Preliminary Studies On The Quality Degradation Of Fujian Oolong Tea In Storage

Fragrance and taste are the most important factors representing Oolong tea quality, but the concerning components are subject to the influence of temperature, light, oxygen and moisture, therefore the Oolong Tea in storage is easy to degrade in quality when improperly treated, such could be examined as with the appearance of the dry tea becoming darkness, the thickness and the strength of the liquor declining or the flavour of the infusion losing. This paper chose Tie Guanyin, Huangdan, Shuixian and Meizhan as test materials, and studied the change of the quality and the chemical components during storage for six months and by sampling each month. At the same time, the test materials were stored under three temperature levels (room temperature, 5°C and - 18°C ) , and at the end of six months, the relative quality, the chemical and aromatic components were examined and checked up. The results were as follows:1. Variations of the chemical components (moisture contents, water extract, tea polyphenols, free amino acids, caffeine, flavones, carbohydrates, catechins, chlorophyll, theaflavins, thearubigins, theabrownine) and sensor qualities were studied and examined, and then the liner regression analysis and multiple linear regression analysis were applied to the correlation of the chemical components and the sensor qualities. The correlation coefficients concerning Tieguanyin were as follows: r (Carbohydrate) =0.920, r (Catechins) =0.994, r (Chlorophyll) = 0.954; The correlation coefficients concerning Huangdan were as follows: r (TP) = 0.940, r (Catechins) =0.966; The correlation coefficient concerning Shuixian were as follows: r (Catechins) =0.969; The correlation coefficient concerning Meizhan were as follows: r (Catechins) =0.959. Which led to the conclusion that the degradation of the above metioned qualities in storage. Oolong Tea was all related to the drop in catechins. After 6 months, the quality of Tieguanyin declined by 9.78%, Huangdan by 10.07%, Shuixian by 8.81% and Meizhan by 8.08%, which proved that the rate of degradation of Oolong Tea in South Fujian was bigger than that in North Fujian. The results also showed that moisture contents of Tieguanyin, Huangdan, Shuixian and Meizhan trended towards increase during storage.2. Tie Guanyin, Huangdan and Shuixian were chosen as test materials, and treated by different temperature levels (room temperature, 5°C and - 18°C). At the end of six months, the qualities, chemical and aromatic components were checked up, and the results revealed that the temperature in storage deeply affected the fragrance of Tieguanyin and Huangdan, but little the fragrance of Shuixian. Besides, the temperature in storage affected the variation of the concerning chemical compents, the taste and the total scoring on the sensor quality of Tieguanyin, Huangdan and Shuixian. This paper also indicated that storage at 5°C was superior to that at - 18°C for the sustaining of quality of the above mentioned Oolong Tea varieties. Therefore it suggested that storing temperature for Oolong Tea, when below or far below 0°C, should be carefully applied to and worthy of being further studied.