Response Surface Optimization of Temperature and Stirring Speed in Shallot (Allium ascalonicum L.) Emulgel Formulation from Brebes

Temperature and stirring speed are two critical factors influencing the homogeneity of emulgel formulations. This study aimed to develop a mathematical model to predict the spreadability and viscosity of emulgel and to determine the optimal combination of temperature and stirring speed using Response Surface Methodology (RSM). Experiments were conducted to evaluate the effects of these two variables on spreadability and viscosity, with data analyzed using the Design Expert® 13 software. A total of 13 combination models, including both linear and quadratic models, were generated to predict the response variables. Model validation identified 86.171°C and 774.612 rpm as the optimal temperature and stirring speed combination. At these conditions, the emulgel exhibited a viscosity of 24.34 cPs and a spreadability of 6.24 cm. The response values were within both the 95% prediction interval (PI) and confident interval (CI) ranges, confirming that the model accurately predicts the outcomes within the expected range.