Journal of Tea Science

The Antiviral Properties of Tea

XIONG Ligui, LIU Sihui, HUANG Jian'an, LIU Zhonghua

Journal of Tea Science. 2021, 41(2): 143-158. doi:10.13305/j.cnki.jts.2021.02.001

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Tea (Camellia sinensis) is known as a global health beverage, and global tea consumption increases due to its biological activities. In the last 30 years, antiviral activities of tea and its components, especially tea polyphenols, with different modes of action were demonstrated on diverse families of viruses, such as influenza virus, coronavirus, hepatitis virus, and human immunodeficiency virus, etc. This review summarized the current knowledge on the antiviral activities of tea and its components. Most of these studies demonstrated antiviral properties of tea and its components by in vitro biochemical or cell experiments with little rodent and clinical studies. Therefore, it is still unclear whether the antiviral effects of daily tea consumption are available. More large-scale randomized intervention and epidemiological/clinical studies are needed to confirm clinical efficacy of tea and its components.

Genome-wide Identification of PPR Gene Family and Expression Analysis of Albino Related Genes in Tea Plants

LIU Dingding, WANG Junya, TANG Rongjin, CHEN Liang, MA Chunlei

Journal of Tea Science. 2021, 41(2): 159-172. doi:10.13305/j.cnki.jts.2021.02.002

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Pentatricopeptide repeat (PPR) proteins are a kind of sequence-specific RNA binding proteins and targeted at semi-autonomous organelles, which play essential roles in play growth and development. In this study, the CsPPR genes were systematically identified by bioinformatics analysis based on the tea genome data. Then, their subcellular localization, physicochemical properties, gene structures, the chromosome locations and distribution were analyzed. The results show that a total of 858 putative CsPPR members were obtained from the genome data, which belong to P and PLS subfamilies. Domain analysis shows that each domains were relatively conservative in tea plants. Subcellular localization prediction indicates more than half of CsPPR proteins were located in the chloroplasts. Gene structure analysis shows that 31% of CsPPR genes lacked intron and the gene family had undergone extensive gene duplication events in the process of evolution. Subsequently, In order to investigate the role of CsPPR gene family in regulating the gene expressions of albino tea plants, transcriptome analysis was performed on the normal leaf color cultivar ‘Shuchazao’ and five albino tea cultivars such as ‘Anji Huangcha’. And 24 differential co-expressed CsPPR genes were identified from transcriptome data of five groups, and the real-time quantitative PCR technology was used to analysis the expression pattern of the 24 CsPPR genes in different cultivars and tissues of tea plants, and the results show that the majority of them were highly expressed in shoots, mature leaves and stems. The research results would provide a basis for CsPPR gene cloning and functional research.

Identification and Analysis of Analogue Theanine Synthase Gene Family in Tomato

MAO Peng, WANG Liyuan, BAI Peixian, WEI Kang, RUAN Li, ZHNAG Yazhen, CHENG Hao

Journal of Tea Science. 2021, 41(2): 173-183. doi:10.13305/j.cnki.jts.2021.02.003

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Theanine synthetase (TS) and some members of the glutamine synthetase (GS) family in tea plants show catalytic activity for the synthesis of theanine from ethylamine and glutamic acid. The enzymes in plants that show catalytic activity for the synthesis of theanine and are highly similar to TS sequence of tea plants are named as the analogue theanine synthase (ATS). To explore the existence of ATS in non-tea plants and effect of ethylamine on theanine synthesis, ‘Mico-Tom’ tomato was used as materials. As tomato seedlings was treated hydroponically with ethylamine, theanine was successfully detected in the leaves of the treated group. The content of glutamine (Gln) in the tomato leaves was also significantly increased, while the content of alanine did not change compared with the control group. Then, 12 and 5 members of the ATS family were identified respectively in tea and tomato through bioinformatics analysis and all of them contained the Gln-synt_C domain of glutamine synthase. Further qRT-PCR results show that the expressions of 2 ATS (SlGS1.1 and SlGS1) in the leaves were significantly increased under the treatment of ethylamine. In conclusion, the ATS may exist widely in plants, and ethylamine would be a key limiting factor in the synthesis of theanine as an important precursor. Meanwhile, ethylamine can greatly accelerate the production of theanine by promoting the transcripts of ATS.

Analysis of Ground-based Spectral Reflection Characteristics and Differences of Three Types of Yunnan Puer Tea

LYU Haitao, WU Wenjun, LIAO Shengxi, WANG Zizhi, ZHOU Junhong, LI Li, CUI Kai

Journal of Tea Science. 2021, 41(2): 184-192. doi:10.13305/j.cnki.jts.2021.02.004

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The type and producing area of tea plants affect the quality of Puer tea, and there are characteristic differences in canopy spectrum of tea plants of different types and producing area. It is great significance to make clear the source of fresh leaves and guarantee the quality of Puer tea by using this characteristic difference. In this study, the ancient tree tea, large tree tea and platform tea from four typical Puer tea mountains of Jingdong, Jinggu, Lancang and Ning'er in Yunnan Province were collected to measure spectral reflectance of their canopy leaves. The characteristics and differences of spectral reflectance were also analyzed and finally the ground-based spectral reflectance of Puer tea trees in Yunnan was revealed. The results showed that: (1) there were differences in spectral reflectance of canopy leaves of different Puer teas. In the near-infrared band, the differences in spectral reflectance of ancient tree tea and platform tea were significant. The spectral reflectance of ancient tree tea was similar to that of large tree tea. Meanwhile, the average reflectance of ancient tree tea was higher than that of large tree tea. (2) The spectral reflectance of different types of canopy leaves was shown as ancient tree tea>large tree tea>platform tea in the near infrared band. The spectral reflectance of canopy leaves of the same type of tea was Lancang>Jingdong>Jinggu, which has a positive correlation with the annual average temperature of the three places and a negative correlation with altitude. (3) Wavelength 754 nm, 801 nm and 891 nm were selected as the best wavelength points to distinguish three types of Puer tea, and 801 nm could be used as a characteristic wavelength point to distinguish ancient tree tea from different regions. This study provided technical support for the source of fresh leaves of Puer tea and the identification of tea species.

Soil N₂O Emission in Different Tea Gardens and Its Affecting Factors

FAN Lichao, ZOU Zhenhao, HAN Wenyan

Journal of Tea Science. 2021, 41(2): 193-202. doi:10.13305/j.cnki.jts.20201209.003

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In this study, we measured the in-situ N₂O emission rate in different types of tea gardens including productivity (high, medium and low) and planting years (10 a, 45 a and 100 a) and their adjacent forest, and analyzed the relationships between N₂O emission rate and soil properties including pH, organic carbon, total nitrogen, water-soluble organic carbon and nitrogen, microbial biomass carbon and nitrogen, ammonium nitrogen, and nitrate nitrogen. The results show that different types of tea gardens had significant effects on the changes of soil properties, and there were significant correlations between the soil properties. The average N₂O emission rate (N emission equivalents) in tea gardens was 3.14 mg·m^-2·h^-1, and the highest was in 100 a tea garden with the value of 4.47 mg·m^-2·h^-1. The N₂O emission rates in tea gardens were 3.1-7.2 times higher than that in forest. Mantel test shows that the N₂O emission rate was significantly and positively correlated with water-soluble organic carbon, organic carbon, total nitrogen, and microbial biomass carbon and nitrogen (P<0.05). Linear regression and structural equation models show that microbial biomass nitrogen (MBN) was the most significant factor affecting the N₂O emission rate in the tested fields.

Feasibility Evaluation of the Appilcation of Unmanned Aerial Vehicle for Tea Plant Protection

CHU Bo, LUO Fengjian, LUO Zongxiu, LIU Yan, LOU Zhengyun, CHEN Huacai, CAI Xiaoming

Journal of Tea Science. 2021, 41(2): 203-212. doi:10.13305/j.cnki.jts.20210315.001

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In order to evaluate the feasibility of unmanned aerial vehicle (UAV) for tea plant protection, the droplet deposition distribution, control effect on small green leafhoppers (Empoasca onukii), and pesticide residues between UAV and knapsack electric sprayer (KES) were tested and compared. The results show that nozzles and adjuvants of UAV had little effect on droplet deposition distribution. The droplet size, droplet density and droplet deposition of UAV were better than those of KES, but the uniformity of droplet deposition was worse. The coefficient of variation of droplet deposition by UAV was 2.44 times higher than that by KES with common spraying-water volumes. With the same amount of chlorfenapyr and common spraying-water volumes, the control efficacy to tea leafhopper by UAV was similar with that by KES. However, when the dosage of chlorfenapyr was reduced by 25%, the control efficacy by UAV was significantly declined. Under the same dosage and regular water consumption, the pesticide residues of 6 pesticides, including chlorfenapyr, deltamethrin, indoxacarb sprayed by UAV were 1.20-2.44 times higher than those by KES. Since significantly increasing the pesticide residues in tea, the application of UAV for tea plant protection should be treated with caution.

Study on the Changes of Main Flavor Components of Yunnan Large Leaf Sun-dried Green Tea Before and After Fungal Fermentation

NING Jing, LI Jianquan, LIU Benying, ZHENG Hongfa, LU Fengmei, CHEN Lei, LIU Zhen, YE Shengtao, HUANG Hao, YANG Peidi, WU Gang, YANG Yang

Journal of Tea Science. 2021, 41(2): 213-227. doi:10.13305/j.cnki.jts.20210315.002

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Yunnan large leaf sun-dried green tea was used as raw material to make light pressed sun-dried green loose Fu tea, hand pressed and machine pressed sun-dried green Fu brick teas by natural fungal fermentation method. Through sensory evaluation and physical and chemical detection, the changes of sensory quality and main flavor components of sun-dried green tea before and after fungal fermentation were studied. The results show that: the bitter and astringent taste of the three fungal fermented sun-dried green teas was obviously weakened, and changed to mellow. The aroma changed from refreshing to aging and had a unique fungus fragrance. The liquor color changed from bright yellow green to bright orange, and the color of dry tea and infused leaves were obviously deepened. The contents of tea polyphenols, catechins, free amino acids, total flavonoids, soluble sugar etc. of the three fungal fermented sun-dried green teas decreased to varying degrees, especially the ester catechin decreased significantly with the decreasing rates of 56.91% (P<0.01), 31.80% (P<0.05) and 64.06% (P<0.01) respectively. The contents of caffeine and water extract increased slightly, while the contents of tea polysaccharide, gallic acid and anthocyanin increased significantly. The relative contents of linalool and its oxides with flower and wood aroma and methyl salicylate with medicinal aroma in the fungal fermented sun-dried green teas increased from 33.94% and 1.92% before fungal fermentation to 56.73%, 57.62%, 45.98% and 8.47%, 8.53% and 7.56% respectively. While the relative contents of other alcohols and most ketones with flower and fruit aroma and aldehydes with refreshing and green grass aroma decreased significantly. Among them, the relative contents of 1,2,3-trimethoxybenzene and 1,2,4-trimethoxybenzene with aging aroma increased significantly from 1.51% and 0.56% before fungal fermentation to 5.87% and 3.75% respectively in machine pressed sun-dried green Fu brick tea. Therefore, the refreshing aroma of sun-dried green tea decreased after fungal fermentation, showing the characteristics of aging aroma, and more obvious aging aroma was identified in the machine pressed sun-dried green Fu brick tea.

Tea Authenticity Verification Method Based on Exclusive Binary Classifier

ZHU Chenpeng, PENG Hongjing, XIAO Qinghua, SHI Haojie, WU Guang

Journal of Tea Science. 2021, 41(2): 228-236. doi:10.13305/j.cnki.jts.2021.02.005

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Owing to blindness in the selection of tea features in traditional filtering methods and the uncertainty of tea categories, a verification method was proposed to equip each type of tea with a exclusive 0-1 classifier. The positive sample is the target tea itself, the label is 1. The negative sample is the remaining tea type, and the label is 0. During the training process, the model is forced to automatically extract the implicit features that are most suitable for distinguishing the target tea for true and false. This method uses the Siamese network to screen the negative samples, which alleviates the problem of imbalance between positive and negative samples. The experimental results show that this method is well adapted to the disturbance of uncertainty of tea categories and has strong robustness. It is an effective and feasible method.

Detection of 18 Prohibited Additives in Health-Protecting Tea by QuEChERS Method and Ultra High Performance Liquid Chromatography Triple Quadrupole Tandem Mass Spectrometry

GAN Ninglan, ZHU Xiaojun, LI Jieli, ZHOU Wei, LIU Changyu

Journal of Tea Science. 2021, 41(2): 237-250. doi:10.13305/j.cnki.jts.2021.02.006

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A method for the simultaneous determination of Sibutramine and other 18 prohibited additives in health-protecting tea by ultra high performance liquid chromatography triple quadrupole tandem mass spectrometry (UPLC-MS/MS) was established．Samples were extracted by ultrasonic extraction from 1% formic acid methanol solution for 20 min and purified by QuEChERS dispersive solid-phase extraction kit. The mobile phase was 0.1% formic acid in acetonitrile and 0.2 mL·min^-1 flow gradient elution was used in Agilent ZORBAX Eclipse Plus-C₁₈ column．Electrospray ion source positive ion scanning, multiple reaction monitoring (MRM) mode were determined and external standard method was used for quantification. The results show that the linearity of 18 kinds of illegal additives was good, with the correlation coefficient more than 0.999. The detection limit was 0.5-5.0 μg·kg^-1. The quantitative limit of the method was 2-18 μg·kg^-1. RSD was 0.5%-5.1% and the recovery rate was 87.3%-103.8%. This method was used to analyze 30 batches of health-protecting tea samples, of which 7 batches were positive samples. This method has strong pertinence,simple operation, high accuracy and fast detection speed. It is suitable for the determination of 18 kinds of forbidden additives in health-protecting tea. This paper also provided a scientific basis for the quality control and safety evaluation of health-protecting tea.

Rapid Detection Method of Tea Polyphenol Content in Black Tea Fermentation Based on Electrical Properties

WANG Shenglin, YANG Chongshan, LIU Zhongyuan, LIU Shanjian, DONG Chunwang

Journal of Tea Science. 2021, 41(2): 251-260. doi:10.13305/j.cnki.jts.2021.02.007

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Tea polyphenols are an important evaluation index for the quality of black tea. The quantitative prediction model of tea polyphenol content in the fermentation process was established by combining electrical characteristics detection technology with chemometric method. The changes of electrical parameters during the fermentation process and the influence of different standardized pretreatment methods and variable optimization algorithms on the model were discussed. The results show that the most sensitive electrical parameters to tea polyphenols were Cp, D and X, all of which were concentrated in the low frequency range (0.05-0.10 kHz). In the construction of tea polyphenol prediction model, normalization processing (Zscore) and mixed variable screening (VCPA-IRIV) can effectively improve the performance of the model. The number of variables introduced in the VCPA-IRIV-PLS model was reduced from 162 to 31, and the compression rate reached 80.86%. RMSECV and RMSEP were reduced to 0.630 and 1.116, respectively. Rp and RPD were increased to 0.941 and 2.956. The research results show that the electrical characteristics detection technology is feasible for the rapid non-destructive detection of the content of tea polyphenols in black tea fermentation.

Construction of Green Tea Recognition Model Based on ResNet Convolutional Neural Network

ZHANG Yi, ZHAO Zhumeng, WANG Xiaochang, FENG Haiqiang, LIN Jie

Journal of Tea Science. 2021, 41(2): 261-271. doi:10.13305/j.cnki.jts.2021.02.008

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Green tea is the tea with the largest variety and output in China. Its appearance is an important basis for its classification. Image classification is one of the core technologies of computer vision, but its application in tea field is almost blank. Tea recognition still relies on the sensory evaluation methods by experts. This study collected 1713 pictures of 8 kinds of green tea (Lishui Xiangcha, Xinyang Maojian, Lu'an Guapian, Taiping Houkui, Anji Baicha, Biluochun, Zhuyeqing and Longjing). Based on the convolutional neural network, we explored the effects of ResNet model depth from the perspectives of model convergence speed, size, efficiency and identification balance. Finally, the ResNet-18 and SGD optimization algorithms were selected and a deep learning model was established to distinguish 8 kinds of green tea. The accuracy reached 90.99%, the recognition time of the single picture was only 0.098 s, and the model size was 43.7 MB. This paper provided the foundation for constructing a tea visual recognition model and applying it to the mobile terminals and provided a new accurate and efficient method for tea recognition.

An Analysis of the Spiritual Core and Value of the Chinese Tea Culture: A Case Study of Etiquette, Customs, Ceremonies and Traditions of Chinese Tea

ZHOU Zhixiu, XUE Chen, RUAN Haogeng

Journal of Tea Science. 2021, 41(2): 272-284. doi:10.13305/j.cnki.jts.20210406.001

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In the Chinese tea cultural system, the etiquette, customs, ceremonies and literatures of tea are interactive and complementary, which build up the major part of Chinese tea culture and become important media of its spiritual core as well. In this paper, the etiquette, customs, ceremonies and literatures of Chinese tea, as an example, are disserted in the aspects of its historical formation and forms. On the basis of previous research, the spirit of Chinese tea culture is investigated, of which the core is concluded as Harmony, Respect, Rectitude, Beauty and Reality, realizing the sublimation from the physical to the spiritual level. The inheritance, promotion and development of Chinese tea culture and its spiritual core are of critically important era value for guiding the construction of socialist core value, firming the confidence in national culture and building a harmonious society.

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