CHANGES IN CHEMICAL CONSTITUENTS AND POLYPHENOL OXIDASE ACTIVITY OF TEA LEAVES WITH SHOOT MATURITY AND COLD STORAGE

Abstract

ABSTRACT The variation in the composition of fresh tea leaves with season and shoot maturity, and to the applicability of cold storage (4C and 90% relative humidity [RH]) for the purpose of withering of tea leaves were studied. The results showed that the levels of polyphenol oxidase (PPO) activity and the polyphenolic content changed significantly with plucking season and shoot maturity. No significant difference was observed between the total polyphenolic content of the cold storage-withered and traditionally withered samples, whereas the loss of PPO activity was less in the cold-stored leaves. No significant difference was observed between the cold storage-withered and traditionally withered samples in terms of the end product quality. Results showed that cold storage at 4C and at 90% RH was suitable for storing fresh leaves after plucking until the time of processing and it is possible to achieve withering during the cold storage of tea leaves. PRACTICAL APPLICATIONS The tea growing season is very short in Turkey. Therefore, the tea processing factories sometimes experience capacity problems, and high amounts of tea leaves are lost because of poor storage conditions until the time of processing. Moreover, the quality losses in fresh tea leaves between the time of harvesting and processing have a negative impact on the final black tea quality. The application of cold storage for long-term withering of fresh tea leaves can help to prevent the postharvest losses and can prolong the period for black tea production.