不同等级普洱熟茶的代谢物差异分析

为探究不同等级晒青茶对其制备的普洱熟茶品质的主要化学成分影响，通过分筛机械把机采机制晒青茶原料分为三个等级，加工得到A、B和C三个不同等级普洱熟茶，应用茶叶感官审评和代谢组学技术对其进行检测。结果表明：B等级的感官审评最优；PCA分析中A明显区别于其余试样；共筛选出的238个差异代谢物中有12个标志性代谢物，除了D-麦芽糖的相对定量是与等级呈负相关，其余都是与等级呈正相关；四类重点物质中氨基酸及其衍生物的相对总量为A（0.053 mg/g）>B（0.007 mg/g）>C（0.006 mg/g），生物碱为A（0.072 mg/g）>B（0.042 mg/g）>C（0.028 mg/g），黄酮及类黄酮为A（0.516 mg/g）>C（0.221 mg/g）>B（0.245 mg/g），儿茶素及其衍生物为A（1.808 mg/g）>B（0.668 mg/g）>C（0.482 mg/g），都是随等级的降低而减少；苯丙氨酸代谢是所有差异代谢物里相关性较强的通路。这些差异代谢物的变化规律可为机采机制晒青茶在后续普洱熟茶加工中的品质提升提供理论依据和科学指导。

Analysis of Differentially Accumulated Metabolites among Different Grades of Ripe Pu-erh Tea

To investigate the influence of different grades of sun-dried green tea on the quality of the roasted Pu-erh tea prepared from them, the raw materials of machine-harvested sun-dried green tea were sieved and divided into three grades. Three different grades of roasted Pu-erh tea, namely A, B and C, were processed and examined through sensory evaluation of tea leaves and metabolomic analysis. Grade B had the best sensory evaluation results, and grade A was notably different from the other specimens in principal component analysis. Of 238 differentially accumulated metabolites, 12 were screened. Of these, D-maltose was negatively correlated with grade, whereas the other 11 metabolites were positively correlated with grade. The relative total content for four key substances were in the order of A (0.053 mg/g) > B ( 0.007 mg/g) > C (0.006 mg/g) for amino acids and their derivatives, A (0.072 mg/g) > B (0.042 mg/g) > C (0.028 mg/g) for alkaloids, A (0.516 mg/g) > C (0.221 mg/g) > B (0.245 mg/g) for flavanones and flavonoids, and A (1.808 mg/g) > B (0.668 mg/g) > C (0.482 mg/g) for catechins and their derivatives. Phenylalanine metabolism was the most involved pathway among all differentially accumulated metabolites. The variation patterns of these differentially accumulated metabolites can provide a theoretical basis and scientific guidance for improvement of the quality of machine-harvested sun-dried green tea and its subsequent processing into roasted Pu-erh tea.