Impact of various foliar diseases on the biochemical, volatile and quality constituents of green and black teas

摘要

The effect of various foliar diseases such as blister blight, brown blight, grey blight, bird's eye spot and sooty mould on physiological functions, important biochemical, volatile and quality parameters of green and black teas were compared and evaluated. The results revealed that there was a considerable reduction in physiological activities such as photosynthetic and transpiration rates. Under natural condition, the diseases caused significant decrease in polyphenols, catechins, and aminoacids contents of green leaf which are known to be important precursors determining the quality of black tea. Consequently, a drastic variation existed between volatile flavor components of diseased leaves when compared to healthy ones. A corresponding decrease in the principal tea quality constituents like theaflavin and thearubigin were substantially reduced in made tea. Due to pathogen invasion in tea leaves, the degree of tea quality is varied in varying levels. Among the various tea pathogens, Exobasidium Vexans affected the overall tea quality extensively when compared to other tea pathogens. In addition, the infestation of diseases declined flavour index value and created difficulty in withering and fermentation during tea processing which ultimately affect the overall quality of tea.