Studies On Quality Formation Mechanism And Mechanizing Technology Of Luyuan Yellow Tea

Luyuan tea, a kind of historic famous tea of Yuanan country in Hubei province, is of yellow tea. In this article the quality formation mechanism of Luyuan tea was stated, the piling and shaping conditions were also optimized. Finally mechanizing technology was confirmed.Changes of biochemistry components and color during processing in orthodox handwork technology were investigated. Contents of tea polyphenols decreased, and that of amino acids, soluble sugar and protein increased first and then decreased. Catechins was determined by HPLC. Results showed that the EGCG and ECG contents decreased and the C and EC contents increased; chlorophyll a, chlorophyll b and total chlorophyll contents declined significantly. Chromatic evaluation method was first applied in Luyuan tea color determination. Results showed that the values of a* of drying tea and liquor were all negative and absolute values dropped during processing; the values of b* of drying tea and liquor were all positive ,b* value of drying tea decreased , but b* value of liquor increased.Results in piling experiments showed that yellow chroma increased, green chroma and luminance(L*) decreased, stewed flavor of aroma and taste sharpened with the piling temperature rising and piling duration delaying. Influence of water content, piling temperature and duration on the contents of tea polyphenols and chlorophyll was signicant, but not significant on the contents of protein , amino acids and soluble sugar. With the increase of water content, piling temperature and duration the contents of tea polyphenols and chlorophyll took on a decreased trend. According to the organoleptic tasting results and the changing trend of biochemistry components, it was regarded that the optimizing condition was: water content 40-50%, piling temperature 35 C, and piling duration 4-7h.Two-pan quhao roasting machine was applied to the shaping procedure of Luyuan tea. Orthogonal design experiment on water content, shaping temperature and duration was chosen to optimize the shaping condition. Results showed that effects of the three factors on main biochemistry components were not significant but signicant on organoleptic quality. Low shaping temperature and more leaf weight led to delaying of shaping duration and formating dull color of dry tea. In the shaping condition that water content was 40-50%, shaping temperature 150C and leaf weight about 2Kg, Luyuan tea appearance twisted tightly and 'huanzijiao' shape appeared. At the last stage of shaping ,if pan temperature rose to 150C, 'Yuzipao' could appear in drying tea.Luyuan tea mechanizing technology was realized first. On the results of piling and shaping experiments, the Luyuan tea mechanizing technical process could be comfirmed as follows: Fresh leaf- spreading-fixation(rotary continuous fixation machine) - firstfiring(rotary continuous fixation machine)-yellowing-shaping(two-pan quhao roasting machine) - blistering(two-pan quhao roasting machine) - drying(famous tea dryer) -improving aroma(famous tea dryer). Compared with traditional technology, mechanizing technology shortened the processing time .reduced the work intension and made the quality of Luyuan tea stable.