Journal of Tea Science

Research Advances of Fluoride Accumulation Mechanisms in Tea Plants (Camellia sinensis)

XING Anqi, WU Zichen, XU Xiaohan, SUN Yi, WANG Genmei, WANG Yuhua

Journal of Tea Science. 2022, 42(3): 301-315. doi:10.13305/j.cnki.jts.20220416.003

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Camellia sinensis (L.) O. Kuntze is a hyper fluoride (F) accumulation plant, whose F content in tea leaves is much higher than other plants, without any toxic symptoms. However, F is not an essential element for tea plant growth, and under high F stress, F affects the normal growth of plants by destroying the cell structure and inhibiting enzyme activities. In order to provide a theoretical basis for the future study of F accumulation in tea plants, the research progresses in the absorption, enrichment and accumulation/detoxification mechanisms of F in tea plants were reviewed.

Research Progress of Tea Quality Evaluation Technology

LIU Qi, OUYANG Jian, LIU Changwei, CHEN Hongyu, LI Juan, XIONG Ligui, LIU Zhonghua, HUANG Jian'an

Journal of Tea Science. 2022, 42(3): 316-330. doi:10.13305/j.cnki.jts.20220416.001

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The quality of tea is the embodiment of the shape and inner quality of tea, and evaluating the quality of tea quickly and accurately is essential for tea trade and processing. Sensory evaluation, composition analysis and detection, and emerging technologies are the main tea quality evaluation techniques at present. This article summarized the research progress of three major evaluation technologies in recent years, and focused on the development trend of emerging technologies. Sensory evaluation is greatly influenced by subjective factors, but combined with quantitative description and analysis can reduce the influence of subjectivity. Component analysis detection has high threshold, difficult operation, time-consuming and labor-consuming, and the results obtained are relatively accurate. Emerging technologies are simple, fast, and non-destructive, but at present they cannot achieve satisfactory accuracy. In the tea product diversification today, only multi-dimensional comprehensive utilization of multiple methods can quickly and efficiently detect the quality of tea, and provide assistance for the healthy and efficient development of the tea industry.

Identification and Transcriptional Regulation of CLH Gene Family and Expression Analysis in Albino Tea Plants (Camellia sinensis)

WANG Tao, WANG Yiqing, QI Siyu, ZHOU Zhe, CHEN Zhidan, SUN Weijiang

Journal of Tea Science. 2022, 42(3): 331-346. doi:10.13305/j.cnki.jts.2022.03.003

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Chlorophyllase (CLH) is the key enzyme in the degradation of chlorophyll, stripping its phytol to form dephytolithochlorophyll a. The full-length cDNA sequences of three CsCLHs genes were obtained from the second leaves of albino tea cultivar ‘Baijiguan', and bioinformatics analysis was performed. The results show that the three CsCLH genes could be divided into two subfamilies. The full length of CsCLHs was 894-975 bp, encoding 297-324 amino acids. The protein molecular weights were 31.99-34.91 kDa. The isoelectric points were 4.89-7.61, and the instability coefficients were 38.94-48.24. CsCLH1.1 and CsCLH1.2 were unstable proteins, while CsCLH2 was a stable protein. The subcellular localization prediction results of Cell Ploc show that three CsCLH proteins were located in chloroplast, while the results of Wolf Psort show that CsCLH1.1 and CsCLH1.2 were located in cytoplasm and CsCLH2 was located in chloroplast. The qRT-PCR results on the ‘Baijiguan' leaves indicated that expressions of CsCLHs were inhibited by shading treatment and light induced CsCLHs' expressions. Expression pattern analysis of CsCLHs shows that CsCLH1s were highly expressed in the albino cultivars. In addition, it was identified that CsCDF5 could bind to the CsCLH1.1 and CsCLH2 promoters according to the yeast one hybrid system. In conclusion, CsCLHs in albino tea leaves might be involved in chlorophyll degradation and play an important role in the process of albino leaf, which provided a reference for further investigation in the function of the CLH gene family and the albinism of leaves in tea plants.

Functional Identification of CsbHLH024 and CsbHLH133 Transcription Factors in Tea Plants

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

Journal of Tea Science. 2022, 42(3): 347-357. doi:10.13305/j.cnki.jts.2022.03.001

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Tea plant leaf trichomes contain various secondary metabolites and play an important role in the tea appearance quality as well as the response of tea plants to biotic and abiotic stresses. In this study, the function of leaf trichome-related genes CsbHLH024 and CsbHLH133 were analyzed using Bimolecular Fluorescent Complimentary (BiFC), GUS staining and overexpression experiments. The results show that CsbHLH024/CsbHLH133 and CsTTG1 could interact in plants, and their promoters could drive downstream gene expression in leaf tissues. They were further transformed into wild Arabidopsis thaliana (Col) and corresponding homozygous mutants, respectively to get overexpression lines. Both genes could affect the leaf trichome formation in Arabidopsis thaliana, restore the phenotype of the mutants, and induce the expression levels of trichome-related genes. This study provided a theoretical basis for further research on the molecular regulation mechanism of trichome formation in tea leaves.

The Control Efficiency of Afidopyropen to Tea Green Leafhoppers and Evaluation of Residue in Tea

GUO Mingming, LI Zhaoqun, LIU Yan, RAO Fuqiang, YU Jiawei, WU Luchao, ZHOU Li, CHEN Zongmao

Journal of Tea Science. 2022, 42(3): 358-366. doi:10.13305/j.cnki.jts.20220506.002

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Afidopyropen is a novel biogenic insecticide derived from the natural fermentation product. This study aimed to evaluate the feasibility of afidopyropen for tea green leafhoppers (Empoasca onukii Matsuda) control and tea safety after the application of afidopyropen in tea garden. The dosage field trials and demonstration trials were conducted to evaluate the control efficiency of afidopyropen to tea green leafhoppers and the terminal residues in tea. The results of the dosage field trials in 2 locations show that 50 g·L^-1 afidopyropen dispersible concentrate was more effective against the green leafhoppers than chlorfenapyr which was commonly used pesticide for the green leafhoppers control. At the dosages of 15.00 g·hm^-2 and 22.50 g·hm^-2, control efficiencies were 88.6%-93.4% on the 1st day after treatment and 75.5%-85.5% on the 14th day, demonstrating a quick control effect and good persistence. At the dosage of 18.75 g·hm^-2 in 7 locations, the control efficiencies were 88.9%-100.0% on the 3rd day after treatment, and 60.2%-100.0% on the 14th day, which were better than the local commonly used pesticides. The terminal residues of afidopyropen in green tea ranged from 0.17-0.64 mg·kg^-1 on the 7th day after the application, the leaching rate of afidopyropen from dry tea to tea brew ranged from 17.1%-19.1% during the brewing process, and the risk quotient values were far less than 1, indicating a very low health risk caused by the afidopyropen intake through drinking tea. In conclusion, afidopyropen is suitable for resistance management and comprehensive management of tea green leafhoppers with the advantages of low dosage, high-efficiency and low-healthy risk for tea consumer.

The Antifungal Effect and Mechanism of Berberine on Different Colletotrichum Species Causing Tea Brown Blight Disease

ZHANG Zhipeng, CHENG Qinghua, XIE Jingkang, WAN Yuhe, TONG Huarong, CHEN Yingjuan

Journal of Tea Science. 2022, 42(3): 367-375. doi:10.13305/j.cnki.jts.2022.03.006

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To explore the application prospects of berberine on the prevention and control of tea diseases, the antifungal activity of berberine against five different Colletotrichum species (C. fioriniae, C. karstii, C. chongqinggense, C. camelliae and C. gloeosporioides) were studied and the differences in antifungal activities were compared. The results show that berberine has the best inhibitory effect on both C. camelliae and C. chongqinggense, reaching 100% at the concentration of 12 mg·mL^-1, followed by C. gloeosporioides, C. karstii and C. fioriniae. The EC₅₀ (Concentration for 50% of maximal effect) of the five Colletotrichum species were 2.828, 3.288, 4.164, 4.778 mg·mL^-1 and 5.104 mg·mL^-1, respectively. The conidial and hyphal morphology of five Colletotrichum species under the treatment of berberine were examined, showing that berberine had a significant impact on the mycelial and conidial growth of five Colletotrichum species. With the increase of berberine concentration, part of hyphae expanded irregularly and the conidia grew abnormally. Results of the biological activity of Colletotrichum species show that the cell structure was damaged, the permeability of cell membrane was increased and the cell oxidative stress response was enhanced. Results of this study firstly confirm the antifungal activity and application prospects of berberine against Colletotrichum species, which provided a new approach and theoretical basis for the prevention and control of tea disease caused by Colletotrichum.

Research and Application of Intelligent Identification of Empoasca onukii Based on Machine Vision

BIAN Lei, HE Xudong, JI Huihua, CAI Xiaoming, LUO Zongxiu, CHEN Huacai, CHEN Zongmao

Journal of Tea Science. 2022, 42(3): 376-386. doi:10.13305/j.cnki.jts.20220506.001

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Deep learning has been widely used in intelligent identification in the progress of real-time monitoring of crop pests. Based on the identification model of tea leafhopper, Empoasca onukii, the application of deep learning in field leafhopper recognition was introduced to improve the precision of field population investigation of E. onukii. In this paper, a method of identification and count of E. onukii in tea garden was designed. Firstly, yellow sticky card was used to attract tea leafhoppers, and images of cards were collected by camera and uploaded to the web server. Then, target detection algorithm deployed by the server was used to identify and count the leafhoppers in the images. Through algorithm screening, YOLOv3 was determined as the recognition algorithm, and the improved soft-NMS was used to replace the original NMS. K-means clustering method was used to calculate the size of the new prior frame, so as to improve the speed and precision of YOLOv3. The results show that the average precision of the optimized algorithm could reach more than 95.35% comparing with the real number of leafhoppers on the sticky card. Therefore, the combination of the sticky card trapping, target recognition algorithm and internet of things technology could realize the real-time monitoring of population for E. onukii, which could provide a reference for other insects with color preference and integrated pest management in tea gardens.

Research on the Classification Method of Tea Buds Combining Improved Capsule Network and Knowledge Distillation

CHEN Xingran, HUANG Haisong, HAN Zhenggong, FAN Qingsong, ZHU Yunwei, HU Pengfei

Journal of Tea Science. 2022, 42(3): 387-396. doi:10.13305/j.cnki.jts.2022.03.002

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The accurate classification of different grades of tea buds is very important for the development of the famous tea industry. The use of traditional sensory evaluation methods for sorting makes the results subjective. In this research, a data set was established after tea leaf images were collected, and a new network model, GA-CapsNet, was proposed by combining the ghost attention bottleneck and capsule network. The model was trained by the method of growing knowledge distillation based on the linear decay scaling coefficient, while migrating the parameter matrix of teacher model, the student model was adaptively reduced with iteration. The experimental result shows that, compared with other similar algorithms, the proposed method had excellent classification performance on small-scale data sets. The accuracy, recall and F1-score were 94.97%, 95.51% and 95.24%, respectively. Here, a GA-CapsNet model based on machine vision and deep learning technology was established, which provided a new idea for solving the tea leaf classification problem.

Characterization of the Key Aroma in Corn-scented Congou Black Tea Manufactured from Camellia nanchuanica by Sensory Omics Techniques

OUYANG Ke, ZHANG Cheng, LIAO Xueli, KUN Jirui, TONG Huarong

Journal of Tea Science. 2022, 42(3): 397-408. doi:10.13305/j.cnki.jts.20220506.003

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Camellia nanchuanica is endemic to Nanchuan district, Chongqing and has a high development value. In this study, the characteristic aroma of corn-scented Congou black tea from Camellia nanchuanica was analyzed by headspace-solid phase microextraction, gas chromatography-mass spectrometry (HS-SPME-GC/MS), gas chromatography-olfactometry (GC-O), odor activity value (OAV) and aroma character impact value (ACI). The results show that 22 key aroma compounds with OAVs≥1 were identified in the corn-scented black tea. Dimethyl sulfide had the highest OAV (1 187.32), and its ACI was 51.56%. A total of 26 odor-active compounds were perceived by GC-O. Dimethyl sulfide had a higher olfactory intensity, which had a “corn-like” odor. The results obtained by the OAV approaches and by GC-O method for key aroma identification were in good agreement. The importance of dimethyl sulfide in corn-scented black tea was verified by aroma recombination and omission test. Focusing on the analysis of the active aromas of corn-scented black tea would provide a theoretical basis for the quality control of this prized tea.

Development of Amplitude Adjustable Imitation Manual Rocking Green Device for Oolong Tea and Research of Process Parameters

BIAN Xianbing, WU Min, JIA Jiangming, DONG Chunwang, ZHANG Chen'an, ZHAO Runmao, CHEN Jianneng, WANG Jinshuang

Journal of Tea Science. 2022, 42(3): 409-422. doi:10.13305/j.cnki.jts.2022.03.005

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To better promote the large-scale standardized processing of oolong tea, improve the rocking green quality and machinery efficiency, and extend the application scope of equipment, an amplitude adjustable imitation manual rocking green device and a single input multi output power transmission mechanism were designed. The kinematics analysis model of the amplitude adjustable rocking green mechanism was established, and the spatial motion trajectory of the spherical screen was simulated by MATLAB. On this basis, a rocking green prototype was developed to carry out the multi index orthogonal test of 2 factors and 4 levels of the rocking green. Then, the multi index was transformed into a single index by comprehensive scoring method, and the best process parameters were btained by the orthogonal test analysis. Under the optimal process parameters, the moderate rate of oolong tea rocking green was 84.10%, the water loss rate was 33.63%, and the comprehensive score was 97.75% of the traditional manual rocking green. The experimental results show that the developed amplitude adjustable imitation manual rocking green mechanism is effective. On the basis of matching the relevant process parameters, it can be applied to the large-scale mechanical rocking green of fresh leaves in different tenderness and seasons. Meanwhile, it also provided a new reference method for the research of relevant process parameters in the field of tea processing.

Econometric Analyses of EGCG Research Literature

ZHANG Yini, JI Zheng

Journal of Tea Science. 2022, 42(3): 423-434. doi:10.13305/j.cnki.jts.20220416.002

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The epigallocatechin gallate (EGCG) has shown the highest biological activity in tea components in most studies, which has shown beneficial effects on anti-cancer, bacterial and viral infections. A review of the advances and hot spots of EGCG studies were summarized through citation analysis. In order to ensure that the review is objective and scientific, literature analysis was performed from the core collection of the data base of ISI Web of Science of the period of 2000-2021 with the key words “EGCG” and “Epigallocatechin gallate”. A total of 6 799 relevant papers were obtained. Then, the CiteSpace visualization software was used for citation analysis and the research hotspots and frontier trends were studied through network analysis including cooperation, co-occurrence and co-citation. Statistical analysis of volume of the publications shows that China, United States and Japan ranked the top three in this field. Analysis of betweenness central indicators shows that United States, Germany and China were the top three in terms of importance. Further citation analysis shows that “nanoparticle”, and “stability” were the hotspots in the recent years. With the deepening of the research on EGCG, it was speculated that the future research would focus on improving the bioavailability of EGCG and exploring the optimal dose level and administration frequency.

Study on the Preference of Large Yellow Tea Based on Consumers with Different Ages

AN Qi, QIU Tong, ZHANG Ying, XIAO Mingji, CHEN Aini, SHENG Caiyan, DAI Qianying

Journal of Tea Science. 2022, 42(3): 435-446. doi:10.13305/j.cnki.jts.2022.03.004

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In this paper, 9-point hedonic scale and 5-point just about right were used to test the preference of large yellow tea and evaluate the acceptance of sensory attributes among consumers with different ages. The results show that young and middle-aged consumers prefer low-roasted and high-tenderness large yellow tea with sweet and mellow flavors while older consumers prefer high-roasted and low-tenderness large yellow tea with the burnt, bitter and paste flavors. Combined the JAR data with the preference data through penalty analysis, the most influential attributes, the direction of attribute optimization and the order of improvement priority were qualitatively obtained from the three age groups, which was of certain reference to design and process large yellow tea products.

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