THE ADSORPTION OF AN ANIONIC SURFACTANT AT THE OIL WATER INTERFACE DURING EMULSION HOMOGENIZATION

Adsorption of sodium dodecylbenzene sulfonate (NaDBS) on the surfaces of dispersed oil globules during homogenization of paraffin oil in water emulsions has been studied. NaDBS concentration was changed over a wide interval comprising critical micelle concentration. For the emulsions homogenized for different time intervals the total quantity and the percentage of NaDBS adsorbed, the amount and number of NaDBS molecules adsorbed per unit inter-facial area, as well as the specific surface area of dispersed phase and the area per emulsifier molecule have been determined.

The amount adsorbed and density of the emulsifier layer, I.e., the area per NaDBS molecule adsorbed on the oil globule surfaces, depend not only on Initial NaDBS concentration but also, on the homogenization time and the homogenization action. This makes a difference between the adsorption behaviour under the conditions of emulsion formation and its subsequent homogenization, and the adsorption behaviour of the emulsifier at a plane quiescent Interface.     

Action of emulsifiers during homogenization of o/w emulsions

Droplet size and size distribution changes at homogenization of paraffin oil emulsions, stabilized by different concentrations of various emulsifiers, were investigated. During homogenization, samples were taken from emulsions and the most frequently occuring diameter, mean droplet diameter and standard deviation (distribution width) were determined. Mathematical relations describing changes of mean diameter and distribution width, as a function of the homogenization period and emulsifier concentration, were derived and applied to the experimental data. Emulsifier efficiencies and capabilities were characterized by physical constants and graphically. Optimal homogenization time interval, optimal emulsifier concentrations and corresponding droplet size distribution parameters were computed.     

Effect of the type of the oil phase on stability of highly concentrated water-in-oil emulsions

The water-in-oil high internal phase emulsions were the subject of the study. The emulsions consisted of a super-cooled aqueous solution of inorganic salt as a dispersed phase and industrial grade oil as a continuous phase. The influence of the industrial grade oil type on a water-in-oil high internal phase emulsion stability was investigated. The stability of emulsions was considered in terms of the crystallization of the dispersed phase droplets (that are super-cooled aqueous salt solution) during ageing. The oils were divided into groups: one that highlighted the effect of oil/aqueous phase interfacial tension and another that investigated the effect of oil viscosity on the emulsion rheological properties and shelf-life. For a given set of experimental conditions the influence of oil viscosity for the emulsion stability as well as the oil/aqueous interfacial tension plays an important role. Within the frames of our experiment it was found that there are oil types characterized by optimal parameters: oil/aqueous phase interfacial tension being in the region of 19–24 mN/m and viscosity close to 3 mPa s; such oils produced the most stable high internal phase emulsions. It was assumed that the oil with optimal parameters kept the critical micelle concentration and surfactant diffusion rate at optimal levels allowing the formation of a strong emulsifier layer at the interface and at the same time creating enough emulsifier micelles in the inter-droplet layer to prevent the droplet crystallization.     

Preparation and Optimization of O/W Emulsions Stabilized by Triglycerol Monolaurate for Curcumin Encapsulation

Curcumin is one of the most studied chemo-preventive agents, which may cause suppression, retardation, or inversion of carcinogenesis. But its application is currently limited because of its poor water-solubility and bioaccessibility. A curcumin O/W emulsion was prepared by high-pressure homogenization, using triglyceride monolaurate as an emulsifier and medium chain triglycerides (MCT) as the oil phase. The effects of emulsifiers, emulsifier concentration, oil type, oil-to-water ratio, and homogenization pressure and processing cycles on the physical stability and droplet size distribution of curcumin-encapsulated O/W emulsions were evaluated in this study. The results showed that the mean droplet size of the O/W emulsions remained remarkably stable during 60 days of storage under both light and dark conditions. Curcumin retentions in O/W emulsions after 60 days of storage under light and dark conditions were 97.9% and 81.6%, respectively. In addition, during the simulated gastrointestinal digestion process, the mean droplet size of the O/W emulsions increased from 260 nm to 2743 nm after incubation with simulated gastric fluid (SGF) for 24 h, while the mean droplet size remained unchanged after incubation with simulated intestinal fluid (SIF). The results displayed negligible changes in curcumin content during incubation with simulated gastrointestinal fluids, indicating that effective protection of curcumin was achieved by encapsulation in the O/W emulsion. It is expected that curcumin will acquire high bioaccessibility and bioavailability when the O/W emulsion is to be used in clinical applications.     

The effects of emulsifier type,phase ratio,and homogenization methods on stability of the double emulsion

The double emulsion technology has a potential effect on the development of diversity and quality of functional foods by means of decreasing oil or salt concentration, encapsulating and controlling release of valuable components. In this study, it was aimed to formulate stable double emulsions to be used in food systems. W1/O ratios of primary emulsions, stabilized by polyglycerol polyricinoleate (PGPR), were designed as 2:8 and 4:6, and (W1/O)/W2 ratios of the double emulsions were used as 2:8 and 4:6. W/O/W phase ratios, homogenization methods applied to primary emulsion (high-speed homogenization, ultrasonic homogenization), and emulsifier types used in W2 phase [sodium caseinate (SC), xanthan gum, lecithin-whey protein concentrate] were used as independent variables. Particle size and distributions, stability, encapsulation efficiency (EE), rheological properties, long-term stability, and morphological properties of the double emulsions were investigated.

The double emulsions prepared with SC and (W1/O)/W2 ratio of 4:6, were found to have the higher stability values, higher apparent viscosity, and lower particle size. High-speed homogenization applied to primary emulsion reduced particle size of the double emulsion and increased apparent viscosity, but did not affect stability and EE of the double emulsions, significantly.     

部分析因法分析油包水型聚乙烯亚胺水溶液/石蜡乳液的稳定性

聚乙烯亚胺(PEI)及其乳状液被广泛用于酶固定化、基因治疗、污水处理等领域。 为提高PEI乳状液的稳定性,促进其应用,本文采用部分析因试验法考察了影响PEI水溶液/石蜡乳状液(W/O)稳定性的主因素和各因素间交互作用。 结果表明,乳化剂用量和PEI的水相质量分数是影响PEI水溶液/石蜡乳液稳定性的主因素。 PEI的水相质量分数和油/水体积比的交互作用最显著。 优化后,制备最稳定的PEI水溶液/石蜡乳状液(W/O)的条件是:m(Span-80):m(Tween-80)=6:1,PEI的水相质量分数为5%,乳化剂用量为0.07 g/mL,V(石蜡):V(PEI水溶液)=6:4,均质时间为3 min,转速为6000 r/min。 在优化条件下制备的PEI水溶液/石蜡乳状液在放置7 d后乳状液的外观无明显变化,这表明所制备的PEI水溶液/石蜡乳状液具有良好的稳定性。     

Effect of Emulsifier Type on the Characterization of O/W Emulsions Using a Spectroscopy Technique

The droplet size distribution (DSD) of emulsions is the result of two competitive effects that take place during emulsification process, i.e., drop breakup and drop coalescence, and it is influenced by the formulation and composition variables, i.e., nature and amount of emulsifier, mixing characteristics, and emulsion preparation, all of which affect the emulsion stability. The aim of this study is to characterize oil-in-water (O/W) emulsions (droplet size and stability) in terms of surfactant concentration and surfactant composition (sodium dodecyl benzene sulphonate (SDBS)/Tween 80 mixture). Ultraviolet-visible (UV-vis) transmission spectroscopy has been applied to obtain droplet size and stability of the emulsions and the verification of emulsion stability with the relative cleared volume technique (time required for a certain amount of emulsion to separate as a cleared phase). It is demonstrated that the DSD of the emulsions is a function of the oil concentration and the surfactant composition with higher stability for emulsions prepared with higher SDBS ratio and lower relative cleared volume with the time. Results also show that smaller oil droplets are generated with increasing Tween 80 ratio and emulsifier concentration.     

Formulation,Rheology, and Hypolepidemic Activity of Vegetable Oil-Based Eggless and Low-Fat Food Emulsions

Common edible oils such as almond, safflower, soybean, and mustard oil were formulated in the form of eggless and low-fat oil-in-water emulsions using a blend of nonionic emulsifier Glycerol monostearate and amphoteric emulsifier soy lecithin. The emulsion parameters such as vegetable oil, emulsifier, additive content and hydrophilic-lipophilic balance number of emulsifier were optimized. The storage stability of formulated emulsions was monitored under accelerated storage stability conditions for six months. Rheological characterization of stable emulsion revealed pseudoplastic flow behavior. In vivo hypolepidemic activity of formulated emulsions in rats showed considerable reduction in total cholesterol and triglyceride level after 14 days as compared with the marketed product. The almond oil emulsion is found superior than safflower oil emulsion.     

Long-term stability of emulsion based on rose oil

This paper was aimed at determining the parameters responsible for the long-term stability of emulsions. Compositions of six emulsions with different amounts of emulsifier and thickener were developed according to the authors’ own specifications and requirements of KT-Skor software (based on Kleeman’s method). Physical properties of the emulsions were evaluated (determination of emulsion type, structure of emulsion, stability tests, viscosity, average particle size, and dispersity index). The results obtained indicate that the emulsion containing 10?g of rose oil and 0.2?g of thickener exhibited the highest stability.     

Formulating Neem Oil Emulsion as Potent Agrochemicals Using a Binary Emulsifier System

Neem oil is a natural pesticide and has excellent insecticidal properties. Hence, in this study the efforts have been made to formulate the Neem oil emulsions which would be used as agrochemicals. In order to formulate stable Neem oil emulsions, a binary emulsifier system of Hydol-6 (Polyoxyethylene Alkyl Ether-6 moles of ethylene oxids) and Hydol-10 (Polyoxyethylene Alkyl Ether-10 moles of ethylene oxids) were employed. Stability of Neem oil emulsions as a function of concentration of Neem oil, Hydol-6, Hydol-10, the amount of water, homogenization speed, and homogenization time was studied in depth. Apart from this, it was observed that the nature of water also affects the stability of the emulsions. The concentration of Neem oil in the stable emulsions was also found to exhibit the varying effects on the properties like dispersibility, spreading power, and droplet size of the emulsions. Larvasidal effects of stable Neem oil emulsions were examined.     

EFFECT OF PREMIX CONDITION,SURFACTANT CONCENTRATION,AND OIL LEVEL ON THE FORMATION OF OIL-IN-WATER EMULSIONS BY HOMOGENIZATION

Oil-in-water emulsions were prepared on a homogenizer from good premixes and poor premixes. The quality of the emulsions was determined by measuring the droplet size distribution using spectroturbidimetry. A good premix to the homogenizer produces a better emulsion than a poor premix. Premix conditions become less important when the concentration of emulsifier is increased in relation to the amount of oil. Increasing oil concentration results in a poorer final emulsion. Large amounts of emulsifier negate the advantage of using the homogenizer, but greater mechanical energy input can compensate for reduced emulsifier concentration, a cost saving when formulating an emulsion.     

Effects of emulsifier type and environmental stress on the stability of curcumin emulsion

The objective of this study was to investigate the effects of environmental stress and emulsifier types on the stability of curcumin emulsions. Results showed that Lecithin and Tween 80 presented good emulsifying capacity. The Tween 80 emulsion was the most stable among the four emulsions.

The particle sizes of Tween 80 and whey protein emulsion were relatively smaller than gum arabic and lecithin. Extensive droplet aggregation appeared in whey protein-stabilized emulsions when the pH was approximately isoelectric point (pI) with salt concentration >200?mM. Lecithin emulsion was unstable when pH?≤?6 with salt concentration >100?mM. There was little impact of pH and ionic strength on gum arabic and Tween 80 emulsions. All of the emulsions were stable at temperatures from 30 to 90°C in the absence of salt. These results help characterize the emulsifying and stabilizing abilities of emulsifier types intended for applications in the food industry.     

Emulsification of Vegetable Oils using a Blend of Nonionic Surfactants for Cosmetic Applications

Sunflower oil and sesame oil contain fairly high percentage of tocopherols and tocotrienols. These oils were emulsified by using a combination of non‐ionic surface‐active agents viz. Span‐80 and Tween‐20 surfactants to get cosmetic emulsions. Stability of the emulsions was enhanced by using natural polymer additives. The effect of various parameters such as pH, oil content, emulsifier content, HLB of blend of emulsifier concentration of additives and temperature on the stability of cosmetic emulsion was studied. These emulsions are “skin compatible” being stable at neutral pH. Xanthan gum was found to be the most effective additive as compared to the other natural polymers. The emulsions showed a “pseudoplastic” flow behavior.     

利用酯化淀粉和油酸甲酯制备高效氯氟氰菊酯水乳剂

以辛烯基琥珀酸淀粉钠和油酸甲酯分别为替代乳化剂和溶剂,采用浓缩乳化法制备了高度稳定的2.5％高效氯氟氰菊酯水乳剂,通过测定乳液油滴粒径分布,结合乳液外观研究了乳化方法、预处理液中辛烯基琥珀酸淀粉钠质量分数、转速和剪切时间等工艺条件对乳液稳定性的影响.研究结果表明,辛烯基琥珀酸淀粉钠对油酸甲酯具有较好乳化效果,以其为乳化剂可制备高度稳定的2.5％高效氯氟氰菊酯水乳剂,油滴平均粒径在1.2 μm左右,且加速试验[即(54±2)℃密封14 d]和常温储存6个月后平均粒径仅增长了0.1～0.3μm,外观无变化;采用浓缩乳化法且预处理液中辛烯基琥珀酸淀粉钠质量分数在15％～25％时乳液稳定性较好,提高转速可降低油滴平均粒径,但对乳液均一性无显著影响,延长剪切时间对油滴平均粒径影响不大,但有利于提高乳液均一性;辛烯基琥珀酸淀粉钠为乳化剂制备的高效氯氟氰菊酯水乳剂稳定性优于常规水乳剂.     

Optimization of Oil-in-Water Emulsion Stability: Experimental Design,Multiple Light Scattering,and Acoustic Attenuation Spectroscopy

To find an optimal formulation of oil-in-water (O/W) emulsions (φ_o = 0.05), the effect of emulsifier nature and concentration, agitation speed, emulsifying time, storage temperature and their mutual interactions on the properties and behavior of these dispersions is evaluated by means of an experimental design (Nemrodw software). Long-term emulsion stability is monitored by multiple light scattering (Turbiscan ags) and acoustic attenuation spectroscopy (Ultrasizer). After matching surfactant HLB and oil required HLB, a model giving the Sauter diameter as a function of emulsifier concentration, agitation speed and emulsification time is proposed. The highest stability of C₁₂E₄-stabilized O/W emulsions is observed with 1% emulsifier.     

Effect of hydrophobic modification of hydroxypropyl methylcellulose on silicone oil emulsions

To study the effect of hydrophobic modification of the emulsifier on the relationship between emulsion stability and polymer emulsifier concentration, silicone oil emulsions were prepared using hydroxypropyl methylcellulose (original HPMC) and HPMC stearoxy ether (hydrophobic HPMC) at concentrations around their overlap concentrations. Both HPMC types completely emulsified the silicone oil. However, the volume fraction of silicone oil in the emulsion prepared using hydrophobic HPMC was less than that that by the original HPMC, and the average oil droplet size in the former emulsion was less than that in the latter emulsion. Increasing HPMC concentration led to increase in both the amount of adsorbed polymer emulsifier and the storage moduli in the linear region, irrespective of which HPMC was used. Stress-strain sweep curves obtained by a rheo-optical method showed that emulsions stabilized by the hydrophobic HPMC flowed slowly, even beyond the yield stress, whereas emulsions prepared using the original HPMC flowed quickly beyond the yield stress. The storage moduli of the emulsions prepared by the hydrophobic HPMC were larger than those prepared using the original HPMC.     

A PHENOMENOLOGICAL MODEL FOR THE SURFACTANT INTERFACIAL CONFIGURATION IN A CONCENTRATED PARENTERAL FLUOROCARBON EMULSION

40% V/V Bis(Perfluorobutyl)ethene (F44E) emulsions were manufactured using 1-6% W/V purified egg yolk lecithin (EYL) as emulsifier. Knowing the surfactant molecular cross sectional area, the volume of the discontinuous phase and the amount of surfactant adsorbed at the interface as a function of its concentration in the emulsion, the theoretical surface volume diameter, D, for either a mono or a bilayer for different EYL concentrations in the emulsions were calculated. These were compared with experimentally determined droplet diameters obtained from centrifugal sedimentation followed by densitometry. Within the parameters used in this study, the results suggest the existence of an anisotropic interfacial film around the F44E droplets whose saturation is emulsifier concentration dependant     

Characterization of Monomer Emulsions in Terms of Droplet Size and Stability: Effect of Emulsifier Concentration

In emulsification processes, the estimation of the droplet size distribution is important data not only because it is linked with the manufacturing process, but also because it is an important parameter affecting the emulsion stability. The aim of this research is to use the ultraviolet-visible transmission spectrum as a tool for emulsion characterization (droplet size and stability) to be a function of monomer concentration, and to verify of emulsion stability using the volume of separated phase's technique. Both techniques are applied to monomer emulsions as a function of emulsifier concentration. Results show correlations between droplet size measurements and stability of emulsions using the spectroscopy technique; results were also found to be in agreement using the cleared volume method.     

Clay-based colloidosomes

Poly(ethylene imine) (PEI) has been adsorbed onto the surface of Laponite clay nanoparticles from aqueous solution at pH 9 in order to produce an efficient hybrid Pickering emulsifier. This facile protocol allows formation of stable sunflower oil-in-water Pickering emulsions via homogenization at 12,000 rpm for 2 min at 20 °C. The effect of varying the extent of PEI adsorption on the Pickering emulsifier performance of the surface-modified Laponite is investigated for five oils of varying polarity using aqueous electrophoresis, thermogravimetric analysis, and laser diffraction studies. A minimum volume-average emulsion droplet diameter of around 60 μm was achieved at a Laponite concentration of 0.50% by mass when utilizing a PEI/Laponite mass ratio of 0.50. Such emulsions proved to be very stable toward droplet coalescence over time scales of months, although creaming is observed on standing within days due to the relatively large droplet size. These conditions correspond to submonolayer coverage of the Laponite particles by the PEI, which ensures that there is little or no excess PEI remaining in the aqueous continuous phase. This situation is confirmed by visual inspection of the underlying aqueous phase of the creamed emulsion when using fluorescently labeled PEI. These Pickering emulsions are readily converted into novel clay-based colloidosomes via reaction of the primary and/or secondary amine groups on the PEI chains adsorbed at the Laponite surface with either oil-soluble poly(propylene glycol) diglycidyl ether or water-soluble poly(ethylene glycol) diglycidyl ether cross-linkers. These colloidosomes were sufficiently robust to survive the removal of the internal oil phase after washing with excess alcohol, as judged by both optical and fluorescence microscopy. However, dye release studies conducted with clay-based colloidosomes suggest that these microcapsules are highly permeable and hence do not provide an effective barrier for retarding the release of small molecules.     

Ultrasound Emulsification—An Overview

Fundamentals and applications of ultrasound emulsification are reviewed. The importance of cavitation is stressed, as also is power input to the multiphase fluid. The influence of surfactants, polymeric stabilizers, temperature, pressure, and ultrasonic parameters such as frequency, residence time, acoustic intensity, and energy density are described. The effects of other physicochemical parameters such as emulsifier concentration, disperse phase volume fraction, and viscosity are discussed. Applications to both water-in-oil and oil-in-water emulsions are discussed.