Emulsion Structure Research Articles

Structural and textural properties of a novel animal fat-trimming analog based on salted butter and alginate

The market for meat analogs has been blooming in the recent decade, but fat analogs slowly releasing lipids during cooking have received less attention. A fat-trimming analog based on sodium alginate (Alg) and salted butter (SB) was developed. The influence of salted butter content on the physicochemical properties of the pre-emulsion and the gelled emulsion was studied.The analog was prepared by homogenizing an Alg dispersion and melted SB, followed by calcium-induced gelation. Rheology showed that pre-gelled emulsions exhibit shear-thinning behavior, and their viscosities, measured at low-shear rates increased, with SB content. After gelation, samples were heat stable and slowly released lipids when heated.Confocal microscopy showed a typical oil-in-water emulsion structure, with lipid droplets flocculated at higher SB content. Differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR) tests, respectively revealed no changes in lipid melting/crystallization or in functional groups, indicating unaltered lipids properties due to their physical entrapment in the gelled polysaccharide matrix. Texture profile analysis (TPA) showed decreased cohesiveness, springiness, and chewiness with increased SB content, whereas hardness was first reduced and then increased at 80 g/100 g SB content. The approach used could be a potential solution for producing fat-trimming analogs with improved texture and heat stability.

Characteristics of insoluble soybean fiber (ISF) concentrated emulsions: Effects of pretreatment on ISF and freeze-thaw stability of emulsions.

The properties of emulsions could be affected by the interactions between the components and network stabilization effect, which are commonly adjusted by changes in pH, ionic strength and temperature. In this work, insoluble soybean fiber (ISF) obtained via homogenization after alkaline treatment was pretreated firstly and then resultant emulsions were freeze-thawed. Heating pretreatment reduced droplet size, enhanced viscosity and viscoelasticity as well as subsequent stability of ISF concentrated emulsions, while both acidic pretreatment and salinized pretreatment decreased the viscosity and weakened the stability. Furthermore, ISF emulsions exhibited a good freeze-thaw performance which was further improved by secondary emulsification. Heating promoted the swelling of ISF and strengthened the gel-like structure of emulsions while salinization and acidization weakened the electrostatic interactions and caused the destabilization. These results indicated that pretreatment of ISF significantly influenced the concentrated emulsion properties, providing guidance for the fabrication of concentrated emulsions and related food with designed characteristics.

New insights into protein stabilized emulsions captured via neutron and X-ray scattering: An approach with β-lactoglobulin at triacylglyceride-oil/water interfaces

HypothesisTo analyze protein stabilized emulsions, SAXS and SANS are emerging techniques capturing oil droplet radius, interfacial coverage and structure. Protein shape, thus protein structure change during interfacial adsorption with partial protein unfolding is detected via SAXS analysis at and below the monolayer concentration for proteins, known as critical interfacial concentration (CIC). SANS determines the same phenomena below and above the CIC, via contrast variation and coarse-grained modelling. Experimentsβ-lactoglobulin concentration dependent SAXS experiments were performed focusing on molecular length scales to characterize protein shape in water, and interfacial structure in emulsions. Complementary SANS experiments with contrast variation via deuterated triacylglyceride-oil provided insight into oil droplet radius, interfacial coverage and structure via data analysis with scattering models and low-resolution shape reconstruction with the DENFERT model. FindingsSAXS and SANS experiments allowed to determine the interfacial structure below and above the CIC, as well as oil droplet radius and interfacial coverage. These findings were identified via Q-4 Porod scattering at low-Q, protein scattering at high Q, and a Q-2 scattering of the interface. Since SANS with accurate contrast variation highlights the interface in comparison to other techniques like FTIR, the presented results show a high impact to understand interfaces in emulsions.

Magnetorheological characterization of oil-in-oil magnetic Pickering emulsions

A magnetic Pickering emulsion is a type of emulsion stabilized by magnetic nanoparticles that accumulate at the droplet interface. This makes the emulsion easy to control using an external magnetic field, which, in turn, makes it useful in many applications. Research and development in this field are ongoing, but regardless of the application, control of the formation process is necessary. Rheological measurements are one of techniques used for evaluating the internal structure and stability of emulsions. The main focus of the current research is to investigate the magnetorheological effect of the rarely tested oil-in-oil (O/O) magnetic Pickering emulsions and compare them with better-characterized oil-based magnetic fluids.The magnetoviscous effect typically occurs when magnetic nanoparticles or magnetic Pickering emulsions align with the magnetic field, and this effect depends mainly on the internal structure, such as the size and shape of the particles and droplets. The experimental results indicate that the magnetic emulsion fabricated utilizing ultrasound and an additional electric field exhibits higher dynamic yield stress as a function of the magnetic field compared with the partially covered droplets. This suggests that the stable emulsion becomes a more rigid system and is more resistant to deformation when a magnetic field is applied. Besides that, the magnetoviscous effect of the magnetic emulsions was lower compared with that of magnetic suspensions with the same mass fraction of magnetic nanoparticles.

Separation of cobalt/lithium in spent NCM-based lithium ion battery leaching solution via reactive extraction-reextraction with microdispersed (G1/L1+G2)/L2 emulsion

Separation of Co and Li in hydrometallurgy for the recovery of valuable metals from waste NCM-based lithium ion battery leaching solution is realized by extraction, with P507/TBP/sulfonated kerosene as extractant. Process intensification is realized via emulsion structure design and novel equipment development, aiming in overcoming operation limitations in traditional equipment caused by increased viscosity and phase ratio. Effects of emulsion structure and operating conditions on extraction are investigated. A multiphase emulsion, (G1/L1+G2)/L2, is designed and prepared by a micro-dispersion module. Efficient extraction is realized with (G1/O+G2)/W emulsion, with which Murphree efficiency of Co2+ reaches 99.1 % within a contacting volume of 7.35 mL, when reverse extraction is realized applying (G1/W+G2)/O emulsion. With (G1/L1+G2)/L2 emulsions, a single-stage extraction and reverse extraction process is realized in 9.11 s, with which Co2+/Li + solution with initial Co2+ concentration of 27.60 mol.% is separated into raffinate of 0.12 mol.% and strip liquor of 81.08 mol.%. The intensification fundamentals are studied, by calculating mass transfer coefficients in formation and flowing stages of varied heterogeneous systems and establishing mathematical models. This study presents simple and effective methods for intensifying extraction and reverse extraction processes with viscous extractants in spent lithium ion battery recycling.

Biocompatible oil-in-water-in-oil double emulsion stabilized synergistically by phytosterol/chitosan complex particle and gelatin

Herein we reported highly biocompatible and stable oil-in-water-in-oil (o/w/o) Pickering double emulsions (PDEs) using a one-step emulsification procedure. Natural phytosterol (PS) particles and chitosan (CS) self-assembled into PS/CS complex paritlces to serve as particulate stabilizers while gelatin was used as viscosity modifier for aqueous phase. By varying the viscosity of aqueous phase, water/oil volume ratio, and homogenization time, the formation and stabilization mechanism of o/w/o PDEs were explored. The viscosity of aqueous phase and occurrence of phase inversion are essential for the formation of PDEs. Additionally, the adsoprtion of PS/CS complex particles on the oil/water interface and high viscosity of aqueous phase both aid in the stabilization of PDEs. Furthermore, the o/w/o PDEs showed good storage stability at 4 °C and 25 °C (at least 2 months), with essentially little change in emulsion structure. And a variety of oils can be used to prepare the PDEs. What's more, the o/w/o PDEs can co-encapsulate hydrophilic and hydrophobic bioactive compounds, shielding them against UV exposure and long-term storage. In summary, these findings will not only aid in the development of biocompatible o/w/o PDEs, but also provide a guidance for co-encapsulating and protecting bioactive compounds that are both hydrophilic and hydrophobic.

Modulating in vitro gastrointestinal digestion of nanocellulose-stabilized pickering emulsions by altering particle surface charge

An in vitro model of human gastrointestinal digestion was introduced to investigate the effects of surface charge of cellulose nanoparticles on emulsion structure during gastric phase, lipase activity, bile salt diffusion, and free fatty acid (FFA) release. Four carboxymethylated cellulose nanofibrils (CNF; C0, C0.36, C0.72, and C1.24) were used, showing different surface charge (p < 0.05). First, four carboxymethylated CNFs had no inhibition effects on lipase activity and bile salt diffusion. Moreover, we found that the lipid emulsion containing CNF formed gel structure to induce oil droplets aggregation during simulated gastric phase. Additionally, the particle surface charge greatly influenced the gel structure of emulsion where a denser gel structure was observed in the C0 (lowest surface charged CNF) stabilized emulsion. Finally, the released FFA results showed that the formed gel structure lowered the lipid emulsion digestion attributed to the restricted adherent area of oil droplets for lipase and bile salt.

Dynamics and Structure of a Bitumen Emulsion as Studied by 1H NMR Diffusometry.

Self-diffusion in a bitumen emulsion was studied by 1H NMR. The emulsion forms two phases: continuous and dispersed. The continuous aqueous phase contains mainly water, with the energy of activation of the diffusion process equal to that of bulk water, while its diffusivity is smaller than that of bulk water by a factor of 2. The dispersed phase consists of bitumen droplets containing confined water, whose dynamics is characterized by a fully restricted diffusion regime in cavities with sizes of ∼0.11 μm. Therefore, the studied bitumen emulsion can be described by a model of a complex multiple emulsion of the water/oil/water (WOW) type. The suggested model does agree well with data from 1H NMR spectroscopy and diffusometry of the bitumen emulsion doped with paramagnetic MnSO4(aq) as well as with an additional 1H NMR study of the emulsion structure, in which emulsion stability was compromised by freezing at 253 K.

Product diversification to boost the sustainability of the shrimp processing industry: The case of shrimp-waste driven chitosan-based food Pickering emulsion stabilizers

Diversifying the product portfolio of the shrimp processing industry using its waste streams could contribute to its environmental sustainability and economic resilience. Considering that this study aimed to increase the commercial value of shrimp shell waste by using chitosan extracted from these wastes as a food emulsion stabilizer. More specifically, chitin was extracted from shrimp shell waste, and chitosan was then prepared from chitin by deacetylation. The findings showed that the extraction efficiency and degree of deacetylation of chitosan were 23% and 83%, respectively. After that, stearic acid was added to chitosan chains to improve its emulsifying properties. Then, the chitosan/stearic acid–stabilized flaxseed oil and olive oil emulsions were prepared in three oil ratios (20, 40 and 60%). The interfacial structure study showed that compared to flaxseed oil droplets, the olive oil droplets’ surface was better covered with the chitosan/stearic acid nanogels. Moreover, the rheological study indicated a stronger gel-like structure in olive oil emulsions than the flaxseed oil emulsions, particularly at 60% oil. The dried emulsions indicated that the olive oil was encapsulated better than flaxseed oil by the chitosan-based particles, and less oil leakage was observed for dried olive oil emulsions. Better encapsulation of olive oil with chitosan/stearic acid nanogels could be attributed to the higher polarity and viscosity of olive oil compared to flaxseed oil and the greater similarity of olive oil fatty acid profile with stearic acid attached to chitosan. In general, these findings showed that the stabilizer developed from shrimp shell waste is suitable for stabilizing emulsions containing more polar oils with less degree of unsaturation. The results obtained could contribute to enhancing the sustainability of the shrimp processing industry by diversifying its product portfolio.

Nanosheet Particles with Defect-Free Block Copolymer Structures Driven by Emulsions Containing Crystallizable Surfactants.

Highly anisotropic-shaped particles with well-ordered internal nanostructures have received significant attention due to their unique shape-dependent photonic, rheological, and electronic properties and packing structures. In this work, nanosheet particles with cylindrical block copolymer (BCP) arrays are achieved by utilizing collapsed emulsions as a scaffold for BCP self-assembly. Highly elongated structures with large surface areas are formed by employing crystallizable surfactants that significantly reduce the interfacial tension of BCP emulsions. Subsequently, the stabilized elongated emulsion structures lead to the formation of BCP nanosheets. Specifically, when polystyrene-block-polydimethylsiloxane (PS-b-PDMS) and 1-octadecanol (C18-OH) are co-assembled within an emulsion, C18-OH penetrates the surfactant layer at the emulsion interface, lowering the interfacial tension (i.e., below 1 mN m-1 ) and causing emulsion deformation. In addition, C18-OH crystallization allows for kinetic arrest of the collapsed emulsion shape during solvent evaporation. Consequently, PS-b-PDMS BCPs self-assemble into defect-free structures within nanosheet particles, exhibiting an exceptionally high aspect ratio of over 50. The particle formation mechanism is further investigated by controlling the alkyl chain length of the fatty alcohol. Finally, the coating behavior of nanosheet particles is investigated, revealing that the deposition pattern on a substrate is strongly influenced by the particle's shape anisotropy, thus highlighting their potential for advanced coating applications.

Fragrance in dermocosmetic emulsions: From microstructure to skin application.

Fragrance is added to almost all dermocosmetic emulsions, as it has been found to be a key driver in consumer choice and contributes to the perception of product performance. Fragrance is a complex mixture of odorant chemicals at different concentrations. When incorporated into a formulation, the individual fragrance chemicals partition between the emulsion phases depending on their physicochemical properties, which can impact the structure, stability, texture and odour of the final product. On the other hand, it is well known in the food industry how the composition and structure of food emulsion matrices influence the release of aroma chemicals. Fragranced dermocosmetic emulsions have been studied to a lesser extent but it is interesting to apply findings from the food domain since emulsion structure, composition and aroma compounds share common features. This review aims to give an overview of the literature dealing with the interactions between fragrance and dermocosmetic emulsions. The effects of fragrance on emulsion microstructure, stability and texture are highlighted and discussed. The effects of composition and structure of emulsion on the release of fragrance molecules are also presented. Finally, the interactions between skin and fragranced emulsions are addressed.

Interfacial properties and structure of Pickering emulsions co-stabilized by different charge emulsifiers and zein nanoparticles

The stability of Pickering emulsions can be improved by the synergistic action of colloidal particles and small molecule emulsifiers. In addition, the interaction between particles and different charge emulsifiers at the interface may result in different interfacial film structures, thus affecting the stability of Pickering emulsions. However, little is currently known about the impact of emulsifier charge on the fabrication and characteristics of these co-stabilized Pickering emulsions. Herein, we investigated the influence of Pickering emulsions co-stabilized by zein nanoparticles and anionic (quillaja saponin, QS), non-ionic (Tween 80), or cationic (lauroyl arginate ethyl hydrochloride) emulsifiers on the interfacial properties. The adsorption kinetics and rheological behavior of the molecular emulsifiers at oil/water interfaces were studied. Changes in interfacial structure and adsorption behavior were studied by confocal laser scanning microscopy (CLSM), and quartz crystal microbalance-dissipation (QCM-D) analysis. The dynamic interface characteristics showed that QS has good emulsification performance. The CLSM images indicated that the emulsifier charge impacted the interfacial structure of the Pickering emulsions. The combination of QS and zein nanoparticles formed a coating at the oil/water interface that was denser than for the other two emulsifiers, which improved the stability of the Pickering emulsions. QCM-D revealed that the interfacial film formed by anionic emulsifiers and zein nanoparticles was the thickest (about 6.6 nm). Moreover, anionic emulsifiers and zein nanoparticles stabilized Pickering emulsions provided the best protection against curcumin. These results may be important for optimizing the performance of Pickering emulsions in the food and pharmaceutical industries.

Effect of variation in basic emulsion structure and polysaccharide content on the physicochemical properties and structure of composite-based emulsion gels as cube fat mimetics

This study aimed to reveal the effect of different basic emulsion structures (W/O/W and O/W) and polysaccharide additions on protein-polysaccharide composite-based emulsion gels utilizing soybean protein isolate, palm oil and konjac glucomannan. The results of texture profile, rheological tests, microstructure observations, and oral tribology showed that basic emulsion structures and konjac glucomannan addition had significant effect on the emulsion gels' properties, while the impact of konjac glucomannan addition was stronger. W/O/W double emulsion gels (DEG) exhibited lower oral friction coefficients and obtained higher scores for oiliness and juiciness during the sensory evaluation. However, O/W single emulsion gels (SEG) displayed a firmer texture and higher chewiness, a 29.62% and 49.57% increase compared to the DEG at 7% konjac glucomannan addition on the hardness and chewiness respectively. It has demonstrated the emulsion gels' potential as cube fat mimetics and feasibility of adjusting their properties by changing the basic emulsion structure.

Application of Pickering emulsion with microcrystalline cellulose in vitamin C double emulsion process with spray drying technology

ABSTRACT This research studies the impacts of microcrystalline cellulose (MCC) concentrations on the physicochemical properties of spray-dried water-in-oil-in-water (W/O/W) vitamin C double emulsion powder Four MCC concentration (1%, 1.5%, 2%, and 2.5%) were used to produce the vitamin C double emulsion powder. The results of the emulsion’s creaming index, flow behaviour index, zeta value, and particle size indicated that these parameters decreased when the MCC concentration increased. Scanning electronic microscopy (SEM) analysis showed that the higher MCC concentration resulted in a smoother surface In general, the MCC concentration increased, the particle size, hygroscopicity, solubility, water content, and water activity of the double emulsion powder decreased. Double emulsion powder containing 2% MCC presented the highest level of antioxidant activity and was mostly stable after storage for 56 days. Before and after drying, transmission electron microscope (TEM) analysis of the morphological characteristics of the liquid emulsion showed that the concentration of 2% MCC in the emulsion could form a W/O/W double emulsion structure. In conclusion, the addition of MCC significantly affect the properties of vitamin C double emulsion.

Tiny, yet impactful: Detection and oxidative stability of very small oil droplets in surfactant-stabilized emulsions

HypothesisThe shelf life of multiphase systems, e.g. oil-in-water (O/W) emulsions, is severely limited by physical and/or chemical instabilities, which degrade their texture, macroscopic appearance, sensory and (for edible systems) nutritional quality. One prominent chemical instability is lipid oxidation, which is notoriously complex. The complexity arises from the involvement of many physical structures present at several scales (1–10,000 nm), of which the smallest ones are often overlooked during characterization. ExperimentsWe used cryogenic transmission electron microscopy (cryo-TEM) to characterize the coexisting colloidal structures at the nanoscale (10–200 nm) in rapeseed oil-based model emulsions stabilized by different concentrations of a nonionic surfactant. We assessed whether the oxidative and physical instabilities of the smallest colloidal structures in such emulsions may be different from those of larger colloidal structures. FindingsBy deploying cryo-TEM, we analyzed the size of very small oil droplets and of surfactant micelles, which are typically overlooked by dynamic light scattering when larger structures are concomitantly present. Their size and oil content were shown to be stable over incubation, but lipid oxidation products were overrepresented in these very small droplets. These insights highlight the importance of the fraction of “tiny droplets” for the oxidative stability of O/W emulsions.

Effect of small molecule surfactant structure on the stability of water-in-lubricating oil emulsions

During automotive engine operation, water may contaminate engine oil, inhibiting its role in maintaining safe engine operation. In many cases, engine oil must be capable of emulsifying any water contamination to avoid such problems. This study focuses on the impact of small molecule surfactant concentration structure and concentration in emulsions comprised of engine oil, water, and E85 fuel to understand the effects on emulsion stability and formulation optimization. Three small molecule surfacatants were tested; glycerol dioleate (GDO), glyceryl monooleate (GMO), and oleamide (OA). Three characterization methods were used to investigate their effects; the current state of the art, ASTM D7563, microscopy, and diffusing wave spectroscopy (DWS). We found that DWS could yield insights into mechanisms of emulsion stability that are otherwise inaccessible through other experimental techniques. Specifically, utilizing DWS, we are able to extract specific emulsion stability mechanisms associated directly with molecular features for the three surfactants examined.

A Double-Emulsion Method for the Fabrication of PLA Single-Hole Hollow Particles

Background: Polymeric hollow particles with a single-hole structure have attracted broad interest due to their combined advantages of a hollow cavity and an opening hole in the shell. Aim: In the past decades, much progress has been made in the fabrication of such particles with various strategies. However, there is a lack of research on the easy fabrication of biodegradable polylactide (PLA) single hole particles (PLA SHHPs). Methods: In this work, we reported a simple double emulsion method for the fabrication of PLA SHHPs. The W/O/W double emulsion was formed by homogenizing PLA chloroform and brilliant blue G (BBG) solution. Scanning electron microscopy and confocal laser scanning microscopy were used for the characterization. It was found that the concentrations of PLA chloroform and BBG solution both had a significant influence on the emulsion structure. Result: PLA SHHPs with a percentage &gt;85% were obtained from the emulsion composed of PLA chloroform (10.0 w%) and BBG solution (4 mM). The particle formation mechanism was also proposed based on the result of the low interfacial tension between PLA chloroform/BBG solution. Conclusion: The results may inspire new development of PLA particles with unique structures, which are promising to be used in drug delivery, catalysis, microreaction and micromotors.

Improved curcumin bioaccessibility in Pickering emulsion fabricated by rice glutelin fibrils

Pickering emulsion fabricated by food grade-solid colloidal particles as templates for delivering sensitive nutrients has attracted increasing interest in recent years. In this work, rice glutelin fibrils-stabilized Pickering emulsion was successfully fabricated for loading curcumin. In addition, the amyloid and non-amyloid structures were separated from the heated rice glutelin (RG) samples, and the emulsifying and encapsulating performances of these fractions were systematically observed. It was noted that the retentates of glutelin fibrils (RGFs)-stabilized Pickering emulsion exhibited a self-standing behavior, along with the highest curcumin encapsulation efficiency (94.17%) among other samples. Compared to the total heated glutelin fibrils (TGFs), a stronger gel strength was observed in emulsion containing purified fibrils, probably due to the closely arranged polyhedral emulsion structure. However, the filtrates of glutelin fibrils (FGFs) particles-prepared emulsion presented a weak gel strength due to the hydrophilic properties, accompanying by a surprisingly rapid release rate of curcumin during digestion. Nevertheless, TGFs-stabilized emulsion achieved a high curcumin bioavailability (35.06%) and sustained controlled release behavior. These findings proved that the sustainable and biocompatible protein amyloid exhibited excellent performance in encapsulating curcumin and improving curcumin bioavailability.

The effect of subzero temperatures on the properties and structure of soy protein isolate emulsions

Different freezing temperatures (−5, −20, −40 and −80 ℃) could change soy protein isolate (SPI) structure and emulsion properties. After freezing at −5 ℃ and −20 ℃, the structure of the SPI loosened, the fluorescence intensity was red shifted, and the proportion of Phe, Tyr and Trp exposed increased. With decreasing temperature, the surface hydrophobicity (H0 × 100), the number of sulfhydryl groups and the number of disulfide bonds all rose, then fell (−40 ℃), and rose again (−80 ℃). The β-sheet content in the protein secondary structure increased from 32.71% (control) to 50.66% (−40 ℃) and then decreased to 37.05% (−80 ℃), while the β-turn and random coil contents showed the opposite pattern, which also confirmed aggregation. The emulsification performance of SPI after freezing treatment was decreased. The results of this study provide theoretical support for future production of frozen foods with added SPI.

Interfacial rheology and morphology of casein and non‐starch polysaccharides mixed layers at oil/water interface

AbstractThis work aims to determine the importance of the interfacial attributes on the emulsion stability of casein and five different non‐starch polysaccharides (NSPs) and to compare the interfacial rheological properties at the O/W interface. Various interfacial properties of the layers were determined as well as the bulk rheological properties and morphological structures of emulsions. The results of steady interfacial viscosity pointed out that the interfacial film formed by the reaction between casein and lemon fiber had the highest mechanical strength. The molecules of the samples prepared with all other NSPs, except for the emulsions prepared with lemon fiber, were rapidly dispersed and absorbed at the O/W interface, and their Gi′ and Gi″ remained nearly constant throughout the test. As a result, it was found that the layers showed non‐negligible influences on the interfacial behavior, the amount of NSPs adsorbed at the interface, and the viscoelasticity of the interfacial layers.Practical applicationsThis study was conducted considering the interfacial properties of emulsions and evaluated the stability along with the steady and dynamic rheological properties. The obtained results of current study highlighted the importance of determining the interfacial characteristics of non‐starch polysaccharides (NSPs) and casein‐stabilized emulsions because they can be used to predict the stability of emulsion throughout the shelf life and to get a deeper knowledge on the effects of the NSPs fortification on the emulsion efficiency in food products. A strong positive correlation was found between apparent viscosity and the presence of NSPs. Without NSPs, emulsions were unstable due to depletion or bridging aggregation. The findings are of great importance in understanding the stability and behavior of protein and NSPs‐stabilized emulsions. Therefore, the findings of this study will contribute for both the literature and food industry.