Characterization of different double-emulsion formulations based on food-grade emulsifiers and stabilizers

This study focused on the preparation and characterization of water-in-oil-in-water (W1/O/W2)-type double emulsions designed by food-grade emulsifiers and stabilizers. The primary objective of this study was to compare different emulsion formulations in terms of droplet size, rheology, and stability and to reduce the amount of polyglycerol poliricinoleate (PGPR). To achieve these goals, PGPR and a PGPR–lecithin blend were utilized in the formation of the primary phase (W1/O), while varying concentrations of guar gum (GG) and gum tragacanth (GT) incorporated in the secondary water phase (W2). Shear thinning behavior was observed for all emulsion formulations. Sauter mean diameters of the emulsions prepared with PGPR as a hydrophobic emulsifier ranged between 30?µm and 75?µm, while those prepared with the PGPR–lecithin blend varied between 25?µm and 85?µm based on the first day’s measurements. In emulsions with the PGPR–lecithin blend, the smallest droplet size was obtained when the GG–GT blend was incorporated in the external aqueous phase. Moreover, GG–GT blends had high consistency coefficients and high apparent viscosity values. It was also observed that PGPR–lecithin containing emulsions were more stable.     

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.     

PREPARATION OF CLOUDY COCONUT OIL EMULSIONS CONTAINING DISPERSED Ti02 USING ATOMIZER

Food Grade Rutile TiO₂ was dispersed in coconut oil with the help of hydrophobic emulsifiers such as sorbitan esters and lecithin. The dispersed mixture was melted and blended with hydrophilic emulsifiers such as ethoxylated sorbitan esters and the preheated (60°C) blend was further sprayed by atomizer into cold water (20°C). The oil-in-water emulsions contained encapsulated TiO₂ in the internal phase. The technique is simple and allows preparation of stable emulsions with average droplet size of 1-10 microns.     

Preparation of Water-in-Diesel Fuel Nanoemulsions Using High-Energy Emulsification Method and a Study of Some of Their Surface Active Properties

In this work, formations of water-in-diesel fuel nanoemulsions using water/mixed nonionic surfactant/diesel fuel system has been studied. The high-energy emulsification method was used to form three emulsions using different water contents: 5, 10, and 14% (v/v) namely; E1, E2, and E3, respectively. These nanoemulsions were stabilized with emulsifiers having different hydrophilic lipophilic balance (HLB), namely, Span 80 (HLB = 4.3), Emarol 85 (HLB = 11), and their mixture (SE) with HLB = 10. The effect of water on the droplet size formation has been investigated. The interfacial tension and thermodynamic properties of the individual and emulsifiers blends have been studied. The interfacial tension (γ) measurements at 30°C were used to determine the critical micelle concentration (CMC) and surface active properties of these emulsifiers. The water droplet sizes were measured by dynamic light scattering (DLS). From the obtained data, it was found that mean sizes between 19.3 and 39 nm were obtained depending on the water content and concentration of blend emulsifiers (SE). Also, the results show that the interfacial tension (γ) gives minimum value (10.85 mN/m) for SE comparing with individual emulsifier (17.13 and 12.77 mN/m) for Span 80 and Emarol 85, respectively. The visual inspection by transmission electron microscopy showed that the obtained results support the data obtained by dynamic light scattering.     

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.     

EMULSIFICATION BY CHEMICALLY MODIFIED OVALBUMIN

Enhancement of emulsifying properties of a model protein, ovalbumin, was achieved by covaient attachment of hydrophobic groups using various esters of N-hydroxysuccinimide. It was found that the resulting modified proteins were much better emulsifiers than the native ovalbumin, even at low modification degree (20-30% of available amine groups): in tetradecan-water emulsions oil separation was observed within a few hours, when 0·7 mg/ml native ovalbumin was used, compared to about one month until separation was observed when the modified proteins were used. The use of highly modified proteins prevented completely oil separation (at least two months); for example, emulsions prepared with 51% modified proteins with C₃, C₆, showed no change in droplet size distribution even 50 days after preparation. The effect of chain length on emulsification was also investigated: an optimal chain length (Cg) was found, for both low and high modifications.     

Influence of free protein on flocculation stability of beta-lactoglobulin stabilized oil-in-water emulsions at neutral pH and ambient temperature

The influence of protein concentration and order of addition relative to homogenization (before or after) on the extent of droplet flocculation in oil-in-water emulsions stabilized by a globular protein was examined using laser diffraction. n-Hexadecane (10 wt%) oil-in-water emulsions (pH 7, 150 mM NaCl) stabilized by beta-lactoglobulin (beta-Lg) were prepared by three methods: (1) 4 mg/mL beta-Lg added before homogenization; (2)10 mg/mL beta-Lg added before homogenization; (3) 4 mg/mL beta-Lg added before homogenization and 6 mg/mL beta-Lg added after homogenization. Emulsion 1 contained little nonadsorbed protein (<3%) and underwent extremely rapid and extensive droplet flocculation immediately after homogenization. Emulsion 2 contained a significant fraction of nonadsorbed beta-Lg and exhibited relatively slow droplet flocculation for some hours after homogenization. Measurements on Emulsion 3 showed that the extremely rapid particle growth observed in Emulsion 1 could be arrested by adding native beta-Lg immediately after homogenization. The extent of particle growth in the three types of emulsions was highly dependent on the time that the salt was added to the emulsions, i.e., after 0 or 24 h aging. We postulate that the observed differences are due to changes in droplet surface hydrophobicity caused by differences in the packing or conformation of adsorbed proteins. Our data suggest that history effects have a strong influence on the flocculation stability of protein-stabilized emulsions, which has important implications for the formulation and production of protein stabilized oil-in-water emulsions.     

MATHEMATICAL AND EXPERIMENTAL ESSENTIALS OF THE MULSIFICATION PROCESS: OPTIMAL PARAMETERS DETERMINATION

The evaluation of the procedure for the determination of optimal parameters for the preparation of 0/W emulsions by the mechanical homogenizer has been studied. The method is based on a general functional dependence of the emulsion droplet-size distribution parameters on various factors (homogenization time interval, emulsifi-er concentration, and homogenization intensity) Calculated parameters of the derived mathematical relations were used for characterization of the specific action and limiting capabilities of a particular emulsifier, as well as for the determination of the optimal emulsifica-tion conditions. Changes in emulsifier concentration cause remarkable effects on the emulsion droplet sizes, but only at lower emulsifier concentrations (below the optimal ones). If the homogenization intensity is insufficient, coarse and very unstable emulsions are obtained; if higher than the optimal one, the homogenization effects are not proportional to the energy expended.     

Oil Base Mud. Part I: Synthesis of Some Local Surfactants Used as Primary Emulsifiers for Oil Base Mud and Evaluation of Their Rheology Properties

Six oil soluble nonionic surfactants with different HLBs have been prepared. Their HLBs situate between 3.9 and 6.7. Transesterification was carried out for glycerol and triethanol amine with oleic acid at different moles to obtain six emusilifiers. They named glycerol momooleate (I), glycerol diooleate (II), glycerol trioleate (III), triethanol amine mono-, di- and tri-oleate (IV), (V,) and (VI). The chemical structure was confirmed using; the elemental analysis, FTIR and ¹HNMR. They were evaluated as a primary emulsifiers (PE) for thdrilling fluids (oil base mud) comparing with a currently used primary emulsifier (Fc). The water in oil base mud (w/o emulsions) was prepared. The concentration of emulsifiers and their HLB exhibited interesting rheology properties including shear-thinning behavior, yield value, viscoelastic effects, thixtropy, gel strength, and filtration loss. The rheology properties of such emulsions strongly depended on the average size distribution of the dispersed droplets that could be varied both with the bulk concentration and HLB value of the emulsifiers. The interfacial and surface properties of these emulsifiers suggest that the droplet size of the dispersed phase and bulk concentration are strongly related to the HLB value of emulsifiers. The w/o emulsion (mud formulation) stability is sensitive to the droplet size of the dispersed phase and HLB value of the used emulsifier. The results were discussed on the light the chemical structure of the primary emulsifiers and the emulsion ingredients.     

A DOE Approach to Investigate the Influence of Process-Parameters and Composition on the Stability of Emulsions Stabilized by Marine Polysaccharides Prepared by High-Pressure Homogenization

The influence of pre-homogenization conditions (speed and duration at a rotor–stator system), homogenization pressure, and quantitative composition of the emulsions on the droplet size and stability of the resulting emulsions is investigated using design of experiments. A mix of marine polysaccharides (e.g., alginate and fucoidane) from Ascophyllum nodosum is used as emulsifier to form O/W-emulsions with medium-chained triglycerides. It was found that the amount of emulsifier is the most relevant parameter for emulsions' stability whereas the influence of the homogenization pressure is more distinct at low polysaccharide contents. In contrast, the parameters of pre-homogenization do not influence the droplet size significantly.      

PREPARATION OF CLOUDY COCONUT OIL EMULSIONS CONTAINING DISPERSED TiO2 USING ATOMIZER

ABSTRACT

Food Grade Rutile TiO₂ was dispersed in coconut oil with the help of hydrophobic emulsifiers such as sorbitan esters and lecithin. The dispersed mixture was melted and blended with hydrophilic emulsifiers such as ethoxylated sorbitan esters and the preheated (60°C) blend was further sprayed by atomizer into cold water (20°C). The oil in water emulsions contained encapsulated TiO₂ in the internal phase. The technique is simple and allows preparation of stable emulsions with average droplets size of 1-10 microns.     

Physicochemical behavior of oil-in-water emulsions: influence of milk protein mixtures, glycerol ester mixtures and fat characteristics

Different emulsions based on two protein mixtures (skim milk powder (SMP) and functional dairy proteins (FDP)), two mono-di-glyceride mixtures (MDG) (saturated and partially unsaturated), three fats (hydrogenated and refined coconut oils and refined palm oil) were studied to investigate the interactions occurring between the oil phase, low molecular weight emulsifiers and proteins. Immediately following the emulsification process, high diameters of fat globules were obtained in FDP-based systems, relevant of an aggregation phenomenon. At this stage, the fat globule size characteristics were dependent on the emulsifier and fat types present in the formulation. In contrast, SMP-based emulsions were characterized by low proportions of aggregated particles regardless the formulations. Ageing (24 h at 4 °C) promoted disaggregation in FDP formulations, while SMP emulsions were well stabilized. Just after the homogenization step, less proteins were required to stabilize the globule interface in FDP systems as compared to SMP ones. Only with SMP, the amount of protein load at the fat globule surface was influenced by the oil nature and/or by the emulsifier type. A competitive adsorption of caseins, over whey proteins, was demonstrated in the case of FDP. The ageing period promoted a displacement of the proteins adsorbed at the oil droplet interface, suggesting a disruption of the interfacial protein interactions. This disruption was more marked with SMP than with FDP and, in both cases, was more or less influenced by the emulsifier and oil phase natures. The variations of the viscosity and rheological parameters (elastic and viscous moduli) were not dependent on one specific component of the formulation.     

Influence of protein concentration and order of addition on thermal stability of beta-lactoglobulin stabilized n-hexadecane oil-in-water emulsions at neutral pH

The influence of protein concentration and order of addition relative to homogenization (before or after) on the extent of droplet flocculation in heat-treated oil-in-water emulsions stabilized by a globular protein were examined using laser diffraction. n-Hexadecane (10 wt%) oil-in-water emulsions (pH 7, 150 mM NaCl) stabilized by beta-lactoglobulin (beta-Lg) were prepared by three methods: (1) 4 mg/mL beta-Lg added before homogenization; (2) 4 mg/mL beta-Lg added before homogenization and 6 mg/mL beta-Lg added after homogenization; (3) 10 mg/mL beta-Lg added before homogenization. The emulsions were then subjected to various isothermal heat treatments (30-95 degrees C for 20 min), with the 150 mM NaCl being added either before or after heating. Emulsion 1 contained little nonadsorbed protein and exhibited extensive droplet aggregation at all temperatures, which was attributed to the fact that the droplets had a high surface hydrophobicity, e.g., due to exposed oil or extensive protein surface denaturation. Emulsions 2 and 3 contained a significant fraction of nonadsorbed beta-Lg. When the NaCl was added before heating, these emulsions were relatively stable to droplet flocculation below a critical holding temperature (75 and 60 degrees C, respectively) but showed extensive flocculation above this temperature. The stability at low temperatures was attributed to the droplets having a relatively low surface hydrophobicity, e.g., due to complete saturation of the droplet surface with protein or due to more limited surface denaturation. The instability at high temperatures was attributed to thermal denaturation of the adsorbed and nonadsorbed proteins leading to increased hydrophobic interactions between droplets. When the salt was added to Emulsions 2 and 3 after heating, little droplet flocculation was observed at high temperatures, which was attributed to the dominance of intra-membrane over inter-membrane protein-protein interactions. Our data suggests that protein concentration and order of addition have a strong influence on the flocculation stability of protein-stabilized emulsions, which has important implications for the formulation and production of many emulsion-based products.     

The Effect of Oil Components and Homogenization Conditions on the Physicochemical Properties of Zedoary Turmeric Oil Submicron Emulsions

Zedoary turmeric oil submicron emulsions were studied. The effects of the oil phase as a mixture (ternary) on the emulsion droplet size were investigated by means of the simplex lattice design. By optimizing the homogenization process and using only 1.2% soya lecithin, emulsions with 20% oil phase consisting of zedoary turmeric oil–MCT–soybean oil ratio of 0.5:0.25:0.25 with particle sizes in the range of 132–148 nm and moderate viscosity (3.6–4.0 mPa · s) could be prepared. These emulsions showed good stability over 6 months. This study showed the dominating influence of composition of the oil phase as well as the importance of the homogenizing conditions on processing and stability of the zedoary turmeric oil submicron emulsions.     

Development of the emulsions containing modified fats formed via enzymatic interesterification catalyzed by specific lipase with various amount of water

The aim of this work was to obtain and evaluate the stability of new emulsion systems, in which diacylglycerols derived from enzymatic interesterification of mutton tallow with hemp oil were used as emulsifiers. In order to achieve a higher content of the polar fat fraction in the final fat blend, a different amount of water was added to the reaction mixtures. The modified fats with a mixture of mono and diacylglycerols served as a fat base for emulsions. Based on the results of Turbiscan test, the droplet size, emulsion texture, and studies of rheological properties, it was found that addition of water to the reaction mixture in the range of 1.00–1.25%, wt./wt., caused the formation of a sufficient amount of emulsifiers stabilizing the dispersion system.

The novelty of this work was to determine the optimal amount of water added to the interesterification of mutton tallow with vegetable oil, ensuring the synthesis of a high-efficiency emulsifying system. Another new aspect of this work was to show that the diacylglycerols obtained during such fat modification constitute effective emulsifiers for new stable emulsion systems that may find potential use as food emulsions (dressings) or cosmetic products dedicated to sensitive skin.     

Impact of oil composition on formation and stability of emulsions produced by spontaneous emulsification

In this study, triglycerides of different chain lengths were mixed with paraffin oil, and their effectiveness in forming emulsions produced by spontaneous emulsification upon the addition of water was investigated. The emulsion droplet size exhibited a similar trend as a function of the triglyceride/paraffin oil composition for medium-chain (MCTs) (C8–C10) and long-chain (C18) triglycerides (LCTs). However, emulsions formulated with MCTs and LCTs have a much smaller droplet size (about 50?nm) than emulsions based upon short-chain (C4) triglycerides (SCTs). The addition of SCTs resulted in droplet sizes around 800?nm and the emulsions formed were very unstable. The droplet size, polydispersity index, zeta potential, and emulsion stability of these systems will be described as a function of the oil phase composition.     

颗粒乳化剂的研究及应用

近年来,颗粒乳化剂因其在食品、采油、化妆品、医药、催化以及功能纳米材料制备等领域具有潜在应用前景而备受关注。本文综述了近来颗粒乳化剂的研究进展,归纳了颗粒乳化剂的种类,包括:无机纳米粒子、表面改性或杂化的无机粒子、有机纳米粒子以及特殊的颗粒乳化剂Janus粒子;并对颗粒乳化剂能够在油水界面稳定吸附的热力学机理和动力学行为进行了阐述,颗粒乳化剂在油水界面接触角以及粒径大小是其在界面稳定吸附的关键参数,而颗粒在油水界面的排布方式则主要受粒子之间相互作用的影响。重点介绍了颗粒乳化剂的热点应用,包括:(1)利用颗粒乳化剂制备Pickering乳液,以及通过对颗粒乳化剂的功能化,使得Pickering乳液具备环境响应性(即pH、盐浓度、温度、紫外光、磁场敏感响应性);(2)以颗粒乳化剂为构筑基元、以Pickering乳液为模板制备Janus颗粒、Colloidosome、具有多级结构的粒子或膜,以及多孔结构材料;(3) Janus粒子在催化领域的应用。     

Formula Optimization of Emulsifiers for Preparation of Multiple Emulsions Based on Artificial Neural Networks

Formulation optimization of emulsifiers for preparing multiple emulsions was performed in respect of stability by using artificial neural network (ANN) technique. Stability of multiple emulsions was expressed by the percentage of reserved emulsion volume of freshly prepared sample after centrifugation. Individual properties of multiple emulsions such as droplet size, δ, viscosity of the primary and the multiple emulsions were also considered. A back‐propagation (BP) network was well trained with experimental data pairs and then used as an interpolating function to estimate the stability of emulsions of different formulations. It is found that using mixtures of Span 80 and Tween 80 with different mass ratio as both lipophilic and hydrophilic emulsifiers, multiple W/O/W emulsions can be prepared and the stability is sensitive to the mixed HLB numbers and concentration of the emulsifiers. By feeding ANN with 39 pairs of experimental data, the ANN is well trained and can predict the influences of several formulation variables to the immediate emulsions stability. The validation examination indicated that the immediate stability of the emulsions predicted by the ANN is in good agreement with measured values. ANN therefore could be a powerful tool for rapid screening emulsifier formulation. However, the long‐term stability of the emulsions is not good, possibly due to the variation of the HLB number of the mixed monolayers by diffusion of emulsifier molecules, but can be greatly improved by using a polymer surfactant Arlacel P135 to replace the lipophilic emulsifier.     

Aging mechanisms of perfluorocarbon emulsions using image analysis

The aging mechanisms of perfluorocarbon emulsions were investigated using image analysis. Oil-in-water emulsions of two perfluorocarbons, n-perfluorohexane and perfluorodecalin, were prepared with three emulsifiers, Lecithin, Span 20, and Pluronic F-68. The effect of the temperature and the replacement of water by an aqueous phase consisting of a microbial culture medium were also studied. The emulsions were prepared by sonication and their stability was followed through analysis of the evolution of mean droplet size. The results indicate that the stability of perfluorocarbon in water emulsions depends on all the parameters investigated and that two aging mechanisms, coalescence and molecular diffusion, may take place. Analysis of the evolution of the mean droplet size during long time periods indicate that coalescence is more common than previously reported for these systems and seems to be favored by a temperature increase.     

Preparation and characterization of W/O/W type double emulsion containing PGPR–lecithin mixture as lipophilic surfactant

The objective of this study is to produce double emulsion by combining polyglycerol polyricinoleate (PGPR) with lecithin as lipophilic surfactant. Although lecithin alone produced only oil-in-water type emulsion, the mixture of lecithin and PGPR could produce water-in-oil type emulsion as well. Moreover, different emulsification treatments were applied to study the influence of homogenization methods on the physicochemical characteristics. The obtained double emulsions were compared in terms of stability and droplet size. It was found that the homogenization method influenced the physiochemical characteristics of the double emulsion and the most stable double emulsion with the smallest droplet size was obtained by high-speed homogenization method.