Emulsions Stabilized by Gum Arabic: Composition and Packing within Interfacial Films

The Use of a Natural Polysaccharide Extracted from the Prickly Pear Cactus (Opuntia ficus indica) as an Additive for Textile Dyeing

The art of dyeing fabrics is one of the oldest human activities. In order to improve the fastness properties of dyeing products, various additives are added to optimize the uniformity of fibers and surfaces and improve dye distribution. Unfortunately, these additives can be harmful and very often are not biodegradable. This article reports on the possibility of using a natural additive for dyeing textiles: a polysaccharide extracted from the prickly pear cactus (Opuntia ficus indica). One type of fabric was tested, silk, with different colors. Several samples were prepared and dyed for each color, adding the same additives but also a commercial chemical aid for one of them and the mucilage of Opuntia for another. The fastness of the applied dyes was evaluated by washing at different temperatures with a common liquid detergent. All samples were analyzed before and after washing with a colorimeter to evaluate the color changes. The results of the analyses reported and compared indicate the potential of prickly pear mucilage as an additive for dyeing silk, which is easily accessible, safe, and sustainable compared to other commonly used additives.

A Feasibility Study on Enhanced Oil Recovery of Modified Janus Nano Calcium Carbonate-Assisted Alkyl Polyglycoside to Form Nanofluids in Emulsification Flooding

Emulsification flooding can effectively enhance crude oil recovery to solve the problem of petroleum shortage. In this work, a modified Janus Nano Calcium carbonate (JNC-12) with a particle size of 30-150 nm was synthesized, and an in situ emulsification nanofluid (ISEN) was prepared with JNC-12 and alkyl polyglycoside (APG). Scanning electron microscope (SEM) showed that the dispersion of JNC-12 in air or APG solution was better than Nano Calcium carbonate (Nano CaCO3). The emulsification properties, interfacial tension, and expansion modulus of ISEN were studied, and the result showed that with the increase in salinity, the emulsification rate decreased, the water yield rate increased, the interfacial tension first decreased and then increased, and the expansion modulus first increased and then decreased. With the increase in temperature, the emulsification rate, emulsion viscosity, and interfacial tension decreased. With the increased oil-water volume, the water yield rate and the emulsion viscosity increased. With increase in the concentration of JNC-12, the water yield rate, the emulsion viscosity, and the interfacial tension decreased but the expansion modulus increased. The emulsion generated by emulsifying ISEN with crude oil was an O/W emulsion, the crude oil viscosity was 4-10 times that of emulsion, and the average particle size of emulsion was 1.107 μm. The addition of ISEN caused the decrease in interfacial tension of oil-water to 0.01-0.1 mN/m. The wettability alteration experiment found that ISEN could change the lipophilic rock to hydrophilic rock. Finally, the core displacement experiments showed that compared with the first water flooding, the oil recovery of the second water flooding after ISEN flooding enhanced by 17.6%. This research has important guiding significance for in situ emulsified nanofluid flooding to enhance oil recovery.

In Situ ATR Spectroscopy Study of the Interaction of Acacia senegal Gum with Gold Nanoparticles Films at the Solid-Liquid Interface

The adsorption process of Acacia gum (A. senegal), a complex heteropolysaccharide, was followed by using a spectroscopic method to unravel the relative contribution of the protein moieties and the carbohydrate blocks on the adsorption process. In situ ATR-FTIR was used to investigate the kinetics and conformational changes associated with the adsorption of A. senegal gum on gold nanoparticle films (Au-NPs) at different pHs. The results of this thorough study highlighted the adsorption of A. senegal gum through its protein moieties, in particular, AGPs of low molecular weight and high protein content, close to the Au-NPs surface. Isotherm experiments, by gradually increasing the concentration, showed that the gum adsorption was heterogeneous and followed the Freundlich model for the amide part, while the polysaccharide part followed the Langmuir model. In addition, the hydration and structural organization of the gum layer depended on the gum concentration. A. senegal gum adsorbed irreversibly on Au-NPs whatever the pHs, but the adsorbed layer presented a different behavior depending on pH. A more aggregated and less hydrated structure was observed at acidic pH, while a very hydrated and continuous layer was detected at higher pH. The secondary structure analysis through amide III band revealed a change in the gum secondary structure at high pH with the increase in β-turn while random coil decreased.

Triumfetta cordifolia Gum as a Promising Bio-Ingredient to Stabilize Emulsions with Potentials in Cosmetics

The cosmetics industry is searching for efficient and sustainable substances capable of stabilizing emulsions or colloidal dispersions that are thermodynamically unstable because of their high surface energy. Therefore, surfactants are commonly used to stabilize the water/oil interface. However, the presence of a surfactant is not always sufficient to obtain stable emulsions on the one hand, and conventional surfactants are often subject to such controversies as their petroleum origin and environmental concerns on the other hand. As a consequence, among other challenges, it is obvious that research related to new-natural, biodegradable, biocompatible, available, competitive-surfactants are nowadays more intensive. This study aims to valorize a natural gum from Triumfetta cordifolia (T. cordifolia) as a sustainable emulsifier and stabilizer for oil-in-water (O/W) emulsions, and to evaluate how the nature of the fatty phase could affect this potential. To this end, O/W emulsions were prepared at room temperature using three different oils varying in composition, using a rotor-stator mixer. Resulting mixtures were characterized using optical microscopy, laser granulometry, rheology, pH and stability monitoring over time. The results demonstrated good potential for the gum as an emulsifying agent. T. cordifolia gum appears efficient even at very low concentrations (0.2% w/w) for the preparation and stabilization of the different O/W emulsions. The best results were observed for cocoglyceride oil due to its stronger effect of lowering interfacial tension (IFT) thus acting as a co-emulsifier. Therefore, overall results showed that T. cordifolia gum is undoubtedly a highly promising new bio-sourced and environmentally friendly emulsifier/stabilizer for many applications including cosmetics.

Anionic Polysaccharide Cryogels: Interaction and In Vitro Behavior of Alginate-Gum Arabic Composites

In the present study, polysaccharide-based cryogels demonstrate their potential to mimic a synthetic extracellular matrix. Alginate-based cryogel composites with different gum arabic ratios were synthesized by an external ionic cross-linking protocol, and the interaction between the anionic polysaccharides was investigated. The structural features provided by FT-IR, Raman, and MAS NMR spectra analysis indicated that a chelation mechanism is the main process linking the two biopolymers. In addition, SEM investigations revealed a porous, interconnected, and well-defined structure suitable as a scaffold in tissue engineering. The in vitro tests confirmed the bioactive character of the cryogels through the development of the apatite layer on the surface of the samples after immersion in simulated body fluid, identifying the formation of a stable phase of calcium phosphate and a small amount of calcium oxalate. Cytotoxicity tests performed on fibroblast cells demonstrated the non-toxic effect of alginate-gum arabic cryogel composites. In addition, an increase in flexibility was noted for samples with a high gum arabic content, which determines an appropriate environment to promote tissue regeneration. The newly obtained biomaterials that exhibit all these properties can be successfully involved in the regeneration of soft tissues, wound management, or controlled drug release systems.

Correlation between interfacial layer properties and physical stability of food emulsions: current trends, challenges, strategies, and further perspectives

Emulsions are thermodynamically unstable systems that tend to separate into two immiscible phases over time. The interfacial layer formed by the emulsifiers adsorbed at the oil-water interface plays an important role in the emulsion stability. The interfacial layer properties of emulsion droplets have been considered the cutting-in points that influence emulsion stability, a traditional motif of physical chemistry and colloid chemistry of particular significance in relation to the food science and technology sector. Although many attempts have shown that high interfacial viscoelasticity may contribute to long-term emulsion stability, a universal relationship for all cases between the interfacial layer features at the microscopic scale and the bulk physical stability of the emulsion at the macroscopic scale remains to be established. Not only that, but integrating the cognition from different scales of emulsions and establishing a unified single model to fill the gap in awareness between scales also remain challenging. In this review, we present a comprehensive overview of recent progress in the general science of emulsion stability with a peculiar focus on interfacial layer characteristics in relation to the formation and stabilization of food emulsions, where the natural origin and edible safety of emulsifiers and stabilizers are highly requested. This review begins with a general overview of the construction and destruction of interfacial layers in emulsions to highlight the most important physicochemical characteristics of interfacial layers (formation kinetics, surface load, interactions among adsorbed emulsifiers, thickness and structure, and shear and dilatational rheology), and their roles in controlling emulsion stability. Subsequently, the structural effects of a series of typically dietary emulsifiers (small-molecule surfactants,proteins, polysaccharides, protein-polysaccharide complexes, and particles) on oil-water interfaces in food emulsions are emphasized. Finally, the main protocols developed for modifying the structural characteristics of adsorbed emulsifiers at multiple scales and improving the stability of emulsions are highlighted. Overall, this paper aims to comprehensively study the literature findings in the past decade and find out the commonality of multi-scale structures of emulsifiers, so as to deeply understand the common characteristics and emulsification stability behaviour of adsorption emulsifiers with different interfacial layer structures. It is difficult to say that there has been significant progress in the underlying principles and technologies in the general science of emulsion stability over the last decade or two. However, the correlation between interfacial layer properties and physical stability of food emulsions promotes revealing the role of interfacial rheological properties in emulsion stability, providing guidance on controlling the bulk properties by tuning the interfacial layer functionality.

Determination of the Emulsion Stabilization Mechanisms of Quaternized Glucan of Curdlan via Rheological and Interfacial Characterization

Interfacial-active quaternized glucan of curdlan (QCD) with different degrees of substitution (DS) was prepared and used as stabilizers of oil-in-water (O/W) emulsions at different concentrations. The adsorption behavior of QCDs, rheology of bulk emulsions and interfacial films, emulsion morphology, and stability were investigated. The emulsifying capacity of QCD was essentially related to the viscoelastic features of the interfacial film and the continuous phase and the electrostatic repulsion among oil droplets. QCD molecules with different DS form structurally different interfacial films. The high-DS QCD formed a viscously predominant interfacial film with certain hydrophobicity, whereas the low-DS QCD molecules formed an elastically predominant film characterized by hydrogen bonds among adsorbed chains. The structuralization of low-DS QCD molecules through physical cross-linking in bulk and interfacial films at high concentrations was conducive to emulsion stability. Excess QCD chains in the bulk formed a weak gel-like network, further hindering the movement of droplets in the emulsions. Relevant emulsification and stability mechanisms were proposed. Finally, the stability of curcumin encapsulated in O/W emulsions was evaluated.

Potential of Wood Hemicelluloses and Their Derivates as Food Ingredients

A holistic utilization of all lignocellulosic wood biomass, instead of the current approach of using only the cellulose fraction, is crucial for the efficient, ecological, and economical use of the forest resources. Use of wood constituents in the food and feed sector is a potential way of promoting the global economy. However, industrially established food products utilizing such components are still scarce, with the exception of cellulose derivatives. Hemicelluloses that include xylans and mannans are major constituents of wood. The wood hemicelluloses are structurally similar to hemicelluloses from crops, which are included in our diet, for example, as a part of dietary fibers. Hence, structurally similar wood hemicelluloses have the potential for similar uses. We review the current status and future potential of wood hemicelluloses as food ingredients. We include an inventory of the extraction routes of wood hemicelluloses, their physicochemical properties, and some of their gastrointestinal characteristics, and we also consider the regulatory route that research findings need to follow to be approved for food solutions, as well as the current status of the wood hemicellulose applications on that route.

Method to prepare aqueous propolis dispersions based on phase separation

Propolis has many benefits for human health. To facilitate its oral consumption, we designed propolis-in-water dispersions to be used as nutraceuticals. Propolis was first dissolved either in ethanol or in a hydroalcoholic solution. Water being a non-solvent for propolis, its addition produced propolis precipitation. We explored the ternary phase diagram of water, propolis and ethanol to identify the line separating the one phase region where propolis is fully dissolved, and the two-phase region where a concentrated propolis solution coexists with a dilute one. Droplets rich in propolis were produced during the phase separation process under mechanical stirring induced by a rotor-stator device or a microfluidizer, and they were stabilized using gum Arabic as an emulsifier. Ethanol was finally removed by distillation under reduced pressure. Propolis dispersions in the micron and submicron size range could be obtained. They contained between 1.75 and 10.5 wt% polyphenols relative to the total mass.

Effect of Gum Acacia on the Intestinal Bioavailability of n-3 Polyunsaturated Fatty Acids in Rats

Lipid emulsification is a technique that is being explored for improving the bioavailability of omega 3 (n-3) long chain (LC) fatty acid (FA). The nature of the emulsifiers can differently impact the lipid bioavailability via a modification of the lipolysis step. Among natural emulsifiers, gum acacia (GA), an indigestible polysaccharide, provides protective encapsulation of n-3 by forming a specifically crown-like shape around lipid drops, which could also impact the digestion step. Despite the interest in lipolysis rate, the impact of GA on lipid bioavailability has never been explored in a complete physiological context. Thus, we followed in a kinetics study the n-3 bioavailability in rat lymph, orally administered DHA-rich oil, formulated based on GA compared to the bulk phase form of the oil. The AUC values were significantly improved by +121% for total TG and by 321% for n-3 PUFA, specifically for EPA (+244%) and for DHA (+345%). Benefits of GA have also been related to the transport of FA in lymph, which was 2 h earlier (Tmax = 4 h), compared to the Tmax (6 h) obtained with the bulk phase oil. All the data showed that GA is one of the most favorable candidates of natural emulsifiers to improve n-3 bioavailability and their rate of absorption for health targets.

Droplet Dispersion States of Cyclodextrin-Based Emulsions from Nonlinear Rheological Properties

Polymers are desirable to improve emulsion stability by stuffing them into the continuous phase. How to get information on the droplet dispersion states of the emulsions remains a challenge, as the emulsion characteristics are dictated by two intertwining components, the polymer matrix and the droplets. Herein, we use an amphiphilic polymer, gum arabic (GA), to mediate the droplet flocculation of cyclodextrin (CD)-based emulsions and compare them with our previous studies on the stabilization of CD-based emulsions by a nonamphiphilic polymer, methylcellulose (MC). We characterize the emulsions by using optical microscopy, confocal laser scanning microscopy, and laser particle analysis, explore their rheological behavior through large-amplitude oscillatory shear experiments, and analyze the nonlinear viscoelasticities through Fourier transform (FT)-rheology and Lissajous-Bowditch plots. There is a great difference between GA and MC in the viscosity effect and the arrangement around emulsion droplets. GA is not an effective flocculation inhibitor due to a bridging flocculation mechanism rather than a direct viscosity effect. Our analysis highlights the role of the intrinsic nonlinearity parameter (Q₀) extracted by FT analysis in reflecting the droplet dispersion states of the emulsions by decoupling structural contributions from the polymers and the emulsion droplets.

Adsorption Behavior of Arabinogalactan-Proteins (AGPs) from Acacia senegal Gum at a Solid-Liquid Interface

Adsorption of five different hyperbranched arabinogalactan-protein (AGP) fractions from Acacia senegal gum was thoroughly studied at the solid-liquid interface using a quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR), and atomic force microscopy (AFM). The impact of the protein/sugar ratio, molecular weight, and aggregation state on the adsorption capacity was investigated by studying AGP fractions with different structural and biochemical features. Adsorption on a solid surface would be primarily driven by the protein moiety of the AGPs through hydrophobic forces and electrostatic interactions. Increasing ionic strength allows the decrease in electrostatic repulsions and, therefore, the formation of high-coverage films with aggregates on the surface. However, the maximum adsorption capacity was not reached by fractions with a higher protein content but by a fraction that contains an average protein quantity and presents a high content of high-molecular-weight AGPs. The results of this thorough study highlighted that the AGP surface adsorption process would depend not only on the protein moiety and high-molecular-weight AGP content but also on other parameters such as the structural accessibility of proteins, the molecular weight distribution, and the AGP flexibility, allowing structural rearrangements on the surface and spreading to form a viscoelastic film.

Spruce Galactoglucomannan-Stabilized Emulsions Enhance Bioaccessibility of Bioactive Compounds

The increasing public awareness of health and sustainability has prompted the development of functional foods rich in health-promoting ingredients. Processing technologies and sustainable multifunctional ingredients are needed for structuring these formulations. Spruce galactoglucomannan (GGM), the main hemicelluloses in softwood cell walls, are an abundantly available, emerging sustainable food hydrocolloid that have the ability to efficiently emulsify and stabilize oil-in-water emulsions. In this study, we illustrate how this lignocellulosic stabilizer affects the digestion of polyunsaturated fatty acids (PUFAs) in vitro. A 100% decrease in the initial TAG content was observed during the in vitro digestion, suggesting that complete hydrolysis of the TAGs was achieved by the digestive enzymes. Besides, no release of mono-, di-, and oligosaccharides or phenolic compounds from GGM was detected. Our results demonstrate that the GGM-stabilized emulsion could potentially deliver lipophilic bioactive ingredients and enhance their bioaccessibility. In addition, this bio-stabilizer itself would remain stable in the upper gastrointestinal track and serve as a prebiotic for gut microbiota. We anticipate GGM to complement or even replace many of the conventional carriers of bioactive components in future health care products and functional foods.

Emulsifying properties of Acacia senegal gum: Impact of high molar mass protein-rich AGPs

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Reconstitution of gums from arabinogalactan proteins (AGP) of Acacia gum.

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Experimental design to optimize their emulsions properties.

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Relevant adsorption of high molar protein-rich AGPs at the interface.

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Combined effect of high molar protein-rich AGPS and total concentration.

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Role of apparent viscosity of bulk to long-term stability.

The impact of high molar mass protein-rich arabinogalactan-proteins (AGPs) on emulsifying properties of Acacia senegal gums were studied using reconstituted gums obtained with two distinct fractions: one containing these specific high molar mass AGPs and the other protein-poor low molar mass AGPs. To produce and stabilize limonene emulsions, the experimental design emphasized not only the role of high molar mass protein-rich AGPs, but also the importance of high total concentration. At low protein contents, reconstituted gums required a slightly higher content in high molar mass protein-rich AGPs than original A. senegal gum, that confirmed the role of low molar mass protein-rich AGPs in the adsorption at interfaces. The comparison of the creaming index between original and reconstituted gums as well as the monitoring of instability phenomena by turbiscan up to 30 days clearly demonstrated the prevalent impact of the bulk apparent viscosity in the long-term stability of emulsions.

Emulsions Stabilized by Gum Arabic: How Diversity and Interfacial Networking Lead to Metastability

Gum arabic is a natural hydrocolloid composed of a diversity of amphiphilic species consisting of protein chains covalently linked to multiscale porous polysaccharides. Gum arabic is notably used as a food additive (E414) to provide metastability to oil-in-water emulsions, even after extensive dilution. Here, we investigate the mechanism underlying the emulsion stabilizing properties of gum arabic, using a combination of scattering and chromatographic analyses and the design of a harvesting method to collect adsorbed species. Increasing the interfacial packing of amphiphilic species leads to their irreversible interfacial aggregation, which is driven by hydrophobic interactions between protein chains. This aggregation is promoted by the size diversity of amphiphilic species, with smaller species first aggregating at intermediate interfacial packings, followed by larger species at higher packings. The resulting adsorbed layer can be considered as a shell composed of a two-dimensional protein network, irreversibly cross-linked through hydrophobic interactions, which is covalently linked to hyperbranched polysaccharide chains displaying severe conformational changes compared to their bulk structure. This shell is strongly anchored at the oil-water interface by the protein network and provides steric repulsions through the hydrated polysaccharides. Consequently, if such a shell is adequately formed during emulsification, emulsions stabilized by gum arabic may resist extensive mechanical stresses and display a long-term metastability even after drastic environmental changes. This paves the way toward more rational uses of gum arabic as an emulsion stabilizer in formulations and processes.