Examination of a Theoretical Model for Drainage of Foams Prepared from Licorice Root Extract Solution

The root of the licorice plant (Glycyrrhiza glabra) is rich in natural surfactants, called saponins. The beneficial properties of this plant have led to different applications, including its use as a foaming agent. In this research, a theoretical model and its validity are discussed for the liquid drainage of foams made from licorice root extract solutions. After stating the important characteristics in the free drainage of foam, a relationship of the drained liquid volume based on effective parameters was obtained via a simplification of the governing equation. The theoretical model is applied to experimental foam drainage data measured at different concentrations of licorice root extract solutions. A comparison of theoretical and experimental results shows good agreement for the volume of drained liquid as a function of time. The characteristics obtained from the combination of effective parameters allows for a quantification of the drainage rate. In addition, the drainage rate at the beginning of the foam decay process, as a measure of stability, can be estimated using measurable properties.