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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.

This article belongs to the Special Issue Food Colloids II