalin A (Con A) can be easily and quickly separated by the HBPM in hydrophilic interaction chromatography (HILIC) mode. These results suggest the HBPMs have great potentials in catalysis, separations, and biomedical applications.

Novel eco-friendly spherical porous adsorbent fabricated from Pickering middle internal phase emulsions for removal of Pb(II) and Cd (II)

Spherical porous materials prepared from the emulsion template used in the water treatment have displayed a vast prospect, as the high surface area, abundant porous structure, convenient operation and excellent adsorption performance. But the tedious fabrication process, high consumption of organic solvent and surfactant limited the application widely. Herein, a facile and eco-friendly spherical porous adsorbent (SPA) is fabricated from the green surfactant-free (corn oil)-in-water Pickering medium internal phase emulsions (Pickering MIPEs) via the convenient ion crosslinking procedure. The Pickering MIPEs synergistically stabilized with the semi-coke (SC), which is the natural particle produced from the shale oil distillation, and sodium alginate (SA) has excellent storage and anti-coalescence stability. The as-prepared porous adsorbent possessed the abundant pore structure, which provided favorable conditions for effective mass transfer in adsorption, and could be tuned by varying the SA dosage. The saturation adsorption capacities of Pb(II) and Cd(II) can be achieved with 460.54 and 278.77 mg/g within 45 min at 25°C, respectively. Overall, this study supplied a viable and eco-friendly route for fabricating the spherical porous adsorbent with a tunable porous structure for heavy metal ion wastewater.

Synthesis and characterization of porous polydimethylsiloxane structures with adjustable porosity and pore morphology using emulsion templating technique

AbstractPorous polydimethylsiloxane (PDMS) framework with adjustable pore structures has been fabricated by polymerization of the continuous phase in the emulsion templates. Different types of surfactants, including nonionic (Triton X‐100), cationic (Benzalkonium chloride), anionic (sodium dodecyl sulfate), and silicone‐based block copolymer were used to stabilize the water‐in‐oil emulsion system. Deionized water with a wide range of internal phases varying from 10% to 60% by weight was employed to make the low internal phase emulsion and medium internal phase emulsion. The effect of surfactant type, surfactant concentration, and the internal phase volume on the stability of the emulsion, pore morphology, and pore size distribution was explored. The stability of the emulsion was investigated by comparing the pore morphology of the cured sample at different set times, such as 0, 6, and 72 h. Scanning electron microscopy was employed for the characterization of the porous structures. The image analysis was conducted, and the pore size distribution, porosity, and open‐cell ratio of each sample were calculated. Interconnected pores have been seen in the porous PDMS made from emulsions with an internal phase larger than 30%. The results demonstrated that the frequency of open‐cell pores and the pore size is dependent on the surfactant types.

Emulsion-templated flexible epoxy foams

Flexible epoxy foams were successfully prepared by curing medium internal phase emulsions (MIPEs) with a continuous organic phase containing epoxy resin and hardener, surfactant and carbon nanotubes and an aqueous internal phase. Curing the MIPEs at ambient temperature resulted in interconnected polyepoxide foams with average pore size of about 10 μm, while curing the MIPEs (with carbon nanotubes as a thickening agent) at 50 °C resulted in epoxy foams with pore sizes of one magnitude higher. The polyepoxide foams were compressible up to a strain of 70% of their original height and did not fracture. The polyepoxide foams were resilient with energy loss coefficients ranging from 40% to 60%, representing their energy adsorption during cyclic loading.

Pickering medium internal phase emulsions based on natural clay particles: Route to a macroporous adsorbent

We synthesized oil-in-water Pickering medium internal phase emulsions (MIPEs) based on (1) natural, unmodified montmorillonite (MMT) nanoparticles as a stabilizer; (2) a trace quantity of Tween-20 (T-20) as a co-stabilizer; and (3) eco-friendly flaxseed oil as the continuous phase. We modulated the stability, rheological properties, and droplet size of the emulsion by adjusting the MMT concentration, Tween-20 concentration, and oil phase volume fraction. We used these emulsions as templates to prepare a macroporous monolithic adsorbent [poly (carboxymethylcellulose-g-acrylamide); PCAM] with a hierarchical pore structure and excellent connectivity that approximates materials derived from Pickering high internal phase emulsions (HIPEs). Even when we decreased the internal phase volume fraction to 30%, there were still interconnecting pores in the material. Compared with Pickering HIPEs, our approach reduced the oil phase volume fraction substantially (approximately 45%), which lowered the production cost of the emulsion. Our Pickering MIPE-derived macroporous monolithic material effectively adsorbed cationic dyes (methyl violet and methylene blue) from water. Our environmentally friendly method of preparing Pickering MIPEs will enable researchers to prepare absorbents with an excellent hierarchical pore structure, which will facilitate rapid mass transport and increased greater specific surface area.

Controllable fabrication of hierarchically porous adsorbent via natural particles stabilized Pickering medium internal phase emulsion for high-efficiency removal of Rb+ and Cs+

Hierarchical porous adsorbent with well-defined macro-pores and interconnected meso- and micro-pores provides better accessibility and active sites for adsorbate. However, most synthesis techniques usually require multiple steps, or based on surfactants and block-copolymers as soft templates, which are time consuming, costly and non-renewable. Herein, we demonstrated a novel strategy to fabricate a highly interconnected hierarchical 3D porous composite adsorbent chitosan-g-poly(acrylamide)/attapulgite (CTS-g-PAM/APT) with tunable pore size via one-step Pickering emulsion polymerization without any surfactant. Stable, low-cost and environment-friendly canola oil-in-water (O/W) Pickering medium internal phase emulsions (MIPEs) was solely stabilized by a pH-responsive APT/CTS composite particle derived from the electrostatic assembly of non-toxic natural APT nanorods and biopolymer CTS. Then, the acrylamide (AM) monomers in Pickering MIPEs were in-situ polymerized to produce CTS-g-PAM/APT composite with hierarchical and interconnected pores. The size of pore can be regulated by varying the pH values due to the pH-dependent of droplet size of emulsion. The composite has large amounts of chelating groups (e.g., –NH2 and –COO−) and high porosity, so it was capable of capturing Rb+ and Cs+ with high adsorption capacities of 178.88 mg/g and 221.56 mg/g, and rapid adsorption rate of 600 and 900 s for Rb+ and Cs+, respectively. Moreover, the composite can be regenerated and reused for multiple cycles. This new approach provided a potential and economical pathway to develop hierarchically porous materials for wastewater treatment.

Preparation of Carboxymethyl Cellulose-g- Poly(acrylamide)/Attapulgite Porous Monolith With an Eco-Friendly Pickering-MIPE Template for Ce(III) and Gd(III) Adsorption.

Due to their high specific surface and metal-binding functional groups in their crosslinked polymeric networks, monolithic materials incorporating a porous structure have been considered one of the most efficient kinds of adsorbents for rare earth element recovery. Herein, a facile and novel monolithic multi-porous carboxymethyl cellulose-g-poly(acrylamide)/attapulgite was synthesized by free radical polymerization via green vegetable oil-in-water Pickering medium internal phase emulsion (O/W Pickering-MIPEs), which was synergically stabilized by attapulgite and tween-20. The homogenizer rotation speed and time were investigated to form stable Pickering-MIPEs. The effects of different types of oil phase on the formation of Pickering-MIPEs were investigated with stability tests and rheological characterization. The structure and composition of the porous material when prepared with eight kinds of vegetable oil were characterized by FTIR and SEM. The results indicate that the obtained materials, which have abundant interconnected porosity, are comparable to those fabricated with Pickering-HIPE templates. The adsorption experiment demonstrated that the prepared materials have a fast capture rate and high adsorption capacities for Ce(III) and Gd(III), respectively. The saturation adsorption capacities for Ce(III) and Gd(III) are 205.48 and 216.73 mg/g, respectively, which can be reached within 30 min. Moreover, the monolithic materials exhibit excellent regeneration ability and reusability. This work provides a feasible and eco-friendly pathway for the construction of a multi-porous adsorbent for adsorption and separation applications.