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The sensory quality and metabolite profiles of the fresh and dried buds and leaves of Lycium from 26 cultivars (lines) were analyzed by sensory evaluation and metabolomics combined with multivariate statistical analysis. The results of sensory evaluation showed that the dried buds and leaves of Lycium had a mellow, fresh and sweet taste, and by liquid chromatography-mass spectrometry (LC-MS), 879 metabolites were identified in Lycium buds and leaves, including amino acids and their derivatives, flavonoids, phenolic acids, saccharides, nucleotides and their derivatives, lignans and coumarins, alkaloids, terpenoids, organic acids, and lipids. Using partial least square discriminant analysis (PLS-DA) model and one-way analysis of variance (ANOVA), 211 differential metabolites were selected, which were mainly enriched in the linoleic acid metabolism, flavonoid biosynthesis, flavonoids and flavanols biosynthesis, phenylpropanol biosynthesis, and galactose metabolism pathways. In addition, it was found that amino acids and their derivatives, flavonoids, sugars, and lipids were important components to discriminate the metabolites of different cultivars (lines). Partial least squares regression (PLSR) analysis showed that 26 metabolites including epicatechin, isoquercitrin, and rutin collectively affected the taste of Lycium tea such as mellow, thick, fresh, sweet and bitter. The results of sensory evaluation and PLSR analysis showed that seven cultivars (lines) of Lycium including ‘Ningqicai No. 1’, ‘Ningqi No. 9’, Z90, Z68, Q3, Q6-13, and Z48 had better sensory quality and rich flavor substances.

To explore the effect of growing altitude on the quality of Zhenghe white tea, the sensory quality and biochemical composition of tea leaves and Zhenghe white tea from different altitudes were evaluated, and multivariate statistical analysis was applied to the obtained data. The results of sensory evaluation showed that there were significant differences in the quality of white tea from different altitudes. The mid- and high-altitude white tea tasted fresh, mellow and clean with a clean and pure aroma, while the low-altitude white tea tasted mellow and thick with a floral aroma. Partial least squares discriminant analysis (PLS-DA) showed that soluble sugars, caffeine, 3-carene, verbenenol, terpene oleene, cis-2-pentenol, 2-ethylfuran and cis-2-hexene-1-alcohol were the key components to distinguish fresh tea leaves from different altitudes. The contents of soluble sugar, cis-2-hexene-1 alcohol and cis-2-pentenol were higher in the mid- and high-altitude samples, while the contents of volatile components such as caffeine, 3-carene, verbenol and terpinolene were higher in the low-altitude samples. Soluble sugar, free amino acid, terpinolene, verbenol, 2-ethyl furan, 2-methylbutyraldehyde, 2-phenylethanol and 3-carene were the key components to distinguish white tea from different altitudes. The contents of soluble sugar and free amino acid were higher in the high-altitude white tea, and the contents of volatile components such as terpinolene, verbenol, phenyl ethanol and 3-carene were higher in the mid- and low-altitude samples, but low in the high-altitude samples. According to odor activity value (OAV) analysis, 2-methyl butyl aldehyde, 3-carene and terpinolene could be used as the characteristic volatile components to identify white tea samples from different altitudes. The results of this study will provide a reference for further exploring the flavor quality of tea from different altitudes.

To explore the effect of storage time on the flavor and quality of white peony tea, sensory evaluation and volatile and non-volatile composition analysis of 12 white peony tea samples made from three different varieties: Fudingdahao (FDDH), Zhenghedabai (ZHDB) and Fujiangshuixian (FJSX) were carried out, and the resulting data were analyzed by multivariate statistical analysis combined with multivariate statistical analysis. The results showed that during the storage process, the content of tea polyphenols and free amino acids decreased, and the ratio of polyphenols to amino and the contents of soluble sugar, flavonoids and thearubigin increased, so that the taste of white peony tea was sweet, mellow, sweet after taste and stale. The large decrease in the content of alcohol substances resulted in a reduction in the refreshing and floral aroma of white peony tea. Totally 12 differential volatiles were key to changing the aroma types of white peony tea. α-Farnesene, linalool oxide II, methyl salicylate, linalool, cis-2-pentene-1-alcohol and hexanal were the key components responsible for the floral, pekoe-like and refreshing aroma. cis-Linalool oxide and neryl oxide were also positively related to the formation of the floral aroma, and the latter was also key to the formation of the pekoe-like aroma. cis-3-Hexen-1-ol and phenethyl alcohol were also positively correlated with the formation of the refreshing aroma. In addition, 4-isopropyltoluene was the key component responsible for the honey-like and herbal aroma. Linalool oxide II and neryl oxide were the key components responsible for the jujube-like aroma. cis-Linalool oxide was the key component responsible for the plum-like aroma. The 4-isopropyltoluene and isobutyraldehyde were the key components contributing to the woody aroma. This study provides scientific insights into the formation of the differences in the flavor and quality of white peony tea of different ages, which could provide a reference for the improvement of tea flavor.

Oolong tea is a semi-fermented tea with strong flavor, which is widely favored by consumers because of its floral and fruity aroma as well as fresh and mellow taste. During the processing of oolong tea, withering is the first indispensable process for improving flavor formation. However, the molecular mechanism that affects the flavor formation of oolong tea during withering remains unclear. Transcriptome sequencing was used to analyze the difference among the fresh leaves, indoor-withered leaves and solar-withered leaves of oolong tea. A total of 10 793 differentially expressed genes were identified from the three samples. KEGG enrichment analysis showed that the differentially expressed genes were mainly involved in flavonoid synthesis, terpenoid synthesis, plant hormone signal transduction and spliceosome pathways. Subsequently, twelve differentially expressed genes and four differential splicing genes were identified from the four enrichment pathways for fluorescence quantitative PCR analysis. The results showed that the expression patterns of the selected genes during withering were consistent with the results in the transcriptome datasets. Further analysis revealed that the transcriptional inhibition of flavonoid biosynthesis-related genes, the transcriptional enhancement of terpenoid biosynthesis-related genes, as well as the jasmonic acid signal transduction and the alternative splicing mechanism jointly contributed to the flavor formation of high floral and fruity aroma and low bitterness in solar-withered leaves. The results may facilitate better understanding the molecular mechanisms of solar-withering treatment in flavor formation of oolong tea.