Aroma is one of the key factors for evaluating the quality of green tea. A tender aroma (NX) and floral-like aroma (HX) are two types of high-quality aroma of green tea. In this work, the different aroma types of baked green tea were classified by sensory evaluation. Then, seven tea samples with a typical tender or floral-like aroma were selected for further volatile component analysis by GC-MS. A total of 43 aroma compounds were identified in two different aroma types of baked green tea samples. The PCA showed that linalool, geraniol, 3-hexenyl butyrate, and 3-hexenyl hexanoate were the major volatiles contributing to the HX. On the other hand, most of the alcohol volatiles, such as 1-octanol, 1-octen-3-ol, 1-dodecanol, 1-hexadecanol, phenylethyl alcohol, benzyl alcohol, aldehydes and some hydrocarbons contributed more to the NX. In addition, the chemical composition analysis showed that the content of free amino acids was higher in NX green tea samples, while the content of catechins was relatively higher in HX tea samples. A proteomic analysis revealed that most of the enzymes involved in VPBs pathways, such as phenylalanine ammonialyase, peroxidase, and shikimate-O-hydroxycinnamoyl transferase, were more abundant in NX than in HX tea samples. These results laid a foundation for the aroma formation mechanism of different aroma types of baked green tea and provided some theoretical guidance for the breeding of specific aroma varieties.

Shading enhances green tea quality by promoting the accumulation of amino acids and reducing the synthesis of catechin. We hypothesize that the expression of amino acid-related genes is related to the accumulation of amino acids in tea plants after shading. To explore the regulatory mechanism of shading-induced amino acid biosynthesis, we performed RNA-Seq and qRT-PCR analyses to examine the expression of amino acid metabolism-related genes. Our results revealed significant upregulation of genes associated with theanine biosynthesis and transport. In addition, non-targeted metabolomics and biochemical quantification revealed that the content of theanine and other amino acids significantly increased after shading. Furthermore, shading was found to promote coordinated regulation between light signaling components (e.g., UVR8, HY5, COP1) and transcription factors (such as CsMYB1/4/7/12 and CsPIF3). These findings reveal key molecular mechanisms behind shade-induced amino acid metabolism and provides new insights into our understanding of regulatory mechanisms for shading enhanced tea quality.

Background/Objectives: The ancient tea plant germplasm resources are rich in genetic diversity and provide an important basis for the genetic diversity in tea germplasm resources. To explore the genetic diversity of ancient tea plant germplasm resources in Jiulong County, Sichuan Province. Methods: 59 ancient tea tree germplasm resources were analyzed using simple sequence repeat (SSR) molecular markers and chemical composition analysis. Results: The results showed that a total of 83 alleles were amplified by 23 pairs of SSR primers, with an average observed allele number (Na) of 3.6 and an effective allele number (Ne) of 2.335. The average Shannon information index (I) and the polymorphic information content (PIC) of the primers were 0.896 and 0.446, respectively. The results of the UPGMA cluster analysis showed that 59 ancient tea tree samples could be classified into five different subgroups. Based on the results of chemical composition analysis, two specific tea germplasm resources with high amino acid content, 10 excellent germplasm resources with tea polyphenol content over 20% and some other tea germplasm resources were identified. Conclusions: This study reveals that Jiulong’s ancient tea tree germplasm exhibits significant genetic diversity and includes valuable tea tree planting resources. These findings provide a foundational framework for the conservation, detailed exploration and sustainable utilization of these resources.

To comprehensively understand the quality characteristics and key characteristic metabolites of Hangzhou Gongmei white tea (HGW), an integrated approach involving sensory evaluation, chemical composition analysis, gas chromatography–mass spectrometry (GC-MS), and liquid chromatography–mass spectrometry (LC-MS) was employed to analyse the volatile and non-volatile metabolites of tea samples from different varieties. Compared to the Fudingdabai (FD) variety, the Jiukeng (JK) and Longjing (LJ) varieties exhibited more pronounced fruity or floral aromas and stronger taste profiles. The elevated concentrations of water extracts, tea polyphenols, and complex catechins in the tea infusion contributed to its increased astringency. A multivariate analysis revealed that linalool, geraniol, 2-ethylhexanol, hexanal, methyl salicylate, linalool oxide I, (E)-hex-2-en-1-al, β-myrcene, (Z)-hex-3-en-1-ol, phenylethanol, benzaldehyde, (E)-citral, nonanal, and trans-β-ionone were the primary differential volatile metabolites in HGW. The non-volatile metabolomic analyses showed that flavonoids were the main differential metabolites in HGW from different varieties. The abundance levels of the differential non-volatile metabolites were higher in JK and LJ compared to those in FD. This study provides theoretical support for the breeding and quality improvement of Hangzhou white tea, as well as the development of flowery and fruity flavoured white tea products.

Baking is commonly used to improve the flavor of stale tea. However, the effects of baking methods on volatiles and non-volatiles in stale Longjing tea remain unclear. In this study, we employed sensomics and metabolomics approaches to analyze the effects of baking methods on the flavor quality of stale Longjing tea. The results showed that far-infrared baking (FIB) eliminated the stale odor and endowed Longjing tea with a pleasant bean-like aroma and a low-astringency, strong and mellow taste. A total of 263 volatile compounds and 379 non-volatile compounds were detected, among which 12 key differential volatile compounds and 139 important differential non-volatile compounds were screened. FIB treatment promoted amino acid acetylation, catechin epimerization, and N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSFs) formation, while regulating thermal lipid degradation and Maillard reaction, thereby conferring a balanced and harmonious flavor profile. These results provide theoretical and technical support for the high-value utilization of Longjing tea.