【摘要】 为深入了解滇青(晒青毛茶)、青饼和普洱茶(熟饼)在化学组成方面的异同,为茶类的区分与界别提供进一步的科学依据,对滇青、青饼和普洱茶(熟饼)的近红外化学指纹图谱采用欧氏距离、主成分分析和系统聚类等方法进行了定性判别分析。结果发现,普洱茶(熟饼)近红外指纹图谱与滇青、青饼图谱间的欧氏距离均大于各自组内最大偏差的绝对阈值,而滇青和青饼的组间差异小于各自的组内阈值;在第一主成分和第二主成分得分值散点图上,熟饼样品与青饼和滇青样品间界限分明,而滇青和青饼样品间无明显界限;所有的熟饼样品在系统聚类分析中聚为一类,而青饼与滇青样品聚为一类。因此,青饼的近红外光谱在各方面都与普洱茶(熟饼)样品差异显著,而与其原料滇青(晒青毛茶)十分接近。从化学本质上来说,青饼更接近于绿茶类产品。更多还原

【Abstract】 Near-infrared fingerprints of three tea sample groups of Dianqing(solar dried green tea as material of Puer tea),Qingbing(compressed tea cake manufactured from Dianqing without fermentation) and Shubing(Puer tea cake compressed after post-fermentation) were studied using Euclidean distance comparison,principal component analysis and hierarchical clustering analysis for further exploring the differences of chemical composition of above three groups of tea samples,as well as providing more evidence to the study of tea product classification.The results showed that both Euclidean distances of Near-infrared fingerprints between Shubing and Dianqing or Shubing and Qingbing were larger than those absolute thresholds of Euclidean distance within each group.And Euclidean distance between groups of Qingbing and Dianqing was smaller than those thresholds within each group.In the scatter diagram made by the scores of principal component 1(PC1) and principal component 2(PC2),all Shubing samples separated distinctly from Qingbing and Dianqing samples,but there was no clear boundary between Dianqing and Qingbing.All Shubing samples clustered into one group when hierarchical clustering analysis was made using principal component scores,while Qingbing samples and Dianqing samples and Dianqing samples were clustered into another.Therefore,near-infrared fingerprint of Qingbing differed remarkably with that of Puer(Shubing) but closely matched that of Dianqing material.It could be concluded that Qingbing was more similar to green tea than black tea from the chemical nature.更多还原