Impact on Morphological Characterization and Emulsion Stability of Lactoferrin–Beet Pectin Electrostatic Complexes

Interfacial protein–polysaccharide complexes can be utilized in emulsion-based delivery system and contained functional component or medical ingredient. In the present work, the interaction of lactoferrin (LF, 0.2 wt%) with beet pectin (BP, 0–0.15 wt%) was researched in aqueous solutions at different pH (2–9) and ionic strength (0–800 mM) to provide the information about properties of complexes. A simulative environment was created to explore the optimal concentration of BP to formulate LF-coated stabilized emulsion and how the emulsion responded to the changing environmental pH (2–9) and ionic strength (0–500 mM). Particle size, particle distribution index, zeta-potential, turbidity, Turbiscan stability index,, and peak thickness were used to characterize the physical stability of emulsions. The confocal laser scanning microscopy was used to derive the microscopy images of droplets. The results indicated that 0.4 wt% was the optimal concentration to formulate emulsions, and the LF-BP-coated bilayer emulsion has a preferable stability in more extensive range than the pure LF-stabilized emulsions under the environmental stresses through electrostatic interactions. The results of this study will play an important role in facilitating the utilization of LF-BP complexes as an emulsifier in the development of incorporating functional component or medical ingredient into commercial products.     

Influence of droplet characteristics on the formation of oil-in-water emulsions stabilized by surfactant-chitosan layers

The objective of this study was to establish the optimum conditions for preparing stable oil-in-water emulsions containing droplets surrounded by surfactant-chitosan layers. A primary emulsion containing small droplets (d32 approximately = 0.3 microm) was prepared by homogenizing 20 wt% corn oil with 80 wt% emulsifier solution (20 mM SDS, 100 mM acetate buffer, pH 3) using a high-pressure valve homogenizer. The primary emulsion was diluted with chitosan solutions to produce secondary emulsions with a range of oil and chitosan concentrations (0.5-10 wt% corn oil, 0-1 wt% chitosan, pH 3). The secondary emulsions were sonicated to help disrupt any droplet aggregates formed during the mixing process. The electrical charge, particle size, and amount of free chitosan in the emulsions were then measured. The droplet charge changed from negative to positive as the amount of chitosan in the emulsions was increased, reaching a relatively constant value (approximately +50 mV) above a critical chitosan concentration (C(Sat)), which indicated that saturation of the droplet surfaces with chitosan occurred. Extremely large droplet aggregates were formed at chitosan concentrations below C(Sat), but stable emulsions could be formed above C(Sat) provided the droplet concentration was not high enough for depletion flocculation to occur. Interestingly, we found that stable multilayer emulsions could also be formed by mixing chitosan with an emulsion stabilized by a nonionic surfactant (Tween 20) due to the fact the initial droplets had some negative charge. The information obtained from this study is useful for preparing emulsions stabilized by multilayer interfacial layers.     

Effect of molecular weight and degree of deacetylation of chitosan on the formation of oil-in-water emulsions stabilized by surfactant-chitosan membranes

The objective of this study was to establish the influence of polyelectrolyte characteristics (molecular weight and charge density) on the properties of oil-in-water emulsions containing oil droplets surrounded by surfactant-polyelectrolyte layers. A surfactant-stabilized emulsion containing small droplets (d32 approximately 0.3 microm) was prepared by homogenizing 20 wt% corn oil with 80 wt% emulsifier solution (20 mM SDS or 2.5 wt% Tween 20, 100 mM acetate buffer, pH 3) using a high-pressure valve homogenizer. This primary emulsion was then diluted with various chitosan solutions to produce secondary emulsions with a range of chitosan concentrations (3 wt% corn oil, 0-1 wt% chitosan). The influence of the molecular characteristics of chitosan on the properties of these emulsions was examined by using chitosan ingredients with different molecular weights (MW approximately 15, 145, and 200 kDa) and degree of deacetylation (DDA approximately 40, 77, and 92%). The electrical charge and particle size of the secondary emulsions were then measured. Extensive droplet aggregation occurred when the chitosan concentration was below the amount required to saturate the droplet surfaces, but stable emulsions could be formed at higher chitosan concentrations. The zeta-potential and mean diameter (d32) of the particles in the secondary emulsions was not strongly influenced by chitosan MW, however the chitosan with the lowest DDA (40%) produced droplets with smaller mean diameters and zeta-potentials than the other two DDA samples examined. Interestingly, we found that stable multilayer emulsions could be formed by mixing medium or high MW chitosan with an emulsion stabilized by a non-ionic surfactant (Tween 20) due to the fact the initial droplets had some negative charge. The information obtained from this study is useful for preparing emulsions stabilized by multilayer interfacial layers.     

Influence of Interfacial Engineering on Stability of Emulsions Stabilized with Soy Protein Isolate

The objectives of this study were to examine the influence interfacial composition on environmental stresses stability of oil in water emulsions. An electrostatic layer-by-layer deposition method was used to create the multilayered interfacial membranes with different compositions: (i) primary emulsion (Soy protein Isolate); (ii) secondary emulsion (Soy protein Isolate – OSA-starch); (iii) tertiary emulsion (Soy protein isolate – OSA-starch – chitosan). Fourier transform-infrared (FTIR) and scanning electron microscopy (SEM) results confirmed the adsorption of charged polyelectrolyte onto oppositely charge polyelectrolyte-coated oil droplets. The stability of primary, secondary, and tertiary emulsions to thermal treatment (30 min at 30–90°C), pH (3–7) and NaCl (0–500 mM) were determined using ζ-potential, particle diameter, and microstructure analysis. Primary emulsions were unstable at pH 4–7, salt concentrations, and thermal treatments. Secondary emulsions were stable to creaming and droplet aggregation at pH 3–5, at ≤50 mM NaCl, and unstable at thermal treatments, whereas tertiary emulsions were stable at all salt concentrations, thermal treatments, and at pH 3–6. These results demonstrate that these polymers can be used to engineer oil in water emulsion systems and improve the emulsion stability to environmental stresses.     

Influence of environmental stresses on stability of oil-in-water emulsions containing droplets stabilized by beta-lactoglobulin-iota-carrageenan membranes

An oil-in-water emulsion (5 wt% corn oil, 0.5 wt% beta-lactoglobulin (beta-Lg), 0.1 wt% iota-carrageenan, 5 mM phosphate buffer, pH 6.0) containing anionic droplets stabilized by interfacial membranes comprising of beta-lactoglobulin and iota-carrageenan was produced using a two-stage process. A primary emulsion containing anionic beta-Lg coated droplets was prepared by homogenizing oil and emulsifier solution together using a high-pressure valve homogenizer. A secondary emulsion containing beta-Lg-iota-carrageenan coated droplets was formed by mixing the primary emulsion with an aqueous iota-carrageenan solution. The stability of primary and secondary emulsions to sodium chloride (0-500 mM), calcium chloride (0-12 mM), and thermal processing (30-90 degrees C) were analyzed using zeta-potential, particle size and creaming stability measurements. The secondary emulsion had better stability to droplet aggregation than the primary emulsion at NaCl 相似文献   

Effects of electrolyte concentration and pH on the coalescence stability of beta-lactoglobulin emulsions: experiment and interpretation

Experimental results are presented about the effects of ionic strength and pH on the mean drop-size after emulsification and on the coalescence stability of emulsions, stabilized by a globular protein beta-lactoglobulin (BLG). The mean drop-size is determined by optical microscopy, whereas the coalescence stability is characterized by centrifugation. In parallel experiments, the zeta-potential and protein adsorption on drop surface are determined. The experiments are performed at two different BLG concentrations, 0.02 and 0.1 wt%. The electrolyte concentration in the aqueous phase, C(EL), is varied between 1.5 mM and 1 M, and pH is varied between 4.0 and 7.0. The experiments show that the mean drop-size after emulsification depends slightly on C(EL), at fixed protein concentration and natural pH = 6.2. When pH is varied, the mean drop-size passes through a maximum at fixed protein and electrolyte concentrations. A monolayer protein adsorption is registered in the studied ranges of C(EL) and pH at low BLG concentration of 0.02 wt%. In contrast, a protein multilayer is formed at higher BLG concentration, 0.1 wt%, above a certain electrolyte concentration (C(EL) > 100 mM, natural pH). The experimental results for the emulsion coalescence stability are analyzed by considering the surface forces acting between the emulsion drops. The electrostatic, van der Waals, and steric interactions are taken into account to calculate the barriers in the disjoining pressure isotherm at the various experimental conditions studied. The comparison of the theoretically calculated and the experimentally determined coalescence barriers shows that three qualitatively different cases can be distinguished. (1) Electrostatically stabilized emulsions, with monolayer protein adsorption, whose stability can be described by the DLVO theory. (2) Sterically stabilized emulsions, in which the drop-drop repulsion is created mainly by overlapping protein adsorption multilayers. A simple theoretical model is shown to describe emulsion stability in these systems. (3) Sterically stabilized emulsions with a monolayer adsorption on drop surface.     

Physicochemical properties and stability of the emulsion prepared with various emulsifiers for enteral nutrition preparations

The mean diameter of emulsion droplets prepared using three different emulsifiers (egg yolk lecithin alone, egg yolk lysolecithin alone, and a mixture of egg yolk lecithin and lysolecithin) was investigated. Considering the nasal administration of enteral nutrients or that through gastric/jejunal fistulae, the stability of each emulsion with artificial gastric fluid (pH 1.2) or intestinal fluid (pH 6.8) was investigated. When adding artificial intestinal fluid, all emulsions prepared with various emulsifiers (egg yolk lecithin, egg yolk lysolecithin, soybean lecithin, soybean lysolecithin, DK ester^® F-140, and Sunsoft^® A-141E) were stable. On the other hand, when adding artificial gastric fluid, emulsions prepared with egg yolk lysolecithin or Sunsoft^® A-141E were stable, but there was a reduction in the stability of emulsions prepared with the other emulsifiers, with an increase in the particle size. Based on these results, we prepared an emulsion using a natural component-derived emulsifier for enteral nutrients, egg yolk lysolecithin, and clarified the pH change-related stability of the emulsion.     

Physical Stability and the Droplet Distribution of Rice Oil–in–Water Emulsion

The objective of the current study was to evaluate long-term stability of emulsions with rice oil by assessing their physical properties. For this purpose, six emulsions were prepared, their stability was examined empirically, and the most correctly formulated emulsion composition was determined using a computer simulation. Variable parameters (oil and thickener content) were indicated with optimization software based on Kleeman's method. Synthesized emulsions were studied by numerous techniques involving determination of particle size and distribution of emulsion, optical microscopy, viscosity, and novelty analysis—Turbiscan test.

The emulsion containing 50 g of oil and 1.2 g of thickener had the highest stability. Empirically determined parameters proved to be consistent with the results obtained using the computer software. The computer simulation showed that the most stable emulsion should contain from 35.93 to 50 g of oil and 0.94 to 1.19 g of thickener. The computer software based on Kleeman's method proved to be useful for fast optimization of the composition and providing parameters of stable emulsion systems. Forming emulsions based on rice oil is a chance to introduce a new, interesting representative of functional food as well as a cosmetic product.     

Making Oil-in-Water Emulsions by Ultrasound and Stability Evaluation Using Taguchi Method

Oil-in-water emulsions containing 40% wt sunflower oil were prepared using ultrasound with the frequency of 30 kHz. The effect of sonication time, stabilizer concentration, NaCl, and pH of aqueous phase on the stability and particle size distribution of samples was investigated using Taguchi statistical method. The results showed that increasing sonication time decreased mean diameter of droplets and narrowed droplet size distribution curves. NaCl was found to have a positive effect on the stability of samples. More stable emulsions were prepared when using xanthan and pectin together at pH 4.     

Behavior and Stability of Naphthenic Acid/Naphthenate Stabilized Emulsions. Mixed C80-Tetraacid and Stearic Acid Stabilization

Previous studies have focused on monomeric naphthenic acids and their ability to stabilize emulsions, but little has been reported on C80-tetraacids and their ability to function as an emulsifier. In this article, we report on the chemistry of the C80-tetraacids as an emulsion stabilizer and also on the role this acid has in mixed monoacid-tetraacid systems. The study focuses on the type of emulsion formed and the stability of these emulsions with respect to water cut, pH, salinity of the water phase, and type of counterion. Interfacial behavior and the electrostatic properties of the emulsion were studied in order to determine which of the acids were present at the interface and which of the acids gave the largest contribution to the emulsion stability. It was found that C80-tetraacids form only O/W emulsion under the conditions studied. Addition of monoacid to the system did not change the type of emulsion formed. Highest stability was seen for emulsions containing both monoacid and tetraacids. When adding NaCl a phase inversion from O/W to W/O emulsion appeared around a concentration of 2 wt% of NaCl.     

Adsorption of Corrosion Inhibitors onto Iron Carbonate (FeCO3) Studied by Zeta Potential Measurements

The adsorption of cetyl trimethyl ammonium bromide (CTAB) and two commercial inhibitor base chemicals, an oleic imidazoline salt (OI) and a phosphate ester (PE), onto iron carbonate (FeCO₃), was studied by zeta potential measurements in a 0.1 wt% sodium chloride (NaCl) solution under 1 bar CO₂ at 22°C, in the absence and presence of a refined low-aromatic oil. The zeta potential of oil-in-water emulsion droplets was also determined. Surface tension of 0.1 wt% and 3 wt% brines was measured as a function of inhibitor concentration. The isoelectric point was pH 6.0 in the 0.1 wt% NaCl solution under 1 bar CO₂. The results show that all three inhibitor compounds adsorbed onto the iron carbonate particles both at pH 4.0 and pH 6.0. Adsorption on both negatively charged surfaces and surfaces with no charge were thus found for all inhibitors. The addition of oil had no significant effect on the measured zeta potential on iron carbonate particles.     

Oil-in-water emulsions stabilized by whey protein aggregates: Effect of aggregate size,pH of aggregation and emulsion pH

Oil-in-water emulsions (60% oil (w/w)) were prepared using whey protein aggregates as the sole emulsifying agent. The effects of whey protein aggregate size (the diameter between 0.92 and 10.9?µm), the pH of emulsions (4–8.6) and storage time on physical properties, droplet size, and stability of emulsions were investigated. The results indicate that increment of whey protein aggregate size caused an increase in the firmness, droplet size, and viscosity of emulsions, and also a decrease in the emulsion creaming. The emulsion viscosity, firmness, and droplet size were reduced by increasing the emulsion pH; however, the creaming process was accelerated. Viscosity, creaming, and droplet size of emulsions were increased slightly during 21 days storage at 40°C.     

Oxidative stability and effect of stress factors on flaxseed oil-in-water emulsions stabilized by sodium caseinate–sodium alginate–chitosan interfacial membrane

The susceptibility of heart healthy ω-3 fatty acids to lipid oxidation has hindered its incorporation into healthful foods and beverages. In this study, plant-based flaxseed oil rich in ω-3 fatty acids were dispersed into primary, secondary and tertiary emulsion system. A primary emulsion containing sodium caseinate-stabilized cationic droplets was prepared by homogenizing flaxseed oil as oil phase and sodium caseinate solution as the aqueous phase in an ultrasonicator. A secondary emulsion comprising of sodium caseinate–sodium alginate anionic droplets were produced by diluting appropriate primary emulsion with alginate solution. Further, a tertiary emulsion composed of sodium caseinate–sodium alginate–chitosan-coated cationic droplets was produced by diluting secondary emulsion with chitosan solution. The resistance of primary, secondary and tertiary emulsions with the same lipid concentration to destabilization by thermal treatment (30–90 °C for 30 min), sodium chloride addition (≤70 mM NaCl) and oxidative degradation (hydroperoxide concentration and TBARS) was determined. The results showed that secondary emulsions could resist variation in environmental stresses of salt and heat as well as protect the oil phase from decomposition better than primary and tertiary emulsions. Interfacial engineering could be used to design emulsion system with desirable characteristics.     

离子/非离子复合型亲水单体的合成及高稳定性聚氨酯乳液的研究

本文合成了离子 非离子复合型亲水单体 (K6 0 0 ) ,并以K6 0 0、IPDI、聚酯二元醇为原料制备了自乳化聚氨酯乳液 .考察了K6 0 0对乳液外观、粒径、粘度、冻融稳定性、高温稳定性、抗电解质能力、pH值稳定性等性质的影响 .结果显示 ,以K6 0 0制得的乳液具有优异的综合稳定性 ,- 2 0℃ ,18h冻融 5次以上仍然稳定 ;可以耐受 80℃的长期高温 ;可与 10 %NaCl溶液以任意比例混合 ;可在pH =1～ 14的范围内性质稳定 ,说明离子 非离子复合型亲水单体对体系的综合稳定性具有很大的作用     

Influence of Polyglycerol Polyricinoleate and Biopolymers on Physical Properties and Encapsulation Efficiency of Water-in-Oil-in-Water Emulsions Containing Mango Seed Kernel Extract

The influence of polyglycerol polyricinoleate (PGPR) and biopolymers (gelatin and sodium alginate) on the stabilization of water-in-oil (W/O) emulsions was investigated to improve the encapsulation efficiency (EE) of water-in-oil-in-water (W/O/W) emulsions containing mango seed kernel extract (MSKE). The physical properties and EE of the emulsions were found to depend more strongly on PGPR than on biopolymers. High EE values of MSKE were obtained when W/O emulsions stabilized by 4–8 wt% PGPR were incorporated with 1–5 wt% gelatin, or by 6–8 wt% PGPR incorporated with 0.5–1.5 wt% sodium alginate in the inner aqueous phase.     

Synthesis and surface properties of self-crosslinking core–shell acrylic copolymer emulsions containing fluorine/silicone in the shell

Stable emulsions of a core–shell acrylic copolymer (non-crosslinkable V0, and crosslinkable V2, V4, V6, and V8, where the numbers indicate the wt% of crosslinking agent based on the total acrylate monomer content) containing butyl acrylate (BA, 45 wt%), glycidyl methacrylate (GMA, 45 wt%), heptadecafluorodecyl methacrylate (PFA, 10 wt%), and various contents of crosslinking agent (vinyltriethoxysilane, VTES) were synthesized using a three-stage seeded emulsion polymerization process with a small amount of surfactant. The average particle size and viscosity of emulsions increased significantly with increasing VTES content. This study examined the effects of the VTES content on the surface/mechanical properties of self-crosslinked copolymer film samples containing a fixed acrylate monomer content to find the optimum VTES content. XPS showed that the film–air surface of the copolymer samples had a higher fluorine/silicone content than the film–dish interface. The tensile strength/modulus, thermal stability, and two Tgs (α and β Tgs) of the film samples increased significantly with increasing VTES content. The contact angle of the film samples increased with increasing VTES content up to approximately 6 wt%, and then decreased slightly. The optimum VTES content was approximately 6 wt% based on the total acrylate monomer content to obtain a high water/oil repellent coating material (V6) with the highest water/methylene iodide-contact angles (118.2°/81.8°) and lowest surface energy (18.4 mN/m).     

Effects of ascorbic acid on the physiochemical,rheological, and antioxidant properties of citrus essential oil-based emulsion stabilized by pectin

The present study was conducted to enhance the peel of Citrus sinensis (sweet orange) by using their essential oils (EOs) as a potential source of natural bioactive molecules. EOs were obtained by hydrodistillation and their chemical profile was determined through GC-MS analysis. O/W EO emulsions were prepared using pectin as biopolymer emulsifier at different proportions, including different amounts of ascorbic acid (0, 0.5, and 1% w/w). The effect of pectin and ascorbic acid concentrations on the stability and rheological behavior of emulsions was investigated. It was found that adding ascorbic acid to the appropriate concentration of pectin enhances the interfacial membranes surrounding the oil droplets and decreases the droplet sizes. As a result both the viscoelastic modules and the resulting viscosity of emulsions increase leading to an improvement of their stability. Antioxidant activity of orange EO emulsion in combination with ascorbic acid was found significantly higher than that without ascorbic acid, and higher than that of individual components. Overall, this study would be helpful in developing more effectives systems with promising physical and antioxidant characteristics for the preservation of foods.     

Na-caseinate/oil/water systems: emulsion morphology diagrams

The concentrated (dispersed phase 50-70 wt%) composition space of Na-caseinate, a family of milk proteins, stabilised emulsions was investigated for three different oils: soybean oil, palm olein and tetradecane with pH 6.8 phosphate buffer continuous phase. The variation of emulsion stability and microstructure were explored using static light scattering, diffusion nuclear magnetic resonance, cryo-scanning electron microscopy, rheology and the time varying macroscopic phase separation of the emulsions. For soybean oil and palm olein a rich diversity of emulsion microstructures and stabilities are realised. Five emulsion domains, each having a different microstructure and macroscopic stability have been identified within the composition space probed. For the lowest concentrations of emulsifier bridging flocculation is evident and emulsions are of low stability. Increasing Na-caseinate concentration leads to an increased stability and the existence of distinct individual oil droplets, visualised using cryo-scanning electron microscopy. Further increases in Na-caseinate concentration reduce emulsion stability due to depletion flocculation. Na-caseinate self-assembly is then initiated. At sufficiently high Na-caseinate and/or oil concentrations the continuous phase of the emulsion is a three-dimensional protein network and emulsion stability is again enhanced. At the limits of the emulsion composition space a gel-like paste is formed. The diversity of emulsion microstructure is reduced when tetradecane is the discrete phase. Na-caseinate self-assembly is limited and there is no evidence for formation of a protein network.     

Further Investigation into the Stability of Water-in-Crude Oil Emulsions Formed in Burgan Oilfield: Effect of Toluene,Resins to Asphaltenes Ratio,and Surfactant

Factors controlling the formation and stabilization of water-in-crude oil (w/o) emulsions in oil fields are of great concern to the petroleum industry for the economic development of underground oil reservoirs. Controlling and minimizing the formation of w/o emulsions and demulsification of water from emulsions are also important for environmental development. Because of its importance, the mechanisms, formation, and stability of w/o emulsions have received considerable attention. This article deals with some of the factors responsible for the formation and stabilization of w/o emulsions formed in Burgan oil field in Kuwait. Some of the factors investigated in this study are the naturally occurred surface active components of crude oils such as asphaltenes and resins. Stability of emulsion samples with resins to asphaltenes ratio (R/A) contents of 3, 5, 9, 12, and 20 has been studied. It was found that Emulsion tightness is correlated with resins to asphaltene content of the sample. As the R/content increases the emulsion becomes unstable. The effect of additives such as toluene and dodecyle benzene sulfonic acid (DBSA) on the stability of various emulsion samples collected from oil field are also reported. A 2 wt% of DBSA was found to resolve all the water from emulsion samples collected from Burgan oilfield.     

Influence of Interfacial Rheological Properties on Stability of Asphaltene-Stabilized Emulsions

A series of oscillating droplet measurements have been performed on asphaltenes at the oil/water interface, in order to correlate the interfacial rheological behavior to their ability to stabilize emulsions. In the concentration sweep, the elastic modulus goes through a maximum around an asphaltene concentration of 0.05–0.10 g/l. This behavior was not in good correspondence with emulsion stability, which increased consistently from low to high concentrations. The decrease above 0.10 g/l was most likely an effect of diffusion of asphaltenes in the bulk to the interface, which became more significant at higher bulk concentrations. The rheology data as a function of concentration has been fitted to Butler's surface equation of state and the Lucassen–van den Tempel model. A decent correlation was found between emulsion stability and elasticity for both the effect of solvent aromaticity and pH. The elastic modulus displayed a gradual increase when xylene was mixed with heptane as the solvent, as was seen with emulsion stability. This was not caused by a significant increase of the adsorbed amount of asphaltene at the interface, as shown by a quartz crystal microbalance (QCM), but a more efficient reorganization of the already adsorbed asphaltenes. The ability asphaltenes displayed in stabilizing emulsions was significantly increased at both low and high pH, according to a previous study. The elastic modulus, on the other hand, only showed a very weak increase at pH 2, but a better correlation with emulsion stability above pH 8. From this it would appear that the dissociation of acid groups in the asphaltene structure at high pH has a bigger impact on the interfacial activity than the protonation of bases at low pH, while their effect on emulsion stability was the same.