Abstract:

The study aimed to investigate the impacts of different drying methods on polyphenol contents and antioxidant
activities of chicory root. The changes in polyphenol oxidase (PPO) activity during drying, as well as flavonoid and total
polyphenol contents of dried chicory root were measured. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, 2,2’-azinobis
(3-ehtylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS+·) radical scavenging capacity and reducing power
of polyphenols extracted from chicory root with different drying methods, including air-drying, freeze-drying and hot airdrying
at different temperatures, were also determined so as to obtain the optimum drying method. The results showed
that the contents of polyphenol in chicory root processed by different drying methods differed significantly, likely due to a
combination of residual PPO activity and heat sensitivity of polyphenol during the drying process. When flavonoid content
and total polyphenol content were taken into account, hot air-drying at 60 ℃ was the best method, followed by freeze-drying
and air-drying methods. The antioxidant activity of chicory root was less closely correlated with the content of flavonoids, but
highly correlated with the content of total polyphenols. The DPPH radical, ABTS+· radical scavenging capacity and reducing power
all displayed a significantly (R2 ≥ 0.85, P < 0.05) positive correlation with the total polyphenol content. In order to achieve higher
polyphenol content in dried chicory root, hot air-drying at 60 ℃ was a recommended drying method for chicory root.

Key words: chicory, root, drying methods, polyphenol, antioxidant activities