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Colorant adulteration is a common problem in tea safety control; thus, a rapid identification method is required. In this study, we optimized the fabrication parameters of various sensors to enhance their performance. R6G was used as a probe molecule, demonstrating that the sensnor remained stable for 120 days. Based on surface-enhanced Raman spectroscopy, the optimized sensors were used to identify and quantify mixed colorants (sunset yellow, lemon yellow, carmine, and erythrosine). Partial least squares prediction models were developed for each colorant (0.5-300 μg/mL), with R 2  > 0.900 and RPD > 2.27; these indicated the accuracy of the sensors. The results also revealed a model recovery range of 95.9 % to 116 %, with RSD < 3.94 %, indicating the universality of our proposed method. Overall, the proposed method enables the detection of mixed-colorant adulteration in black tea within 3 min, thereby representing a novel method for the assessment of tea quality., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Methyl jasmonate (MeJA), a volatile organic compound, is a principal flowery aromatic compound in tea. During the processing of black tea, MeJA is produced by jasmonic acid carboxyl methyltransferase (JMT) of the jasmonic acid (JA) substrate, forming a specific floral fragrance. CsJMT was cloned from tea leaves; the three-dimensional structure of CsJMT was predicted. Enzyme activity was identified, and protein purification was investigated. Site-directed deletions revealed that N-10, S-22, and Q-25 residues in the beginning amino acids played a key functional role in enzyme activity. The expression patterns of CsJMT in tea organs differed; the highest expression of CsJMT was observed in the fermentation process of black tea. These results aid in further understanding the synthesis of MeJA during black tea processing, which is crucial for improving black tea quality using specific fragrances and could be applied to the aromatic compound regulation and tea breeding improvement in further studies.

Tea is a healthy beverage made from the leaves of the tea plant [Camellia sinensis (L.) O. Kuntze]. The tea plant is a perennial evergreen plant that is widely distributed in tropical and subtropical regions. PR proteins (pathogenesis-related proteins, PRs) are defense-related proteins induced under pathogenesis-related conditions. Currently, there are a few studies on PRs in plants. Tea leaf color mutants have been of wide interest to scientists as special materials. A tea plant displaying variegated spontaneous albinism found in a local tea plantation in Huangshan City, Anhui Province, China, was used as the material sample in this study. An analysis of preexisting transcriptomic and proteomic data revealed the significant upregulation of three classes of PRs. In order to investigate the correlation between PRs and variegated tea plants, a series of studies were conducted on PR genes. The results revealed the identification of 17 CsPR1, 3 CsPR4 and 31 CsPR5 genes in tea plants using bioinformatics methods, and their structures and promoter sequences. The expression of three PR1, two PR4 and one PR5 genes was determined to be induced in stress treatment experiments involving mechanical damage, insect bites, low temperature treatment, and fungal infections. Additionally, the ribonuclease activity of CsPR4 was successfully verified. This is the first study to report the ribonuclease activity of CsPR4 in tea plants. The results can serve as a reference for future studies on PRs in tea plants, offering new insights into information on albinism in tea plants. [ABSTRACT FROM AUTHOR]

White tea (WT) is a slightly fermented tea, and withering is a critical step in its processing. The withering treatment can affect white tea's aroma; different treatments' effects were investigated in this study. White tea was withered indoors (IWT), in a withering-tank (WWT), or under sunlight (SWT). Quantitative descriptive analysis (QDA) results showed that SWT had a more obvious flower aroma, and WWT had a more pronounced grassy aroma. Volatile compounds were extracted and subsequently detected with solvent-assisted flavor evaporation (SAFE) and headspace solid-phase microextraction (HS-SPME) combined in addition to gas chromatography–mass spectrometry (GC-MS). A total of 202 volatile compounds were detected; 35 of these aroma-active compounds met flavor dilution (FD) factor ≥ 4 or odor activity value (OAV) ≥ 1. The nine key potent odorants for which both conditions were met were dimethyl sulfide, 2-methyl-butanal, 1-penten-3-one, hexanal, (Z)-4-heptenal, β-Myrcene, linalool, geraniol, and trans-β-ionone. These results were used with QDA to reveal that SWT had a stronger floral aroma mainly due to an increase of geraniol and linalool. Moreover, WWT had a stronger grassy aroma mainly due to increased hexanal. The results could be used to select processing methods for producing white tea with a superior aroma. [ABSTRACT FROM AUTHOR]

Main conclusion: A normal tea plant with one albino branch was discovered. RNA sequencing, albinism phenotype and ultrastructural observations provided a valuable understanding of the albino mechanism in tea plants.Tea plants with a specific color (white or yellow) have been studied extensively. A normal tea plant (Camellia sinensis cv. quntizhong) with one albino branch was discovered in a local tea plantation in Huangshan, Anhui, China. The pure albino leaves on this special branch had accumulated a fairly high content of amino acids, especially theanine (45.31 mg/g DW), and had a low concentration of polyphenols and an extremely low chlorophyll (Chl) content compared with control leaves. Ultrastructural observation of an albino leaf revealed no chloroplasts, whereas it was viable in the control leaf. RNA sequencing and differentially expressed gene (DEG) analysis were performed on the albino leaves and on control leaves from a normal green branch. The related genes involved in theanine and polyphenol biosynthesis were also investigated in this study. DEG expression patterns in Chl biosynthesis or degradation, carotenoid biosynthesis or degradation, chloroplast development, and biosynthesis were influenced in the albino leaves. Chloroplast deletion in albino leaves had probably destroyed the balance of carbon and nitrogen metabolism, leading to a high accumulation of free amino acids and a low concentration of polyphenols in the albino leaves. The obtained results can provide insight into the mechanism underlying this special albino branch phenotype, and are a valuable contribution toward understanding the albino mechanism in tea plants. [ABSTRACT FROM AUTHOR]

[Display omitted] • IDA was composed of phenylboronic acids, pyrocatechol violet, and alizarin red S. • TP, TC, and EGCG were key quality indicators of black tea fermentation. • SVM model achieved accurate qualitative evaluation of fermentation degrees. • SCARS-SVR model achieved accurate prediction of TP, TC, and EGCG. • In-situ quality monitoring of black tea fermentation was realized. Herein, a new indicator-displacement array (IDA) sensor was developed for the quality evaluation of black tea fermentation. On the principle of the reversible covalent binding of phenylboronic acid and catechol, phenylboronic acids were selected as acceptors for targeted binding to polyphenols. Pyrocatechol violet and alizarin red S were used as indicators of the reaction. The IDA sensors have sensitive differential responses to fermented tea samples, achieving an assessment of the fermentation degree with accuracies of 80.39–88.00% by support vector machine (SVM). In addition, the key polyphenol components of the fermentation process were accurately predicted by the IDA and SVM regression with ratio of prediction to deviation values of 1.55–1.72, 2.03–2.21, and 2.03–2.08 for total polyphenols, total catechins, and epigallocatechin-3-O-gallate, respectively. In conclusion, the developed IDA sensor is capable of the in-situ quality monitoring of black tea fermentation, with the advantages being cost-effectiveness, sensitivity, and rapidity. [ABSTRACT FROM AUTHOR]

• JMD black tea aroma profiles and its characteristic aromas were found. • JMD black tea has a strong fruity flavor. • Jasmine lactone is the most important fruity flavor substance. • Tea cultivar affect the aroma formation. Jinmudan (JMD) black tea is processed from the JMD cultivar (Camellia sinensis (L.) O. Kuntze cv. Jinmudan). Dried JMD black tea (JMD-D) received a score of 7.43 in the quantitative descriptive analysis, indicating that it had the strongest fruity flavor. Many volatile compounds (129) were identified by solvent assisted flavor evaporation and gas chromatograph mass spectrometry. In total, 26 aroma active compounds, including (Z)-methyl epi-jasmonate (flavour dilution factor (FD): 128–1024), benzeneacetaldehyde (FD: 512–1024), linalool (FD: 256–1024), geraniol (FD: 256–512), jasmine lactone (FD: 64–1024), were identified in JMD-D and controls through an aroma extract dilution analysis and gas chromatography-mass spectrometry olfactometry. On the basis of the FD values, odor activity values, and relative quantification results, the volatiles of fruit flavor derived from lipids, such as jasmine lactone, were prominent in JMD-D compared to the controls. During the processing of the four types of black tea, the volatile fraction concentration increased mainly from the fresh leaf to the fermentation stage and decreased in the drying stage. [ABSTRACT FROM AUTHOR]

• An ecologically insensitive variegated tea plant was studied in this research. • The component, tissue structure, gene and protein expressions were analyzed. • Reduced catechins and increased amino acids were found in variegated tea leaves. • Related genes and proteins were down-regulated in flavonoid biosynthetic pathway. • The high expression of CLH1, showed an active chlorophyll degradation in variegated leaves. Globally, tea plant (Camellia sinensis (L.) O. Kuntze) is a crucial commercial crop. In this study, a variegated tea plant identified in Huangshan, China. The variegated and residual normal leaves were used as the research material. The variegated leaves of the plant were ecologically insensitive. The components, tissue structure, gene expression patterns, and protein expression profiles of the variegated tea plant were analyzed. Ultrastructural analysis of the variegated leaves revealed that the chloroplasts of the leaves were abnormally developed, with no obvious thylakoids. Compared with normal leaves, the albino leaves had lower total catechins content and higher total free amino acid content. Through RNA sequencing and proteomic analysis, chlorophyll biosynthesis and degradation, photosynthesis, chloroplast development, and flavonoid biosynthesis of the variegated leaves were affected. The less chlorophyll content in the variegated tea leaves could probably attributed to the destruction of chloroplast structure. Besides, the relatively high expression and enzyme activity of CLH, showed an active chlorophyll degradation; the lower expression of Lhcb1, Lhcb3 ; and POR in chlorophyll synthesis, might be related to the low chlorophyll in variegated leaves. In terms of flavonoid biosynthesis, expression of the related genes was down-regulated and the target protein content of ANR, CHI) was also reduced. These results may provide insight into the catechins mechanism of such variegated phenotypes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solar withering (SW) increases the bitterness and astringency of white tea (WT). • SW affects the upregulation of genes involved in flavonoid biosynthesis. • 27 genes responding to light and heat stress are up-regulated in SW. • Metabolism and taste presentation are related to stress response. • A comprehensive view on WT quality formation by metabolomics and transcriptomics. The mechanism through which solar withering (SW) affects the quality of white tea is unclear. To address this gap in the literature, in this study, we used metabolomics and transcriptomics to investigate the effect of SW on the quality of WT. WT that underwent SW was slightly more bitter and astringent than WT that underwent natural withering (control group). Specifically, SW considerably increased the concentration of astringent flavonoids and flavone glycosides in WT. This increase was mainly attributed to the upregulated expression of key genes in the shikimic acid, phenylpropanoid, and flavonoid biosynthesis pathways, such as shikimate kinase, chalcone synthase, and flavonol synthase. In addition, SW experienced considerable heat and light stress. The levels of glycerophosphatidylcholine and carbohydrates increased in response to the stress, which also affected the taste of WT. The results of this study indicate the mechanism through which SW affects the quality of WT. [ABSTRACT FROM AUTHOR]