Study on Quality Components and Variation of Longnan Summer Tea

Wu Peng; Li Yonghua; Xu Jianhan; Jiang Yuying; Yuan Xuexia; Gao Rui; Zhao Tong; Bi Jingxiu; Hao Haining; Wang Huijun; Liu Pingxiang; Wang Yutao

doi:10.14083/j.issn.1001-4942.2026.02.008

Abstract：In order to improve the utilization rate of summer tea in Longnan,this experiment used fresh tea leaves of Longjing 43(LJ43),Xiaoye Seed-propagated Variety(XY),Xiaoye Seed-propagated Variety Old Trees(LXY),and Fuding Dabai Tea Old Trees(FD)harvested on May 10th,June 10th and July 10th in the Longnan region as materials.The contents of tea polyphenol,total free amino acid,theanine,γ-ami-nobutyric acid(GABA),six kinds of catechins,three kinds of purine alkaloids,and 20 kinds of common free amino acids were determined.Subsequently,the data were processed using principal component analysis(PCA),hierarchical cluster analysis(HCA)and orthogonal partial least squares discriminant analysis(OPLS-DA)to comprehensively evaluate the suitability of different tea varieties for summer tea processing and to investigate the formation mechanism of Longnan summer tea raw material quality.The results indicated that Longnan summer tea had a relatively high tea polyphenol content,meeting the standards of famous,special and high-quality agricultural products,but its amino acid content was slightly low.Significant differences exis-ted in quality components of fresh leaves among different varieties and picking dates.Regarding processing suitability,the phenol-to-amino acid ratio was the highest in XY fresh leaves picked on July 10th as 17.68,followed by XY and LXY leaves picked on May 10th.The phenol-to-amino acid ratio of LJ43 fresh leaves was only 6.56 when picked on May 10th,and it was lower compared to other varieties picked on different dates.Therefore,the clonal Longnan varieties LJ43 and FD were more suitable for processing green tea,while the lo-cal seed-propagated varieties were more suitable for processing black tea.Concerning different growth stages within the season,the changes in tea quality were greater in the later part of summer compared to the earlier part.From May 10th to June 10th,the total free amino acid content in the seed-propagated varieties(XY and LXY)increased significantly,while the tea polyphenol content did not change significantly.Therefore,for the local XY and LXY,the quality of early summer tea(June 10th)was superior to that of late spring tea(May 10th).Among the 31 compounds analyzed,the levels of GABA,methionine(Met)and epigallocatechin(EGC)increased from May 10th to June 10th in fresh leaves of all the four tea varieties,while the levels of other compounds either decreased significantly or remained unchanged.From June 10th to July 10th,only the level of theophylline showed a significant increase in all the four tea varieties,indicating a conducive environ-ment for theophylline anabolism during summer.In contrast,the levels of most catechins,such as gallocate-chin(G)and epigallocatechin gallate(EGCG)decreased,which might be associated with accelerated cate-chins decomposition under high midsummer temperatures.The findings of this study could provide technical references for high-quality development of the tea industry in the Longnan region.