Research On Deterioration Process And Qualityforming Mechanism Of Black Tea With Rich Flavor

Yunnan province is the origin of tea in the world and the origin of Pu-erh tea. Because ofrain in summer and autumn, the tea produced during this time is lack of flavor and has bittertaste, the consumer acceptance of which is low. Thus most tea farmers do not pick these tealeading to resource waste. In this research, the process of traditional black tea was combinedwith the process of oolong tea and was applied to the fresh tea leaves grown in summer orautumn. Then the flavor and the quality of black tea were improved. By selecting differentway of deterioration, a suitable process for developing black tea which leaves picked insummer and autumn was studied and the critical parameters were optimized. At last, the flavorforming mechanism was briefly discussed.Firstly, the aroma composition of black tea, main composition and sensory quality ofprocessed by traditional indoor deterioration, sun-withering deterioration and sunwithering-green making deterioration developed in this thesis were determined respectively.Compared with traditional black tea, the linalool content in rich flavor black tea increased by28%, the hexenal content decreased by 54%; amino acid which contribute the sweetness of teaand soluble sugar increased by 30% and 15% respectively. Caffeine content and teapolyphenol content which contributed to bitterness decreased by 13% and 10% respectively;the theaflavin content and thearubigins content which contribute to the color of tea increasedby 40% and 12% respectively; theabrownin content which is bad for tea quality decreased by7%. The sensory value for rich flavor black tea was 89.6 which was better than traditionalblack tea(86.2).Secondly, the effect of parameters in deterioration process on the quality of black tea wasstudied. And it was found that the sun withering time, green making times, green makingtemperature and deterioration degree all had shown great effect on the sensory quality andbiochemical parameters. So single factor experiment was conducted with these parameters,response surface method was used to optimize the deterioration parameters. The bestdeterioration process was achieved subsequently as follows: sun greening time was 45 min,green making times was 3, green making temperature was 26℃, water loss rate in greenmaking is 35%.Thirdly, changing patterns of main components and the activity of critical enzymes werestudied subsequently, and the relationship between them were also discussed. The resultsshowed that the content of aroma components and main taste substances as well as theactivities of polyphenol oxidase and β-glucosidase were all improved by the new witheringtechnology of rich flavor black tea.Finally, the quality of rich flavor black tea were compared with Yunnan black tea andwhich proved that the overall quality of the rich flavor black tea prepared in this thesis by sunwithering-green making deterioration was higher than the first class- Yunnan black tea. Therich flavor black tea was characterized by rich in flower aroma, red color and highconcentration of tea soup, mellow taste and the red and shine button of leaves. The tea met thestandard of high quality black tea.