Drying characteristics of Cistanche deserticola with different pretreatment and degradation mechanism of phenylethanoid glycosides during drying

Cistanche deserticola (C. deserticola), a medicine food homology plant, has been widely cultivated, produced and processed, and has high commodity value. Due to the degradation of active components during the processing of C. deserticola caused by enzymatic browning, the aim of this paper is to evaluate the drying characteristics of C. deserticola with different pretreatments including steam, hot water and microwave treatment. Furthermore, the degradation mechanism of phenylethanoid glycoside (PhGs) by enzymatic reaction and thermal degradation during drying was revealed with a new perspective. The results showed that microwave pretreatment promoted the drying characteristics. The degradation rates of echinacoside (ECH) and acteoside (ACT) in untreated samples were 0.30-0.75 and 0.54-2.45 mg mL-1 h-1, respectively, which were significantly higher than those in thermal simulation systems and microwave pretreated sample systems. Interestingly, the degradation activation energy of PhGs in untreated samples was negative, indicating that the enzymatic reaction was a non-elementary reaction, and the pathway of the reaction was speculated.