Journal of Tea Science

Research Progress on the Biosynthesis of Monomeric and Polymeric Catechins in Camellia sinensis

LIU Yajun, WANG Peiqiang, JIANG Xiaolan, ZHUANG Juhua, GAO Liping, XIA Tao

Journal of Tea Science. 2022, 42(1): 1-17.

Abstract ( 691 )

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Catechin compounds, mainly including monomeric catechins and polymericcatechins, are the main components of tea polyphenols in Camellia sinensis and the decisive components of the "taste" of green tea. The synthesis and accumulation of tea catechin compounds have remarkable tissue- and organ- specificity. The leaves mainly biosynthesize monomeric catechins, and roots mainly accumulate polymeric catechins. The downstream enzymes of flavonoid metabolism pathway, leucoanthocyanidin reductase (LAR) and anthocyanin reductase (ANR) are the key enzymes determining the types of catechins. This paper mainly reviewed the research progress on the biosynthesis, accumulation, and transcriptional regulation of catechins in Camellia sinensis, with emphasis on the latest research progress in the function and transcriptional regulation of LAR, ANR and leucoanthocyanidin dioxygenase (LODX). Our views on the unsolved problems in catechin synthetic pathway were also proposed.

Purine Alkaloid Evaluation and Excellent Resources Screening of Fujian Wild Tea

CHEN Xiaomin, ZHAO Feng, WANG Shuyan, SHAO Shuxian, WU Wenxi, LIN Qin, WANG Pengjie, YE Naixing

Journal of Tea Science. 2022, 42(1): 18-28.

Abstract ( 485 )

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A total of forty-three wild tea resources in Fujian Province were applied in the research and the contents of purine alkaloids were determined by ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The descriptive statistical analysis and cluster analysis were carried out to systematically analyze and explore the composition characteristics of purine alkaloids in Fujian wild tea resources. The results show that large variations in the purine alkaloids were identified in tea resources, which could be divided into four specific groups: group Ⅰ with similar contents of purine alkaloids as those in normal tea cultivars, group Ⅱ with higher purine alkaloids especially high caffeine content and low theophylline and theobromine, group Ⅲ with higher purine alkaloids especially high bitter theophylline and theophylline contents, group Ⅳ with high purine alkaloids especially bitter theophylline. After comprehensive evaluation, 14 tea resources with specific purine alkaloid composition were identified, including five germplasm resources with high purine alkaloids (>60 mg·g^-1), seven germplasm resources with high caffeine (>50 mg·g^-1) and seven germplasm resources with high bitter theophylline (>30 mg·g^-1). Through this study, it provided more information and a scientific basis for the protection, innovation, breeding, production and utilization of tea germplasm resources.

The Genetic Variation of the Chemical Components of the ‘Jinxuan' × ‘Zijuan' F₁ Segregating Population Based on UPLC

LIU Qingshuai, QU Furong, WEI Mengyuan, ZHONG Hong, WANG Yi, CHEN Liang, JIN Jiqiang

Journal of Tea Science. 2022, 42(1): 29-40.

Abstract ( 418 )

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In order to innovate new germplasms with high methylated catechins, a F₁ segregating population was constructed with ‘Jinxuan' and ‘Zijuan' as parents. At the same time, an ultra-high performance liquid chromatography method was established to analyze the metabolite content and genetic variation of individual plants in the population. Our study found that most metabolites conformed to the normal and slightly steep distribution. The coefficient of variations were between 20% and 30%. There was a clear heterosis and several individual plants rich in methylated catechins were selected from the population. It also found that the contents of most metabolites in autumn were higher than those in spring, and the amount of total catechins decreased with the purple degree of leaves. The UPLC technology established in this study would provide a more efficient determination method for the future identification and screening of elite tea germplasms and breeding materials. The genetic variation of the chemical components of the ‘Jinxuan' ×‘Zijuan' F₁ segregating population identified in this study also provided an important foundation for the high functional component breeding and discovery of genes governing traits through forward genetics.

The Screening and Identification of Key Transcription Factor Genes for Theacrine Metabolism

LIU Yufei, PANG Dandan, LI Youyong, JIANG Huibing, TIAN Yiping, SUN Yunnan, CHEN Linbo

Journal of Tea Science. 2022, 42(1): 41-50.

Abstract ( 467 )

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Kucha is a unique tea resource rich in theacrine (1,3,7,9-tetramethyluric acid) in southwest China. Theacrine has a variety of physiological activities such as sedation, hypnosis and antidepressant. Theacrine synthesis enzyme, the key gene for theacrine biosynthesis, had been cloned and studied. However, there were few reports on the regulation mechanism of theacrine metabolism. In order to obtain the transcription factors related to theacrine metabolism, kucha (GKC and LKC) and normal tea cultivar (YK10) were used as research materials. Purine alkaloid content and related gene expressions in the samples were detected by HPLC and RNA-seq, respectively. And the reliability of the transcriptome data were verified by quantitative real-time PCR (qRT-PCR). The results show that the contents of theacrine in GKC and LKC were 21.82 mg·g^-1 and 14.70 mg·g^-1, respectively, while the content of theacrine in YK10 was not detected. In addition, the caffeine contents of GKC and LKC were both lower than 15.00 mg·g^-1. Based on RNA-seq, 3 948 differentially expressed genes (DEGs) had the consistent expression trends in GKC vs YK10 and LKC vs YK10. These DEGs included 96 transcription factors belonging to 29 families. Among them, 30 candidate transcription factors might be the key genes involved in the regulation of theacrine metabolism, especially NAC and HD-ZIP family transcription factors such as CSS0012182, CSS0013789, CSS0041233, novel.16084 and CSS0014547.

Differences of Phenolic Components in Puer Raw Tea with Various Storage Periods and Their Effects on the in vitro Antioxidant Capacities

MA Bingsong, WANG Jiacai, XU Chengcheng, REN Xiaoying, MA Cunqiang, ZHOU Binxing

Journal of Tea Science. 2022, 42(1): 51-62.

Abstract ( 671 )

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To explore the changes of phenolic compounds and other quality components and their influences on antioxidant abilities during the storage and aging of puer tea, contents of 17 phenolic compounds, 3 purine alkaloids and other quality components in 18 puer tea samples of 6 series with 3 different storage periods were determined by high performance liquid chromatography (HPLC) and other methods. Additionally, in vitro antioxidant abilities including ferric ion reducing antioxidant power (FRAP), DPPH scavenging ability (DPPH), ABTS free radical scavenging capacity (ABTS), hydroxyl radical scavenging ability (HSA) and superoxide anion radical scavenging ability (SSA) were determined in all puer raw teas. Combined with sensory evaluation results, multivariate statistical analyses including principal component analysis (PCA) and orthogonal partial least square-discriminate analysis (OPLS-DA) were used to realize the discrimination between new and aged tea during the storage. One-way analysis of variance (ANOVA) showed 7 catechins were highly significantly (P<0.01) decreased, while ellagic acid and flavonoids like quercetin, luteolin and kaempferol levels were also highly significantly (P<0.01) increased during the storage and aging. And, new puer tea had the highest FRAP, DPPH, ABTS, but the lowest SSA compared with the aging and aged puer teas. Bivariate correlation analysis revealed that the catechins including catechin (C), gallocatechin (GC), epigallocatechin (EGC), epicatechin gallate (ECG) and epigallocatechin gallate (EGCG) impacted FRAP, DPPH and ABTS of puer raw tea during the storage and aging.

Effect of Fu Brick Tea on Improving Metabolic Disorders in Type 2 Diabetes Mice

DAI Xinyue, GE Binggang, ZHANG Xuwen, LIU Wenwu, DUAN Jichun, FU Donghe

Journal of Tea Science. 2022, 42(1): 63-75.

Abstract ( 467 )

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To investigate whether Fu brick tea (FBT) water extract can attenuate metabolic disorders in Type 2 Diabetes (T2DM) by regulating gut microbiota, a T2DM mouse model was established with streptozocin and 400 mg·kg^-1 FBT water extract administration. Diet, and water consumption, body weight, fasting glucose and glucose tolerance in mice were observed. Serum levels of insulin (INS), total bile acid (TBA), total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), interleukin-1beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) were examined. Histopathological changes of ileum and pancreas were also observed. Furthermore, fecal samples were analyzed by 16 S rRNA gene sequencing. The results show that FBT reduced the serum lipid metabolism levels, blood glucose, and inflammatory cytokines. Simultaneously, FBT treatment significantly ameliorated pathological changes in the pancreas and ileum. Moreover, the diversity, structure and composition of T2DM-disrupted gut microbiota were restored by the supplementation of FBT. T2DM-induced increase in the relative abundance of Verrucomicrobia was remarkably restored by FBT. FBT increased the growth of many key beneficial bacteria, including Firmicutes, Bifidobacterium, Enterorhabdus, Prevotella_9, A2, Acetatifactor, Eubacterium_coprostanoligenes_group, Faecalibacterium, Coriobacteriaceae and Eggerthellaceae. Collectively, the study showed that FBT might alleviate dysbacteriosis and metabolic disorders in T2DM by increasing beneficial flora.

Effect of the Tea with Different Degrees of Fermentation on the Formation of Tea Scum

ZHOU Shaofeng, QIAN Yunfei, ZHAO Zhen, CHEN Xuan, LI Xinghui

Journal of Tea Science. 2022, 42(1): 76-86.

Abstract ( 590 )

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This study used tap water to infuse tea with different degrees of fermentation: green, yellow, oolong and black tea. The mass, FTIR, MALDI-TOF-MS and SEM-EDS of these tea scums were analyzed, respectively. The results show that the amount of black tea scum was significantly less than that of the others, while there was no significant difference in the amount of tea scum among green, yellow and oolong tea. The FTIR of different tea scums were similar, and they all contained functional groups such as -OH, -C=O, benzene ring and -COC-. The relative molecular mass of main components of different scums were same, which were all 454.8. SEM-EDS indicates that tea scum showed an appearance of cracked shape, and it mainly consisted of organic elements C, O and inorganic elements Ca, K, Mg, Si. In addition, the biochemical compositions of 4 kinds of tea infusions were analyzed, and it was found that the amount of tea scum was positively correlated with the total tea polyphenols. This study also infused tea polyphenols powder with tap water, and compared the scum with green tea scum. The results further confirmed that the tea scum was mainly composed of organic tea polyphenols and inorganic elements.

Identification of a Tea Rhizosphere Bacterium and its Biocontrol of Tea Anthracnose Disease

ZHU Yongshan, LUO Xiaoxin, LIANG Haoran, CHEN Zhengtong, LIU Cheng, CAO Kai, LIU Shaoqun, ZHOU Erxun, SHU Canwei, ZHENG Peng

Journal of Tea Science. 2022, 42(1): 87-100.

Abstract ( 449 )

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Tea anthracnose (Colletotrichum gloeosporioides) is one of the most important fungal diseases of Camellia sinensis worldwide, which causes serious damage to tea growth and production. The control of tea anthracnose is mainly dependent on chemical fungicides. To promote green prevention and control in tea plantation, development of biocontrol agents is critically important. A bacterium named JT68 isolated from tea rhizosphere was identified based on physiological and biochemical analysis and PCR. The inhibition effects of fermented broth JT68 on confrontation culture, mycelia growth and spores germination were determined. The effect of volatile organic compounds (VOCs) of JT68 was tested and the components were identified by GC-MS. The control effect of JT68 was determined using detached leaf method. The results of this study shows that the strain JT68 was identified as Bacillus amyloliquefaciens. Plate confrontation shows that the inhibition rate of fermentation broth of JT68 against C. gloeosporioides was 80.94%. Co-culture shows that the inhibition rate of spore germination of C. gloeosporioides was 99.18%, and the mycelia of pathogen shrank and formed chlamydospores. The VOCs of JT68 could inhibit 50.73% mycelia growth of C. gloeosporioides. Ketones such as 2-Nonanone and 2-Undecanone were revealed as major components in VOC through GC-MS analysis. Leaf detached inoculation shows that the relative inhibition rates of the original fermentation broth, 10-fold, and 100-fold dilutions were 83.20%, 79.70% and 72.66%, respectively. Furthermore, our study found that JT68 strongly inhibited the growth of Magnaporthe grisea, Fusarium oxysporum, C. capsici, C. higginsianum, Verticillium dahlia and Sclerotium rolfsii with the inhibition rates of 70.0%- 93.2%. Our study provided a biocontrol agent B. amyloliquefaciens from tea rhizosphere, which showed superior biocontrol effect against C. gloeosporioides. This strain had been applied to develop biofertilizer and widely used in the field, which would reduce the use of chemical fungicide and implement prevention and control in tea plantation.

Sex Pheromone of Andraca bipunctata Mainland Population in China: Identification and Population Monitoring

CUI Shaowei, ZHAO Dongxiang, ZHANG Jiaxia, SHANG Jiannong, CAI Xiaoming, LI Zhaoqun, BIAN Lei, XIU Chunli, FU Nanxia, CHEN Zongmao, LUO Zongxiu

Journal of Tea Science. 2022, 42(1): 101-108.

Abstract ( 400 )

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Andraca bipunctata Walker is a severe defoliator species in Chinese tea plantation. The larvae of A. bipunctata can eat all the tea leaves in case of severe attack, and cause a significant damage. In this study, the sex pheromone of mainland population was identified. The crude pheromone was extracted from abdominal tips of virgin females by n-hexane during their courtship peak period. The extracts were analyzed by gas chromatography-electroantennographic detection (GC-EAD) and gas chromatography-mass spectrometry (GC-MS). The electrophysiological activity of sex pheromone components was tested by electroantennogram (EAG), and the optimal dose of sex pheromone was determined by the field trapping test. Ultimately, the sex pheromone of A. bipunctata was used to monitor the population dynamics in Wuzhishan city of Hainan province. The GC-EAD analyses revealed only one component that elicited responses for the male moth antennae. Based on the mass spectrum, the component was identified as E11, E14-18Ald. The pheromone component was proved to be correctly identified by EAD tests and field trapping results. The data of field trapping show the dose dependent attraction of the pest, with the maximum attractiveness at 0.9 mg sex pheromone loaded on rubber septum lure. The results of population monitoring show that the sex pheromone was a promising tool for monitoring the pest population. It is clear that there were two generations of A. bipunctata in Wuzhishan city of Hainan Province from May to October, and the peak emergence of adult were 17 June and 27 August respectively. The results of this study provided a theoretical basis for the application of sex pheromones for attracting and killing or monitoring pest population in the main tea producing areas of China.

Analysis of Diversity and Temporal Patterns of the Insect Communities in Tea Gardens

LIU Yanan, LIU Mengyuan, HUANG Liyun, KANG Zhiwei, XU Yongyu, CHEN Zhenzhen

Journal of Tea Science. 2022, 42(1): 109-119.

Abstract ( 581 )

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In order to clarify the diversity, dominant species and temporal pattern of insect community in tea gardens, the community characteristics of main pests and natural enemies in typical tea gardens in Shandong Province were studied. The classification and statistics of pests and natural enemies were recorded by visual method, yellow plate method, net scanning method and indoor observation method. A total of 27 species of pests (including mites) and 15 species of natural enemies (including spiders) were found. The main dominant pests in tea gardens were Aleurocanthus spiniferus, Matsumurasca onukii, Toxoptera aurantii, Apolygus lucorμm and Scirtothrips dorsalis. The main dominant natural enemies were Eretmocerus sp., Aphid flies, ladybirds, green lacewings and spiders. Before overwintering, the species abundance and evenness were high in tea gardens, and the community diversity also maintained a high level. During overwintering, the ecological dominance increased rapidly and the community diversity decreased, indicating that the main factor affecting the community dynamics in tea gardens was temperature. The temporal patterns of the main insect pest and natural enemy communities were divided into four stages by using the optimal sorting method. In the first period, from 9th June to 17th July, the dominant pests were A. spiniferus and T. aurantia. In the second period, from 25th July to 12nd September, the dominant pests were A. spiniferus and M. onukii. In the third period, from 20th September to 17th October, the dominant pests were S. dorsalis, A. spiniferus and M. onukii. In the fourth period, from 27th October to 23rd December, the dominant pests were M. onukii and A. lucorμm. The results laid a foundation for guiding the precise prevention and control in tea gardens.

EDEM-based Optimization of Classification Parameters of Machine-picked Tea Fresh Leaf Vibratory Classifier

LYU Haowei, WU Chuanyu, TU Zheng, CHEN Jianneng, JIA Jiangming, CHEN Zhiwei, YE Yang

Journal of Tea Science. 2022, 42(1): 120-130.

Abstract ( 471 )

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In view of the low grading efficiency and large damage to fresh leaves of the current machine-picked tea fresh leaf grading equipment, a vibrating machine-picking fresh tea leaf classifier was used in this study as the test object, and a new tea leaf viscoelastic material modeling method was proposed. The vibration frequency, vibration direction angle, and amplitude were used as independent variables. The sieving rate and famous tea sieving rate were used as target optimization values. The simulation test was carried out based on the EDEM software. Using the response surface optimization method, the optimized parameters were obtained as the vibration frequency of 29.0 Hz, the amplitude of 9.0 mm, and the vibration direction angle of 34.7°. Under this parameter, the sieving rate obtained by the simulation test was 75.38%, and the sieving rate of famous tea was 95.65%. According to the optimal parameter combination, the simulation and prototype verification test were carried out, and the results show that the sieving rate obtained by the prototype verification test was 71.07%, and the sieving rate of famous tea was 93.26%. Combining the simulation test and prototype test results, the accuracy of the screening rate reached 93.9%, and the accuracy of the screening rate of famous tea reached 97.4%. The simulation optimization parameters based on response surface analysis had high reliability. Under this optimal parameter, the classifier had a better classification effect. This study provided a reference for the optimization of machine-picked tea fresh leaf grading equipment.

Visualization Analysis in Research Status of Theaflavins Based on CiteSpace

ZHOU Yufei, ZHOU Lin, YU Lijun, XU Shuai, YANG Yihuan

Journal of Tea Science. 2022, 42(1): 131-139.

Abstract ( 499 )

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Aiming to grasp the progress and hotspots of theaflavin research and objectively reflect the influence of different countries, authors, research institutions and journals in this field, bibliometrics and CiteSpace.5.7.R5W visualization analysis software were used in this study to analyze 725 and 391 Theaflavin/Theaflavins (TF/TFs) literatures collected by Web of Science (WOS) and China National Knowledge Infrastructure (CNKI) from 1964 to 2021. It was found that China, India, the United States and Japan were the countries with the most research on theaflavin. Tanaka of Nagasaki University in Japan had the most researches. The catechin oxidation products related to theaflavins had been reported the most. Liu Zhonghua, Jiang Heyuan and Tu Youying were the leaders of theaflavins research in China. Food Science Technology and Journal of Tea Science were the English and Chinese journals with the highest publication volume of theaflavin. Keyword analysis showed that Chinese literature mainly focused on the preparation and separation of theaflavins and their effects on the quality of black tea. English literature focused on the pharmacological research of theaflavins, and the preparation and pharmacological effects of theaflavins were still the research hotspots in the future.

Research on the Impact of Consumer Cognition and Trust on Purchase Intention of Traceable Tea Products

HE Wenli, PAN Shan, GUAN Xi

Journal of Tea Science. 2022, 42(1): 140-150.

Abstract ( 506 )

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Based on the survey data of 646 consumers, this paper analyzed the impact of consumers' cognition, trust and purchase intention on the traceable tea products by using structural equation model. The results show that consumers' cognition of the traceable tea products had a significantly positive impact on trust and trust had a significantly positive impact on their purchase intention. However, their cognition had a positive effect on purchase intention, but it was not significant. At the same time, trust played a mediating role in the relationship between cognition and purchase intention. Based on the empirical results, the government and tea enterprises should pay more attention to the promotion and guidance of the traceable tea products, enhance consumers' cognition and trust of the traceable tea products, so as to enhance consumers' purchase intention of the traceable tea products.

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