Variations in the activities of the enzymes involved in the formation and interconversion of polyphenols during black tea manufacture

The role of enzymes contributing towards the quality of tea liquor such as polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL) and peroxidase (PO) were studied during withering, rolling, fermentation and drying till the formation of the end product. Significant decrease was observed in the activity of PPO during fermentation and prefiring phases of tea processing. Increased activity of PPO and PO during rolling stage of tea processing was observed with no significant changes in PAL activity.