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Influence of fermentation time on the development of compounds responsible for quality in black tea 总被引:3,自引:0,他引:3
The compounds responsible for tea quality, such as theaflavins (TFs) and thearubigins were found to increase with fermentation time. However, TF reached a maximum, declining subsequently. The water extract of black tea decreased with fermentation time. Caffeine concentration remained unchanged. The digallate equivalent of theaflavin, colour index and briskness index were found to peak at the optimum fermentation time. Polyphenols declined more quickly during the initial stages, followed by a steadily declining trend. Fermentation time had little impact on the gallic acid concentration. Among the catechins, epigallocatechin oxidized fastest, followed by epigallocatechin gallate and epicatechin gallate. 相似文献
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研究了以碎茶为原料获得了在一次工艺中制取茶叶抗氧剂、咖啡碱、叶绿素的最佳工艺条件,并对茶多酚的纯度与抗氧性的关系,柠檬酸对茶多酚的抗氧增效作用进行了研究,指出茶多酚作为抗氧剂产品必须具有较高的纯度。 相似文献
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Contents of various elements in dyferent parts of the tea plant (shoot, mature leaf, small stem, thick wood and root), black tea manufactured by the crush-tear-curl and orthodox processes, and tea brew after 1 and 5 min of infusion were determined by inductively coupled plasma atomic emission spectrometry. From these, the amount of each element assimilated in the production of 1000 kg of marketable tea, as well as the quantity of each element brought into infusion and thus possib f y taken up through drinking tea, were calculated and discussed. Among the various elements assimilated by the tea plant, the shoot jraction (economically important for manufacturing commercial tea) contained high concentrations of N, P, K and Mg while the mature leaf accumulated Al, Bu, Ca, Cd, Mn, Pb and Sr. Of the dgerent elements brought into infusion while brewing black tea, the amount of K was found to be the largest (> 10000 μg g−1 tea) followed by P (700–1200 μg g−1), Mg (300–700 μg g−1), Ca and A1 (each 150–300 μg−1), Mn (60–150 μg g−1), Cu, Na, Si and Z n (each 6–50 μg g−1), B, Ba, Cr, Fe, Ni and Pb (each Id μg g−1), and Sr, Co and Gd (each <1μg g−1). The proportion of the totalamount of an element brought into infusion showed that the elements Ba, Ca, Fe and Sr were less soluble (<10 % of total amount), Al, B, Cd, Co, Cr, Cu, Mg, Mn, P, Pb, Si and Zn were moderately soluble (10–50 %), and K, Nu and Ni were highly soluble (>50%). The overall mean of the extent of solubility of all elements in 1 and 5 min showed that, out of the amount soluble in 5 min, about 68% was dissolved within 1 min. 相似文献
79.
藏中电网规模较小,网架结构相对较弱,青藏直流联网工程投运后给藏中电网的安全稳定运行带来诸多挑战,交直流系统稳定问题突出。从联网工程投运前藏中电网的电源特性、大机小网等固有特性出发,结合青藏直流联网以来青藏直流以及藏中电网运行中存在的各种稳定问题,深入分析了青藏直流投运后藏中电网的电源特性变化、稳定特性转化、虎曲线功率送出、直流换相失败、以及交直流影响等安全稳定问题。同时针对西藏电网的运行特性,分析并指出了青藏直流几个重要而特殊的安全稳定运行特性。 相似文献
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Schizosaccharomyces pombe cells are rod-shaped and grow along a single axis from their two ends. Microtubules extend from the cell centre terminating at the cell ends. The ERM(ezrin/radixin/moesin)-like proteins Tea1p and Tea3p, and the Dyrk-like kinase Pom1p are cell end markers involved in the regulation of growth and microtubular dynamics at the cell ends. We have analysed the relative contribution of these three proteins to the determination of cell ends as sites both for cell growth and for microtubular termination. Pom1Delta, in combination with Tea1Delta or Tea3Delta, has the greatest difficulty in relocalizing actin to the cell ends following actin depolymerization and generates the most defective growth pattern. Tea1Delta, in combination with Pom1Delta or Tea3Delta, displays the highest number of microtubules bending round the cell ends. Tea1DeltaPom1Delta, which has the most defective growth pattern and microtubules, also displays the highest number of branched cells. We show that Tea1p, Tea3p and Pom1p all contribute, to different extents, to the determination of cell ends, as sites for both cell growth and microtubular termination. We also show that the fission yeast cell relies on both the positioning of landmarks and a properly organized microtubule cytoskeleton to direct cell growth. 相似文献