The use of medicinal plants has been considered these days due to fewer side effects than
chemical and combined drugs. Extraction is one of the most important stages of post-harvest
processing in medicinal plants. The first step in preparing the extract is the drying operation.
Therefore, choosing the best method and applying the most suitable conditions for drying a
product is important. Therefore, this study aims to use a new method of combined hotmicrowave air dryer in drying licorice root and its effect on the glycyrrhizic acid content of
the extract. The experiments were designed using the response surface method, and the
amount of glycyrrhizic acid was estimated using high-performance liquid chromatography
(HPLC). The results show that with increasing power from 180 to 360 watts, glycyrrhizic acid
has increased and reached 14.03 mg/g dry weight. Also, at 40 °C, the amount of glycyrrhizic
acid equals 12.81 mg/g dry weight; at 50 °C, this amount equals 14.03 mg/g dry weight; then
at 60 °C it equals 68. It reaches 14 mg/g dry weight. In other words, the amount of licorice
root active ingredient has increased with increasing microwave power intensity and increasing
temperature. However, after exceeding a threshold, increasing these two variables has reduced
the amount of glycyrrhizic acid. The study and modelling of licorice root drying kinetics
showed that the relation of Page's model, with a coefficient of determination of 0.99 and a
square value of 0.025, has the best agreement with the experimental data related to the drying
process. In this study, the amount of glycyrrhizic acid at the oven's drying temperature of 60
degrees Celsius has reached its maximum value equal to 15.54 mg/g.