To investigate the differences in the quality of Huangguanyin oolong tea from different geographical origins, the aroma composition of Huangguanyin oolong tea produced in Yunxiao and Wuyishan was analyzed by using electronic nose and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The electronic nose data showed that orthogonal partial least squares-discriminant analysis (OPLS-DA) could distinguish Huangguanyin oolong tea from different geographical origins. By HS-SPME-GC-MS, a total of 79 aroma components were identified, of which 17 aroma components were found to be significantly different between the two production regions and therefore could be used to distinguish the geographical origin of Huangguanyin oolong tea. According to odor activity values (OAV), methyl jasmonate, indole, jasmonone, E-nerolidol and jasmonolacton contributed greatly to the floral aroma of Yunxiao Huangguanyin tea, while linalool, decanal, laurelene, isovaleraldehyde and hexanal contributed greatly to the floral and fruitaroma of Wuyi Huangguanyin tea. The results of geographical origin authentication showed that the discrimination accuracy of the support vector machine (SVM) model based on the 17 differential aroma compounds was only 83.33%, compared to 100% based on five important aroma components (linalool, E-lactone, jasmonolactone, methyl jasmonate and indole). Our results will provide useful information for elucidating the quality characteristics of Huangguanyin oolong tea from Yunxiao and Wuyishan.

To explore the effects of Empoasca onukii puncturing on metabolites in beauty tea produced from the cultivar Qingxindamao, sensory evaluation, ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and gas chromatography-mass spectrometry (GC-MS) were used to compare the sensory quality and metabolites of beauty tea processed from fresh tea leaves punctured or not punctured by E. onukii. The results showed that the quality of beauty tea with E. onukii puncturing was better. The contents of flavones, flavanols and their glycosides, phenolic acids, theaflavins, glycoside derivatives and tannins increased compared with beauty tea without E. onukii puncturing, while the contents of amino acids, saccharides and lipids decreased. Based on odor activity value (OAV) and partial least squares discriminant analysis (PLS-DA), a total of five characteristic volatile components, including geraniol, linalool, β-myrcene, methyl salicylate and D-limonene, were identified.

To explore the effect of variable-temperature baking technology on the quality of ‘Beauty’ tea, tea samples were prepared by indoor natural withering (IW) or outdoor solar withering (OW) alone or followed by one of three variable-temperature baking treatments, A: 65 ℃ for 4 h-75 ℃ for 2 h-85 ℃ for 1 h, B: 75 ℃ for 4 h-85 ℃ 2 h-95 ℃ for 1 h, and C: 85 ℃ for 4 h-95 ℃ for 2 h-105 ℃ for 1 h, and their taste quality was assessed by sensory evaluation, biochemical composition analysis and non-targeted metabolomics analysis. The results showed that for each withering method, the woodiness and mellowness of ‘Beauty’ tea decreased as the baking temperature increased, and the taste became mellower and richer. The floral and fruity aroma of the tea initially increased and subsequently decreased, and the sweet aroma continued to increase. The overall aroma changed from clean and woody to floral, fruity, nectar-like to sweet. The variations in the contents of caffeine, free amino acids, flavonoids, theaflavins and theabrownin were key to the formation of the difference in the flavor of ‘Beauty’ tea samples. In terms of specific metabolites, umami, sweet and bitter amino acids, as well as catechin components including epigallocatechin, catechin, epigallocatechin gallate and gallic acid, and theobromine were found to be the key differential metabolites, which played a key role in the mellow flavor of IW ‘Beauty’ tea and in the mellow, brisk, prominent honey-like flavor of OW ‘Beauty’ tea. Myrcene, geraniol, cis-linalool oxide, cis-linalool oxide (furans), β-ionone, phenylacetaldehyde and nerolidol were found in ‘Beauty’ tea regardless of the withering method used or the baking temperature, and their contents were the key factors affecting the difference in aroma. For IW, baking treatment B performed best among all baking treatments, being beneficial for the formation of the mellow, honey-like, elegant aroma of IW ‘Beauty’ tea. In contrast, baking treatment A imparted the best quality to OW ‘Beauty’ tea, contributing to the formation of the mellow and brisk taste and the honey-like, nectar-like and elegant aroma of OW ‘Beauty’ tea.

The aroma and taste profiles of Qingxiang Tieguanyin tea from different regions were determined through sensory evaluation and quantitative descriptive analysis of sensory attributes. By gas chromatography-mass spectrometry (GC-MS), biochemical composition analysis, ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and metrological statistical analysis, the aroma and taste constituents of the tea were determined. The correlation between aroma and taste components and aroma and taste attributes was explored by correlation analysis and regression analysis, and the correlation between taste components and taste attributes was verified through experiments. The results showed that the sensory quality of Qingxiang Tieguanyin tea had regional characteristics and the aroma composition was dominated by terpenoids, followed by esters. Water content, water extract content, total tea polyphenols content and theaflavins content were the major biochemical factors responsible for the taste quality.

The phenylalanine ammonia-lyase (PAL) gene family in tea plants (Camellia sinensis L.) encodes the enzyme that catalyzes the first reaction of the phenylpropane metabolic pathway. The present study aimed to characterize the PAL genes in tea plants, and get better insights on the CsPALs in anthocyanins accumulation. Seven CsPAL genes were identified and characterized in tea plants by bioinformatics analysis. Systematic analysis of CsPALs was conducted for its phylogenetic relationship, gene structure, chromosomal location, and protein conserved motifs based on tea plant genome. The cis-elements of CsPALs were responsive to light, abiotic stress, hormone, and MYB-binding site. Furthermore, tissue-specific expression analysis showed that CsPAL4 was expressed preferentially in young leaves and buds. Correlation analysis was performed in purple-leaf tea with anthocyanin components, and it was suggested that CsPAL4 was closely related with different anthocyanin accumulated, especially with cyanidin 3-O-galactoside, cyanidin 3-O-glucoside, and delphinidin 3-O-glucoside. Additionally, the putative upstream regulation factors CsMYBs (CsMYB59, CsARR1, CsSRM1, CsMYB101, and CsMYB52) and CsbHLHs (CsbHLH104, CsbHLH3, CsbIM1, CsTCP14, and CsPIF4) could bind to the promoter of CsPALs, thereby activating its transcription. This study provides a theoretical basis for further research to elucidate the functions of the CsPAL genes.