Ultrasonic velocity measurements as a method for investigating phase transitions of monoglyceride emulsifier systems in pearlescent cosmetic creams

The phase transitions of monoglyceride emulsifier systems and pearlescent effects in cosmetic creams are investigated using ultrasonic velocity measurements. The transitions between the different phases of monoglyceride emulsifier systems—the coagel, liquid–crystalline lamellar phase, and gel phase—are detected in creams by changes in the ultrasonic velocity with variation of the temperature. The phase transition temperatures correspond to DSC results. Furthermore, the slope of the ultrasound velocity curve correlates with the amount of bound water in the different phases. These insights into the ultrasonic velocity properties of the monoglyceride emulsifier system of creams make it possible to more closely study the pearlescent effect of the coagel. The temperature domain of the short time reversibility of the pearlescence as well as the back-formation time of the coagel can be determined with this method, which enable the optimization of the formulation of pearlescent creams.