Journal of Tea Science

Recent Advances in Catechin Biomedical Nanomaterials

YU Rongxin, ZHENG Qinqin, CHEN Hongping, ZHANG Jinsong, ZHANG Xiangchun

Journal of Tea Science. 2022, 42(4): 447-462. doi:10.13305/j.cnki.jts.2022.04.004

Abstract ( 583 )

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Catechins are a kind of bioactive substances rich in tea, which have the functions of anti-oxidation, anti-tumor, anti-virus, anti-inflammatory and immune regulation. However, due to the high activity of phenolic hydroxyl groups, catechins are easy to lose in vitro and in vivo activities, resulting in lower bioavailability. The recent development of nanobiotechnologies is expected to solve the problem of low bioavailability of catechins through ligand design, accurate synthesis and intelligent regulation, which can expand its application in the field of life and health. In this review, a summary on the progress of catechin biomedical nanomaterials in recent years, including the anti-tumor, antibacterial, anti-inflammatory, drug delivery and anti-virus activities, was firstly made. Later, the construction and biological mechanism of catechin biomedical nanomaterials were discussed in detail. Finally, future perspectives on the design and application of novel catechin nanomaterials were provided.

Expression Analysis and Functional Identification of CsTT2 R2R3-MYB Transcription Factor in Tea Plants

WANG Yuyuan, LIU Renjian, LIU Shaoqun, SHU Canwei, SUN Binmei, ZHENG Peng

Journal of Tea Science. 2022, 42(4): 463-476. doi:10.13305/j.cnki.jts.2022.04.005

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Catechin is one of the most characteristic secondary metabolites in tea plants and the main component affecting tea quality and flavor. It possessesrich pharmacological effects, such as anti-oxidation, anti-virus, lipid lowering and weight loss, etc. In this study, the function of a catechin biosynthetic regulator CsTT2 was preliminarily identified using phylogenetic analysis, gene expression pattern analysis and molecular biology experiments. The results show that CsTT2 was a R2R3-MYB transcription factor that shares a branch withthe MYB transcription factor in Arabidopsis thaliana that regulates secondary metabolites. The expression levels of CsTT2 and catechin biosynthesis genes were relatively high in the apical bud tissue of tea plants with higher total catechin content. The results of subcellular localization, yeast assay and dual luciferase reporting system further reveal that CsTT2 was located into the nucleus and the protein it encodes possessed transcriptional activation capacity. CsTT2 could bind to the promoter of a key catechin biosynthetic gene ANR to activate its expression.

Effects of Tea Polyphenols on Agrobacterium-mediated Plant Genetic Transformation System

LI Jing, LIN Cairong, HUANG Yan, DENG Xuming, WANG Yiqing, SUN Weijang

Journal of Tea Science. 2022, 42(4): 477-490. doi:10.13305/j.cnki.jts.2022.04.003

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In order to study the effect of tea polyphenols on the infection efficiency of Agrobacterium in tea plant genetic system mediated by Agrobacterium tumefaciens, four Agrobacterium strains LBA4404, EHA105, ATCC15834 and K599 were used as research objects. The phenolic resistance, membrane integrity, adsorption, vir gene and chv gene expression and genetic transformation of Agrobacterium tumefaciens under different concentrations of tea polyphenols were analyzed. The results show that: (1) the phenolic resistance of the four strains followed the order of LBA4404>K599>EHA105>ATCC15834, and EHA105 and ATCC15834 were more sensitive to tea polyphenols. (2) The ratio of ATCC15834 with intact membrane was negatively correlated with the concentration of tea polyphenols and the standing time, and the lowest intact membrane rate of EHA105 appeared 48 h after treatment with 600 mg·L^-1 tea polyphenols. (3) The adsorption capacities of ATCC15834 and EHA105 on tobacco mesophyll cells decreased with the increase of tea polyphenol concentrations. After treatment with tea polyphenols for 24 h, the expressions of chvB and chvB2 in ATCC15834 and EHA105 were significantly inhibited. The expression of virA was positively correlated with the sensitivity to low concentration phenols. (4) After infecting tobacco by the Agrobacterium tumefaciens solution (containing tea polyphenols), the transient and stable transformation efficiencies were inhibited to varying degrees, and the induction rate of hairy roots was greatly reduced. When the concentration of tea polyphenols was 1 000 mg·L^-1, ATCC15834 achieved the lowest root induction rate of 13.85% and the highest necrosis rate of 33.85%. In conclusion, tea polyphenols could reduce the activity and membrane integrity rate of Agrobacterium tumefaciens, and reduce the expression of chv gene to affect its adsorption, which finally suppress the instantaneous conversion efficiency and the stable conversion efficiency in tobacco conversion system to varying degrees.

Nomenclature, Typification, and Natural Distribution of Camellia sinensis var. assamica (Theaceae)

ZHAO Dongwei

Journal of Tea Science. 2022, 42(4): 491-499. doi:10.13305/j.cnki.jts.2022.04.007

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Camellia sinensis var. assamica (Theaceae) is a globally cultivated plant for beverages. The efforts to clarify its nomenclature and type are reviewed here. Griffith proposed Camellia sect. Thea (L.) Griff. as a name at new rank rather than a new taxon in 1854 based on Art. 41.4 of the Shenzhen Code. Camellia sealyana T.L. Ming is excluded from sect. Thea because of its abaxially punctate leaves and free styles. Masters did not validly publish Thea assamica in 1844, but this Latin name was validated in 1847 by Hooker. Steenis first proposed the new combination, Camellia sinensis (L.) Kuntze var. assamica (Hook.) Steenis, in 1949, and this is the accurate scientific name for Assam tea. The specimen, W. Griffith s.n. (K000939670) at herbarium K, was designated as the neotype of T. assamica in 2021. Seven known heterotypic synonyms of C. sinensis var. assamica and their protologues and types were summarized here. Although Darlington and Ammal proposed the new combination, C. assamica, in 1945, Assam tea is, however, widely accepted as a variety of C. sinensis based on morphological, geological, and phylogenetic analyses. If the specific rank was applied, the earlier heterotypic name of Assam tea, C. theifera published in 1838, would gain priority over C. assamica. Then the widely used epithet “assamica” might be conserved under Art. 14 of the Shenzhen Code. The natural distribution of Assam tea was summarized based on the comprehensive examination of specimens collected from China, India, Laos, Myanmar, Thailand, and Vietnam. The status of natural populations of Assam tea in each country was discussed with the different applications of utilization and conservation.

Effects of Light Waves on the Aroma Substances of Fresh Tea Leaves in Summer and Autumn During Spreading and the Quality of Final Green Tea

LIU Jianjun, ZHANG Jinyu, PENG Ye, LIU Xiaobo, YANG Yun, HUANG Tao, WEN Beibei, LI Meifeng

Journal of Tea Science. 2022, 42(4): 500-514. doi:10.13305/j.cnki.jts.20220520.001

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The rough aroma is an important factor affecting the quality of summer and autumn green tea. In order to improve the quality of summer and autumn green tea, this experiment took Fuding Dabai tea as the research object, and irradiated fresh leaves in vitro with red light, yellow light, blue light and purple light, and the nature light was used as the control. Headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to qualitatively and quantitatively detect the volatile components of the fresh leaves. Supplemented by Hierarchical Cluster Analysis (HCA), Principal Component Analysis (PCA) and Partial least squares discriminant analysis (PLS-DA), the optimal light wave and key substances that promote the formation of tea's floral and fruity aroma were identified. The results show that different light qualities had significant effects on the types and contents of aroma substances. A total of 36 aroma substances were identified from 5 samples, of which alcohols and terpenes were the most numerous, and the average content of esters was the highest, followed by alcohols. Red light was the best light to promote the accumulation of tea aroma components. 3-Carene, β-Myrcene and phenylethyl alcohol were the key substances for improving the aroma in tea leaves. All light treatments could promote the free amino acids and caffeine in fresh leaves, and reduce the ratio of phenol to ammonia. After light treatment, the fresh and floral flavor of green tea was more obvious, and the taste was fresh. The comprehensive score of the tea samples treated with red light was the best. The research has shown that red light irradiation of fresh tea leaves in summer and autumn could increase the types and contents of tea aroma substances, significantly improve the key substances in the formation of flower and fruit aroma, and increase the freshness of tea soup.

Predation of Plexippus setipes on Ectropis grisescens Larvae

WANG Weitong, ZHOU Xiaogui, ZHANG Xinxin, WANG Zhibo, ZHANG Dayu, XIAO Qiang

Journal of Tea Science. 2022, 42(4): 515-524. doi:10.13305/j.cnki.jts.2022.04.002

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To clarify the control potential of Plexippus setipes on Ectropis grisescens, studies about the predator functional response, predation selectivity and intraspecific competition of P. setipes on E. grisescens larvae were conducted under indoor conditions. The results show that the P. setipes preferred to feed on the early stage larvae of the E. grisescens. There were significant differences in the predation ability among different developmental stages of P. setipes. Specifically, the adult spider had the strongest predation ability to hunt 17.44 larvae per day of the first instar of the E. grisescens, while the juvenile spider had relatively weak predation ability with only a daily of 2.33 larvae of the first instar. The predator functional response of P. setipes was in accordance with the Holling Ⅱ model. The Searching efficiency of P. setipes decreased with the increase of E. grisescens population. The predation selectivity shows that P. setipes showed positive preference (Ci > 0) for 1^st and 2^nd instar E. grisescens larvae along with negative preference (Ci < 0) for 3^rd instar larvae. The predatory effect of P. setipes on E. grisescens larvae was also influenced by their own population density. There was a strong intraspecific competition, which was consistent with the Hasse Ⅱ model. This study indicates that P. setipes had a strong predatory ability and control potential on E. grisescens larvae, providing a theoretical basis for exploring the use of spiders in tea plantations.

Effects of Air Conditions Preset for Withering on Flavor Quality and Chemical Profiles of White Teas

ZHANG Yinggen, XIANG Lihui, CHEN Lin, LIN Qingxia, SONG Zhenshuo, WANG Lili

Journal of Tea Science. 2022, 42(4): 525-536. doi:10.13305/j.cnki.jts.2022.04.011

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To realize the quality control of white tea based on withering environment, indoor temperature and relative humidity were preset at (30±2)℃ with RH (35±5)% or (20±2)℃ with RH (55±5)% to investigate the effects of four different air conditions on the sensory quality and chemical profiles of 6 tea cultivars (Camellia sinensis), including Fuan-dabaicha, Huangdan, Huangguanyin, etc. According to whether the indoor temperature and relative humidity were mutually switched at the point when the weight loss rate of tea shoots reached 45% during the whole withering procedure, the levels of each withering treatment were named as Low-Low, Low-High, High-Low and High-High, respectively. The results show that the flavor quality of white tea was mainly determined by the physical and chemical characteristics of raw materials (tea cultivars). White teas obtained under Low-Low treatment had a slightly light taste and a little grassy flavor, while the white teas from the same tea cultivars had the similar quality characteristics in appearance and soup color when they were treated with High-High and Low-High, just as High-Low and Low-Low during withering. The ultraviolet and near-infrared spectra of all white tea samples had similar fluctuations, and the near-infrared spectra could provide more abundant chemical information for their pattern recognition. The contents of gallic acid, epicatechin gallate, gallocatechin, caffeine and theobromine in white tea samples were different among tea cultivars, but withering treatment had no significant effect on the contents of detected biochemical components (catechins and purine alkaloids). Moreover, principal component analysis based on ultraviolet spectra, especially near-infrared spectra or biochemical compositions of white tea samples could better discriminate white tea samples into the same groups according to their raw materials (tea cultivars). The effects of different air conditions on the profiles of spectra or biochemical compositions were exclusively drowned by the characteristics of raw materials. However, the influence of withering treatment on the profiles of near-infrared spectra and biochemical compositions of white tea samples manufactured from different raw materials could be effectively revealed by multilevel principal component analysis, and the classification and identification results of all white tea samples were almost consistent with the characteristics of sensory quality. These facts could provide a reference for the technological regulation of white tea flavor quality.

Residue Determination of Sixteen Pesticides in Green Tea by UPLC-MS/MS

LI Ziqiang, YANG Mei, ZHANG Xinzhong, LUO Fengjian, ZHOU Li, LOU Zhengyun, SUN Hezhi, WANG Xinru, CHEN Zongmao

Journal of Tea Science. 2022, 42(4): 537-548. doi:10.13305/j.cnki.jts.20220416.004

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An analytical method was developed for the simultaneous determination of 16 pesticide residues in green tea by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The target pesticides in tea samples were extracted by acetonitrile with 1% formic acid, cleaned up by a TPT-SPE column, ionized in electrospray positive ionization source (ESI⁺) mode, and scanned for determination of the target parent and daughter ions by mass spectrometry in multiple reaction monitoring mode (MRM). The results show that the target pesticides were linear in the range of 0.005-1.000 mg·kg^-1 with the correlation coefficient R²>0.992 6. The average recoveries ranged from 74.0% to 105.4% at the four spiked levels of 0.010, 0.050, 0.100、1.000 mg·kg^-1, and the relative standard deviations (RSD) were <20.0%. The limits of quantification were 10-50 μg·kg^-1. The method is fast and sensitive, and the technical parameters are in accordance with the relevant domestic and international regulations and standards. And it can meet the requirements of simultaneous determination of various pesticide residues in green tea.

Tea Buds Detection Model Using Improved YOLOv4-tiny

FANG Mengrui, LÜ Jun, RUAN Jianyun, BIAN Lei, WU Chuanyu, YAO Qing

Journal of Tea Science. 2022, 42(4): 549-560. doi:10.13305/j.cnki.jts.2022.04.009

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Precise detection of tea buds is a prerequisite for intelligent mechanical picking of tea. Aiming at the problems of poor salience and high missed detection rate of small-scale buds caused by different sizes of tea leaves and the cover of other tea leaves, this paper proposed a kind of tea buds detection model based on improved YOLOv4-tiny. In this model, a 52×52 shallow feature layer was added in the neck network to promote the attention of YOLOv4-tiny network to small target buds. A convolutional block attention module (CBAM) was introduced to suppress the background noise and improve the salience of buds, and a bidirectional feature pyramid network (BiFPN) was used to integrate characteristic information of different scales, so as to propose the YOLOv4-tiny-Tea, a high performance light weight tea buds detection model. The results of model training and performance testing on the same training set and test set show that for the YOLOv4-tiny-Tea model, the detection precision and recall rate were 97.77% and 95.23% respectively, which were 5.58% and 23.14% higher than those before modification. An ablation experiment verified the effectiveness of the modified network structure in detecting different scales of buds, and a comparison of YOLOv4-tiny-Tea model with three YOLO algorithms found that the F1 value of YOLOv4-tiny-Tea model was 12.11%, 11.66% and 6.76% higher than F1 values of YOLOv3, YOLOv4 and YOLOv5l models respectively. The number of parameters in YOLOv4-tiny-Tea model was merely 13.57%, 13.06% and 35.05% of the three network models. The experimental results demonstrate that the method proposed in this paper effectively improved the detection precision of buds under different scales, greatly reduced the missed detection rate of buds for small size or under shading, and significantly bettered the detection precision based on a lightweight computation overhead. Therefore, the method can meet the needs of agricultural robots for real-time detection and embedded development, thus providing a reference for intelligent tea buds picking.

Clinical Trial on the Effect of Drinking Jinhua Xiangyuan Tea for 3 Months on the Improvement of Glucose and Lipid Metabolism in A Small Sample Hyperlipidemia Population

SUN Ying, CHEN Xin, YANG Hua, YING Jian, SHAO Danqing, LÜ Xiaohua, XIAO Jie, CHEN Zhixiong, LI Song, QIN Junjie, ZHENG Bin, GAO Jianshe

Journal of Tea Science. 2022, 42(4): 561-576. doi:10.13305/j.cnki.jts.2022.04.010

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This study is aimed at investigating the clinical effect of drinking Jinhua Xiangyuan tea for 3 months on the glucose and lipid metabolism in a small sample patients with hyperlipidemia (with/without non-alcoholic fatty liver). Jinhua Xiangyuan tea was produced by the new process using Eurotium cristatum. In this study, before-and-after control design was used. The body composition (body weight, BMI, waist hip ratio, percentage of body fat, visceral fat grade), blood biochemical indicators (fasting blood glucose, uric acid, blood lipid), fatty liver, and gut microbiota were examined before and after the test. After drinking Jinhua Xiangyuan tea for 3 months, the body weight, BMI, percentage of body fat, visceral fat grade, serum total cholesterol, low-density lipoprotein cholesterol, and fasting blood glucose of 38 volunteers were significantly reduced (P<0.05). Fatty liver was less severe. Gut microbiota’s diversity and richness were increased. The relative abundance of Phascolarctobacterium, Ruminococcus, Haemophilus and Veillonella were increased, and Dialister and Butyricimonas were decreased. Jinhua Xiangyuan tea could increase the relative abundance of short-chain fatty acid-producing bacteria, increasing short-chain fatty acids, and improving insulin resistance, then improving glucose and lipid metabolism. The results of this study still need to be further confirmed by more rigorous long-term experimental observation.

Study on the Application of Three-dimensional Vial Fermentation Technology of Puer Tea

TIAN Haixia, WEI Zhenzhen, MA Yue, LI Song, DAI Shen, LIU Haixin, HAO Binxiu

Journal of Tea Science. 2022, 42(4): 577-587. doi:10.13305/j.cnki.jts.2022.04.006

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In order to improve the clean processing conditions and the automatic level of post-fermented Puer tea, three-dimensional vial fermentation technology (TVFT) was developed. Using this technology, the traditional large batch of fermentation materials was divided into independent small units, packaged in vials. Equipped with automatic control system, loading, fermentation and discharging were completed by assembly line, without turning over the pile and replenishing water in the fermentation process, fermentation temperature and humidity were accurately controlled, the problems of low level of traditional pile fermentation production equipment and poor environmental controllability were solved. The level of automatic fermentation of Puer tea was also improved. The results show that the Puer tea produced by TVFT met the national standards, and automatic fermentation on a large scale was feasible. Compared with traditional fermentation process, using new technologies, the production capacity per unit area was increased by 40%, the fermentation duration was shortened by 15-20 d, and the labor cost was reduced by 75%. Twisted appearance of tea leaves was more complete. The contents of tea polyphenols, theabrownin, amino acid nitrogen and pH value were significantly increased. The stability of product quality has been improved.

Construction and Application of Optimal Eco-economical Cultivar Evaluation Model for Strip-shaped Green Tea

CHEN Minyi, TING Yujie, FANG Shiming, ZHANG Xiasheng, XU Aodi, ZHU Junyan, LI Yeyun, LIU Shengrui, WEI Chaoling

Journal of Tea Science. 2022, 42(4): 588-600. doi:10.13305/j.cnki.jts.2022.04.008

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More than 300 state- and provincial-level tea plant cultivars have been selected according to the agronomic traits in our country. However, few studies about the selection of eco-economical cultivars through comprehensive value method was reported. In this study, to screen optimal tea plant cultivars suitable for eco-economic strip-green tea, 24 tea cultivars were evaluated using Delphi and Analytic Hierarchy Process (AHP) methods. A comprehensive evaluation system containing 6 first-level indicators and 19 secondary indicators was formed based on the experts’ evaluated scoring and suggestions by a comprehensive discussion. Among them, the experts’ positivity degree of the first two rounds based on Delphi method were 82.5% and 100%, respectively. The degrees of experts’ authority were 0.93 and 0.90, respectively. The Coefficients of Variation were 0.19 and 0.16, respectively. While the Kendall’s W were 0.296 and 0.358, respectively (P<0.05). The weights of the first-level indicators were 0.364, 0.204, 0.128, 0.108, 0.124 and 0.072, respectively. The weights of secondary indicators were between 0.101-0.805 (all parameters were passed the consistency test). Among them, the expert positivity, degree of expert authority, Coefficient of Variation and Kendall’s W of the final round were 100%, 0.91, 0.36 and 0.11 (P<0.05), respectively. In summary, ‘Longjing Changye’, ‘Shuchazao’ and ‘Juhuachun’ ranked the top three, with scores of 3.714, 3.624 and 3.581, respectively.

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