Effects of drying methods on the polyphenol content and antioxidant activities of chicory leaf

The study was aimed to investigate the impacts of different drying methods on the polyphenol content and antioxidant activities of chicory leaf.The change of polyphenol oxidase(PPO)activity during drying process,the flavonoid and total polyphenol content of dry chicory leaf were measured,and the DPPH free radical,ABTS+ · free radical scavenging capacity and reducing power of the polyphenol extraction from chicory leaf were also determined under different drying methods including air drying,freeze drying and hot air drying at different temperatures so as to obtain the optimum drying method.The results showed from the following aspects.1)The content of polyphenol in chicory leaf processed by different drying methods was significantly different,which could be due to a combination of residual PPO activity and heat sensitivity of polyphenol during the drying process.2)When the flavonoid content and total polyphenol content were taken into account,hot air drying at 60 ℃ was the best result,freeze drying was the second and air drying was the last one.3)The DPPH free radical scavenging capacity,ABTS+· free radical scavenging capacity and reducing power all had a significant positive correlation with the flavonoid and total polyphenol content in chicory leaf(R2≥0.888,P0.05).In order to have the higher polyphenol content and antioxidant activity in dry chicory leaf,the hot air-drying at 60 ℃ was a recommended drying method for chicory leaf.