Abstract
<p class="03Abstract">Emulsions are thermodynamically unstable systems where droplet size is one of the main factors that affect its physical stability and consequently their quality. In this context, this work analyses the incorporation of a high shear homogenization step in the manufacturing process of an emulsion with the objective of maintaining its physical stability. In order to demonstrate the effects of this homogenization in the manufacturing process, the emulsion characterization was carried out by microscopy, rheology, laser diffraction and analytical photo-centrifugation techniques. The effect of high shear homogenization into the emulsion physical results was dependent on the speed applied to the homogenizer pump, with an effective 3600 rpm speed. There was no evidence of change on pH attributes and emulsion density, although there was a change in volumetric relationship between the droplet family presented in each sample, reducing the population of larger droplets to form a third family of intermediate droplets and increasing the volumetric proportion of the population of smaller droplets. This profile change in the droplet size distribution contributed to increased viscosity and emulsion without the presence of separation after it was submitted to the stress condition of temperature and agitation.</p>
Highlights
Emulsions are widely used as vehicles for cosmetic and pharmaceutical industry where various cosmetic or semi-solid pharmaceutical products are formulated as water in oil emulsion (W/O) or oil in water (O/W)
This work focused on studying the influence of high shear homogenization process in maintaining the physical stability of an oil-in-water emulsion, having the same qualitative and quantitative formula composition
The benefit of high shear homogenization at the end of the manufacturing step was confirmed, due to modification of the volume ratio between the families of droplets sizes present in each sample, thereby reducing the population of larger drops, and forming a third family of intermediate drops and increasing the population of smaller droplets. This effect was observed in optical microscopy where there was drop polydispersity reduction for the tests that used the homogenization at 3600 rpm, resulting in a slight increase in the emulsion viscosity
Summary
Emulsions are widely used as vehicles for cosmetic and pharmaceutical industry where various cosmetic or semi-solid pharmaceutical products are formulated as water in oil emulsion (W/O) or oil in water (O/W). Emulsions are systems with two immiscible liquids (oil and water) and may contain an emulsifying agent with the function of promoting emulsion stability due to its property of allocating in the oil and water interface decreasing the interfacial tension between these phases. Because the emulsion is considered a thermodynamically unstable system, it may present lack of long term stability. It was reported in a publication by Raikar et al (2011) that commonly used techniques for emulsification require the application of mechanical energy to the two immiscible phases and stabilization of the newly formed interfaces by surfactants. The use of emulsifiers in order to stabilize an emulsion certainly requires a change in the qualitative or quantitative formula of the product. There are other published works with guidance for stabilization of an emulsion, based on studying of the manufacturing process with the aim of improving the manufacturing step. Schultz et al (2004) classify the different equipment used in the emulsion homogenization step as high pressure homogenizers, and high shear homogenizers; it is possible to observe that such equipment promotes reduction of droplet diameter, ensuring emulsion physical stability
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