Characterization of the Sensory Properties and Quality Components of Huangjin Green Tea Based on Molecular Sensory-Omics.

Huangjin green tea (HJC) is one of the most famous regional green teas in China, and has gained attention for its unique flavor. Research on HJC has focused mainly on the synthesis of L-theanine, with fewer studies concentrating on sensory characteristics. In this study, molecular sensory science techniques, including color analysis, gas chromatography-ion mobility spectrometry, and E-tongue, were used to characterize the sensory properties of HJC, with Fuding Dabai and Anji Baicha teas used as conventional and high amino acid controls, respectively. The sensory characteristics and main quality components of HJC lie somewhere between these two other teas, and somewhat closer to the conventional control. They were difficult to distinguish by color, but significant differences exist in terms of volatile organic compounds (VOCs), E-tongue values on bitterness and astringency, and their contents of major taste components. VOCs such as (E)-2-octenal, linalool, ethyl acrylate, ethyl acetate, and 2-methyl-3-furanethiol were found to be the main differential components that contributed to aroma, significantly influencing the tender chestnut aroma of HJC. Free amino acids, tea polyphenols, and ester catechins were the main differential components responsible for taste, and its harmonious phenol-to-ammonia ratio was found to affect the fresh, mellow, heavy, and brisk taste of HJC.

Topics and trends in fresh tea (Camellia sinensis) leaf research: A comprehensive bibliometric study.

Tea plant (Camellia sinensis) is a widely cultivated cash crop and tea is a favorite functional food in the world. Fresh tea leaves (FTLs) play a critical role in bridging the two fields closely related to tea cultivation and tea processing, those are, tea plant biology and tea biochemistry. To provide a comprehensive overview of the development stages, authorship collaboration, research topics, and hotspots and their temporal evolution trends in the field of FTLs research, we conducted a bibliometric analysis, based on 971 publications on FTLs-related research published during 2001-2021 from Web of Science Core Collection. CiteSpace, R package Bibliometrix, and VOSviewer were employed in this research. The results revealed that the development history can be roughly divided into three stages, namely initial stage, slow development stage and rapid development stage. Journal of Agricultural & Food Chemistry published most articles in this field, while Frontiers in Plant Science held the highest total citations and h-index. The most influential country, institution, and author in this field was identified as China, the Chinese Academy of Agricultural Sciences, and Xiaochun Wan, respectively. FTLs-related research can be categorized into three main topics: the regulation mechanism of key genes, the metabolism and features of essential compounds, and tea plants' growth and stress responses. The most concerning hotspots are the application of advanced technologies, essential metabolites, leaf color variants, and effective cultivation treatments. There has been a shift from basic biochemical and enzymatic studies to studies of molecular mechanisms that depend on multi-omics technologies. We also discussed the future development in this field. This study provides a comprehensive summary of the research field, making it easier for researchers to be informed about its development history, status, and trends.

Complete mitochondrial genome assembly and comparison of Camellia sinensis var. Assamica cv. Duntsa.

Camellia sinensis var. Assamica cv. Duntsa (C.duntsa), a valuable Theaceae from Hunan Province, has been looked at as a precious tea resource by local farmers because of its economic and ecological value. Genomics study on C.duntsa is essential for the domestication and enhancement of tea tree varieties. In the present study, we used a hybrid approach based on Illumina and PacBio data to sequence and assemble the mitochondrial genome of C.duntsa. The mitochondrial genome of C.duntsa was estimated to be 1,081,996 base pairs (bp) and eighty-one genes consisting of one pseudogene, three ribosomal RNA (rRNA) genes, thirty transfer RNA (tRNA) genes, and forty-seven protein-coding genes (PCGs). Tetramer repetitions made up 43.90% of simple sequence repeats (SSRs). The codon usage bias of the Theaceae mitochondrial gene atp9 was altered by mutation, but the codon usage of other genes was shaped by natural selection. Besides, there are eighteen gene-containing homologous regions between the chloroplast and mitochondrial genomes of C. duntsa.Some genomes including atp8, cox1, cox3, nad7, nad9, rpl16, rpl2, rps19, rps4, and sdh4 are absent in the mitochondrial genome of several Theaceae plant. However, C. duntsa maintains these genes integrity and functionality. Another gene, rps16, is either lacking from the mitochondrial genome of C. duntsa or is present as a pseudogene. C. duntsa and C. sinensis (OM809792) are very similar, as shown by a collinear match across four species of Theaceae; the most conservative genes are nad5, atp9, cox2, rps3, trnA-TGC, trnI-GAT, rrn18, trnV-GAC, and ccmFN. Similarly, the genome's phylogenetic trees revealed that C. duntsa was the sister species to C. sinensis. The results confirmed that the C. duntsa and C. sinensis (OM809792) mitochondrial genome underwent gene rearrangement.In general, our results shows that genomic information from organelles can help us understand plant phylogeny and can also be used to make molecular markers and study how genetic traits change over time. Our research will contribute to the population genetics and evolution of tea plant.

Microbial Succession and Interactions During the Manufacture of Fu Brick Tea.

Fu Brick tea is a very popular post-fermented tea that is known for its "golden flower fungus," Aspergillus cristatus, which becomes the dominant microbe during the maturation process. This study used both culture-dependent methods and high-throughput sequencing to track microbial succession and interactions during the development of the golden flower fungus, a crucial component of the manufacturing process of Fu Brick tea. Among the bacterial communities, Klebsiella and Lactobacillus were consistently cultured from both fresh tea leaves and in post-fermentation Fu Brick tea. Methylobacterium, Pelomonas, and Sphingomonas were dominant genera in fresh tea leaves but declined once fermentation started, while Bacillus, Kluyvera, and Paenibacillus became dominant after piling fermentation. The abundance of A. cristatus increased during the manufacturing process, accounting for over 98% of all fungi present after the golden flower bloom in the Fu Brick tea product. Despite their consistent presence during culture work, network analysis showed Lactobacillus and Klebsiella to be negatively correlated with A. cristatus. Bacillus spp., as expected from culture work, positively correlated with the presence of golden flower fungus. This study provides complete insights about the succession of microbial communities and highlights the importance of co-occurrence microbes with A. cristatus during the manufacturing process of Fu Brick tea.

Comparative Transcriptome Analysis of Agrobacterium tumefaciens Reveals the Molecular Basis for the Recalcitrant Genetic Transformation of Camellia sinensis L.

Tea (Camellia sinensis L.), an important economic crop, is recalcitrant to Agrobacterium-mediated transformation (AMT), which has seriously hindered the progress of molecular research on this species. The mechanisms leading to low efficiency of AMT in tea plants, related to the morphology, growth, and gene expression of Agrobacterium tumefaciens during tea-leaf explant infection, were compared to AMT of Nicotiana benthamiana leaves in the present work. Scanning electron microscopy (SEM) images showed that tea leaves induced significant morphological aberrations on bacterial cells and affected pathogen-plant attachment, the initial step of a successful AMT. RNA sequencing and transcriptomic analysis on Agrobacterium at 0, 3 and 4 days after leaf post-inoculation resulted in 762, 1923 and 1656 differentially expressed genes (DEGs) between the tea group and the tobacco group, respectively. The expressions of genes involved in bacterial fundamental metabolic processes, ATP-binding cassette (ABC) transporters, two-component systems (TCSs), secretion systems, and quorum sensing (QS) systems were severely affected in response to the tea-leaf phylloplane. Collectively, these results suggest that compounds in tea leaves, especially gamma-aminobutyrate (GABA) and catechins, interfered with plant-pathogen attachment, essential minerals (iron and potassium) acquisition, and quorum quenching (QQ) induction, which may have been major contributing factors to hinder AMT efficiency of the tea plant.

Development and Application of a Fast Gas Chromatographic Method Offer New Insights into l-theanine Production Regulation in Camellia sinensis L.

Tea is the most consumed beverage worldwide, and l-theanine in tea leaves significantly affects their flavor and market quality. We have developed and validated a fast and reliable gas chromatographic method with flame ionization detection (GC-FID) to quantify l-theanine after its extraction from Camellia sinensis (tea plant) and derivatization. The procedure was completed in 40 min, from extraction to chromatographic analysis, with a recovery rate of more than 93% and allowing a high sample throughput. The GC-FID intraday precision was within 0.57-2.28%, while the interday precision ranged from 1.57 to 13.48%. The intraday accuracy ranged from -6.84 to 5.26%, while the interday accuracy ranged from -1.08 to 3.12%. The limit of detection was 2.28 µg/mL, and the limit of quantification was 6.47 µg/mL. The GC-FID method was validated by high-performance liquid chromatography with UV detection (HPLC-UV) and was used to investigate the biosynthesis and regulation of l-theanine in tea plants. We found that plants fed with ethylamine significantly increased l-theanine concentrations in roots, while exogenous supplementation of glutamic acid, carbamide, and glutamine did not significantly affect the l-theanine level in roots. Our results also indicated that roots were not indispensable for the biosynthesis of l-theanine, which was detected in undifferentiated embryonic calluses in concentrations (g/100 g dry weight) as high as in leaves of whole plants (1.67 and 1.57%, respectively) and without any exogenous theanine precursor supplementation.

Enhanced Antiarthritic Efficacy by Nanoparticles of (-)-Epigallocatechin Gallate-Glucosamine-Casein.

This work aims to improve the antiarthritic activity of (-)-epigallocatechin gallate (EGCG) and glucosamine (GA) through fabrication and optimization of casein protein nanoparticles (EGC-NPs). Optimized EGC-NPs were obtained with a EGCG/GA/casein ratio of 1:2:8 (w/w/w). The EGC-NPs gave a mean size of 186 ± 3.5 nm and an entrapment efficiency of 86.8 ± 2.7%, and they exhibited a greater inhibitory activity against human fibroblast-like synoviocytes-osteoarthritis cells and human fibroblast-like synoviocytes-rheumatoid arthritis cells compared with that of the EGCG-GA mixture by 33.5% and 20.8%, respectively. Freeze-dried EGC-NPs stored at 25 °C during 12 months showed high dispersion stability. Moreover, the redispersion of the freeze-dried EGC-NPs produced almost no significant changes in their physicochemical properties and bioactivity. Rat experiments demonstrated that the antiarthritis effect of the EGC-NPs was significantly higher than that of EGCG-GA mixture, as assessed through an analysis of anti-inflammatory efficacy, radiographic images and histopathological assessments of paw joints, and immunohistochemical changes in serum cytokines. The enchanced antiarthritic activity in vivo was consistent with that in vitro. The EGC-NPs demonstrate potential as a food supplement for the treatment of arthritis.

Biochemical Components Associated With Microbial Community Shift During the Pile-Fermentation of Primary Dark Tea.

Primary dark tea is used as raw material for compressed dark tea, such as Fu brick tea, Hei brick tea, Hua brick tea, and Qianliang tea. Pile-fermentation is the key process for the formation of the characteristic properties of primary dark tea, during which the microorganism plays an important role. In this study, the changes of major chemical compounds, enzyme activities, microbial diversity, and their correlations were explored during the pile-fermentation process. Our chemical and enzymatic analysis showed that the contents of the major compounds were decreased, while the activities of polyphenol oxidase, cellulase, and pectinase were increased during this process, except peroxidase activity that could not be generated from microbial communities in primary dark tea. The genera Cyberlindnera, Aspergillus, Uwebraunia, and Unclassified Pleosporales of fungus and Klebsiella, Lactobacillus of bacteria were predominant in the early stage of the process, but only Cyberlindnera and Klebsiella were still dominated in the late stage and maintained a relatively constant until the end of the process. The amino acid was identified as the important abiotic factor in shaping the microbial community structure of primary dark tea ecosystem. Network analysis revealed that the microbial taxa were grouped into five modules and seven keystone taxa were identified. Most of the dominant genera were mainly distributed into module III, which indicated that this module was important for the pile-fermentation process of primary dark tea. In addition, bidirectional orthogonal partial least squares (O2PLS) analysis revealed that the fungi made more contributions to the formation of the characteristic properties of primary dark tea than bacteria during the pile-fermentation process. Furthermore, 10 microbial genera including Cyberlindnera, Aspergillus, Eurotium, Uwebraunia, Debaryomyces, Lophiostoma, Peltaster, Klebsiella, Aurantimonas, and Methylobacterium were identified as core functional genera for the pile-fermentation of primary dark tea. This study provides useful information for improving our understanding on the formation mechanism of the characteristic properties of primary dark tea during the pile-fermentation process.