Effect of withering, rolling, fermentation and drying steps of Gilan's black tea on its phenolic content and antioxidant properties

Gilan’s black tea is obtained via the fermentation of the fresh leaves of Camelia sinensis var. assamica. In this study, the effect of tea production process and brewing methods, microwave and conventional methods were studied on their phenolic and flavonoid content and antioxidant activity (DPPH radical scavenging assay, iron atom reducing power). The results showed that due to the fermentation process, the antioxidant properties and phenolic content of tea were changed and also the tea brewing method was effective on these properties and the highest phenolic and flavonoid contents and antioxidant activity were determined in the rolling step on the microwave brewing method. While the lowest phenolic and flavonoid contents were observed in the withering step on microwave brewing method and the lowest antioxidant activity was related to the tea treatment under conventional brewing. Therefore, the microwave method with high extraction capability and reduced the processing time can be an alternative to the conventional methods in the food industry.