In recent years, Turkish black tea has been manufactured by a combination of orthodox + rotorvane + orthodox systems, especially developed for the conditions of Turkey. The optimum fermentation time of black tea manufactured by this system was investigated at the factory level by measuring the theaflavin contents during the fermentation step, which starts with rolling and ends with drying processes. Optimum fermentation times from the start of rolling in the ORO system were determined to be 83 min and 80 min for coarse tea and sieved fine tea, respectively, by theaflavin analysis. Low levels of theaflavin in Turkish black tea were attributed to the very low quality of the fresh tea leaves and of the plucking standards. (C) 1997 Elsevier Science Ltd.