Fat crystals and water-in-oil emulsion stability

Stabilization of all-natural water-in-oil high internal phase pickering emulsion by using diosgenin/soybean phosphatidylethanolamine complex: Characterization and application in 3D printing

This study aimed to prepare an all-natural water-in-oil high internal phase Pickering emulsion (W/O-HIPPE) using diosgenin/soybean phosphatidylethanolamine complex (DGSP) and investigate the 3D printing performance. Results suggested that the self-assembly of diosgenin crystal was modified by SP in DGSP (diosgenin-SP ratios at 3:1 and 1:1), revealing a variation from large-size outward radiating needle-like to small-size granular-like shape, which facilitated closely packing at the interface. Hydrophilicity of DGSP was also increased (contact angle varying from 133.3 o to 106.4 o), ensuring more adequate interfacial adsorption to reduce interfacial tension more largely (6.5 mN/m). Thus, the W/O-HIPPE made by DGSP with diosgenin-SP = 1:1, exhibited smaller droplets and better freeze/thawing stability. The W/O-HIPPE was also measured improved rheological properties for 3D printing: satisfied shear-thinning behavior, higher recovery and self-supporting (viscoelasticity and deformation resistance). Consequently, the W/O-HIPPE allowed for printing more delicate patterns. This work provided guidance to prepare W/O-HIPPE for 3D printing.

Impact of Air Bubbles on the Saltiness Perception of NaCl-Loaded Oleogel-Stabilized Water-in-Oil Emulsions

Reducing salt intake without affecting the saltiness perception remains a great challenge for the food industry. Herein, the demulsification of water droplets and air bubbles was controlled to modulate the release of sodium from oleogel-stabilized water-in-oil emulsions (OGEs) stabilized by monoglyceride crystals. The effect of monoglycerides with carbon chain length (glycerol monolaurate-GML, glyceryl monostearate-GMS, and glycerol monopalmitate-GMP) and homogenization methods (hand-shaking or high-speed blender) on sodium release and saltiness was investigated by in vitro and in vivo oral processing tests. Milky-white stable emulsions were formed with both water droplets and air bubbles dispersing in the oil phase, regardless of the selected homogenization methods. Air bubbles were more unstable than water droplets during oral digestion. GML OGEs with more and larger air bubbles and the lowest hardness exhibited the highest sodium release rate and the strongest saltiness, independent of homogenization methods. The balance between air bubbles and water droplets in the GMS and GMP OGEs caused slower sodium release and lower saltiness. Overall, the presence of air bubbles in NaCl-loaded W/O oleogel-based emulsions was shown to have important implications for tailoring their sodium release and saltiness.

Fabrication and Stability Improvement of Monoglyceride Oleogel/Polyglycerol Polyricinoleate-Stabilized W/O High Internal Phase Pickering Emulsions

To decrease the lipid content in water-in-oil (W/O) emulsions, high internal phase Pickering W/O emulsions (HIPPE) were fabricated using magnetic stirring using a combination of monoglyceride (MAG) oleogel and polyglycerol polyacrylate oleate (PGPR) as stabilizers. Effects of MAGs (glyceryl monostearate-GMS, glycerol monolaurate-GML and glycerol monocaprylate-GMC) and internal phase components on the formation and properties of HIPPEs were investigated. The results showed that milky-white stabilized W/O HIPPE with up to 85 wt% aqueous phase content was successfully prepared, and the droplet interfaces presented a network of MAG crystals, independent of the MAG type. All HIPPEs exhibited great stability under freeze-thaw cycles but were less plastic. Meanwhile, GML-oleogel-based HIPPEs had larger particle size and were less thermal stable than GMS and GMC-based HIPPEs. Compared to guar gum, the internal phase components of sodium chloride and sucrose were more effective in reducing the particle size of HIPPEs, improving their stability and plasticity, and stabilizing them during 100-day storage. HIPPEs presented great spreadability, ductility and plasticity after whipping treatment. This knowledge provides a new perspective on the use of oleogels as co-stabilizers for the formation of W/O HIPPEs, which can be used as a potential substitute for creams.

Recent advances in studying crystallisation of mono- and di-glycerides at oil-water interfaces

This review focuses on the current understanding regarding lipid crystallisation at oil-water interfaces. The main aspects of crystallisation in bulk lipids will be introduced, allowing for a more comprehensive overview of the crystallisation processes within emulsions. Additionally, the properties of an emulsion and the impact of lipid crystallisation on emulsion stability will be discussed. The effect of different emulsifiers on lipid crystallisation at oil-water interfaces will also be reviewed, however, this will be limited to their impact on the interfacial crystallisation of monoglycerides and diglycerides. The final part of the review highlights the recent methodologies used to study crystallisation at oil-water interfaces.

Self-constructed water-in-oil Pickering emulsions as a tool for increasing bioaccessibility of betulin

Self-constructed water-in-oil emulsions can be stabilized by a natural pentacyclic triterpenoid, betulin. A higher betulin concentration (3%) results in smaller emulsion droplet sizes. Microscopy, confocal laser scanning microscopy and rheology indicate that the stabilizing mechanism is attributed to betulin crystals on the emulsion interface and within the continuous phase, thereby enabling excellent freeze/thaw and thermal stability. The betulin Pickering emulsion (1%) significantly increased betulin bioaccessibility (22.4%) compared to betulin alone (0.2%) and betulin-oil physical mixture (7.9%). A higher level of betulin at 3% leads to smaller emulsion particle size, potentially resulting in a greater surface area. This, in return, promotes a higher release of free fatty acids (FFA), contributing to the release and solubilization of betulin from emulsions. Additionally, it leads to the formation of micelles, further increasing betulin bioaccessibility (29.3%). This study demonstrates Pickering emulsions solely stabilized by phytochemical betulin provides an innovative way to improve its bioaccessibility.

Physical, textural and crystallization properties of ground nut oil-based diacylglycerols in W/O margarine system

Enzymatic glycerolysis produced ground nut oil-based diacylglycerols (GNO-DAG) with a purity of 43.28 ± 0.89% (GNO-DAG40). GNO-DAG80 (with a DAG purity of 87.33 ± 0.61%) was obtained after purification using molecular distillation. Traditional palm oil was mixed with the "liquid" DAG as margarine base oils. Subsequent evaluations of palm oil-DAG-based fats (PO-GNO DAG) as a margarine replacement in a W/O model system showed that the material was an ideal functional base oil with improved aeration properties and plasticity during application. The binary system physical, textural and crystallization property were determined, and the compatibility of the binary mixed system was analyzed by constructing a phase diagrams. The PO-GNO DAG showed decent compatibility between the two phases and had better texture and rheological properties. In addition, PO-GNO DAG40 showed better apparent viscosity and aeration characteristics than PO-GNO DAG80, with potential application in the food specialty fats industry.

Mechanisms of lipid oxidation in water-in-oil emulsions and oxidomics-guided discovery of targeted protective approaches

Lipid oxidation is an inevitable event during the processing, storage, and even consumption of lipid-containing food, which may cause adverse effects on both food quality and human health. Water-in-oil (W/O) food emulsions contain a high content of lipids and small water droplets, which renders them vulnerable to lipid oxidation. The present review provides comprehensive insights into the lipid oxidation of W/O food emulsions. The key influential factors of lipid oxidation in W/O food emulsions are presented systematically. To better interpret the specific mechanisms of lipid oxidation in W/O food emulsions, a comprehensive detection method, oxidative lipidomics (oxidomics), is proposed to identify novel markers, which not only tracks the chemical molecules but also considers the changes in supramolecular properties, sensory properties, and nutritional value. The microstructure of emulsions, components from both phases, emulsifiers, pH, temperature, and light should be taken into account to identify specific oxidation markers. A correlation of these novel oxidation markers with the shelf life, the organoleptic properties, and the nutritional value of W/O food emulsions should be applied to develop targeted protective approaches for limiting lipid oxidation. Accordingly, the processing parameters, the application of antioxidants and emulsifiers, as well as packing and storage conditions can be optimized to develop W/O emulsions with improved oxidative stability. This review may help in emphasizing the future research priorities of investigating the mechanisms of lipid oxidation in W/O emulsion by oxidomics, leading to practical solutions for the food industry to prevent oxidative rancidity in W/O food emulsions.

Differences of wax-based emulsion gel in 3D printing performance: Crystal distribution and droplet stability

Six kinds of natural waxes were used for emulsion gels preparation. The differences in printing performance were explored based on the crystal distribution and droplet stability. Firstly, the effect of crystal distribution was investigated through microstructures and rheological properties. It was found that the dense crystal network/interfacial crystallization could stabilize the droplet and provide modulus to ensure the self-supporting behavior after printing, whereas excessive crystal could lead to droplet rupture and coalescence. Furthermore, all emulsion gels could recrystallize by heating, which could enhance the performance of 3D printing. Then, the droplet stability was investigated after storing/freeze-thawing. It was found that emulsion gels with dense crystal networks/interfacial crystallization had more stable droplets, which ensure the continuous extrusion during printing. Finally, printing performance was investigated comprehensively. Three emulsion gels with denser crystal networks/interfacial crystallization had higher recovery rates (16.17-21.15%) and more stable droplets, which perform better in 3D printing correspondingly.

Surfactant-free oleogel-based emulsion stabilized by co-assembled ceramide/lecithin crystals with controlled digestibility

BACKGROUND

There is increasing interest in the development of oleogel-based emulsions. However, they usually contained surfactants for stabilization, especially small-molecular weight surfactants, which may have adverse health impacts.

RESULTS

Herein, a surfactant-free oleogel-based emulsion stabilized by co-assembled ceramide/lecithin (CER/LEC) crystals was developed. The formation and stabilization mechanisms were explored. The different molar ratios of gelator (LEC and CER) in emulsions resulted in different crystal morphology, crystallinity as well as different emulsion properties. This suggested that appropriate crystallinity, crystal size, and interfacial distribution of these crystals provided higher surface coverage against droplets coalescence, thus better emulsion stabilization. Both X-ray diffractograms and contact angle results confirmed that the crystals which were primarily responsible for emulsion stabilization, are co-assembled crystals consisted of both gelators (CER and LEC). Furthermore, the percentage of free fatty acids (FFAs%) results revealed a negative relationship between lipid digestibility and crystal concentration.

CONCLUSIONS

This strategy greatly enriched surfactant-free oleogel-based emulsion formulations, as well as their potential applications in healthy lipid-based products and novel food delivery systems with controlled lipid digestibility. © 2022 Society of Chemical Industry.

Carnauba Wax and Beeswax as Structuring Agents for Water-in-Oleogel Emulsions without Added Emulsifiers

This research aims to explore the potential of waxes as ingredients in the formulation of food-grade water-in-oleogel emulsions without added emulsifiers. The effects of the wax type, wax concentration and water concentration were tested on systems containing exclusively water, sunflower oil, and wax. Beeswax and carnauba wax were used in the formulation of water-in-oleogel emulsions with 20%, 30% and 40% w/w of water. For the continuous phase, three different levels of wax were used, namely 50%, 100%, and 150% of the critical gelling concentration. More specifically, carnauba wax emulsions were prepared at 2.5%, 5.0% and 7.5% of wax, while concentrations of 0.75%, 1.5% and 2.25% of wax were utilized for the beeswax experiments. Samples were assessed over time regarding stability, rheology and microstructure (polarized light microscopy, cryo-scanning electron microscopy and confocal scanning laser microscopy). Our findings suggest that, if present in sufficient concentration, carnauba wax and beeswax can stabilize emulsions in the absence of additional added emulsifiers. The resulting systems were inherently different based on the wax used, as crystal morphology and droplet configurations are determined by wax type. The yield strain was dictated by the nature of the wax, while the complex modulus was mostly influenced by the wax concentration. To test the scaling-up potential, systems were crystallized in a pilot-scale scraped surface heat exchanger, resulting in notably smaller crystal sizes, reduced rigidity and a storage stability of over one year. These findings represent a starting point for the formulation of scalable water-in-oleogel emulsions without added emulsifiers.

Chitosan-based Pickering emulsion: A comprehensive review on their stabilizers, bioavailability, applications and regulations

BACKGROUND

Chitosan-based particles are one of the most promising Pickering emulsions stabilizers due to its cationic properties, cost-effective, biocompatibility, biodegradability. However, there are currently no comprehensive reviews analyzing the role of chitosan to develop Pickering emulsions, and the bioavailability and multiple uses of these emulsions.

SCOPE AND APPROACH

This review firstly summarizes the types, preparation and functional properties of chitosan-based Pickering emulsion stabilizers, followed by in vivo and in vitro bioavailability, main regulations, and future application and trends.

KEY FINDINGS AND CONCLUSIONS

Stabilizers used in chitosan-based Pickering emulsions include 6 categories: chitosan self-aggregating particles and 5 types of composites (chitosan-protein, chitosan-polysaccharide, chitosan-fatty acid, chitosan-polyphenol, and chitosan-inorganic). Chitosan-based Pickering emulsions improved the bioavailability of different compounds compared to traditional emulsions. Current applications include hydrogels, microcapsules, food ingredients, bio-based films, cosmeceuticals, porous scaffolds, environmental protection agents, and interfacial catalysis systems. However, due to current limitations, more research and development are needed to be extensively explored to meet consumer demand, industrial manufacturing, and regulatory requirements. Thus, optimization of stabilizers, bioavailability studies, 3D4D printing, fat substitutes, and double emulsions are the main potential development trends or research gaps in the field which would contribute to increase adoption of these promising emulsions at industrial level.

Oxidation and oxidative stability in emulsions

Emulsions are implemented in the fabrication of a wide array of foods and therefore are of great importance in food science. However, the application of emulsions in food production is restricted by two main obstacles, that is, physical and oxidative stability. The former has been comprehensively reviewed somewhere else, but our literature review indicated that there is a prominent ground for reviewing the latter across all kinds of emulsions. Therefore, the present study was formulated in order to review oxidation and oxidative stability in emulsions. In doing so, different measures to render oxidative stability to emulsions are reviewed after introducing lipid oxidation reactions and methods to measure lipid oxidation. These strategies are scrutinized in four main categories, namely storage conditions, emulsifiers, optimization of production methods, and antioxidants. Afterward, oxidation in all types of emulsions, including conventional ones (oil-in-water and water-in-oil) and uncommon emulsions in food production (oil-in-oil), is reviewed. Furthermore, the oxidation and oxidative stability of multiple emulsions, nanoemulsions, and Pickering emulsions are taken into account. Finally, oxidative processes across different parent and food emulsions were explained taking a comparative approach.

Comparative study of natural wax-based W/O emulsion gels: Microstructure and macroscopic properties

In this paper, six kinds of natural wax, including sunflower wax (SFX), rice bran wax (RBX), carnauba Brazilian wax (CBX), beeswax (BWX), candelilla wax (CDX), and sugarcane wax (SGX) were used to prepare water-in-oil (W/O) emulsion gels. Microstructures and rheological properties of all emulsion gels were investigated by microscopy, confocal laser scanning microscope (CLSM), scanning electron microscopy (SEM), and rheometer, respectively. By comparing polarized light images of wax-based emulsion gels and corresponding wax-based oleogels, it could be found that dispersed water droplets greatly affected the crystal distribution and hindered crystal growth. Polarized light microscopy and CLSM images proved that natural wax could perform a dual-stabilization mechanism by interfacial crystallization and crystal networks. SEM images illustrated all waxes except SGX were platelets and formed networks by stacking on top of each other, while flocs-like SGX was easier to adsorb on the interface and formed a "crystalline shell". The surface area and pore formed by different wax varied wildly, which accounted for their differences in the gelation ability, oil binding capacity, and strength of the crystal network. The rheological study showed that all wax had solid-like properties and wax-based oleogels with denser crystal networks correspond to emulsion gels with higher modules. The dense crystal network and interfacial crystallization could improve the stability of W/O emulsion gels proved by recovery rates and critical strain. All the above proved that natural wax-based emulsion gels can be used as stable, low-fat, and thermal-sensitive fat mimics.

New food, new technology: innovative spreadable cream with strawberry syrup

A strawberry spreadable cream was developed, valorizing regional raw materials, contributing to food waste reduction and agri-food ecosystem sustainability. Spreadable creams are water-in-oil emulsions whose lipid phase normally contains a blend of vegetable oils, natural colourants, stabilizers, emulsifiers, flavourings, antioxidants, lecithin, and fat-soluble vitamins. The aqueous phase normally contains skim milk proteins and small quantities of other ingredients, such as salt, preservatives, thickeners, and water-soluble vitamins. The methodology involved the experimental technological development articulated with microbiological, proximal, physicochemical, and sensorial analysis. This new product revealed nutritional advantages over similar products already on the market. The final prototype was subjected to food pairing and food design with incremental acceptance according to gastronomic use, in addition to its direct use as a spreadable cream. This work was part of the project Agrio et Emulsio—new products development (POCI-01-0145-FEDER-023583), whose main objective was the formulation and design of innovative food emulsions based on processed raw materials, with potential application in certain markets such as gourmet, diet, and vegan.

Capsules templated from water-in-oil Pickering emulsions for enzyme encapsulation

HYPOTHESIS

Encapsulation of sensitive water-soluble bioactive materials such as fragrances, polyphenols and enzymes poses an immense challenge with capsules templated from water-in-oil (w/o) emulsions. Generation of radicals, heating, and extreme pH that are necessary for shell formation through interfacial reactions may have undesired influences on the active ingredients and thus lower their activity.

EXPERIMENTS

To overcome these limitations, we present a method to encapsulate sensitive ingredients, whereby capsules are templated from a w/o Pickering emulsion stabilized by binary particles of different hydrophilicity levels; the particles assembled at the water/oil interface are then crosslinked by polydiisocyanate (PHDI) at room temperature and neutral pH. Zein and casein nanoparticles were used as hydrophilic stabilizers and lipase was chosen as a model sensitive biomolecule that was encapsulated in the water core.

FINDINGS

Our results indicated that the enzymes encapsulated in colloid capsules had higher activity than those encapsulated in traditional w/o Pickering emulsion without shell crosslinking. The capsule structure effectively protected enzymes from the outer environment. This method is well suited for the encapsulation and protection of sensitive ingredients and shows great application in food, drug, and cosmetic industries.

Fabrication of Stable Oleofoams with Sorbitan Ester Surfactants

Sorbitan esters have been extensively used as surfactants to stabilize emulsions in many fields. However, the preparation of an oleofoam with sorbitan ester alone has not been reported. Here, we apply a novel protocol to fabricate stable oleofoams of high air volume fraction from mixtures of vegetable oil and sorbitan ester. To incorporate more air bubbles into the oil matrix, aeration is first carried out in the one-phase region at high temperatures, during which the highest over-run can reach 280%. Due to foam instability at high temperatures, the foam is then submitted to rapid cooling, followed by storage at low temperatures. For high-melting sorbitan monostearate, the resulting foams containing many crystal-encased air bubbles are ultrastable to drainage, coarsening, and coalescence for several months. On the contrary, the cooled foams with low-melting sorbitan monooleate go through a gradual decay lasting for more than 1 month. We highlight the importance of hydrogen bond formation between surfactant and oil in enhancing foam stability. The generic nature of the above findings is demonstrated by preparing oil foams with various vegetable oils and sorbitan monooleate.

W/o/w multiple emulsions: A novel trend in functional ice cream preparations?

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The possible applications of w/o/w multiple emulsions (MEs) in ice creams are described.

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W/o/w MEs enable the encapsulation of sensitive compounds.

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Fat content is reduced using w/o/w MEs without losing the creaminess of the final products.

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Ice cream is a very suitable matrix for application of Pickering emulsions.

Ice cream is a popular product worldwide. Unfortunatelly, it contains a significant amount of fat. In this review, promising strategies for the use of w/o/w multiple emulsion structures in creams are assessed. W/o/w multiple emulsions (MEs) enable reduction the fat without losing the creamy taste and mouthfeel and also encapsulation of sensitive compounds. The encouraging application and formation of MEs in ice cream mixtures is supported by the use of natural food ingredients, such as fiber, which helps to stabilize the whole system and improves nutritional value. The future trends may be focused on the target stabilizations using Pickering paticles (PPs). The possible advantages, manufacture, evaluation methods, and predicted future prospects of MEs in ice creams are discussed.

Pickering Emulsions Stabilized by Binary Mixtures of Colloidal Particles: Synergies between Contrasting Properties

Pickering emulsions that are stabilized by colloidal particles have attracted substantial research attention because of their potential applications in various industries. Previously, single colloidal particles have usually been used to fabricate Pickering emulsions and to investigate the stabilization mechanism. However, surface modification of the colloidal stabilizer is normally required to adjust the particle wettability, which often involves chemical modification, the adsorption of a surfactant or polymer, and the addition of an electrolyte. Such a modification is expensive, time-consuming, and thus only partially effective. In this Perspective, we describe an alternative approach that uses binary mixtures of particles as stabilizers and could be an effective solution to the above-described problems with Pickering emulsions. We introduce various types of Pickering emulsions stabilized by binary mixtures of particles with different functional groups, opposite charges, or opposite wettabilities (i.e., they are hydrophilic or hydrophobic). Examples of stabilizing mechanisms are discussed, showing that compared with emulsions stabilized by single colloidal particles, emulsions stabilized by binary mixtures of particles are generated via simpler particle-pretreatment processes and have higher stability and customizable properties and thus can enable the exploration of the next generation of Pickering emulsions.

Water-in-oil emulsions enriched with alpha-linolenic acid in diacylglycerol form: Stability, formation mechanism and in vitro digestion analysis

This study developed an alpha-linolenic acid (ALA) supplement with emulsion form using ALA-rich diacylglycerol (ALA-DAG) and ALA-DAG stearin (DAG-SF) as a new source of ALA and emulsifier. Stable, commercial surfactant-free W/O emulsions with 90 wt% oil phase (including DAG-SF and ALA-DAG with 10:90 - 20:80 wt ratio) was fabricated. Microstructure and Raman spectra revealed that the compact crystal networks and high amounts of solid acyl chains were responsible for high emulsion stability. These emulsions exhibited good potential in improving the ALA nutritional status (with ALA release level of 60.49% - 62.98%). Furthermore, the emulsifier-to-oil ratio greatly impacted the emulsion texture (solid-like or liquid-like) and emulsions showed great oxidation stability (2.80 - 3.09 meq/kg lipid of peroxide value at 6th week). The tunable texture and high oxidation stability make this emulsion system useful for a wide range of food products. This developed emulsion system could provide valuable information for other important fatty acids supplement.

Crystallization of lipids and lipid emulsions treated by power ultrasound: A review

The actual food system with fat is always complex and fat crystal and fat crystal networks have important effects on the physical properties of food. Recently, power ultrasound (PU) had been widely recognized as an auxiliary technology of fat crystallization to modify food properties. This review expounded on the mechanism of ultrasonic crystallization, and summarized effects of various factors in the process of ultrasonic treatment on fat crystallization. Based on the above, combined with the application of ultrasound in emulsions, the ultrasonic fat crystallization effect in the emulsion system was judged and described. Research results indicated that PU could shorten the induction time of crystallization, accelerate the formation of crystal nuclei, and change the polymorphism of fat crystals. The product treated by PU formed smaller and more uniform crystals to produce a more viscoelastic fat crystal network. In emulsion systems, ultrasonic treatments showed the same effect, but the effect of ultrasonic crystallization on the emulsion stability was different due to fat crystals in different emulsion systems. Meanwhile, the importance of ultrasonic crystallization in lipid emulsions was emphasized, thus ultrasonic crystallization had great potential in emulsion systems.

Water-In-Oil Pickering Emulsions Stabilized by Microcrystalline Phytosterols in Oil: Fabrication Mechanism and Application as a Salt Release System

Recently, Pickering emulsions stabilized by edible particles have attracted significant attention from the scientific community and food industry owing to their surfactant-free character. However, those edible particles are mostly used for stabilizing oil-in-water emulsions, whereas those for water-in-oil emulsions are very limited. In this article, stable water-in-oil Pickering emulsions were prepared through dispersing phytosterol particles in oil phase, and the effects of antisolvent treatment, the type of oil, particle concentration, and water fraction on the stability, type, and morphology of these emulsions were investigated. In addition, the release profile of salt as a model aqueous compound from these emulsions has also been studied. Results showed that due to its higher water content, the antisolvent pretreatment of phytosterol in the ethanol/water system facilitated the dispersion of dried phytosterol particles into oil phase as microcrystals. Water-in-oil Pickering emulsions with droplet sizes of 80-100 μm were fabricated at phytosterol concentrations of 1.5-3% w/v and water fractions of 0.2-0.6. The dissolved phytosterol molecules in oil phase could help in emulsion stabilization through interfacial crystallization during emulsification, evidenced by polar microscopic observations. Moreover, the salt release from phytosterol-stabilized Pickering emulsions showed a temperature-dependent profile which could have potential application in a controlled-release system. The current study provided important information for fabrication of stable water-in-oil emulsion using natural particles.

Freshly Milled Quartz Particles Obtained from River Sand as an Efficient Natural Demulsifier for Crude Oil Emulsions

Saline water necessarily contained in crude oil forms complex and stable water-in-oil (w/o) emulsions with oil. Due to the negative impact of this emulsion on the oil’s transportation and refining, special materials are added to help break the emulsion and separate water. Herein, a comparative study of the demulsifying ability concerning w/o emulsion of the original and freshly milled quartz (FMQ) particles isolated from river sand was carried out. The effect of quartz with a mesh size of 75 μm on reducing emulsion stability was investigated using rheological measurements, interfacial tension measurements, demulsification tests, as well as routine methods for characterizing solid and liquid materials. With the addition of 3 wt% FMQ, 97% demulsification efficiency was achieved after 100 min of settling, against 140 min for the original quartz. The role of milling quartz is to increase the ability of water to adhere and thus locally increase the pH value; this results in a reduction in the stability of the emulsion and its destruction. The prolonging effect of quartz milling lasted about 2.5–3.0 h, after which the demulsifying ability of milled quartz became comparable to that of the starting material.

Review on the Regulation of Plant Polyphenols on the Stability of Polyunsaturated-Fatty-Acid-Enriched Emulsions: Partitioning Kinetic and Interfacial Engineering

The plant polyphenols are normally presented as natural functional antioxidants, which also possess the potential ability to improve the physicochemical stability of polyunsaturated fatty acid (PUFA)-enriched emulsions by interface engineering. This review discussed the potential effects of polyphenols on the stability of PUFA-enriched emulsions from the perspective of the molecular thermodynamic antioxidative analysis, the kinetic of interfacial partitioning, and the covalent and non-covalent interactions with emulsifiers. Recently, research studies have proven that the interfacial structure of emulsions can be concurrently optimized via promoting interfacial partitioning of polyphenols and further increasing interfacial thickness and strength. Moreover, the applied limitations of polyphenols in PUFA-enriched emulsions were summarized, and then some valuable and constructive viewpoints were put forward in this review to provide guidance for the use of polyphenols in constructing PUFA-enriched emulsions.

The effect of emulsifier type on the secondary crystallisation of monoacylglycerol and triacylglycerols in model dairy emulsions

Dairy emulsions contain an intrinsically heterogeneous lipid phase, whose components undergo crystallisation in a manner that is critical to dairy product formulation, storage, and sensory perception. Further complexity is engendered by the diverse array of interfacially-active molecules naturally present within the serum of dairy systems, and those that are added for specific formulation purposes, all of which interact at the lipid-serum interface and modify the impact of lipid crystals on dairy emulsion stability. The work described in this article addresses this complexity, with a specific focus on the impact of temperature cycling and the effect of emulsifier type on the formation and persistence of lipid crystals at lipid-solution interfaces. Profile analysis tensiometry experiments were performed using single droplets of the low melting fraction of dairy lipids, in the presence and absence of emulsifiers (Tween 80 and whey protein isolate, WPI) and during the temperature cycling, to study the formation of monoacylglycerol (MAG) crystals at the lipid-solution interface. Companion experiments on the same lipid systems, and at the same cooling and heating rates, were undertaken with synchrotron small angle X-ray scattering, to specifically analyse the effect of emulsifier type on the formation of triacylglycerol (TAG) crystals at the lipid-solution interface of a model dairy emulsion. These two complementary techniques have revealed that Tween 80 molecules delay MAG and TAG crystal formation by lowering the temperature at which the crystallisation occurs during two cooling cycles. WPI molecules delay the crystallisation of MAGs and TAGs during the first cooling cycle, while MAG crystals form without delay during the second cooling cycle at the same temperature as MAG crystals in an emulsifier free system. The crystallisation of TAGs is inhibited during the second cooling cycle. The observed differences in crystallisation behaviour at the interface upon temperature cycling can provide further insight into the impact of emulsifiers on the long-term stability of emulsion-based dairy systems during storage.

Application of X-ray Microcomputed Tomography for the Static and Dynamic Characterization of the Microstructure of Oleofoams

Oleofoams are a novel, versatile, and biocompatible soft material that finds application in drug, cosmetic or nutraceuticals delivery. However, due to their temperature-sensitive and opaque nature, the characterization of oleofoams' microstructure is challenging. Here, synchrotron X-ray microcomputed tomography and radiography are applied to study the microstructure of a triglyceride-based oleofoam. These techniques enable non-destructive, quantitative, 3D measurements of native samples to determine the thermodynamic and kinetic behavior of oleofoams at different stages of their life cycle. During processing, a constant bubble size distribution is reached after few minutes of shearing, while the number of bubbles incorporated keeps increasing until saturation of the continuous phase. Low amounts of solid triglycerides in oleofoams allow faster aeration and a more homogeneous microstructure but lower thermodynamic stability, with bubble disproportionation and shape relaxation over time. Radiography shows that heating causes Ostwald ripening and coalescence of bubbles, with an increase of their diameter and sphericity.

Recent progress in oil-in-water-in-oil (O/W/O) double emulsions

Oil-in-water-in-oil (O/W/O) double emulsions are recognized as an advanced design route for oil structuring that shows promising applications in the pharmaceutical, cosmetic, and food fields. This review summarizes the main research advances of O/W/O double emulsions over the past two decades. It mainly focuses on understanding the preparation strategies, stabilization mechanism, and potential applications of O/W/O double emulsions. Several emulsification strategies are discussed, including traditional two-step emulsification method, phase-inversion approach, membrane emulsification, and microfluidic emulsification. Further, the role of interfacial stabilizers and viscosity in the stability of O/W/O double emulsions will be discussed with a focus on synthetic emulsifiers, natural biopolymer sand solid particles for achieving this purpose. Additionally, analytical methods for evaluating the stability of O/W/O double emulsions, such as advanced microscopy, rheology, and labeling assay are reviewed taking into account potential limitations of these characterization techniques. Moreover, possible innovative food applications are highlighted, such as simulating fat substitutes to decrease the trans- or saturated fatty acid content and developing novel delivery and encapsulation systems. This review paves a solid way for the exploration of O/W/O double emulsions toward large-scale implementation within the food industry.

Structuring of Edible Liquid Oil into Smart Thermo-Triggered Soft Matters for Controlled Bioactive Delivery

Growing interest is being dedicated to smart soft matters because of their potential in controlling bioactives upon exposure to an appropriate stimulus. Herein, structuring of edible liquid oil into oleogels and emulgels as smart thermo-triggered soft vehicles for controllable release of diverse nutrients was developed. Edible liquid oil was trapped inside the crystal network structure of phytosterols and monoglycerides resulting in bicomponent solidlike oleogels. Subsequently, both water-in-oleogel (W/O) emulgels and glycerol-in-oleogel (G/O) emulgels were further fabricated by spatial distribution of the stabilizing interfacial crystals around dispersed droplets as well as the network crystals in the continuous phase. Rheological measurements showed that the gel strength of the oleogel-based emulgels depends on the fraction of the aqueous phase and is greater than that of corresponding oleogels due to a filler effect of dispersed aqueous droplets within the crystal network, offering an additional strategy to tune the structure and rheology. Comparatively, introducing glycerol endowed a higher gel strength for the oleogel-based emulgels than water, particularly at increased filler loads. In addition, these soft matters exhibited interesting thermoresponsive nature, which exhibit the flexibility for programmed release of coencapsulated bioactive components upon exposure to an appropriate thermal triggered switchable. The resulted smart thermo-triggered soft matters have emerging opportunities for application in functional active ingredient delivery by on-demand strategies.

Microfluidic production of monodisperse emulsions for cosmetics

Droplet-based microfluidic technology has enabled the production of emulsions with high monodispersity in sizes ranging from a few to hundreds of micrometers. Taking advantage of this technology, attempts to generate monodisperse emulsion drops with high drug loading capacity, ordered interfacial structure, and multi-functionality have been made in the cosmetics industry. In this article, we introduce the practicality of the droplet-based microfluidic approach to the cosmetic industry in terms of innovation in productivity and marketability. Furthermore, we summarize some recent advances in the production of emulsion drops with enhanced mechanical interfacial stability. Finally, we discuss the future prospects of microfluidic technology in accordance with consumers' needs and industrial attributes.

Water-in-oil Pickering emulsions stabilized solely by a naturally occurring steroidal sapogenin: Diosgenin

In this study, stable water-in-oil emulsions stabilized solely by a naturally occurring steroidal sapogenin was reported for the first time. The results show that a concentrated emulsion with an internal water ratio of up to 60% can be obtained with only 3% of diosgenin concentration. The concentration of diosgenin had a significant effect on the microstructure and rheological properties of the emulsions. More importantly, the emulsion has excellent freeze/thaw stability and thermal stability. The results of polarized light microscopy, CLSM, and XRD indicate that the great structural properties and high stability of the emulsion can be attributed to the combined action of the diosgenin crystal shells on the droplet surface and needle-crystals in the continuous phase. That is, Pickering stabilization and network stabilization acting synergistically on stabilization of the emulsions. This novel food grade water-in-oil emulsions demonstrated great potential for application in food and biomedical-related fields.

Margarines: Historical approach, technological aspects, nutritional profile, and global trends

Margarines are an expanding market worldwide due to large-scale commercial, lower cost, growth of bakery and confectionery markets, and seasonal independence. The fatty acid composition, solid fat content, consistency, and melting point of the fats used in margarine determine their functional properties. Due to its proven association with increased risk of cardiovascular diseases, the recommendations of the World Health Organization and the enactment of laws in several countries to eliminate industrially produced trans fatty acids (TFA) have resulted in the prohibition or progressive reduction in the use of partially hydrogenated fat. However, issues related to high levels of TFA and saturated fatty acids still constitute a challenge in the formulation of this product category. Current trends on margarine production addition of phytosterols, non-lipid components, organogels, and new interesterified fat bases are reviewed. This review aims to present a historical view and the technological evolution of margarines, including their production processes, formulations, and physical and nutritional characteristics, as well as legislation, and main trends.

Recent advances on food-grade water-in-oil emulsions: Instability mechanism, fabrication, characterization, application, and research trends

Owing to their promising application prospects, water-in-oil (W/O) emulsions have aroused continuous attention in recent years. However, long-term stability of W/O emulsions remains a particularly challenging problem in colloid science. With the increasing demand of consumers for natural, green, and healthy foods, the heavy reliance on chemically synthesized surfactants to achieve long-term stability has become the key technical defect restricting the application of W/O emulsions in food. To design and manufacture W/O emulsions with long-term stability and clean label, a comprehensive understanding of the fundamentals of the W/O emulsion system is required. This review aims to demystify the field of W/O emulsions and update its current research progress. We first provide a summary on the essential basic knowledge regarding the instability mechanisms, including physical and chemical instability in W/O emulsions. Then, the formulation of the W/O emulsion system is introduced, particularly focusing on the use of natural stabilizers. Besides, the characterization and application of W/O emulsions are also discussed. Finally, we propose promising research trends, including (1) developing W/O high internal phase emulsions (HIPEs) as fat mimetic and substitute, (2) promising formulation routine for long-term stable double emulsions, and (3) searching for novel plant-derived stabilizers of W/O emulsions.

Oleogel-based emulsions: Concepts, structuring agents, and applications in food

This review discusses the application of oleogel technology in emulsified systems. In these systems of mimetic fats, water-in-oil or oil-in-water emulsions can be obtained, but, here, we cover emulsions with an oil continuous phase in detail. Depending on the percentage of water added to the oleogels, systems with different textures and rheological properties can be developed. These properties are affected by the characteristics and concentration of the added components and emulsion preparation methods. In addition, some gelators exhibit interfacial properties, resulting in more stable emulsions than those of conventional emulsions. Oleogel-based emulsion are differentiated by continuous and dispersed phases and the structuring/emulsification components. Crucially, these emulsions could be applied by the food industry for preparing, for example, meat products and margarines, as well as by the cosmetics industry. We present the different processes of emulsion elaboration, the main gelators used, the influence of the water content on the structuring of water-in-oleogel emulsions, and the structuring mechanisms (Pickering, network, and combined Pickering and network stabilization). Finally, we highlight the applications of these systems as alternatives for reducing processed food lipid content and saturated fat levels.