The bioactive properties and quality attributes of Chrysanthemum morifolium Ramat as affected by pulsed vacuum drying

Chrysanthemum as a traditional Chinese herb has a long history of medicinal use, for which the efficient drying processing after harvest to maintain the active compounds is extremely important. Therefore, the drying kinetics and quality of chrysanthemum under pulsed vacuum drying (PVD) were explored in this research. Results demonstrated that shorter vacuum duration time can improve drying efficiency, and obtained similar drying rate curve comparing to high temperature. PVD is capable on reservation of its total phenolic and flavonoid content, and the highest value was 52.81 mg GAE/g DW and 133.15 mg RTE/g DW, respectively. Moreover, the antioxidant activity of PVD dried chrysanthemum was enhanced, which showed higher capacity of quenching ABTS+ radical than DPPH radical. When temperature was 75 °C and pulsed ratio was set as 15:5, the highest value of Chlorogenic acid (3.32 mg/g), Luteolin-7-O-glucoside (1.59 mg/g) and 3,5-Dicaffeoyl quinic acid (8.96 mg/g) can be obtained. GC-MS combined with principal component analysis showed that lower temperature and pulsed ratio are more conducive to the retention of volatile components. The color of chrysanthemum was well preserved under lower temperature and longer vacuum duration time.