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Studies on the Chemical Quality of Raw Dark Tea during Storage

Author: XieJiaoMei
Tutor: ZhuQi
School: Hunan Agricultural University
Course: Tea Science
Keywords: raw dark tea storage chemical quality temperature humidity microorganism
CLC: TS272.5
Type: Master's thesis
Year: 2013
Downloads: 3
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Abstract

Raw dark tea is the material and primary quality of making made dark tea. Before processed into brick tea, the new made raw dark tea should be stored for at least1to2years, it means maturation. Sensory evaluation is usually used in the judgment of stored raw dark tea quality in the production, but there is no research and report on the content and change of biochemical components in raw dark tea during storage.The third grade raw dark tea made in fall and the second and third grade raw dark tea made in summer were studied in this paper. The third grade tea made in fall was stored for almost3years in storehouse with a natural environment, the second and third grade raw dark tea made in summer were stored for a year and a half at the same condition as the third grade tea made in fall. Samples of stored tea were taken every two months, and the sensory quality and biochemical components content were tested and analyzed. During the storage of the second and third grade raw dark tea made in summer, the temperature and humidity of storehouse was observed and recorded, the microbial amount in different season was detected.The results were analyzed and compared, showed as follows:1、The change of environment condition during storage was first tracking analyzed in this paper. Results showed that our province has four distinct seasons, and the temperature and humidity in storehouse had a great effect upon microorganism in raw dark tea. The microorganism amount increased more in a natural environment with high temperature and low humidity, and the most in summer. The greater impact of storage environment on bacteria as the change of bacteria amount was more significant than fungus.2、The quality of raw dark tea during storage was first analyzed, and results showed that the longer storage, the greater the quality of raw dark tea changed. The sensory quality was almost the same between the third grade new raw dark tea made in the fall of2009and which made in the summer of2011, similar sensory quality after a year and a half of storage, but marked different from their beginning storage, and both become better. After the storage of another a year and a half, the dry tea color became brown, it tasted purer, harsh and astringency taste almost disappeared.During the storage most biochemical components of tea reduced variedly in content from time to time. Compared with the third grade raw dark tea stored for a year and a half, the one stored for3years lossed more water extract, tea polyphenols, catechins, theobromine, caffeine and theanine.3、The quality change of different grade raw dark tea during storage was first discussed in this paper. Results showed that the second grade raw dark tea was easier to be maturated than the third grade raw dark tea, and raw dark tea with piling processing easier to be maturated. After one year storage, the aroma of the second raw dark tea tested in tea samples become more fragrant, the soup color turned to orange-yellow, and tasted purer. And the third grade raw dark tea should be stored for almost3years to reach to the similar quality.Except theophylline, lactic acid and malic acid, most of biochemical components content in the second grade raw dark tea were higher than that in the third grade raw dark tea. During storage, tea polyphinols, EC, caffeine, oxalic acid etc. content in the second grade raw dark tea lost more than that in the third grade raw dark tea, but amino acids, EGC, theobromine, theophylline, Asp, Arg and Theanine reduced less.4、The temperature and humidity in storehouse affected on the quality of raw dark tea. Water content of raw dark tea got great influenced from the temperature and humidity in storehouse. The temperature is lower, humidity is higher, tea water content become more, or become less. Theophylline, catechins and part of amino acids easy to be influenced by the environment to become less. Some other components also lost but changed less. Flavones and soluble sugar stayed normal, and the effect of environment on them is not obvious.

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