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Properties of leaf and infusion colours, chemical components and volatile flavour compounds of oolong teas and their correlation with perceived quality score given by tea-tasting panel were analysed. The scores for appearance and infused leaf correlated strongly with concentrations of chlorophyll a (chl a), chlorophyll (chl b) and chlorophyll (chl) ( r = 0.355–0.433, P < 0.05) and the total quality score (TQS) positively correlated with concentrations of chl a, chl b and chl ( r = 0.517–0.533, P < 0.01). The perceived taste score and TQS positively correlated with the concentration of total free amino acid ( r = 0.514, 0.694, P < 0.01) and theanine ( r = 0.500, 0.684, P < 0.01). The volatile composition and their quantities varied widely among oolong tea samples. Nerolidol, indole, benzeneacetaldehyde, linalool, linalool oxide I, hexanal, benzyl nitrile, geraniol and 1-penten-3-ol were prevailing volatile compounds detected in most of oolong tea samples. Principal component analysis screened ten principal components with the first three (glutamic acid, total catechins and benzeneacetaldehyde) explaining 27.86%, 20.00% and 14.46% of the total variance, respectively. Regression analysis upon the ten principal components formulated a prediction model on the total quality score with 78.5% probability. The result showed that oolong teas could be partially classified by cluster analysis based on principal components. [ABSTRACT FROM AUTHOR]

Properties of leaf and infusion colours, chemical components and volatile flavour compounds of Longjing teas and their correlation with perceived quality score given by tea-tasting panel were analysed. The scores for appearance, infused leaves and for the Total Quality Score (TQS) negatively correlated with concentrations of chlorophyll-a (Chl-a), Chl-b and total chlorophyll ( r = −0.723 to −0.846, P < 0.01). The perceived taste score positively correlated with the concentration of total free amino acid ( r = 0.527, P < 0.05) and theanine ( r = 0.511, P < 0.05), whereas the TQS positively correlated with total free amino acid ( r = 0.533). The volatile composition and their quantities varied widely among Longjing tea samples. (E)-geraniol, linalool, hexanal, pentanal, heptanal, nonanal and jasmone were prevailing volatile compounds detected in all samples. Principal component analysis (PCA) screened twelve principal components with the first three explaining 18.82%, 15.31% and 11.83% of the total variance respectively. The concentrations of total free amino acids, pentanal and epigallocatechin gallate were with the highest component score coefficients for the first three principal components respectively. Regression analysis upon the twelve principal components formulated a prediction model on the TQS with 77.0% probability. [ABSTRACT FROM AUTHOR]

Tea (Camellia sinensis L.) is a perennial woody plant that is widely cultivated to produce a popular non-alcoholic beverage; this beverage has received much attention due to its pleasant flavor and bioactive ingredients, particularly several important secondary metabolites. Due to the significant changes in the metabolite contents of the buds and the young expanding leaves of tea plants, high-performance liquid chromatography (HPLC) analysis and isobaric tags for relative and absolute quantitation (iTRAQ) analysis were performed. A total of 233 differentially expressed proteins were identified. Among these, 116 proteins were up-regulated and 117 proteins were down-regulated in the young expanding leaves compared with the buds. A large array of diverse functions was revealed, including roles in energy and carbohydrate metabolism, secondary metabolite metabolism, nucleic acid and protein metabolism, and photosynthesis- and defense-related processes. These results suggest that polyphenol biosynthesis- and photosynthesis-related proteins regulate the secondary metabolite content of tea plants. The energy and antioxidant metabolism-related proteins may promote tea leaf development. However, reverse transcription quantitative real-time PCR (RT-qPCR) showed that the protein expression levels were not well correlated with the gene expression levels. These findings improve our understanding of the molecular mechanism of the changes in the metabolite content of the buds and the young expanding leaves of tea plants. [ABSTRACT FROM AUTHOR]