Influence of high wave sound pretreatment on drying quality parameters of echinacea root with infrared drying

Echinacea is a perennial and herbaceous herb containing the most active phenolic compounds and valuable antimicrobial and antioxidant content, such as chicoric acid, which increases the body immune function. The root of this plant is mainly used in pharmaceutical fields to treat inflammation, kidney infections and colds. In the present study, we investigated the drying of echinacea root in an infrared dryer with airborne ultrasonic pretreatment aiming to determine shrinkage, color changes, extraction, total phenolic content, flavonoid content and radical inhibition of 2,2-diphenyl-1-picrylhydrazyl (DPPH). The experiments were performed in an infrared dryer at three temperature levels of 40, 45 and 50 °C, with ultrasonic pretreatment at frequencies of 2000, 3000 and 4000 Hz and a time duration of 20, 40 and 60 min in three replications.

Shrinkage and color changes of the samples varied in the range 27.2-6.3% and 39.82-39.64%, respectively. According to all of the evaluated physical and chemical factors, the optimal conditions for echinacea root processing were a drying temperature of 40 °C, a frequency of 3000 Hz and an ultrasound duration of 60 min, in which case shrinkage was 3.35% and color changes were 38.25%. Total phenolic content was 27.41 mg g^-1 , flavonoid content was 39.36 mg g^-1 and DPPH radical inhibition was 34.87%.

Therefore, the use of airborne ultrasound pretreatment demonstrates increased chemical properties compared to the optimal state when drying the echinacea root with an infrared dryer by 54/21-81/64%. Hence, ultrasound pretreatment preserves the quality and quantity of active ingredients in the therapeutic root of Echinacea. © 2021 Society of Chemical Industry.