The Influence of Complementary Processing Methods to Emulsification on the Sunscreen Emulsion Properties

Different processing conditions to produce emulsions can modify the dispersion of ingredients, visual aspect, and viscosity, influencing the final product’s effectiveness. In this study, a primary sunscreen emulsion was produced by the conventional stirring process and subsequently subjected separately to complementary processing methods. A Box-Behnken 23 factorial design was applied to each complementary processing method: the High-Shear Method (CP-HS) and the High-Pressure Homogenization Method (CP-HPH). The present study aimed to investigate the influence of these complementary processes on particle size distribution (PSD), Zeta potential, pH, rheological properties, in vitro SPF, and photostability. In the CP-HS factorial design, the factors explored at three levels were stirring speed and stirring time, while in the CP-HPH design, the factors varied at three levels of pressure and the number of cycles through the high-pressure homogenizer. Results indicated that both complementary processing methods significantly influenced (p < 0.05) the physicochemical characteristics of the primary sunscreen emulsion, which was applied as the starting point. In CP-HS, the sample subjected to 15,000 rpm for 15 min exhibited the highest in vitro SPF (p < 0.05), with an average value of 42 at T0, while the primary sunscreen emulsion had an SPF of 30. In CP-HPH, a more pronounced reduction and uniformity in PSD among the studied methods were observed (p < 0.05), and the range of data was 0.20–0.34 μm. These results emphasize how different processing methods can influence the final characteristics of an emulsion and where suitable choices can significantly benefit the product.