s.h. roofigari haghighat

Variations in theaflavin and thearubigin content during fermentation and the effects of these variations on brightness and total color in black tea were evaluated at the Tea Research Center in Lahijan in the year 2004.  Percentages of theaflavin (TF), thearubigin (TR), total color and brightness were determined in two clones 100 and in the natural Chinese hybrid during flushing in the months of June, August and October and different fermentation time (30, 60, 90, 120 and 150 minutes). It is evident from the results obtained that apart from genetic differences in the clones under study, changes in climatic conditions during different periods of flushing and fermentation time can to a great extent influence the amount of TF, TR, total color and brightness in black tea. Results obtained also indicated significant interacting effects of clones, different flushing and fermentation times on the quality-determining characteristics of black tea. No significant correlations were found between TR and brightness however, significant correlations were found between other characteristics studied at the 1% probability level. On the basis of regression analysis with fermentation time (independent variable) and each of the characteristics studied (dependent variable), linear relationships were detected between fermentation time and brightness and TF content. Multi-variable regression analysis between brightness (dependent variable) and TF and TR (independent variables) showed that more than 56% of variations in brightness in black tea was related to TF and TR. Also multi-variable regression analysis between total color (dependent variable) and TF and TR (independent variable) indicated that more than 43% of variations in total color in black tea can be attributed to TF and TR percentages

To study the effects of plucking time and fermentation of green leaf on quality parameters of black tea an experiment was conducted at Tea Research Foundation of Lahijan in 2004 using two different varieties. Two varieties (Var. No. 100 and Chinese Natural Hybrid) with different time of plucking and five different time of fermentation, i.e. 30, 60, 90, 120 and 150 minutes, were considered in the experiment. Percentage of theaflavins, thearubigins, total color, brightness, and tannins was measured as quality parameters. The results showed that in spite of difference between varieties, changing climates at different plucking time and fermentation time, also affected the amounts of theaflavins, thearubigins, total color, brightness, tannins and caffeine. Interaction of var × plucking time × fermentation time was significant with respect to black tea. Therefore, each variety in specific time of plucking and fermentation, will provide a best quality of black tea.