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The storage process has a significant impact on tea quality. Few is known about effect of storage on quality of oolong tea. This study aimed to assess the effect of different storage times on the key chemical components of oolong tea by measuring changes in catechin, free amino acid, and alkaloid content. Variation in the main substances was determined by principal component analysis and heat map analysis. The results revealed notable effects of the storage process on the levels of theanine, epigallocatechin gallate (EGCG), and glutamine. These findings suggest that these compounds could serve as indicators for monitoring changes in oolong tea quality during storage. Additionally, the study observed an increase in the antibacterial ability of tea over time. Correlation analysis indicated that the antibacterial ability against Micrococcus tetragenus and Escherichia coli was influenced by metabolites such as aspartic acid, threonine, serine, gamma-aminobutyric acid, ornithine, alanine, arginine, and EGCG. Overall, this study presents an approach for identifying key metabolites to monitor tea quality effectively with relatively limited data., (© 2024. The Author(s).)

To explore the relationship between the moisture content of withered tea leaves and their physical properties (i.e., elasticity, plasticity, flexibility, and texture) during withering, texture analyzer was employed to test the elasticity and flexibility of withered tea leaves with different moisture contents. The texture was evaluated by computer vision technology. The withered tea leaves with different moisture contents were used to process congou black tea, which was then subjected to sensory evaluation. Results showed that good elasticity, optimal flexibility, and plasticity were achieved when the moisture content of the withered tea leaves of Fudingdabai comprising two leaves and one bud varied arranging from 65.51 to 61.48%. The sensory evaluation of congou black tea revealed that moderate withering was better than long-term withering and that both moderate and long-term withering were better than no withering during processing. The moisture content was significantly correlated with the flexibility and plasticity of the withered tea leaves. Fresh tea leaves undergoing moderate withering with moisture content of 65.51-61.48% to process congou black tea, good tea shape and liquor color were achieved. This study provided new evidence that the moisture content of withered tea leaves significantly affected the quality of black tea., (© 2019 Wiley Periodicals, Inc.)

We produced low temperature (15 °C) processed green tea (LTPGT) with higher aroma contents than normal green tea (Sencha). Normal temperature processed green tea (NTPGT), involved storing at 25 °C, and Sencha had no storing process. Sensory evaluation showed LTPGT had higher levels of floral and sweet odorants than NTPGT and Sencha. Aroma extract dilution analysis and gas chromatography-mass spectrometry-olfactometry indicated LTPGT had 12 aroma compounds with high factor dilution values (FD). Amongst LTPGT's 12 compounds, indole, jasmine lactone, cis-jasmone, coumarin, and methyl epijasmonate contributed to floral, fruity and sweet characters. In particular, indole increased initially, peaking at 16 h, then gradually decreased. Feeding experiments suggested [(15)N]indole and [(15)N]oxygenated indoles (OX-indoles) were produced from [(15)N]anthranilic acid. We proposed the increase in indole was due to transformation of anthranilic acid during the 16 h storage and the subsequent decline in indole level was due to its conversion to OX-indoles., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The plant hormone salicylic acid (SA) plays critical roles in plant innate immunity. Several SA derivatives and associated modification are identified, whereas the range and modes of action of SA‐related metabolites remain elusive. Here, the study discovered 2,4‐dihydroxybenzoic acid (2,4‐DHBA) and its glycosylated form as native SA derivatives in plants whose accumulation is largely induced by SA application and Ps. camelliae‐sinensis (Pcs) infection. CsSH1, a 4/5‐hydroxylase, catalyzes the hydroxylation of SA to 2,4‐DHBA, and UDP‐glucosyltransferase UGT95B17 catalyzes the formation of 2,4‐DHBA glucoside. Down‐regulation reduced the accumulation of 2,4‐DHBA glucosides and enhanced the sensitivity of tea plants to Pcs. Conversely, overexpression of UGT95B17 increased plant disease resistance. The exogenous application of 2,4‐DHBA and 2,5‐DHBA, as well as the accumulation of DHBA and plant resistance comparison, indicate that 2,4‐DHBA functions as a potentially bioactive molecule and is stored mainly as a glucose conjugate in tea plants, differs from the mechanism described in Arabidopsis. When 2,4‐DHBA is applied exogenously, UGT95B17‐silenced tea plants accumulated more 2,4‐DHBA than SA and showed induced resistance to Pcs infection. These results indicate that 2,4‐DHBA glucosylation positively regulates disease resistance and highlight the role of 2,4‐DHBA as potentially bioactive molecule in the establishment of basal resistance in tea plants. [ABSTRACT FROM AUTHOR]