Sensorial and stability of cosmetic formulations containing UV filters

TF25

Freitas, LS (1); Gaspar, LR (1); Camargo Jr,FB (1), Maia Campos, PMBG (1)

Faculdade de Ciências Farmacêuticas de Ribeirão Preto – FCFRP/USP

Rheological behavior has a fundamental importance in the formulation of sunscreens, because the formation of an evenly distributed film is critically influenced by the flowing properties and in the performance of the formulations, as well, since sunscreen products need to be applied as a thicker film, which must stay on the skin surface. On the other hand, sensorial properties of cosmetic products are key characteristics and many of these properties are often related with rheological properties. Thus, the aim of this work is to evaluate the physical stability (rheology) and to perform sensorial analysis of different sunscreen formulations. Four formulations containing two different polymers and three different types of self-emulsifying bases were developed: Acrylates/C10-30 alkyl acrylate crosspolymer and Cetearyl alcohol ceteth-10 phosphate dicetyl phosphate (F1), HEC and Batyl Alcohol, Stearic Acid, Lecithin (F2), HEC and Behenyl Alcohol, Polyglyceryl-10 Pentastearate, Sodium Stearoyl Lactylate (F3) and HEC with Cetearyl alcohol ceteth-10 phosphate dicetyl phosphate (F4). These formulations were supplemented with the following UV filters: octocrylene, benzophenone-3, octyl methoxycinnamate and submitted to preliminary stability studies (centrifugation, pH and visual analysis) when stored at room temperature and at 37ºC and 45ºC for a week. In the study of the physical stability by the determination of rheological behavior, the formulations were stored at room temperature, 37ºC and 45ºC, for 28 days. Viscosity, consistency, flow index and thixotropy of the formulations were determined using a Brookfield rheometer. These 4 formulations were applied on the volunteers forearm skin, who answered a questionnaire about their perception concerning the cosmetic properties, as well sense of touch, spreadability, skin feeling just after the application, skin appearance of the formulations (sensorial analysis) and purchase intention. All formulations under study were considered stable in preliminary stability tests and were submitted to the determination of rheological behavior. All formulations under study had pseudoplastic behavior, with a flow index below 1 and lower thixotropy values, which are important characteristics for sunscreen products. Formulation F3 presented more pronounced alterations in all analyzed rheological parameters and showed a pronounced reduction of viscosity after 7 days stored at 45ºC. Formulations F1 and F3 presented the higher degree of acceptance, showing the best sensorial attributes, when compared to F2 and F4. In the experimental conditions of this study, it can be concluded that F1 and F3 presented the higher degree of acceptance in subjective analysis, showing the best sensorial properties, however F1 were considered more stable in rheological analysis.