Effect of rolling methods and storage on volatile constituents of Turkish black tea

The leaves of harvested tea [Camellia sinensis (L.) O. Kuntze] can be processed into different products such as black tea, green tea and oolong tea. Black tea is the mostly consumed worldwide among these products. Black tea production is achieved by a series of processing steps namely withering, rolling, fermentation, drying, sieving and packaging. Rolling is one of the most important steps in the production as it ensures uniform maceration of tea leaves and promotes oxidation reactions catalysed by phenol oxidase enzymes during the fermentation process. The rolling of tea leaves is generally performed by either Crushing-Tearing-Curling (CTC), rotorvane or Orthodox methods. However, in Turkey, rolling is also performed using a combination of rotorvane and orthodox which is called the “CAYKUR” method. The rolling method provides a unique taste and flavours. Thus, this study was conducted to compare volatile constituents of the black teas produced by the above rolling methods and to determine the volatiles during the 6-month storage period. Some specific compounds such as 2,6-nonadienal, 3-hexen-2-one and dodecanal for CAYKUR, 2,5-octanedione for Orthodox and methylpyrazine for CTC were identified to differentiate the rolling system. This study also showed that a few compounds can be used as markers of storage. The number and amounts of volatiles, especially compounds with a high molecular weight, increased by storage. In addition, the flavour quality of the teas was evaluated by the Wickremasinghe–Yamanishi ratio (WYR), Mahanta ratio (MR) and Owuor Flavour Index.