Emulsion Gels Research Articles

Enhancing the storage stability and shelf-life of plant-based Pickering emulsions through emulgel formation

Plant-based food Pickering emulsions which are rich in nutrients have recently attracted wide attention due to their plant origin and new functionalities that can be introduced. However, the storage stability and shelf-life are significant concerns for plant-based food. In this study, we report enhanced stability of oat flour-based Pickering emulsions (PEs) through emulgel formation by thermal treatment with minimal processing. The PEs stabilised using oat particles with and without mild-chemical treatment were prepared and heated at varying temperatures (50, 65, 75, and 90 °C) and for different durations (0.5, 1, 5 and 15 min). Subsequently, they were characterised based on particle size and microstructural analysis. The PEs subjected to mild chemical treatment exhibited enhanced thermal stability compared to the control, showing smaller droplet sizes and no coalescence, even at high temperatures. The treatment at higher temperatures (75 °C and 90 °C) afforded the formation of emulsion gels or ‘emulgels’ as evidenced by the results on flow behaviour, dynamical rheology, and texture. The heat-treated PEs displayed a gel-like structure and desirable characteristics (viscoelastic behaviour, firm gel-like texture). In particular, the PEs based on mild-chemically treated oat particles exhibited exceptional properties upon heat treatment at 90 °C for 15 min, displaying a strong 3D gel-like network structure and high storage modulus value.

Influence of furcellaran and safflower oil concentration on the properties of model emulgel systems

The aim of this study was to investigate the effect of varying concentrations of furcellaran (FUR) and safflower (Carthamus Tinctorius) oil on the functional properties of emulgels as potential carriers of bioactive substances. The textural, mechanical, thermal and structural properties of twenty different formulations were characterised. The pH stability and zeta-potential of the emulgels was also examined. It was found clear correlation between gelling agent and oil fraction content and investigated properties. The hardness, strength, thermal stability expressed as melting point of the investigated systems increased with increasing concentration of the furcellaran and decreasing proportion of safflower oil, which indicated a significant weakening of the structure as a result of the addition of the oil fraction. Stored under refrigeration, emulgels appeared to be relatively stable showing a slight decrease in pH values after 7 days. Swelling ratio (SW) of emulgels increased with increasing both, polysaccharide and oil content, in emulgels. Based on the microstructure analyses, it can also be concluded that only part of the added safflower oil chemically bound to the functional groups of the polysaccharide, while the vast majority of it was only physically immobilized in the furcellaran matrix. Colour of furcellaran – safflower oil emulsion gels depended largely on the amount of oil fraction. The presented research demonstrating the wide spectrum of functional properties of polysaccharide-oil systems is a first step to developing a carrier composition for lipophilic compounds at further stages of research.

A Novel Pickering High Internal Phase Emulsion Gels Fabricated by Starch Nanocrystals and Bovine Serum Albumin Complexes

A Novel Pickering High Internal Phase Emulsion Gels Fabricated by Starch Nanocrystals and Bovine Serum Albumin Complexes

3D-Printed Interfacially Jammed Emulsion Aerogels.

3D printing ultralightweight porous structures using direct ink writing (DIW) while maintaining their mechanical robustness is highly challenging. This difficulty is amplified when low ink concentrations are used to create complex geometries. Herein, this shortfall was addressed by interfacially jammed emulsion gels. The gel emerged from the electrostatic interaction among synergized nanomaterials (graphene oxide (GO) and cellulose nanocrystals (CNCs)) in the aqueous phase and a ligand in the oil phase. This interaction led to the jamming of the nanoparticles and the creation of stable emulsion gels. The formed interfacial assemblies were further treated by post-jamming ionic cross-linking with NaHCO3, which dictated the emulsion gels' rheological characteristics, enhancing the ink's viscoelastic properties for high-resolution 3D printing. The customizable emulsion system allows control over porosity from the macro- to the micro-scale and generates complex geometries with desired compositions. By manipulating post-annealing processes and varying concentrations, it is possible to achieve aerogels that feature a remarkably low density (∼2.63 mg/cm3) and adjustable mechanical robustness (elastic modulus of 0.45 MPa). Additionally, this method allows for producing aerogels with flexible or stiff characteristics as required, alongside the capability to tailor specific electromagnetic shielding effectiveness (ranging from 6791 to 19615 dB cm2/g), showcasing the technique's versatility and engineerability.

Stabilizing Bicontinuous Emulsions with Sub-Micrometer Domains Solely by Nanoparticles.

Nanoparticle-stabilized, bicontinuous interfacially jammed emulsion gels (bijels) find potential applications as battery, separation membrane, and chemical reactor materials. Decreasing the liquid domain sizes of bijels to sub-micrometer dimensions requires surfactants, complicating bijel synthesis and postprocessing into functional nanomaterials. This work introduces surfactant-free bijels with sub-micrometer domains, solely stabilized by nanoparticles. To this end, the covalent surface functionalization of silica nanoparticles is characterized by thermogravimetric analysis, mass spectrometry, Fourier-transform infrared spectroscopy, and contact angle measurements. Bijels are generated with the functionalized nanoparticles via solvent transfer induced phase separation (STrIPS), enabling the optimization of nanoparticle functionalization and surface ionization. Nanoparticles of intermediate functionalization and controlled negative surface charge stabilize bijels with sub-micrometer liquid domains. This remarkable control over bijel synthesis provides urgently needed progress to facilitate the widespread implementation of bijels as nanomaterials in research and applications.

Cholic Acid/Glutathione-Assembled Nanofibrils for Stabilizing Pickering Emulsion Biogels.

Achieving the delicate balance required for both emulsion and gel characteristics, while also imparting biological functionality in gelled emulsions, poses a significant challenge. Herein, Pickering emulsion biogels stabilized is reported by novel biological nanofibrils assembled from natural glutathione (GSH) and a tripod cholic acid derivative (TCA) via electrostatic interactions. GSH, composed of tripeptides with carboxyl groups, facilitates the protonation and dissolution of TCA compounds in water and the electrostatic interactions between GSH and TCA trigger nanofibrillar assembly. Fibrous nuclei initially emerge, and the formed mature nanofibrils can generate a stable hydrogel at a low solid concentration. These nanofibrils exhibit efficient emulsifying capability, enabling the preparation of stable Pickering oil-in-water (O/W) emulsion gels with adjustable phase volume ratios. The entangled nanofibrils adsorbed at the oil-water interface restrict droplet movement, imparting viscoelasticity and injectability to the emulsions. Remarkably, the biocompatible nanofibrils and stabilized emulsion gels demonstrate promising scavenging properties against reactive oxygen species (ROS). This strategy may open new scenarios for the design of advanced emulsion gel materials using natural precursors and affordable building blocks for biomedical applications.

Physicochemical properties and in vitro digestive behavior of astaxanthin loaded Pickering emulsion gel regulated by konjac glucomannan and κ-carrageenan

This study aimed to elaborate the combination effect of polysaccharides on physicochemical properties and in vitro digestive behavior of astaxanthin (AST)-loaded Pickering emulsion gel. AST-loaded Pickering emulsion gel was prepared by heating Pickering emulsion with konjac glucomannan (KGM) and κ-carrageenan (CRG). The microstructure revealed that adding the two polysaccharides resulted in Pickering emulsion forming a network structure. It exhibited a denser and more uniform network structure, enhancing its mechanical properties four times and increasing its water-holding capacity by 20 %. In vitro digestion experiments demonstrated that the release of free fatty acids from the Pickering emulsion gel (4.25 %) was notably lower than that from conventional Pickering emulsion (17.19 %), whereas AST bioaccessibility was remarkably low at 0.003 %. It provided a feasible strategy to regulate the bioaccessibility in Pickering emulsion, which has theoretical significance to guide the current eutrophic diet people.

Blackcurrant Pomace Extract as a Natural Antioxidant in Vienna Sausages Reformulated by Replacement of Pork Backfat with Emulsion Gels Based on High Oleic Sunflower and Flaxseed Oils.

The incorporation of a blackcurrant pomace extract (BPE) at 2.5%, 5.0% and 10.0% into an emulsion gel based on high oleic sunflower and linseed oils was examined in order to obtain a functional ingredient to be used as a pork backfat replacer in Vienna sausages. The replacement of the pork backfat with the control emulsion gel reduced the cooking loss but negatively affected the color by decreasing L* and a* values as compared with the traditional product. A decrease in the n-6/n-3 ratio from 10.99 to around 1.54 (by 7 times) was achieved through reformulation, while the PUFA/SFA ratio increased from 0.49 to 1.09. The incorporation of BPE did not have a major impact on the fatty acid profile and improved color by increasing redness, but negatively affected the texture by increasing hardness, gumminess and share force as compared with the sausages reformulated without extract. BPE reduced the pH and the thermal stability of the emulsion gels, increased cooking loss and decreased moisture retention in sausages. BPE increased the oxidative stability of Vienna sausages enriched in polyunsaturated fatty acids; however, the incorporation of BPE into the emulsion gels above 5% affected the sensory scores for appearance, texture and general acceptability of the reformulated sausages.

Preparation and characterization of fish-derived protein gel as a potential dysphagia food: Co-mingling effects of inulin and konjac glucomannan mixtures

The study aimed to create a fish-derived protein gel with inulin/konjac glucomannan (KGM) mixture for dysphagia. The inulin/KGM complex improved the swallowing properties of myofibrillar protein (MP) emulsion gel. Interactions, physicochemical, and flavor properties were analyzed. Inulin/KGM mixture inhibited hydrophobic groups exposure, and maintained MP structure during thermal induction. Inulin/KGM-protein gels exhibited shear-thinning behavior, low deformation resistance and hardness. IDDSI test also indicated inulin/KGM gels is suitable for dysphagia. Inulin/KGM mixture improved flavor by increasing ethanol and 2-octen-ol while decreasing ichthyological substances such as hexanal and nonanal, enhancing the sensory experience of patients with dysphagia. An 8% inulin/KGM mixture effectively modulated mechanical, swallowing, and sensory properties of MP emulsion gels, offering insights for future marine-derived dysphagia foods development.

Cellulose nanocrystal-stabilized Pickering emulsion gels as vehicles for follicular delivery of minoxidil

Minoxidil (MXD) is the only topical over-the-counter medicine approved by the United States Food and Drug Administration for the treatment of androgenetic alopecia. For the purpose of targeting the delivery of MXD to dermal papilla in the hair follicle, MXD Pickering emulsion gels were fabricated based on the designability of deep eutectic solvent (DES) and the versatility of cellulose nanocrystal (CNC) and sodium carboxymethyl cellulose (CMC-Na). Structural studies and theoretical calculations results suggest that CNC can stabilize the interface between the MXD-DES and water, leading to the formation of Pickering emulsions. The rheological properties and stabilities of MXD Pickering emulsions were enhanced through gelation using CMC-Na, which highlights the good compatibility and effectiveness of natural polysaccharides in emulsion gels. Due to the particle size of emulsion droplets (679 nm) and the rheological properties of emulsion gel, the fabricated MXD formulations show in vivo hair regrowth promotion and hair follicle targeting capabilities. Interestingly, the MXD Pickering emulsion-based formulations exert therapeutic effects by upregulating the expression of hair growth factors. The proposed nanodrug strategy based on supramolecular strategies of CNC and CMC-Na provides an interesting avenue for androgenetic alopecia treatment.

3D printing of pickering emulsion gels of protein particles prepared by high pressure homogenization and heating

In this study, oil-in-water Pickering emulsion gels stabilized by soybean protein isolate microgel particles were prepared by a combination of high pressure homogenization and heating. These particles swiftly adsorbed onto the oil-water interface stabilizing drops. Cryo-SEM showed the formation of small droplets wrapped in a three-dimensional network structure of protein particles. Heating and increasing the oil content and particle concentration can improve the viscosity, energy storage modulus and gel strength of the system, which is conducive to improving the ability to 3D print these emulsions. The shear-thinning properties allow the system to be extruded smoothly through the nozzle with good printability. When the oil content was 60%, the accuracy and stability of the printed modeling reached 91.8% and 97.2%, respectively. In the future, the excellent properties of Pickering emulsion gel can be further utilized to load active ingredients, optimize and adjust the taste, and prepare food suitable for the elderly and other people with swallowing disorders with the help of 3D printing technology, and achieve the delivery of precise nutrition.

Structure, characterization, and application of a novel thermoreversible emulsion gel fabricated by citrate agar

A novel thermoreversible emulsion gel was successfully prepared with citrate agar (CA) as the sole emulsifier. Compared with native agar gel emulsion, CA gel emulsion (CAGE) formed a stable emulsion gel when the CA concentration was increased to 1.25 % (w/w). Results of time-temperature scanning experiments showed that the emulsion gel rapidly transformed into liquid emulsion when heated to 40–50 °C and then solidified into emulsion gel after cooling to the critical temperature of solidification. The emulsion gel had stable sol–gel transformation ability after seven cycles repeated heating–cooling treatment (HCT) at 85 °C and 4 °C. However, the stability of emulsion gels gradually decreased because of the large-droplet formation during heating, which affected the CA molecular-reconfiguration network structure in cooling. The conjunction analysis of microstructure and properties of the emulsion gel indicated that its stability depended primarily on the spatial repulsion and electrostatic repulsion provided by CA gel, and the main factor driving thermal reversibility was the temperature-responsive gelation performance of CA. The retention of quercetin was >90.23 % after seven HCTs because CAGEG enhanced the homogeneity and stability of the droplets.

Rheology and Extrusion Printing of κ-Carrageenan/Olive Oil Emulsion Gel Tablets with Varying Surface Area to Volume Ratios for Release of Vitamin C and Curcumin.

In this work, κ-carrageenan and olive oil at different oil to κ-carrageenan ratios (OCR) are homogenized to create emulsion gels. Interestingly, confocal imaging shows that the oil droplets are stabilized in the κ-carrageenan-structured gel matrix without using any surfactants. Rheological studies show that the oil droplets enhanced the oscillatory yield stress and the maximum printable height of the emulsion gels. The creation of the emulsion gels with an OCR of 1:9-3:7 led to an improvement in the structural integrity of extrusion printed structures. The emulsion gel with an OCR of 3:7 efficiently encapsulates vitamin C in the aqueous phase and curcumin in the hydrophobic oil phase, enabling the extrusion 3D printing of tablets with varying surface area to volume (SA/V) ratios. The release of vitamin C and curcumin is influenced by the preparation method of printing versus casting and the SA/V ratio of the tablets. The hollow cylinder with the highest SA/V ratio was observed to have the highest vitamin C release, whereas for curcumin, the printed tablets had a higher release compared to the cast tablet. Additionally, through rheo-dissolution experiments, we observe a lower modulus and higher vitamin C release from the 3D-printed disc versus the higher modulus and lower vitamin C release from the cast disc tablet.

Developing fish oil emulsion gel enriched with Lentinula edodes single cell protein and its effect on controlling the growth of Acinetobacter baumannii

In this study, the characterization of fish oil (FO) emulsion gel (EGEL) containing single cell protein (SCP) produced from Lentinula edodes (L. edodes) and its potential inhibition against Acinetobacter baumannii (A. baumannii) were investigated. Oil extracted from the fish liver was emulsified with tween 80 and water, and then gelled using gelatin with the assistance of an ultrasonic homogenizer. The characteristics and surface analysis of SCP-EGEL were examined using FTIR (Fourier-transform infrared spectroscopy) and SEM (Scanning electron microscope). The particle size distribution and zeta potential of SCP-EGEL were measured using a Malvern Zetasizer. When SCP-EGEL was applied to the surface of the medium inoculated with A. baumannii, the inhibition zone (IZ) was 8.2 mm. An expansion of the IZ was observed (10.2 mm) when SCP-EGEL was applied to a fish skin (FS) surface prepared in the shape of a 6-mm diameter disc. In the SEM images, when SCP was added to lipo gel, the gel structure appeared flattened or swollen in some areas. The appearance of SCP cells being covered with gel gave the impression that they have a secondary wall. Therefore, the resulting complex can potentially be used as an additive in animal and human nutrition, in functional food coatings to suppress A. baumannii, and in fish feed to enrich it with protein.

Effects of various acids on physical stability, rheological characteristics and curcumin encapsulation of whey protein isolate Pickering emulsion gels

Acid treatment can alter the functional properties of whey protein isolate (WPI), but the effect of different acids on properties of WPI‐stabilised Pickering emulsion gel (PE) is unknown. Compared with WPI‐PE, droplet size of the acid‐treated WPI‐PE decreased but its zeta potential, apparent viscosity, binding water capacity and curcumin encapsulation were enhanced. Due to the formation of the tightest gel structure of malic acid‐Pickering emulsion gel, it showed the highest viscoelastic modulus, bound water content and gel stability. This work would introduce a novel method for the development of PEs with good gelatinisation and curcumin delivery system for food processing.

Understanding the textural enhancement of low-salt myofibrillar protein gels filled with pea protein pre-emulsions through interfacial behavior: Effects of structural modification and oil phase polarity

This study investigated the effects of pea protein pre-emulsions containing triglyceride- or diglyceride-oil on the emulsifying and gelling properties of low-salt myofibrillar protein (MP). Pea protein isolates treated with pH12-shifting (PPIpH) or ultrasonication (PPIU) demonstrated superior initial interfacial adsorption and higher final interfacial pressure than native pea protein. Within MP/PPI blends, an increased ratio of MP led to a decrease in interfacial pressure, while simultaneously enhancing film elasticity at both polar and non-polar interfaces. Polar diglyceride promoted protein adsorption and fostered interfacial interactions between modified pea proteins and MP, enhancing the cross-linking of transglutaminase (TG) in the composite emulsion gels. Combining diglyceride-type PPIU and PPIpH emulsions with TG increased gel strength to 0.58 N and 0.63 N, respectively, from an initial 0.33 N, yielding a denser protein network with uniformly dispersed oil droplets. Therefore, the utilization of diglyceride and modified PPI can serve as structural enhancers in comminuted meat products.

Food-grade emulsion gels and oleogels prepared by all-natural dual nanofibril system from citrus fiber and glycyrrhizic acid

The natural dual nanofibril system consisting of the rigid semicrystalline nanofibrils disintegrated from citrus fiber (CF) and soft semiflexible nanofibrils self-assembled from glycyrrhizic acid (GA) has been recently shown to be effective structural building blocks for fabrication of emulsion gels. In this work, the effect of the CF nanofibrils prepared by different mechanical disintegration approaches (i.e., high-pressure microfluidization and hydrodynamic cavitation) on the interfibrillar CF-GA interactions and the subsequent formation and properties of emulsion gels were investigated, with the aim of evaluating the potential of the dual nanofibril-stabilized emulsion gels as templates for synthesizing all-natural edible oleogels. The obtained results demonstrate that compared to the cavitation, the high-pressure microfluidization is more capable of generating CF nanofibrils with a higher degree of nanofibrillation and individualization, thus forming a denser CF-GA gel network with higher viscoelasticity and structural stability due to the stronger multiple intrafibrillar and interfibrillar interactions. The emulsion gels stabilized by the dual nanofibril system are demonstrated to be an efficient template to fabricate solid-like oleogels, and the structural properties of the oleogels can be well tuned by the mechanical disintegration of CF and the GA nanofibril concentration. The prepared oleogels possess high oil loading capacity, dense network microstructure, superior rheological and large deformation compression performances, and satisfactory thermal stability, which is attributed to the compact and ordered CF-GA dual nanofibrillar network via multiple hydrogen-bonding interactions in the continuous phase as well as at the droplet surface. This study highlights the unique use of all-natural dual nanofibrils to develop oil structured soft materials for sustainable applications.

Investigating viscoelastic properties and structural stability mechanisms of oil bodies emulsion gels: Role of non-intrinsic protein

This research aims to investigate the mechanism of the effect of intrinsic and non-intrinsic protein content on the stability of oil bodies (OBs) emulsion gels. We employed small amplitude oscillation shear (SAOS) and large amplitude oscillation shear (LAOS) to measure the linear and nonlinear rheological properties of the OBs emulsion gels. The SAOS test indicated that an increase in non-intrinsic protein content weakened the interaction between OBs, decreasing their storage modulus (G'). The LAOS test demonstrated that the increase in non-intrinsic protein content affected the structural recombination and destruction behavior of OBs emulsion gels under large strains. Overall, the content of non-intrinsic protein during the extraction process is a crucial factor affecting the stability of OBs emulsion gels. These findings provide insights into the potential strategies for improving oil extraction efficiency and offer a foundation for further investigation into the functional properties of OBs.

Development of corn starch-sodium alginate emulsion gels as animal fat substitute: Effect of oil concentration

Emulsion gels were prepared utilizing corn starch (CS), sodium alginate (SA), and corn oil through calcium ion induction for animal-fat analogs. The influence of oil concentration on the rheological properties, microstructure and lipid oxidation of the emulsion gel was analyzed. Results revealed that the emulsion gel containing 30% (v/v) oil exhibited no surplus oil leakage and demonstrated the highest gel strength. The results of the small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS) test proved that the emulsion gel exhibited the greatest elasticity and deformation resistance when the oil content was 30% (v/v), imparting suitable mouth feel and transport stability as an animal fat substitute. Microstructure analysis indicated that SA crosslinked with Ca2+ to generate a network structure accompanied by the reinforcing effect of starch granules, enabling the dense network to capture an optimal quantity of oil to form a uniform gel network structure. Furthermore, the emulsion gel exhibited markedly lower lipid oxidation compared to bulk oil after 14 days of storage. As a new fat analog system, the CS-SA emulsion gel holds promising potential for applications in the food industry.

Utilizing chia flour-based gelled emulsion for the development of functional beef patties with enhanced nutritional profile.

This study evaluated chia flour, egg white powder, and peanut oil gelled emulsion (GE) as a fat replacer in beef patties. Four formulations were prepared, replacing beef fat with different levels of gelled emulsion: 0% (C), 50% (G50), 75% (G75), and 100% (G100). The beef patties with GE showed improved nutritional properties, technological parameters, and cooking characteristics. A remarkable reduction in SFAs was achieved with the substitution of beef fat by the GE, with reductions of 33.71%, 46.64%, and 72.04% for 50%, 75%, and 100% substitution levels, respectively. AI and TI indices decreased, indicating healthier profiles. Reformulated samples exhibited lower hardness, gumminess, and chewiness values. Color and appearance were similar to the control, with higher sensory scores for G75 and G100. GE impacted color parameters, increasing L* and b* values. The utilization of GE effectively minimized voids in the beef patty structure, leading to improved cooking yield and a more compact structure. GE influenced oxidative stability, with average onset temperatures of 126.33°C (50% GE), 140.58°C (75% GE), and 127.04°C (100% GE). In conclusion, gelled emulsions could successfully contribute to producing healthier meat products.