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Emulsion and Emulsification Technology

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Abstract

Emulsion is one of the most common products in our lives and used to manipulate biological systems in nature and our bodies. This chapter introduces basic concepts of emulsion, for example, definition, classification, relation with surfactants, disruption process, and will give hints how to prepare a stable emulsion. The most important term on emulsion is “non-equilibrium,” which allows us to distinguish from the other solution states and help us to understand why emulsion technologies are so complicated that any beginner cannot simply find a way to form a stable emulsion. In addition, this chapter shows as many emulsification technologies and their fundamental theories as possible.

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... However, water in oil emulsions will likely increase engine corrosion, which has been attributed to the higher acidity of emulsified fuel due to utilizing surfactants [11,12] and an increase of the fuel viscosity [13], which reduces the tendency of fuel breakup and atomization. An emulsion is a mixture of liquids that are immiscible with each other, and will eventually separate into individual phases [14]. Debnath, et al. [10] found that water-emulsified palm oil methyl ester (POME) improved the brake thermal efficiency (BTE) of a diesel engine by 11%, and POME that had not been emulsified resulted in a BTE that was 3% lower than diesel and released 20% more NOx than its emulsified counterpart. ...
... The stability of an emulsion is driven by the droplet size of the water which forms in the oil. Smaller droplet sizes indicate a greater stability, since larger droplets favour the emulsion breakdown process driven by Ostwald Ripening and Coalescence [14]. The complete phase separation of an emulsion can happen due to a variety of particulate processes, such as flocculation, creaming or sedimentation, coalescence and Ostwald's Ripening [15,16]. ...
... In comparison, the same emulsion that was produced through mechanical homogenisation only remained stable for 15 h. The higher stability obtained by ultrasonication can be attributed to the smaller droplet sizes [14]. Figure 3 shows that the growth of cavitation bubbles is dependent on the frequency of the applied ultrasonication. ...
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Targets to reduce CO2 emissions by 75% and NOx emissions by 90% by 2050 in aviation have been set by The Advisory Council for Aviation Research and Innovation in Europe. Sustainable fuels, e.g., emulsified biofuel, have demonstrated promise in reducing emissions and greenhouse gases. The aim of this project is to investigate the stability of a water in oil emulsion using sunflower oil. The primary objective is to achieve an emulsion which is stable for at least 4 days, and the secondary objective is to investigate how altering the emulsification parameter values of the surfactant hydrophilic-lipophilic balance (HLB), energy density and sonotrode depth in an ultrasonication procedure can impact the stability. The stability of each emulsion was measured over a period of 14 days. The main outcome is that two of the 14 emulsions made remained stable for at least 14 days using a surfactant HLB of five, which proved to be the optimum value from those tested. The results also show that, by using the sonotrode in a higher starting position, emulsions achieved a greater stability. Furthermore, over-processing of the emulsion was determined, with the point of over-processing lying between an energy density of 75 and 200 W.s/mL.
... Following this trend, the use of surfactants and biosurfactants may be an efficient option to assist soil treatment. Surfactants are amphiphilic compounds consisting of a hydrophilic portion (head) with high chemical affinity for water and a hydrophobic (tail) strongly repulsed by it, which are capable of reducing the surface tension of the liquids in which they are dissolved [105][106][107] (Figure 10). Many methods are being developed to improve existing technologies, as well as to find new alternatives to treat polluted soil. ...
... Following this trend, the use of surfactants and biosurfactants may be an efficient option to assist soil treatment. Surfactants are amphiphilic compounds consisting of a hydrophilic portion (head) with high chemical affinity for water and a hydrophobic (tail) strongly repulsed by it, which are capable of reducing the surface tension of the liquids in which they are dissolved [105][106][107] (Figure 10). The use of surfactants has become an attractive technology for soil washing in recent years, as hydrophobic pollutants adhere to the surface of soil particles that generally are poorly hydrosoluble. ...
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Petroleum hydrocarbons, heavy metals and agricultural pesticides have mutagenic, carcinogenic, immunotoxic and teratogenic effects and cause drastic changes in soil physicochemical and microbiological characteristics, thereby representing a serious danger to health and environment. Therefore, soil pollution urgently requires the application of a series of physicochemical and biological techniques and treatments to minimize the extent of damage. Among them, bioremediation has been shown to be an alternative that can offer an economically viable way to restore polluted areas. Due to the difficulty in choosing the best bioremediation technique for each type of pollutant and the paucity of literature on soil bioremediation enhanced by the use of specific additives, we reviewed the main in situ and ex situ methods, their current properties and applications. The first section discusses the characteristics of each class of pollutants in detail, while the second section presents current bioremediation technologies and their main uses, followed by a comparative analysis showing their respective advantages and disadvantages. Finally, we address the application of surfactants and biosurfactants as well as the main trends in the bioremediation of contaminated soils.
... MEs and NEs can be defined as the nanometric dispersion of one liquid phase into another one in which it is not soluble. They are generally composed of a water and an oil phase; their dispersion of one in the other is allowed by the presence of amphiphilic molecules able to decrease the interfacial tension between the two immiscible phases, called surfactants [34]. ...
... Co-surfactant should decrease the stability of lecithins crystalline lamellar structures. Moreover they help the spontaneous curvature of the lipid layer [34]. ...
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The interest around essential oils is constantly increasing thanks to their biological properties exploitable in several fields, from pharmaceuticals to food and agriculture. However, their widespread use and marketing are still restricted due to their poor physico-chemical properties; i.e., high volatility, thermal decomposition, low water solubility, and stability issues. At the moment, the most suitable approach to overcome such limitations is based on the development of proper formulation strategies. One of the approaches suggested to achieve this goal is the so-called encapsulation process through the preparation of aqueous nano-dispersions. Among them, micro- and nanoemulsions are the most studied thanks to the ease of formulation, handling and to their manufacturing costs. In this direction, this review intends to offer an overview of the formulation, preparation and stability parameters of micro- and nanoemulsions. Specifically, recent literature has been examined in order to define the most common practices adopted (materials and fabrication methods), highlighting their suitability and effectiveness. Finally, relevant points related to formulations, such as optimization, characterization, stability and safety, not deeply studied or clarified yet, were discussed.
... Also, Griffin presented another relation for calculating the HLB number of ester compounds based on the saponification number and acid number as follows (Yamashita et al., 2017): ...
... Kawakami also provided a relation for HLB as follows (Yamashita et al., 2017): ...
Article
The effluent produced in refineries is in the form of an oil/water emulsion that must be treated. These emulsions are often stable and a suitable method must be used to separate the oil from the emulsion. Recently, biosurfactants or biodemulsifiers have received much attention to reduce the interfacial tension between two liquids. Biodemulsifiers are produced by microorganisms and have several benefits over chemical demulsifiers such as low-toxic, biodegradability, eco-friendly and easy synthesis. They can eliminate two phases by changing the interfacial forces between the water and oil molecules. Biosurfactants are categorized based on the molecular weight of their compounds (low or high molecular weight). Sophorolipids, lipopeptides rhamnolipids, trehalolipids, glycolipid, lipoproteins, lichenysin, surfactin, and polymeric biosurfactants are several types of biosurfactants, which are produced by bacteria or fungi. This review study provides a deep evaluation of biosurfactants in the demulsification process. To this end, different types of biosurfactants, the synthesis method of various biosurfactants using various microorganisms, features of biosurfactants, and the role of biodemulsifiers in the demulsification process are thoroughly discussed. Also, the impact of various efficient factors like pH, microorganism type, temperature, the oil content in the emulsion, and gravity on biodemulsificaion was studied. Finally, the mechanism of the demulsification process was discussed. According to previous studies, rhamnolipid biodemulsifier showed the highest biodemulsification efficiency (100%) in the removal of oil from an emulsion.
... A decrease in the interfacial surface area will reduce the interfacial surface energy [101,118]. If the interfacial surface energy is decreased without causing any reduction in the interfacial surface area, the stability of the emulsion is increased. ...
... If the HLB value is greater than 20, then the presence of co-surfactants reduces their effective HLB to a value within the range which is required for the formation of microemulsion [89]. The HLB value can be determined by Megahed and Nashy [64], Yamashita et al. [118], S = Saponification value, A = acidity of the residue. ...
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“Fatliquor” is the most widely used wet chemical applied in the form of an emulsion at the end process of leather tanning. It keeps the leather soft, smooth, light, and heat fasting by preventing the fibrils from the aggregation and filling the voids. It pronounces most effectively on the softness, tensile properties, antifungal, and antimicrobial properties. Here this review article represents different fatliquors, its formation, applications and contemporary developments, and new challenges in producing the environment-friendly fatliquors. Applications of new novel classes of multifunctional fatliquors with excellent surface activities, biodegradability, antifungal, antimicrobial properties which are the keys to the effective fatliquoring have been focused.
... Surfactants are amphipathic compounds with hydrophilic and hydrophobic portions that preferably partition at the interface between liquid phases with different degrees of polarity, such as oil/water or air/water interfaces [19], as illustrated in Fig. 1. This characteristic reduces the surface tension of liquids through specific, preferential interactions at surfaces and interfaces due to the presence of hydrophilic and hydrophobic portions in the same molecule [21,22]. The non-polar portion of a surfactant is often a hydrocarbon chain, whereas the polar portion (hydrophilic head group) may be ionic (cationic or anionic), non-ionic, or amphoteric [9]. ...
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Science has greatly contributed to the advancement of technology and to the innovation of production processes and their applications. Cleaning products have become indispensable in today’s world, as personal and environmental hygiene is important to all societies worldwide. Such products are used in the home, in most work environments and in the industrial sectors. Most of the detergents on the market are synthesised from petrochemical products. However, the interest in reducing the use of products harmful to human health and the environment has led to the search for detergents formulated with natural, biodegradable surfactant components of biological (plant or microbiological) origin or chemically synthesised from natural raw materials usually referred to as green surfactants. This review addresses the different types, properties, and uses of surfactants, with a focus on green surfactants, and describes the current scenario as well as the projections for the future market economy related to the production of the different types of green surfactants marketed in the world.
... As shown in Fig. 5 CL (class 2), a large droplet is formed by merging two or more small droplets. This phenomenon is driven by the thinning and disruption of the liquid film during droplet contact (Yamashita et al., 2017;Che;Matar, 2018). Moreover, feature images of FL (class 1) and KSD (class 3) exhibit clusters of droplet aggregation and many individual droplets kept a certain distance, respectively. ...
... An emulsion is a mixture of two or more mutually immiscible liquids, in which at least one of them forms a continual phase and the other occurs as a discrete phase, usually in the form of small droplets. The size of droplets is in the range from 0.1 to 10 μm, which relates to the range of visible light wavelengths [15]. Emulsions instabilities are important feature and contribute to separation process in deep-bed filtration Emulsion instabilities can be generally divided into five groups, as shown in Figure 2 [16,17]. ...
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This review covers various aspects of the treatment of emulsified oil/water mixtures and is particularly focused on tertiary treatment, which means the reduction of the oil content from 70–100 ppm to below 10 ppm, depending on national regulations for water discharge. Emulsified oil/water mixtures frequently occurs in water treatment processes because, in the petroleum industry, chemically enhanced oil recovery leads to the production of a vast amount of oil-emulsified wastewater. This review is focused on various aspects of tertiary treatment via granular deep-bed filtration. The importance of polymeric materials, as well as carbon nanostructures, which may be an alternative to the current media have been highlighting. The particular potential of polymers is based on their broad availability and low price (particularly for polyolefins), the simple treatment of their surfaces through a variety of chemical and physical methods to design surfaces with tailored surface free energy (wettability), and the porosity. Polymer technology offers a variety of well-established methods for designing foams with tailored porosity, which, together with appropriately tuned surface energy and controlled roughness, would open new avenues for the production of foamy media for efficient oil/water separation. Additionally, a crucial inventions in deep-bed filtration is discussed.
... They are defined as dispersion made of oil, water, and surfactant(s) made of an isotropic and thermodynamically stable system with dispersed domain diameter and droplet sizes formed at the nano scale (within the range 20-200 nm) by means of mechanical forces [85,95,96]. NEs are divided into two categories, oil-in-water (O/W) and water-in-oil (W/O) types, in which water or oil is the continuous phase, respectively [97]. To facilitate the in situ pathway of the delivery system to the skin, nanoparticulates are used. ...
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Limited permeability through the stratum corneum (SC) is a major obstacle for numerous skin care products. One promising approach is to use lipid nanoparticles as they not only facilitate penetration across skin but also avoid the drawbacks of conventional skin formulations. This review focuses on solid lipid nanoparticles (SLNs), nanostructured lipid nanocarriers (NLCs), and nanoemulsions (NEs) developed for topical and transdermal delivery of active compounds. A special emphasis in this review is placed on composition, preparation, modifications, structure and characterization, mechanism of penetration, and recent application of these nanoparticles. The presented data demonstrate the potential of these nanoparticles for dermal and transdermal delivery Citation: Khater, D.; Nsairat, H.; Odeh, F.; Saleh, M.; Jaber, A.; Alshaer, W.; Al Bawab, A.; Mubarak, M.S. Design, Preparation, and Characterization of Effective Dermal and Transdermal Lipid Nanoparticles: A Review. Cosmetics 2021, 8, 39.
... Emulsion coalescence is triggered by the thinning and disruption of the liquid film between the droplets. This can occur when emulsion droplets form a cream layer, a floc, or during Brownian diffusion [115]. Ostwald ripening is caused by changes in solubility between oil droplets of various sizes. ...
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Building on their dual functionality for solar photothermal absorption and storage, slurries/dispersions of micro/nano-encapsulated phase-change materials (ePCMs) are capable of revolutionizing the solar-thermal industry. Yet, to facilitate their transition from the research and development stage into market adoption and penetration, there is a dire need for a methodical understanding of the design criteria, fabrication techniques, application areas, and technical challenges of these novel solar concepts in light of state-of-the-art advances. This work thoroughly addresses these needs with a focus on slurries/dispersions with solid-liquid PCM cores for latent heat storage and surface-engineered shells for solar radiation extinction. By dividing this study into four parts, we start with an overview of the material types, desired attributes, and key challenges of PCMs; the different types of PCM systems; and their potential applications in the solar energy industry. We then focus in the second part on ePCMs in indirect (surface-based) and direct (volume-based) solar-absorption systems in terms of their functional requirements, encapsulation methods, stability metrics and assessment, compositional and structural characterization techniques, measurement of thermophysical properties, and key design parameters. The third part of this work is dedicated to the theoretical foundation necessary to model and simulate solar ePCM systems, including continuum, discrete, and multi-scale modeling approaches for flow and heat transfer in ePCM slurries/dispersions; thermophysical property correlations; melting theory in PCM capsules; radiation transfer and optical properties evaluation; and energy performance analysis. In the final part, recent breakthroughs in multi-functional shell engineering, molten-salt encapsulation, multi-scale modeling, contrasting ePCMs and nanofluids, and ePCM-based optical filtration are highlighted. By striking a balance between fundamentals and applications, this work aims to serve as a comprehensive foundation for newcomers into this promising field of research as well as an updated critique for experts looking to identify knowledge gaps, technical bottlenecks, latest advances, and future directions.
... 4 The application of surfactant-stabilised emulsions are commonly encountered in numerous industrial practices, for example, oil refinery, food, cosmetics and pharmaceuticals, as well as being a by-product in many manufacturing processes, such as wood and metal processing. [5][6][7][8] Emulsion pollution has reported an increase in biochemical oxygen demand (BOD) in the environment. However, these toxic chemicals not only pose a serious threat to maintaining a sustainable aquatic ecosystem but also cause unprecedented harms to human beings. ...
Article
A novel continuous fluid circulation system was designed and employed for the impregnation seeding and fabrication of zeolitic imidazolate framework (ZIF) crystals on the internal surface of polymeric hollow fibre membranes. Application of impregnation seeding has been proven effective to decrease crystal size, consequently increasing surface roughness and wettability of the membrane. Evaluation of the as-synthesised membrane demonstrated excellent separation efficiencies (>99%) of surfactant stabilised oil-in-water emulsions. Owing to the simple impregnation strategy assisted by the continuous fluid circulation, the active ZIF layer formed was visibly thinner and denser than typical seeding techniques, hence a high pure water flux of >1,150 L m-2 h-1 bar-1 was achieved. The membranes were highly selective and ultra-permeable to water, however, almost impermeable to oils in a water environment, e.g., n-hexane, n-heptane, chloroform and dichloromethane, as well as their emulsion mixtures, with a separation efficiency higher than 99%. Besides, this new continuous fluid circulation method was also found promising for the synthesis of other types of ZIF on hollow fibre membranes.
... The emulsification index was measured over 25 days to approach the emulsifying stability provided by each extraction condition. A cloudy and pale white phase is indicative of emulsion formation (Yamashita, Miyahara, & Sakamoto, 2017). EI was calculated by dividing the height of the emulsion layer by the mixture total height and multiplying by 100 (Fontes, Fonseca Amaral, Nele, & Zarur Coelho, 2010; Morales-Jiménez, Gouveia, Yáñez-Fernández, Castro-Muñoz, & Barragán-Huerta, 2020). ...
Article
Microalgae are a promising and sustainable ingredient for functional food development, due to their rich nutritional and health-promoting effects. Moreover, microalgae generally contain large amounts of structural biopolymers such as proteins and polysaccharides, which might display interesting technological features and rheological properties. This study aims at unravelling Phaeodactylum tricornutum extracts (PTE) potential role as structuring agents for food applications. Distilled water and a mixture of water/ethanol (75/25, v v⁻¹) were used as solvents. Extracts’ physicochemical properties were analysed regarding protein folding, molecular weight distribution, polymer interactions, and their main functional groups. PTE thermal properties, rheological behaviour, and emulsifying capacities were also evaluated. PTE showed different gelling mechanisms, with 40 °C aqueous purified extracts reporting the strongest gel character. Moreover, 80 °C ethanolic purified extracts showed the greatest emulsifying potential, with an initial emulsification index (EI) of around 90%. This EI decreased to 60% after 10 days, but remained constant for the following 15 days, showing an interesting emulsion stability. Overall, these findings suggest that PTE have a great potential for further application as thickening or emulsifier food ingredients. This diatom revealed to be a valuable source of structurally diverse, technologically active compounds.
... A summary of the statistical analysis of all samples can also be seen in Table 1. From this table, it was observed a pattern of growth and reduction of particle size after increasing the synthesis time, which can be attributed to the phenomenon of Oswald ripening [47,48]. After a synthesis time of 5 min, polycrystals with a particle size of 143 ± 42 nm are obtained. ...
Article
Although an astounding variety of Metal-Organic Frameworks (MOFs) has been synthesized so far, the search for fast and efficient methods that yield greener and superior crystalline structures is yet an ongoing challenge. For the first time, the Hong Kong University of Science and Technology (HKUST-1) MOF has been synthesized by an efficient non-conventional solvothermal method through a Monowave 50 (Anton Paar) reactor. The synthesis has been carried out at 5, 10, 15, and 30 min instead of staggering times of 10 to 24 h. Its crystalline structure, crystallite size, morphology, particle size, specific surface, and optical properties have been characterized. The presumed presence of monocrystalline structures along with a roughly band gap energy at 3.5 eV makes them compelling nanostructures for a variety of applications.
... In human body and in nature, different types of emulsion systems are found. Bile acid is an example of an emulsifier that aids digestion and absorption of fat by the production of finely spread emulsion droplets [1]. The action of combining two liquids substances together in order to compose emulsions is called emulsification while the process of separating them is called demulsification. ...
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There has been an increase in demand for green demulsifiers that will be as effective as the chemical demulsifiers but without the negative environmental effects. This demand has been partly addressed with the production of some bio-based demulsifiers. It is of importance to know the substances that act as emulsifiers in the production of crude oil and understand the mechanism of emulsification. This paper has reviewed emulsifiers and the mechanism of emulsification as well as bio-based demulsifiers and their mechanisms. This will enhance our knowledge on the type of compounds that can be used in the formation of effective demulsifiers. Innovation of these demulsifiers will enhance crude oil production and in the long run boost profitability and environmental sustainability. Currently, cashew nut shell liquid (CNSL) derivatives are in use for the formulation of effective green demulsifiers for water-in-crude oil emulsions.
... There are two main types of emulsions: water-in-oil (W/O) and oilin-water (O/W) [2], with notable examples being milk (O/W) or margarine (W/O). Multiple emulsions can also form -W/O/W (water-inoil-in-water) or O/W/O (oil-in-water-in-oil), with W/O/W found in more applications than O/W/O [3]. ...
... Oil polarity is a factor involved in consumer acceptance of cosmetic products as polar oils often improve both skin feel and cosmetic aesthetics. As reported in the literature [38], the required hydrophilic-lipophilic balance (rHLB) can be used to estimate the polarity of natural and synthetic oils. By determining the rHLB values of the oily formulations under investigation, we observed that the incorporation of vegetable oils did not affect such parameters. ...
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Some vegetable oils have many biological properties, including UV-absorbing capacity. Therefore, their use has been suggested to reduce the content of organic UV-filters in sunscreen products. In this work, we investigated the feasibility of developing oil-based vehicles with a high sun protection factor (SPF) using pomegranate oil (PMG) and shea oil (BPO) in association with different percentages of organic UV-filters (octyl– methoxycinnamate, butyl methoxydibenzoylmethane, and bemotrizinol). We characterized the spreadability, occlusion factor, pH, and required hydrophilic lipophilic balance of the resulting formulations, and did not observe relevant differences due to the incorporation of vegetable oils. The in vitro spectrophotometric determinations of SPF values highlighted that the addition of BPO (1% (w/w)) and PMG (1% (w/w)) resulted in an increase in SPF in comparison with the same formulations that contained only organic UV-filters. The SPF increase was more significant for the formulations that contained lower amounts of organic UV-filters. The results of this study supported the hypothesis that including suitable vegetable oils in sunscreen formulations could be a promising strategy to design products with a lower content of organic UV-filters.
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Nanoemulsions represent one of the most promising colloidal systems for the vehiculation and delivery of hydrophobic molecules, exploitable in several fields such as pharmaceutical, cosmetic, food and agricultural. In this study, we investigated the influence of the formulation parameters, in particular the type of surfactant, on the physico-chemical properties of oil in water nanoemulsions. Six different surfactants were selected based on the similar HLB value (around 15) but different chemical features, such as linear and steric hindrance molecules, PEGylated and PEG-free compounds or the presence of saturated or unsaturated fatty tails. All the surfactants were preliminary characterized in term of surface and interface tension and cytotoxicity. Nanoemulsionssystems were then obtained through a high-pressure homogenization process and evaluated in terms of physico-chemical properties and stability (180 days). The results showed no remarkable differences in the mean diameter of nanoemulsions prepared with the six tested surfactants, suggesting that the size of the oil droplets is mainly dependent by the action of the disruptive forces generated during the homogenization process. However, the nanoemulsions stability was strongly affected by the used surfactants, varying from few weeks up to more than six months. Specifically, the polyglycerol and glucoside derived amphiphiles were the less effective while polysorbate-80 and oleth-20 were able to give optimal nanosystems in terms of both physico-chemical properties and thermodynamic stability. Interestingly, despite polysorbate 80 and oleth 20 showed comparable efficacy, their safety profiles were markedly different. Overall, it has been observed that the surfactant ability to reduce the tension at the O/W interface is closely related to the stability of the nanoemulsions, allowing the prediction of to predict their medium or and long-term stability.
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Aqueous suspension of polyisobutylene (PIB) was stabilized via application of anionic surfactant of sodium lauryl sulfate (SLS) and co-surfactants of stearyl and cetyl alcohols. Suspensions were produced via the so-called direct emulsification technique. Some characterization tests including zeta potential, particle size, turbidity, conductivity, and rheology measurements were demonstrated to analyze the stability of produced suspensions. Turbidity and particle size measurements showed that just some of the samples were stable while the others exhibited partial aggregation of particles. The characterization tests showed that the sample contained 2 g of polyisobutylene, 0.45 g SLS, 0.175 g stearyl, and 0.263 g cetyl alcohols, i.e., co-surfactant ratio of 0.66, in 80 mL of water exhibited appropriate stability. Possession of high zeta potential of − 93.65 mV, conductivity of 570 mS/cm, an average particle size of 10 μm, and good rheological behavior besides the stable appearance revealed that this sample did not undergo agglomeration, flocculation, or any phase separation. Graphical abstract
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The impact of rhamnolipids (RL) biosurfactants presence on the phase-separation equilibrium, micellar properties and partitioning behavior of systems containing the aliphatic non-ionic surfactant Tergitol 15-S-7 (Tg7) was studied in this work. The cloud points of Tg7 solutions (1–10% w/w) in water and sodium citrate (NaCit) buffers pH 7.00 were increased after the RL addition (0.25% w/w) while they were decreased in NaCit pH 5.00. The most marked changes were verified for those systems with low Tg7 concentrations (< 4% w/w) and high RL/Tg7 mass ratio (>7°). As expected, the zeta potential (ζ) of non-ionic Tg7 systems was close to zero; however, ζ became clearly negative (≅ −20 mV) in NaCit pH 7.00 after the addition of RL. This finding suggested that RL, which is negatively charged at pH 7.00, self-incorporated into Tg7 micelles and conferred them its charge. Hydrodynamic diameter (Dh) was either increased (in citrate media) or decreased (in water) by the RL, depending on the changes caused in the critical packing parameter of mixed micelles. Interestingly, an exponential decay equation, useful for predictive purpose, was found to correlate the cloud point with the hydrodynamic diameter, thus evidencing the crucial role of micelle size/shape on the phase separation. The partitioning behavior of cibacron blue (CB) and malaquite green (MG), negatively and positively charged dyes respectively, in Tg7 aqueous micellar two-phase systems (AMTPS) was significantly affected by the RL 0.25% w/w. In AMTPS with pH 7.00, the RL induced opposite effects, either duplicating the partition coefficient of MG or reducing it to a half for CB. Attractive and repulsive electrostatic interactions between the negatively charged mixed micelles and the partitioned molecules would be responsible of these trends. These results demonstrate the role of RL as a modulator of partitioning behavior of charged molecules and its potential use to improve recoveries and selectivity in a purification protocol.
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Emulsion-based formulations are widely exploited in medicine, food and cosmetics, where surfactants and emulsifiers play contrasting, but equally important roles. Both are able to adsorb at the oil and water interface enabling dispersion of droplets of one phase in the second. The main function of surfactants is lowering the interfacial tension, while emulsifiers, adsorb more slowly to the droplet surface and give longer-term stability. High toxicity and high ecological impact of many synthetic surfactants/emulsifiers have led to interest in other, natural molecules such as biosurfactants and bioemulsifiers. These bio-based surface-active agents are interesting for the main industries linked to human health – pharmaceuticals, food and cosmetics, with several having been discovered and already widely applied. However, the commercialisation of the production of bio-surfactants/emulsifiers is often limited by optimisation difficulties, high purification costs and low yields, all of which have an impact on their wider application. Therefore, much effort is required to find stable and cost effective methods to produce bio-surfactants/emulsifiers on a large scale. This review focuses on the main properties of bio-emulsifiers and bio-surfactants, followed by an overview of their current use in consumer product formulations. Finally, the potential of bio-surfactants/emulsifiers to replace the currently used counterparts will be assessed.
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The aim of this work was to evaluate the influence of high intensity ultrasound (HIUS) treatment on the molecular conformation of whey protein isolated (WPI) as a previous step for complex coacervation with iota carrageenan (IC) and its effect on the surface functional properties of complex coacervates (CC). Both biopolymers were hydrated (1% w/w) separately. A WPI suspension was treated with an ultrasonic bath (40 kHz, 600 W, 30 and 60 min, 100% amplitude). A non-sonicated protein was used as a control. Coacervation was achieved by mixing WPI and IC dispersions (10 min). FTIR-ATR analysis (400–4000 cm ⁻¹ ) detected changes after sonication on WPI secondary structure (1600–1700 cm ⁻¹ ), electrostatic interaction between WPI and IC by electronegative IC charged groups like sulfate (1200–1260 cm ⁻¹ ), anhydrous oxygen of the 3.6 anhydro-D-galactose (940–1066 cm ⁻¹ ) and the electropositive regions of WPI. Rheology results showed pseudoplastic behavior of both IC and WPI-IC with a significant change in viscosity level. Further, HIUS treatment had a positive effect on the emulsifying properties of the WPI-IC coacervates, increasing the time foaming (30 min) and emulsion stability (1 month) percentage. HIUS and complex coacervation proved to be an efficient tool to improve the surface functional properties of WPI.
Chapter
In this chapter, material balance and its importance in the field of food science/engineering have been discussed. To do this, first, material balance is explained in detail using mass, i.e., mass flows and not volumetric flows. It must be remembered that masses are additive, but volumes are not always additive. Then, we provide a brief explanation of what is a process and state that the chapter focuses on continuous material balance problems under steady-state conditions. The core of the chapter details a proposed strategy to solve simple and complex material balance problems. We developed a five-step procedure, which is explained and then applied in examples. The chapter concludes with 3 solved problems and then proposes 24 problems, each one with the corresponding answer.
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The role of cosmetic products is rapidly evolving in our society, with their use increasingly seen as an essential contribution to personal wellness. This suggests the necessity of a detailed elucidation of the use of nanoparticles (NPs) in cosmetics. The aim of the present work is to offer a critical and comprehensive review discussing the impact of exploiting nanomaterials in advanced cosmetic formulations, emphasizing the beneficial effects of their extensive use in next-generation products despite a persisting prejudice around the application of nanotechnology in cosmetics. The discussion here includes an interpretation of the data underlying generic information reported on the product labels of formulations already available in the marketplace, information that often lacks details identifying specific components of the product, especially when nanomaterials are employed. The emphasis of this review is mainly focused on skincare because it is believed to be the cosmetics market sector in which the impact of nanotechnology is being seen most significantly. To date, nanotechnology has been demonstrated to improve the performance of cosmetics in a number of different ways: 1) increasing both the entrapment efficiency and dermal penetration of the active ingredient, 2) controlling drug release, 3) enhancing physical stability, 4) improving moisturizing power, and 5) providing better UV protection. Specific attention is paid to the effect of nanoparticles contained in semisolid formulations on skin penetration issues. In light of the emerging concerns about nanoparticle toxicity, an entire section has been devoted to listing detailed examples of nanocosmetic products for which safety has been investigated.
Chapter
Heat transfer, as an operation that is present in the processing of almost every food, occurs repeatedly in baking, cooking, sterilizing, drying, and freezing in the food industry. Hence, realizing the heat transfer mechanism is essential to control food processing. Radiation as an efficient method of heat transfer at high temperature is the transfer of heat energy via electromagnetic waves that does not need any interaction between the heat source and heated body. In this chapter, the fundamental concepts of radiation heating are discussed. Electromagnetic waves and the electromagnetic spectrum, with special emphasis on thermal radiation, are explained. This is followed by discussion of the perfect black body, radiation of black body, and the role of black body radiation, in cooperation with the Stefan-Boltzmann law, Planck’s law, and Wien’s displacement law.
Chapter
Food material properties can be analyzed thanks to rheology. Rheology is a branch of physics studying the mechanical properties of complex systems and, in the last few years, it has been applied successfully to many complex food systems. All the individual components and phases in the food matrix influence its final texture and structure. Moreover, to obtain high quality and controlled foods, it is necessary to have a deep knowledge of individual phases or the contribution of single ingredients and processes. In light of the above, this chapter deals with the principal aspects of food rheology, from empirical to fundamental tests, focusing on relevant food systems.
Article
Aging is spontaneous and inevitable process in all living beings. It is a complex natural phenomenon that manifests as a gradual decline of physiological functions and homeostasis. Aging inevitably leads to age-associated injuries, diseases, and eventually death. The research on aging-associated diseases aimed at delaying, preventing or even reversing the aging process are of great significance for healthy aging and also for scientific progress. Numerous plant-derived compounds have anti-aging effects, but their therapeutic potential is limited due to their short shelf-life and low bioavailability. As the novel delivery system, nanoemulsion can effectively improve this defect. Nanoemulsions enhance the delivery of drugs to the target site, maintain the plasma concentration for a longer period, and minimize adverse reaction and side effects. This review describes the importance of nanoemulsions for the delivery of phyto-derived compounds and highlights the importance of nanoemulsions in the treatment of aging-related diseases. It also covers the methods of preparation, fate and safety of nanoemulsions, which will provide valuable information for the development of new strategies in treatment of aging-related diseases.
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An increasing global population and a sharply upward trajectory of per capita energy consumption continue to drive the demand for fossil fuels, which remain integral to energy grids and the global transportation infrastructure. The oil and gas industry is increasingly reliant on unconventional deposits such as heavy crude oil and bitumen for reasons of accessibility, scale, and geopolitics. Unconventional deposits such as the Canadian Oil Sands in Northern Alberta contain more than one-third of the world’s viscous oil reserves and are vital linchpins to meet the energy needs of rapidly industrializing populations. Heavy oil is typically recovered from subsurface deposits using thermal recovery approaches such as steam-assisted gravity drainage (SAGD). In this perspective article, we discuss several aspects of materials science challenges in the utilization of heavy crude oil with an emphasis on the needs of the Canadian Oil Sands. In particular, we discuss surface modification and materials’ design approaches essential to operations under extreme environments of high temperatures and pressures and the presence of corrosive species. The demanding conditions for materials and surfaces are directly traceable to the high viscosity, low surface tension, and substantial sulfur content of heavy crude oil, which necessitates extensive energy-intensive thermal processes, warrants dilution/emulsification to ease the flow of rheologically challenging fluids, and engenders the need to protect corrodible components. Geopolitical reasons have further led to a considerable geographic separation between extraction sites and advanced refineries capable of processing heavy oils to a diverse slate of products, thus necessitating a massive midstream infrastructure for transportation of these rheologically challenging fluids. Innovations in fluid handling, bitumen processing, and midstream transportation are critical to the economic viability of heavy oil. Here, we discuss foundational principles, recent technological advancements, and unmet needs emphasizing candidate solutions for thermal insulation, membrane-assisted separations, corrosion protection, and midstream bitumen transportation. This perspective seeks to highlight illustrative materials’ technology developments spanning the range from nanocomposite coatings and cement sheaths for thermal insulation to the utilization of orthogonal wettability to engender separation of water–oil emulsions stabilized by endogenous surfactants extracted during SAGD, size-exclusion membranes for fractionation of bitumen, omniphobic coatings for drag reduction in pipelines and to ease oil handling in containers, solid prills obtained from partial bitumen solidification to enable solid-state transport with reduced risk of damage from spills, and nanocomposite coatings incorporating multiple modes of corrosion inhibition. Future outlooks for onsite partial upgradation are also described, which could potentially bypass the use of refineries for some fractions, enable access to a broader cross-section of refineries, and enable a new distributed chemical manufacturing paradigm.
Chapter
In keeping with emerging consumer trends, the food industry is continually searching for cheaper and sustainable resources for the production of oils as food ingredients. Corn (maize) is the leading crop all over the world and is consumed as a staple food in many countries. Although corn only contains about 3%–6% of oil, which is less than most of the oilseeds, it has been widely used as cooking oil, frying oil, salad oil, or as an ingredient to prepare other products like margarine, butter, snacks, and bakery products. Corn oil from the germ is preferred by the consumer because of its pleasant taste, light delicate flavor, healthy fatty acid content, and good physical and chemical properties. In addition, corn oil is beneficial for human health since corn oil contains up to 65.5% of linoleic acid, as well as other bioactive compounds, including sterols (β-sitosterol, campesterol, and stigmasterol), phenolic acids, and flavonoids. This chapter summarizes the necessary processing to produce corn oils from the kernels, including corn germ separation by milling, crude oil extraction, and refining. Moreover, the important physical properties and chemical characteristics that impact the quality of corn oil are also highlighted. Finally, the novel utilization of corn oil in the production of various food systems such as emulsions, oleogels, and oleofoams is highlighted.
Article
Essential oils are highly demanded in recent decades due to their antioxidant and antimicrobial properties, protecting food from spoilage. However, their incorporation into low-fat foods is a challenge due to their hydrophobic nature, strong aroma, and flavor. Encapsulation is an effective approach to overcome these drawbacks. This review addresses currently investigated techniques for encapsulating essential oils. The use of emulsion-based delivery systems was developed in combination with encapsulation processes for lipophilic ingredients dispersed in aqueous media. Several techniques used in preparing emulsions are reported, and unlike conventional methods, membrane emulsification has emerged as a potential tool for designing new emulsified products. The main characteristics of essential oils and their applications in the food industry are also emphasized, and future research opportunities are highlighted.
Chapter
Consumer awareness about clean label has driven the industries to utilize natural additives in their food products. The emulsifiers are essential food additives with the ability to stabilize the foods comprising of immiscible phases. In addition to this, they perform several other functions like lubrication, crystal modifier, texture enhancer, shelf-life enhancer, moisture barrier, etc. The natural emulsifiers are obtained from plant, animal, and microbial sources. They are mainly categorized as proteins, polysaccharides, phospholipids, and bio-emulsifiers. The present chapter provides details about various natural emulsifiers, their origins, and possible applications in multiple foods, pharmaceutical and cosmetic products. The behavior of these emulsifiers towards interface and factors (pH, ionic strength, temperature) affecting their functionality as well as emulsion stability have also been discussed.
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It has been shown that structured lipids, formed in the process of enzymatic modification of natural hard fat with walnut oil, are capable of stabilizing emulsion systems without the need to add additional emulsifiers. This is especially true for emulsions containing fat formed during enzymatic modification when the amount of added water to the reaction catalyst was in the range of 12–16 wt%. Physicochemical evaluations, i.e., the average particle size, its growth, distribution, and dispersity coefficient, were comparable with the reference emulsion where the emulsifier was lecithin, well-known for its emulsifying properties. Microstructure studies also confirmed the above observations. Rheological studies performed on a set of emulsions containing structured lipids of variable composition confirmed that interesterified lipid blends can be directly utilized as a fat base in the preparation of stable emulsions. The consistency, thixotropic behavior, long-term shelf life, and thermal stability of these emulsions were found to be comparable to systems stabilized with conventional emulsifiers, i.e., sunflower lecithine. Our approach offers the opportunity for the preparation of stable emulsion systems, free from additional emulsifiers, for the food or cosmetics industry, which is extremely important from the point of view of the preparation of products free from allergens.
Conference Paper
Protocatechuic acid is a phenolic compound that has excellent antioxidant, antimicrobial, and some bioactivity activities. Protocatechuic acid can be reacted with fatty acids through a Fischer esterification reaction to increase its hydrophobicity. In this study, esterification between ricinoleic acid and protocatechuic acid was conducted. The phenolipid compound is purified using the chromatography of the silica gel column with eluent n-hexane: ethyl acetate (9:1, v/v). TLC analysis for fraction A purification results of phenolipid methyl ricinoleic-protocatechuic acid showed an Rf value of 0.55. Characterization using FT-IR indicates a new absorption at a wavenumber of 1198.81 cm⁻¹, indicating the presence of an aromatic C-O ester group and at a wavenumber of 771.56 cm⁻¹, indicating the presence of an aromatic C-H group. The type of emulsion shown is water in oil (W/O). Antioxidant activity test results showed that phenolipid compound was classified into moderate-strength antioxidants with an IC50 value of 150.67 ppm. The results of testing toxic properties with the BSLT method showed that phenolipid compound was categorized as a compound with moderate toxic properties with a value of LC50 of 351.30 ppm.
Article
With this study, we want to analyse the different techniques used to develop emulsions and then apply a new mechanism to manufacture a water-in diesel emulsion that would be stable for a relatively long period. After the research on previous studies, we confidently applied the knowledge acquired during the time of personal study and the research to develop a system that brought us to keep in a semi-stable state an emulsion of water and diesel for a period of 24 hours. In this research we are not focusing on one of the two aspects that should be noted once you study emulsions: we are trying to develop a stable emulsion through the employment of vibrations without considering the employment of such emulsion in an engine, for the moment.
Article
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The objective of this study is to raise the solubilizing ability of vesicles consisting of didodecyldimethylammonium bromide (DDAB), a double chain cationic surfactant. We investigated the effects of β-cyclodextrin (β-CyD, a water-soluble oligosaccharide capable of incorporating molecules of proper sizes) added to the inner aqueous phase of the vesicles on the solubilization of aromatic compounds with the equilibrium dialysis, fluorescent probe, and dynamic light scattering methods.The size of DDAB vesicles loaded with β-CyD was found to be 60 nm when they were prepared under ultrasonic irradiation for a sufficiently long time. The solubilization equilibrium constant (K) of benzilic acid, which is a solubilizate hardly incorporated by the cyclodextrin, was noticeably larger for the β-CyD-loaded vesicles than that for DDAB vesicles containing no cyclodextrin (60 nm), whereas no remarkable increase was found in the K value of 3-phenylpropionic acid (HCA), which is a solubilizate easily incorporated by the cyclodextrin. Consequently, it was concluded that oily substances which are hardly incorporated by β-CyD are solubilized easily in the vesicle bilayers through the change in the bilayer property caused by the cyclodextrin in the inner aqueous phase of the vesicles.
Article
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Only 10 seconds: Hydrocarbons and water do not mix under standard conditions, but they do mix freely at high temperature and high pressure near the gas/liquid critical point of water (Tc=374 °C, P c=22.1 MPa). Quenching of homogeneous solutions of dodecane and water at such extreme conditions in the presence of a surfactant results in bottom-up formation of nanosized oil droplets in water in only 10 seconds. © 2013 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of Creative Commons the Attribution Non-Commercial NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Book
This reference describes the role of various intermolecular and interparticle forces in determining the properties of simple systems such as gases, liquids and solids, with a special focus on more complex colloidal, polymeric and biological systems. The book provides a thorough foundation in theories and concepts of intermolecular forces, allowing researchers and students to recognize which forces are important in any particular system, as well as how to control these forces. This third edition is expanded into three sections and contains five new chapters over the previous edition.
Article
Effect of additives (inorganic salts and polyols) on the cloud point of water-polyglycerol didodecanoate ((C11)2Gn) system was investigated as a function of the weight fraction of polyglycerol chain in whole surfactant, WH/WS, which is directly related to Griffin’s HLB number (=20×WH/WS). The average number of dodecanoic acid residues attached to polyglycerol, m, is in the range of 1.6-2.3. Unlike an ordinary commercial polyglycerol surfactant, the surfactants used in this study contain a very small amount of unreacted polyglycerol. Compared with poly(oxyethylene)-type nonionic surfactant aqueous solutions, NaCl and Na2SO4 largely decrease the cloud point, whereas NaSCN and 1,3-butanediol abruptly increase it with increasing the salt concentration at a fixed WH/WS. However, in the absence of additive, the cloud point drastically increases with a small increase in the hydrophilic chain length or WH/WS. It means that the solubility of polyglycerol surfactant in water is not largely influenced by temperature but is highly dependent on WH/WS. The apparent large effect of additive on the cloud point is mainly attributed to the temperature-insensitiveness of the phase behavior of (C11)2Gn. Single-phase or three-phase microemulsions are formed at the water/oil ratio=1 in water/(C11)2Gn/hydrocarbon(heptane, decane, hexadecane, and m-xylene) systems. As well as the cloud point, the three-phase temperature or HLB temperature is abruptly increased with a small increase in WH/WS. However, both WH/WS for the HLB temperatures are coincident around 25°C, since the hydrophilicity of polyglycerol chain per weight is almost similar to that of poly (oxyethylene) chain at room temperature.
Article
Two coarsening mechanisms of emulsions are well established: droplet coalescence (fusion of two droplets) and Ostwald ripening (molecular exchange through the continuous phase). Here a third mechanism is identified, contact ripening, which operates through molecular exchange upon droplets collisions. A contrast manipulated small-angle neutron scattering experiment was performed to isolate contact ripening from coalescence and Ostwald ripening. A kinetic study was conducted, using dynamic light scattering and monodisperse nanoemulsions, to obtain the exchange key parameters. Decreasing the concentration or adding ionic repulsions between droplets hinders contact ripening by decreasing the collision frequency. Using long surfactant chains and well-hydrated heads inhibits contact ripening by hindering fluctuations in the film. Contact ripening can be controlled by these parameters, which is essential for both emulsion formulation and delivery of hydrophobic ingredients.
Article
The phase diagrams of water-cyclohexane systems containing 3 and 7 wt. % of polyoxyethylene (9.7) nonylphenylether have been determined as a function of temperature. In addition to solubilized regions in aqueous and in nonaqueous solutions, the importance of the three-phase realm (water, hydrocarbon, and surfactant phases) has been emphasized. The characteristic temperature at which the mutual solubility of oil and water increases markedly by the aid of nonionic surfactant is closely related to the phase inversion temperature in emulsions. The marked increase in mutual solubility may result from the sandwich-like structure of surfactant, water, and oil layers. The dispersion types of the system have been determined over a wide temperature range. Besides the usual type and type, , , , , and types have been observed, where D represents the surfactant phase. Except for the extreme volume fraction range, the water phase is continuous at low temperature, the oil phase is continuous at high temperature, and the surfactant phase is continuous at a medium temperature near the phase inversion temperature.
Article
Methods were developed to determine the interfacial tension (IT) of vegetable oil/water systems as a function of time, and to remove interfacially active contaminants from commercial vegetable oils. Interfacial tensions between commercial vegetable oils and water decreased with time due to the presence of impurities. Interfacial tensions of purified oils against water were substantially higher than those reported in the literature, and remained unchanged with time, thereby indicating the absence of surface chemical impurities in the oil. The lowering of IT in the case of commercial oils was ascribed to the presence of mixtures of monoglycerides.
Article
The fluorescence behavior of pyrene in oil droplets of a surfactant-free oil-in-water emulsion was studied for benzene, fluorobenzene, n-hexane and cyclohexane droplets in water. The excimer–monomer fluorescence ratio immediately after sonication, I E/I M(0), of the benzene/water emulsion was 8–10 times larger than for the benzene solution. The ratio I E/I M(t) increased in the first 10–20 min before it decreased to zero. Similar behavior was observed for the fluorobenzene/water emulsion, while I E/I M(0) for emulsions with n-hexane and cyclohexane was smaller than for benzene and fluorobenzene/water emulsions. I E/I M(t) hardly changed with time for the n-hexane and cyclohexane/water emulsions. This different behavior was attributed to the increased solubility of nanometer-size droplets with benzene and fluorobenzene.
Article
Water-in-soybean oil-in-water (W/O/W) emulsions with an internal water phase content of 10–30% (vol/vol) were prepared by a two-step emulsification method using microfluidization and straight-through microchannel (MC) emulsification. A straight-through MC is a silicon array of micrometer-sized through-holes running through the plate. Microfluidization produced water-in-oil (W/O) emulsions with submicron water droplets of 0.15–0.26 μm in average diameter (d av,w/o) and 42–53% in CV (CVw/o) using tetraglycerin monolaurate condensed ricinoleic acid esters (TGCR) and polyglycerin polycondensed ricinoleic acid esters (PGPR) as surfactants dissolved in the oil phase. The d av,w/o and viscosity of the W/O emulsions increased with an increase in internal water phase content. Straight-through MC emulsification was performed using the W/O emulsions as the to-be-dispersed phase and polyoxyethylene (20) sorbitan monooleate (Tween® 80) as a surfactant dissolved in the external water phase. Monodisperse W/O/W emulsions with d av,w/o/w of 39.0–41.0 μm and CVw/o/w below 5% were successfully formed from a straight-through MC with an oblong section (42.8×13.3 μm), using the TGCR-containing systems. The d av,w/o/w of the monodisperse W/O/W emulsions decreased as the internal water phase content increased because of the increase in viscosity of the to-be-dispersed phase. Little leakage of the internal water droplets and no droplet coalescence or droplet break-down were observed during straight-through MC emulsification.
Article
A novel emulsification method was developed for making monodispersed regular-sized cells. Both oil in water (O/W) and water in oil (W/O) emulsion cells were generated by permeating an internal phase into a continuous phase through a silicon microchannel, which was designed and prepared by using semiconductor technology. The microprocessing of O/W (or W/O) emulsion cells was monitored and controlled with a microscope video system. Regular-sized O/W cells were made by a normal hydrophilic microchannel and a glass plate with use of an appropriate surfactant. On the other hand, W/O emulsion cells were made by a hydrophobic microchannel and a glass plate modified with a silane coupler reagent. Regular-sized W/O cells were also obtained; therefore, a suitable combination of organic phase, surfactant, and electrolyte should be carefully selected. There is a possibility for creating artificial biological cells with this method. In the water/triolein and lecithin system, when the amount of oil was decreased on the permeate side, polygon or fiber cell types were created, and each cell contacted its neighbors across a thin oil layer like a biological tissue.
Article
A stable formula using oil-in-water-in-oil (O/W/O) type multiple emulsions was investigated. The components consisted of hydrophilic nonionic surfactant (HCO-60), organophilic montmorillonite, and lipophilic nonionic surfactant (DIS-14). O/W/O emulsions were prepared by a double-step procedure in which an O/W emulsion was prepared in the first step, and then the O/W emulsion was “re-emulsified” in an oil phase with organophilic montmorillonite. The diameter of the innermost oil droplets decreased with increasing HCO-60 content (0.1–3%), while the viscosity showed a maximum at 1% of HCO-60, indicating that the yiel of re-emulsification is highest at this condition. Viscosity of the O/W/O emulsion increased with increasing organophilic montmorillonite and DIS-14. According to the results of a phase ratio study, viscosity and stability of the O/W/O emulsion decreased at high weight fraction of inner oil phase (0.4–0.5), indicating that the excess amount of inner oil phase is absorbed by the outer oil phase. These results revealed that the weight fraction of inner oil phase should be kept below 0.3 for a stable O/W/O emulsion. A similar study on the weight fraction of O/W phase [фO/W)/O] suggested that the O/W/O emulsion is stable at ϕ(O/W)/O=0.65–0.70.
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