15 April 2020, Volume 40 Issue 2

    

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  Research Progress of Tea Aroma Based on CiteSpace Visual Analysis

  YIN Xia, HUANG Jian'an, HUANG Jing, BAO Xiaocun, ZHOU Lingyun, LI Wei, LIU Hongyan, ZHANG Shuguang, LIU Zhonghua

  Journal of Tea Science. 2020, 40(2): 143-156. https://doi.org/10.13305/j.cnki.jts.2020.02.001

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  In this paper, the literatures collected by WOS (Web of science) and CNKI from 1979-2019 were taken as the research object. CiteSpace's bibliometric method was used to analyze the aroma quality of tea from the aspects of age, author, institution, country, research hotspot, evolution trend, etc. The results show that the literatures of tea aroma research had a significant growth trend since 2006. Currently, a stable core group of authors had been formed but there were little cooperation among these groups. China had the largest research influence in this field, followed by Japan and the United States. The hot research areas mainly focused on the following topics: the mechanism of aroma formation, the extraction and detection methods of aroma substances, and the key aroma compounds. According to the time zone map, the research progress and development stage of tea aroma at present were pointed out.
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  The Inhibitory Role and Mechanism of White Tea Extracts on Pulmonary Fibrosis Induced by Nano-sized SiO₂ in Rats

  PARK Soomi, KIM Eunhye, CHEN Xinghua, WANG Qianchao, HE Puming, TU Youying

  Journal of Tea Science. 2020, 40(2): 157-164. https://doi.org/10.13305/j.cnki.jts.2020.02.002

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  Fifty-four Wistar rats were randomly divided into six groups: control group, model group, white silver needle extract group, high and low dose white peony extracts and EGCG group, with 9 rats in each group. The other five groups except the control group were treated with nano-sized SiO₂ dust (80 mg·mL^-1) by non-exposed endotracheal intubation. After two weeks of intragastric administration, the contents of hydroxyproline(HYP), nitric oxide (NO), superoxide dismutase (SOD), malondialdehyde (MDA), glutathione peroxidase (GSH-Px) and the morphological changes of lung tissues were detected. The results show that compared with the model group, the pathological changes of each white tea extract treatment group and EGCG group were alleviated in varying degrees, and the effect of white silver needle extract group was the best. The content of NO and inflammatory factor IL-6 in lung of rats treated with white tea extract and EGCG were significantly lower than those of model group (P<0.05), GSH-Px activity was higher than that of model group (P<0.05). High-dose white peony extract group had the best effect on reducing NO content and increasing GSH-Px activity. This study shows that white tea extract had a significant effect on oxidative stress injury of lung fibrosis induced by nano-sized SiO₂ in rats. The slow and repairing effects are mainly related to the antioxidant effect and the inhibition of inflammatory reaction.
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  Effects of ‘Eurotium cristatum Loose Tea’ and ‘Eurotium cristatum Powder’ on the Expressions of JAK2/STAT3 Inflammation and Phosphorylated Proteins in Lung Tissue of Passive Smoking Mice

  ZENG Hongzhe, HUANG Xiangxiang, YU Lijun, ZHOU Yufei, XU Shuai, QU Furong

  Journal of Tea Science. 2020, 40(2): 165-172. https://doi.org/10.13305/j.cnki.jts.2020.02.003

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  In order to investigate the prevention and recovery mechanism of ‘Eurotium cristatum Loose Tea’ and its ‘Eurotium cristatum powder’ on mouse lung tissues which were injured by passive smoking, passive cigarette smoking environment (CSE) model on SPF C57BL/6 female mice were established. Mice were fed by 600 mg∙kg^-1 Eurotium cristatum tea extract (ECTE) and Eurotium cristatum powder extract (ECPE). Comparing with the CSE model mice, the morphology integrity of lung tissue in passive smoking mice feeding with ECPE and ECTE were significantly protected by observing the pathological slice of lung tissue. The up-regulation levels of IL-6, IL-8, IL-1β, IFN-γ and TNF-α in the serum of mice were inhibited by ELISA analysis. Western blot results show that the expression levels of p-JAK2, p-STAT3, p-JAK2/JAK2, p-STAT3/STAT3 in lung tissues of passive smoking mice fed with ECPE and ECTE were inhibited. These results reveal the prominent protective roles of ECPE and ECTE in the lung injury of passive smoking mice. As a whole, ECPE feeding groups were superior to ECTE feeding groups, while prevention groups were better than treatment groups.
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  Study on Soil Selenium Content and Its Influencing Factors in Typical Tea Garden of Fujian Province

  YU Wenquan, WANG Feng, CHEN Yuzhen, SHANG Riyang, YOU Zhiming, ZANG Chunrong, CHEN Changsong

  Journal of Tea Science. 2020, 40(2): 173-185. https://doi.org/10.13305/j.cnki.jts.2020.02.004

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  A total of 60 samples of surface soils (0-20 cm) were collected from main tea producing areas of Fujian province to assess the total and available soil selenium. Their relations with soil physical and chemical properties were also discussed. The results show that content of total selenium in the surface soils ranged from 0.22 mg·kg^-1 to 2.20 mg·kg^-1 with an average of 0.73 mg·kg^-1, and 86.67% of the soils belonged to Se-rich soils. The ranges of available selenium in soil were from 5.21 to 448.86 μg·kg^-1, with a mean of 62.98 μg·kg^-1. The available rate of selenium ranged from 1.10% to 31.64%, with a mean of 8.76%. The total and available selenium contents in soils from glutenite and tuff were higher, and those in soils from purple sandstone and river alluvium were lower. For different soil types, alpine meadow soil showed the highest total and available selenium content, while moisture sand yand paddy soils were relatively lower. The total and available selenium contents in mature and old tea gardens were the highest, and the young tea garden was the lowest. The total and available selenium contents in the middle-high elevation tea garden were the highest, and the low elevation tea garden was the lowest. Selenium content in tea garden soil was significantly positively correlated with soil organic matter and total nitrogen contents. Whereas the soil pH also significantly affect the selenium content in red soil and young tea garden. And, the soil available phosphate was also a significant effect on selenium content in mature and middle-high elevation tea garden. In general, the Se-enriched soils in the tea gardens provided a source guarantee for the development of Se-enriched tea. However, the effectiveness of soil selenium was not high and should be adjusted in tea garden via different cultivation measures (additional application of organic fertilizers, ameliorant and calcium magnesium phosphate fertilizers) to increase availability selenium content.
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  Acidification Characteristics and Nutrient Contents in Soils of Tea Garden and Adjacent Woodland in Subtropical Region

  LIN Cheng, CHEN Zicong, WU Yiqun, YAN Mingjuan

  Journal of Tea Science. 2020, 40(2): 186-193. https://doi.org/10.13305/j.cnki.jts.2020.02.005

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  In this study, 38 tea garden and adjacent woodland were chosen in An’xi county to investigate soil pH and nutrient changes. The results show that, soil pH was decreased by 0.031 units per year from 4.81 in woodland to 4.17 in tea garden. Contrast to woodland, the ratio of tea-grown soils with pH 4.0-4.5 and pH<4.0 were increased by 27% and 36.8%, which significantly increased the contents of total exchangeable acid, exchangeable H⁺ and exchangeable aluminum Al³⁺. After the conversion of forest land to tea garden, the contents of soil total nitrogen, hydrolysable nitrogen, available phosphorus and available potassium were increased by 0.29 g·kg^-1, 33.39 mg·kg^-1, 59.06 mg·kg^-1 and 29.75 mg·kg^-1, respectively. Furthermore, the C/N ratio was significantly decreased by 5.67. With the increase of tea planting years in tea garden, the contents of total nitrogen, hydrolysable nitrogen, available phosphorus were increased significantly. The change of soil pH was significantly and negatively correlated with those of soil hydrolysable nitrogen, available phosphorus and available potassium. The average contents of hydrolysable nitrogen, available phosphorus and available potassium would be increased by 63.92 mg·kg^-1, 52.45 mg·kg^-1 and 55.84 mg·kg^-1 when soil pH was decreased by 1 unit. When the environmental threshold is reached, there is a risk of phosphorus pollution to the environment. The survey results show that the tea garden in Anxi County needs to increase the input of organic fertilizer and carry out targeted formula fertilization to slow down the acidification trend of soil.
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  Study on the Changes of Physical and Chemical Components during the Frying Process of Green Tea by Computer Vision

  WU Xun, LIU Fei, CHEN Zhiwei, WANG Yuwan, CHEN Lin, TU Zheng, ZHOU Xiaofen, YANG Yunfei, YE Yang, TONG Huarong

  Journal of Tea Science. 2020, 40(2): 194-204. https://doi.org/10.13305/j.cnki.jts.2020.02.006

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  In order to find out the physical and chemical changes during the frying process of green tea, the computer vision technology was applied to real-time monitor the changes of color and shape, and chemical changes were simultaneously measured. The results show that with the increase of frying time, (1) the radius of curvature of unfinished tea gradually decreased, which showed the highest decreasing rate from 10-30 min. R, G, B and average gray value decreased first and then rose. The consistency value was opposite to their trends, with the extreme value in 20 min. H value increased significantly, S value decreased significantly. (2) Epigallocatechin gallate (EGCG), epigallocatechin (EGC), chlorophyll a, chlorophyll b and carotenoids decreased significantly, while gallocatechin gallate (GCG) increased significantly. Experimental results show that the radius of curvature was highly correlated with water content and leaf temperature. H was significantly correlated with chlorophyll a, chlorophyll b. S was significantly correlated with chlorophyll a, carotenoids and epicatechin gallate (ECG). The linear fit of EGCG and H values showed the highest value at 0.922 1. In the future, water content, leaf temperature and H value could be monitored online to predict changes of the radius of curvature and chemical composition during frying.
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  Estimation of Greenhouse Gas Emissions from Fertilization, Production and Transportation of Synthetic Nitrogen for Tea Garden in Typical Region of China

  WANG Feng, CHEN Yuzhen, WU Zhidan, JIANG Fuying, ZHANG Wenjin, WENG Boqi, YOU Zhiming

  Journal of Tea Science. 2020, 40(2): 205-214. https://doi.org/10.13305/j.cnki.jts.2020.02.007

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  In this research, the amount of greenhouse gas emissions from fertilization, production and transportation of synthetic nitrogen for tea garden in typical region of China was assessed based on the analysis of statistical data using a data mining method. The results show that direct N₂O emissions from soil and greenhouse gas emissions (CO₂ emission equivalents) from the production of synthetic N fertilizers were the main sources of greenhouse gas emissions from synthetic N fertilization in tea garden. In 14 typical regions, the total greenhouse gas emissions from synthetic N fertilization were 168.1-3 448.0 kt CO₂ equivalent per year. And Guizhou, Yunan, Hubei and Sichuan were the top four provinces with high greenhouse gas emissions from synthetic N fertilization. Over 2 000 kt CO₂ equivalent per year occurred in each province, which accounted for 59.98% of the total emissions. The greenhouse gas emissions per unit area, per yield and per output value was 3.22-9.76 t CO₂ equivalent per hectare, 2.10-12.96 t CO₂ equivalent per ton of dry semifinished tea and 0.39-1.90 t CO₂ equivalent per 10 000 yuan. In general, the total greenhouse gas emissions, emissions per unit area, per yield and per output value from synthetic N fertilization were mainly concentrated in Guizhou, Yunan, Hubei, Hunan and Sichuan provinces, and the relatively low total emissions and emission intensity were happened in Fujian, Henan provinces and Chongqing city. It was concluded that reducing the synthetic N application rate for tea garden in China to a reasonable level of 300 kg·hm^-2 and 450 kg·hm^-2 could greatly reduce the emission of greenhouse gases. And the estimated mitigation potential of greenhouse gas emissions for these provinces were 6 170.7, 2 289.4 kt CO₂ equivalent per year, and reduce the total greenhouse gas emissions by 34.12% and 12.66%. Notably, Hubei, Sichuan, Guizhou, Hunan and Jiangxi provinces were the leaders of the mitigation potential of greenhouse gas emissions, and these areas should focus on reducing greenhouse gas emissions.
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  Effects of Different Types of Water Quality on the Sensory Properties and Main Chemcial Compositions of Longjing Tea Infusions

  GONG Zhiping, YIN Junfeng, CHEN Gensheng

  Journal of Tea Science. 2020, 40(2): 215-224. https://doi.org/10.13305/j.cnki.jts.2020.02.008

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  In order to understand the effect of water quality on the flavor of tea infusions, six typical drinking water (including tap water, Wahaha Purified water, Hupao cold spring water, C cell vitality small molecule group water, 5100 Tibet glacier mineral water, Jianlong volcano cold mineral water) were selected as the research objects. The effects of different types of water quality on the flavor quality and chemical composition of tea infusions were studied by sensory evaluation and component analysis. The results show that the purified water and Hupao cold spring water were weakly acidic, and had low Ca²⁺, Mg²⁺ and total ion contents, which were more suitable to brew Longjing tea. In terms of the quality of flavor, it could better control the bitterness, astringency and freshness of tea soup, and reflect the richness and purity of the unique aroma of the tea infusions. Through the analysis of flavor substances, with the increase of ion concentration of drinking water, the contents of tea polyphenols, amino acids, EGCG, ester catechins and oxalic acid in the tea infusions were significantly reduced. The contents of caffeine and total sugar were not significantly different. The flavonoid content slightly increased. The mineral water with higher concentrations of Ca²⁺ and Mg²⁺ effectively inhibited the release of 17 characteristic aroma components of Longjing tea infusions, such as linalool, Trans-butyrate-3-hexene ester, dodecane, tetradecyl, cis-3-Hexenyl isovalerate, geraniol and β-ionone. This study analyzed the effect of water quality on the composition of tea flavor substances and the volatility of aroma substances, and preliminarily determined that the water quality factor was the main reason for the taste difference of Longjing tea infusions. This research preliminarily illuminated the effect of water quality on the flavor composition and aroma volatilization of tea infusions,and the results provided a theoretical basis for tea flavor chemistry, scientific tea making and water selection for tea beverage manufacturing.
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  Study on the Characteristic Aroma Components of Jasmine Tea

  AN Huimin, OU Xingchang, XIONG Yifan, ZHANG Yangbo, LI Juan, LI Qin, LI Qian, LI Shi, HUANG Jian'an

  Journal of Tea Science. 2020, 40(2): 225-237. https://doi.org/10.13305/j.cnki.jts.2020.02.009

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  Jasmine tea is unique to China reprocessing tea. The aroma is the most important factor for its quality. In this study, a Headspace solid phase microextraction (HS-SPME) and gaschromatography-mass spectrometry (GC-MS) technique was used for the qualitative and quantitative determination of volatile components in green tea and jasmine tea. Orthogonal partial least squares discriminant analysis (Orthogonal projections to latent structures discriminant analysis, OPLS-DA) and aroma activity value method (Odor activity value, OAV) were used to identify characteristic aroma of jasmine tea ingredients, and explore their effects on tea quality. The results show that: 70 kinds of volatile components were identified in green tea and jasmine tea. Totally 13 characteristic aroma components were identified in jasmine tea, namely 3-hexene-1-ol, benzyl alcohol, linalool, phenylethyl alcohol, leaf alcohol esters of acetic acid, methyl benzoate, benzyl acetate, methyl salicylate, cis-3-hexenyl isovalerate, methyl 2-aminobenzoate, cis-3-hexenyl benzene formate, indole and α-farnesene. These characteristic aroma components were closely correlated with the jasmine tea quality, except phenylethanol. The results of this study provided a theoretical basis for the evaluation, regulation and promotion of Jasmine tea quality.
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  The Changes of Metabolites during the Withering Process of White Tea Based on HILIC LC-QqQ MS Method

  CHEN Xiang, TIAN Yueyue, ZHANG Lixia

  Journal of Tea Science. 2020, 40(2): 238-249. https://doi.org/10.13305/j.cnki.jts.2020.02.010

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  In this study, the metabolic profiles of fresh leaves (F), two indoor withered samples for 29 h (W) and 53 h (P) respectively were investigated by HILIC-QqQ MS based targeted metabolomics. Totally 111 metabolites were detected in the QC sample, including 47 amino acids and their derivatives, 29 nucleic acid metabolites, 12 vitamins and coenzymes, 17 sugar metabolites and 6 glycerophospholipid metabolites. Compared with the fresh leaves (F), 39 and 41 metabolites were significantly increased in withered samples W and P, with 35 overlapped metabolites. On the other hand, 9 and 11 metabolites were dramatically reduced, with 8 overlapped metabolites. The metabolite changes suggested that the cell membranes were damaged, DNA and RNA were degraded, amino acids derivatives were significantly increased and glucose metabolism was abnormal. Furthermore, according to the variations of metabolite contents and compositions, the marker metabolites of the withered leaves were identified which could reflect the physiological states of cell membrane, nucleic acid and glucose metabolism. Eventually, based on the characteristic changes in amino acids and nucleotides, the necessities of characterizing the flavor properties of amino acids and their derivatives as well as exploring the possibility of using metabolic profiling as white tea withering standards were proposed.
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  Genetic Diversity and Structure of Chengbudong Tea Population Revealed by nSSR and cpDNA Markers

  LIU Zhen, CHENG Yang, YANG Peidi, ZHAO Yang, NING Jing, YANG Yang

  Journal of Tea Science. 2020, 40(2): 250-258. https://doi.org/10.13305/j.cnki.jts.2020.02.011

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  The 81 accessions were detected by 15 nuclear SSR and 3 cpDNA markers. A total of 142 observed number of alleles were detected, and the expected homozygosty (Ho), expected heterozygosity (He), Nei’s expected heterozygosity (Nei) of Chengbudong tea were 0.49, 0.62 and 0.62, respectively, suggesting Dong tea had a high genetic diversity. The STRUCTURE software was applied to the nSSR data to infer the genetic structure in the 79 Chengbudong tea accessions. When K=3, the Delta K value was maximized, but the five populations belonged to a mixed population without any clear genetic structure. F test showed that the inbreeding coefficient of Chengbudong tea was positive (F_IS=0.177 5). Genetic differentiation coefficient F_ST was 0.034 5, indicating a low degree of differentiation and high gene flow (Nm=7.01). The aligned chloroplast DNA sequences of rbcL, matK and trnH-psbA were 473 bp, 704 bp, 320 bp in length. The polymorphic site percentages were 0.42%, 0.71% and 1.25%, respectively. A total of 9 haplotypes (H1-H9) were identified across the 81 tea accessions including two outgroup accessions. TXZ population had the highest haplotypes (6), followed by DZC (4), DPS (4), TYS (3) and HJZ (2). The total haplotype diversity (Hd) and nucleotide diversity (π) were 0.732 and 0.001 39, respectively. Among 9 cpDNA haplotypes, haplotypes H1 and H5 were the ancestral haplotypes. The sources of genetic differentiation were revealed within and among populations by the AMOVA method. The results of nSSR and cpDNA analysis were basically consistent, with variations within populations of 96.69% (nSSR) and 80.54% (cpDNA), respectively.
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  A Quantitative Method for Brightness Evaluation of Congou Black Tea Infusions Based on Color Difference Analysis

  WANG Jiaqin, YAO Yuefeng, YUAN Haibo, JIANG Yongwen, LI Jia

  Journal of Tea Science. 2020, 40(2): 259-268. https://doi.org/10.13305/j.cnki.jts.2020.02.012

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  The brightness of tea infusion is one of the important factors reflecting the quality of black tea. At present, the evaluation of the brightness of tea infusion is dependent on the human sensory evaluation, which lacks a quantitative assessment. In this study, based on the brightness of the infusions obtained by the sensory evaluation, 43 congou black tea infusions with different brightness were measured using color difference analysis in combination with multivariate analysis and linear regression, and an equation for brightness prediction was established. The results show that bright and dark black tea infusions could be discriminated based on their color difference profiles in combination with principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA). Based on linear regression, the key variables L99 (lightness) and C* (chroma) were selected and the established prediction equation was L_pre=-46.028+0.519×L99+0.117×C^*. It was revealed that, the predicted brightness showed high correlation with that obtained by human sensory evaluation with the Pearson correlation of 0.92 (P<0.01). Besides, the effectiveness of established prediction equation for quantitative evaluation of tea infusion brightness had been further proved using validation set. In summary, in this study, a rapid and effective method based on color difference analysis and multi statistical approaches was developed which enabled quantitative evaluation of the brightness of black tea infusions. This study could provide new insights into the intelligent evaluation of black tea quality, as well as oriented manufacture of highly-bright black tea.
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  Volatile Components from Cymbopogon citratus and the Activity Research on Their Main Elements Against Three Fungal Pathogens of Tea

  YANG Wen, LIU Huifang, CHEN Yao, SU Sheng, LI Tianxing, LIU Yaoguo, ZHOU Yufeng

  Journal of Tea Science. 2020, 40(2): 269-278. https://doi.org/10.13305/j.cnki.jts.2020.02.013

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  The volatile components from Cymbopogon citratus (DC.) Stapf were extracted by solid phase microextraction and analyzed by gas chromatography mass spectrometry. Fifty one volatile components from stems and leaves were identified. Citral [Contains two compounds (E)-citral and (Z)-citral] and geraniol were found to be the major components. Their relative contents in stems were 81.39% (58.48% and 22.91%) and 4.79%, respectively. Meanwhile, the contents in leaves were 78.50% (51.63% and 26.87%) and 3.68%, respectively. The activities of citral and geraniol to Colletotrichum gloeosporioides, Pestalotiopsis theae and Phoma adianticola were determined using mycelium growth rate method. The preliminarily test results show that the inhibition rate of the two compounds against P. theae were lower than 56% under the tested concentration of 500 mg·L^-1 for 96 h. By contrast, they exerted high activities against C. gloeosporioides and P.adianticola with a inhibition rate of 100%. Further evaluated results show that the EC₅₀ of citral to C. gloeosporioides and P.adianticola were (230.56±3.49) mg·L^-1 and (124.79±10.29) mg·L^-1, respectively. The EC₅₀ of geraniol to the two fungi were (238.38±5.51) mg·L^-1 and (115.38±10.96) mg·L^-1, respectively. The present study preliminarily revealed the volatile components of C. citratus and the main active fractions against two pathogenic Fungi on tea. The results could provide a theoretical basis for the potential disease prevention of the interplanting of C. citratus and tea.
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  Comparative Study on the Competitiveness of Chinese Tea Exportation Based on Fermented Tea

  GUAN Xi, DOAN BA TOAI, HE Wenli, TONG Yaonan, YUAN Ting, XIE Xiangying

  Journal of Tea Science. 2020, 40(2): 279-288. https://doi.org/10.13305/j.cnki.jts.2020.02.015

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  Basing on the analysis of existing research on competitiveness of Chinese tea export, the perspective of comparability on category, packaging and targeted market should be considered when we compare the competitiveness of tea exportation between different countries. The paper took the Chinese fermented tea as an example and used the United Nations merchandise trade statistics to compare the export competitiveness of different packaged fermented teas in China and other major countries in different markets. The conclusion of the study shows that the diversification of Chinese tea exports and packaging determines the competitiveness of Chinese tea exports not only in different target markets, but also in the same target market. Therefore, the integrated processing and analysis of Chinese tea exports would indeed mask the significant differences in the competitiveness of different teas in the target market segments and it is of great significance to accurately identify the competitiveness of Chinese tea exports in market segments for promoting targeted tea exports in the future.