Emulsion Rheology
Laba Dennis in Rheological Proper ties of Cosmetics and Toiletries, 2017
An emulsion in its simplest form is a two-phase system containing two immiscible liquids, one of which is dispersed in the other in the form of microscopic or submicroscopic droplets (Sherman, 1983). The two phases are usually oil and water, producing either an oil-in-water (O/W) or a water-in-oil (W/O) emulsion. Traditional nomenclature for these and other emulsions always places the dispersed phase first. The presence of an emulsifier as a stabilizer extends the inevitable separation of the phases and frequently is the major contributor to the flow characteristics of the entire system (Rogers, 1978). This is due to the emulsifier’s effect on the viscosity of the continuous phase, rather than any effects caused by changes in particle size or concentration of the internal phase.
Lipid peroxidation and its measurement
Roger L. McMullen in Antioxidants and the Skin, 2018
Cosmetic formulations, especially skin care products, typically employ emulsion systems, be it an oil-in-water (o/w) or water-in-oil (w/o) emulsion. In the case of an o/w emulsion, oil droplets are dispersed in a continuous water phase, while the contrary is true for a w/o emulsion. Emulsifiers are typically employed to stabilize an otherwise thermodynamically unstable emulsion. Other common colloidal systems—usually formed by surface active compounds—also used in cosmetic products consist of liposomes and micelles. Emulsions, especially o/w, are very common in food chemistry. For this reason, a great deal of research has been conducted on food colloidal systems and their oxidative stability. This is in sharp contrast to the cosmetic industry, where there is little literature available in the public domain that discusses lipid oxidation in emulsion systems or other common colloidal structures found in cosmetics. One reason for greater attention in the area of food chemistry is the more frequent use of PUFAs in food emulsions. Historically, saturated or monounsaturated fatty acids were probably more commonly found in most commercial cosmetic products. However, as we enter the green age and find increasing levels of naturals/botanicals in cosmetic formulations, we will likely find higher concentrations of PUFAs.22 Regardless, we will draw from much of the literature associated with food chemistry to gain a better understanding of lipid oxidation in emulsions and other colloidal structures.
Formulation aspects of the preservation of hair and skin products
R. M. Baird, S. F. Bloomfield in Microbial quality assurance in cosmetics, toiletries and non-sterile Pharmaceuticals, 2017
The majority of lotions and creams are emulsions of oil and water. In general a lotion is pourable whereas a cream is not. The emulsion in these products may be oil in water (o/w), water in oil (w/o) or more complex multiple systems (e.g. o/w/o). The nature of the dispersed and continuous phases is largely determined by the surfactants used to stabilize the systems, with high HLB materials used for o/w and low HLB used for w/o systems. In practice, however, more complex mixtures are often used, with mixed high and low HLB systems giving the greatest stability. The relative proportions of water and oil is secondary in determining the type of emulsion but may be important when other forces are balanced.
In-vitro and in-vivo evaluation of taste-masked ibuprofen formulated in oral dry emulsions
Published in Drug Development and Industrial Pharmacy, 2021
Haojun Qi, Jiening Dun, Feng Zhao, Xiaodan Qi
An emulsion is a dispersion of two immiscible liquids, in which one liquid is dispersed in the other liquid in the form of droplets under the influence of an emulsifier. The oil-in-water emulsion has been recognized as an effective and stable carrier delivery system for lipophilic drugs. The taste-masking effect is realized by encapsulating the drug in emulsion drops to reduce contact with taste receptors. However, the emulsion is a thermodynamically unstable system, in which unstable physical phenomena such as creaming, flocculation, and demulsification occur easily [18], which can adversely affect production, storage, transportation, and application. These problems can be mitigated by transforming a liquid emulsion into a dry emulsion [19]. Dry emulsions are typically prepared by adding water-soluble materials into liquid emulsions, and the moisture is removed by e.g. spray drying, freeze-drying and vacuum distillation, to give solid particles or powder. The oil phase remains, so the dry emulsion can be rapidly dispersed in added water and restored to a homogeneous emulsion [20] suitable for oral administration to children.
Antimicrobial activity of Curcuma xanthorrhiza nanoemulsions on Streptococcus mutans biofilms
Published in Biofouling, 2020
Mu-Yeol Cho, Si-Mook Kang, Eun-Song Lee, Baek-Il Kim
An emulsion is a mixture of two liquids that are normally immiscible, such as oil and water. Nanoemulsification refers to the process of transforming such emulsions into nanoemulsions by reducing the size of the oil or water droplets to 10–100 nm (McClements 2011). In particular, the nanoemulsification of natural essential oils can enhance their antimicrobial, anticaries, and anti-biofilm activities (Lee et al. 2010; Ramalingam et al. 2012; Quatrin et al. 2017). In addition, nanoemulsification has been used for the solubilization of oils (Zhang et al. 2014). There are numerous nanoemulsification methods, including microfluidization and high-pressure homogenization. However, sonication has been established as the most effective and convenient method for reducing droplet size (Modarres-Gheisari et al. 2019). Soybean oil nanoemulsions prepared via sonication showed a stable droplet size of 29.6 nm and a strong antimicrobial activity against Escherichia coli (Ghosh, Mukherjee, and Chandrasekaran 2013). However, there have been no reports on the antimicrobial activity of Xan nanoemulsions prepared using sonication. Therefore, if Xan, with its antimicrobial activity on oral microorganisms, is nanoemulsified via sonication, it is expected to show strong antimicrobial activity and stable solubilization.
Microencapsulation of retinyl palmitate by melt dispersion for cosmetic application
Published in Journal of Microencapsulation, 2020
Aditi Nandy, Eliza Lee, Abhyuday Mandal, Raha Saremi, Suraj Sharma
The fundamental principle of melt dispersion method is based on the atomisation of a molten matrix such as waxes (melting point ranging from 32 °C to 85 °C) in finely dispersed microdroplets that contain the active ingredient, followed by solidification to provide powder-like microparticles (Djordjević et al.2015). In an oil-in-water emulsion system, the oil phase disperses into the continuous bulk phase to make droplets of oil surrounded by water. Surfactants reduce the interfacial tension, cage the droplets, and stabilise the droplet shape by minimising the surface area as well as surface energy (Mokhatab et al.2018). As a result, spherical droplets form. A shear force such as mixing is required to break up the structure of the droplet into smaller droplets and prevent their coalescence. When the dispersion is cooled, the melted wax in the oil phase get solidified, entrapping retinyl palmitate in the matrix.
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