| Summary: | 碩士 === 國立臺灣大學 === 森林學研究所 === 93 === For many strains of tea tree, manufacturing procedures and process control profoundly influence the chemical composition and sensory qualities of tea leaf. Full leaf black teas were produced from four strains of tea trees, selected by Yu-chih branch, Tea Research and Extension Station, COA. Sensory quality evaluation and tealeaf chemical composition analysis were conducted for temporal control of rolling and fermentation process. Qualities for different black tea of tea tree strains can be compared, and optimal schemes for tealeaf treatments were proposed for future commercial production.
From the chemical composition analysis of tea leaf, total catechins, total polyphenols, total free amino acids and total soluble contents were not significantly changed with respect to various treatments. However, total catechins and total polyphenols decreased with increasing duration of rolling and fermentation process. For spring and summer teas, total theaflavins differed significantly for more than 5% with respect to various processes. Total theaflavins increased with increasing duration of rolling and fermentation process. Among all strains tested, R120-F60 treatment of TTES No. 18 summer tea has highest total theaflavins of 11.98μmol/g. On the other hand, R60-F90 treatment of B-69-80-21 spring tea has lowest total theaflavins of 5.99μmol/g. In addition, increasing rolling time raised liquor colour score and related negatively to total catechins.
Sensory quality evaluation, including analyzing taste, flavour, liquor colour score for spring and summer teas, was conducted for four strains. Ranking of tea qualities from the best strain is: TTES No. 18, B-69-80-21, B-56-70-66-1 and B-56-70-211-1. Among strains tested, TTES No. 18 had a special flavour, but affected by orange liquor colour. Qualities of strains B-69-80-21 and B-56-70-66-1 were similar, with different pros and cons, and could be blended to amend each other. Spring tea was found to have significant correlation between sensory quality evaluation scores and total theaflavins. For TTES No. 18, significance of correlation between total theaflavins and taste (r = 0.929), liquor colour (r = 0.900) was P≦0.05; significance of correlation between total theaflavins and taste contenting liquor colour (r = 0.992) was P≦0.01. The above correlations for summer tea were also found significant.
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