Comparative transcriptome and metabolome analyses revealed quality difference between beauty tea processed through indoor withering and outdoor solar withering.

BACKGROUND: Withering is the first processing procedure of beauty tea, and there are few reports on the impact of withering methods on the quality of beauty tea and its regulatory mechanisms. RESULTS: Through comparison of fresh tea leaves (FT) with the leaves after indoor natural withering for 18 h (IWT-18) and outdoor solar withering for 6 h (OWT-6), which were collected at the end of the two withering processes, 17 282 and 13 984 differentially expressed genes (DEGs) were respectively screened and 267 and 154 differential metabolites (DMs) were respectively identified. The coexpression network revealed that a large number of DEGs and DMs were enriched in phenylpropanoid, flavonoid, and adenosine triphosphate binding cassette (ABC) transporter pathways, and the number of DMs and DEGs in IWT-18 versus FT exceeded that in OWT-6 versus FT. Both withering methods promoted a significant increase in content of phenylalanine and upregulation of ß-glucoside expression in the phenylpropanoid metabolism pathway. Five theaflavin-type proanthocyanidins in the flavonoid synthesis pathway were more significantly accumulated in FT versus IWT-18 than in FT versus OWT-6. Meanwhile, both withering methods can affect the ABC transporter pathway to promote the accumulation of amino acids and their derivatives, but different withering methods affect different ABC transporter families. Outdoor withering with more severe abiotic stress has a greater impact on the ABCG family, whereas indoor withering has a more significant effect on the ABCC family. Sensory evaluation results showed that the dry tea of IWT-18 was slightly better than that of OWT-6 because of the longer withering time and more thorough substance transformation. CONCLUSION: In conclusion, the formation of honey flavor in beauty tea may be closely related to the DEGs and DMs in these three pathways. Our research provides theoretical data support for further revealing the mechanism of quality formation during the withering process of beauty tea. © 2023 Society of Chemical Industry.

Comparative Metabolomic Analysis Reveals the Differences in Nonvolatile and Volatile Metabolites and Their Quality Characteristics in Beauty Tea with Different Extents of Punctured Leaves by Tea Green Leafhopper.

The fresh leaves were processed into beauty tea from the Camellia sinensis "Jinxuan" cultivar, which were punctured by tea green leafhoppers to different extents. Low-puncturing dry tea (LPDT) exhibited a superior quality. Altogether, 101 and 129 differential metabolites, including tea polyphenols, lipids, and saccharides, were identified from the fresh leaves and dry beauty tea, respectively. Most metabolite levels increased in the fresh leaves punctured by leafhoppers, but the opposite was observed for the dry beauty tea. According to relative odor activity values (rOAVs) and partial least-squares discriminant analysis (PLS-DA), four characteristic volatiles, including linalool, geraniol, benzeneacetaldehyde, and dihydrolinalool, were selected. Mechanical injury to leaves caused by leafhoppers, watery saliva secreted by the leafhopper, and different water contents of the fresh leaves in different puncturing degrees are the possible reasons for the difference in the quality of the beauty tea with different levels of puncturing. Overall, this study identified a wide range of chemicals that are affected by the degrees of leafhopper puncturing.