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Abstract
O/W emulsions with liquid crystals are complex systems for the delivery of actives into the skin surface since they modulate the release rate in the structure, and they increase the stability and solubility of slightly soluble substances in oil or aqueous phase and support moisturing by decreasing the transepidermal water loss (TEWL). The development of emulsions with vegetable oils is interesting due to their properties; in addition it allows the use of natural raw materials of Brazil's biodiversity, and it has attracted growing attention in the market because of the marketing value of natural products. Following this trend, emulsions were developed containing annatto oil as oily phase. HLB system was used for selection of emulsifying agents because it aids in the correct determination of the ratio of surfactant in a mixture for a better emulsification. In this study, the HLB value of annatto oil was established using nonionic surfactants, such as oleth‐3 and oleth‐20. With the replacement of these by ceteareth‐5, which presents the same HLB, the formation of liquid crystals phases was observed by polarization microscopy. Cetostearyl alcohol was added to change the rheological characteristics, which was analyzed for the purpose of characterization, which is of great importance for emulsion performance evaluation before use in manufacturing conditions.
Acknowledgments
This work was supported by a grant from CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico). The authors thank Beraca Sabará Ingredients, Croda do Brasil, Ely Martins, and Oxiteno for supplying the raw materials.
