Assessing biochemical and sensory changes of tea during standardization of a modern green tea processing unit for manufacturing quality green tea

A programmable logic controller (PLC) based modern green tea factory was recently launched at Bangladesh Tea Research Institute to meet the demand of some good quality green tea for the people of the country and also to strengthen research in this area to support the tea industry. This necessitated to carry out research with this processing unit to standardize the manufacturing technique for the production of quality green tea. Different parameters were changed during processing according to the treatments and the product green tea samples were analyzed biochemically for the determination of quality. From the results, it was observed that total polyphenols and caffeine contents decreased significantly with the increase of withering period from 1 hour to 3 hours. If the fixation temperature increased from 250°C to 270°C, the caffeine content almost remained unchanged but the total polyphenols content increased, though not significantly. The total polyphenols and caffeine contents increased as the rolling time increased from 45 minutes to 55 minutes. Immediate after rolling, application of high temperature to dry the leaves was found detrimental for the final green tea quality and thus lowering the roll-drying temperature from 220°C to 200°C significantly enhanced the quality. It was observed that after cooling the roll-dried leaves, increase of temperature in the dryer from 100°C to 120°C enhanced tea quality. From the findings of the present study, it can be suggested that 1 hour Withering ® Fixation at 270°C ® 55 min Rolling ® Roll Drying at 200°C ® Final Drying at 120°C can be set as a common procedure for manufacturing quality green tea using the newly established green tea factory of Bangladesh Tea Research Institute.