Investigation of combined hot air -microwave dryer on glycyrrhizic acid content of licorice root extract

The use of medicinal plants has been considered these days due to fewer side effects thanchemical and combined drugs. Extraction is one of the most important stages of post-harvestprocessing 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 aproduct 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 ofthe extract. The experiments were designed using the response surface method, and theamount of glycyrrhizic acid was estimated using high-performance liquid chromatography(HPLC). The results show that with increasing power from 180 to 360 watts, glycyrrhizic acidhas increased and reached 14.03 mg/g dry weight. Also, at 40 °C, the amount of glycyrrhizicacid equals 12.81 mg/g dry weight; at 50 °C, this amount equals 14.03 mg/g dry weight; thenat 60 °C it equals 68. It reaches 14 mg/g dry weight. In other words, the amount of licoriceroot active ingredient has increased with increasing microwave power intensity and increasingtemperature. However, after exceeding a threshold, increasing these two variables has reducedthe amount of glycyrrhizic acid. The study and modelling of licorice root drying kineticsshowed that the relation of Page's model, with a coefficient of determination of 0.99 and asquare value of 0.025, has the best agreement with the experimental data related to the dryingprocess. In this study, the amount of glycyrrhizic acid at the oven's drying temperature of 60degrees Celsius has reached its maximum value equal to 15.54 mg/g.