Journal of Tea Science

Construction of Polyphenol Self-assembly Antibacterial Biomaterials and Progress in Their Applications

XU Wei, YU Rongxin, ZHANG Xiangchun, ZHANG Yiwen, CHEN Hongping, TIAN Baoming, ZHENG Qinqin, WU Yuanyuan, XIA Chen, WEI Bing

Journal of Tea Science. 2024, 44(1): 1-15. doi:10.13305/j.cnki.jts.2024.01.004

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Bacterial infection, a leading cause of global mortality, can result in various diseases. While antibiotics are the primary treatment for infections, their excessive and irrational use has led to the emergence of a variety of bacterial drug resistance, posing a serious threat to human health. Plant polyphenols have natural antibacterial properties, but the instability of the phenolic hydroxyl structure limits their bioavailability. To solve this problem, researchers have explored the self-assembly of polyphenols with other substances to construct new nano-biomaterials. These biomaterials not only enhance the stability and bioavailability of polyphenols but also exhibit synergistic antibacterial activity, showing a great promise in the field of antibacterial applications. This review examined the construction strategies and antibacterial properties of different types of polyphenol self-assembled biomaterials developed in recent years, including polyphenol-metal, polyphenol-hydrogel, polyphenol-chitosan, polyphenol-protein and polyphenol-liposome. Furthermore, the challenges and future prospects of the novel polyphenol self-assembling biomaterials in the field of antibacterial application were discussed.

Research Progress on the Mechanism of Natural Tea Components in Alleviating Acne

WU Zhiyuan, WANG Kaibo, CHEN Silin, ZHAO Bi, SHEN Shiquan

Journal of Tea Science. 2024, 44(1): 16-26. doi:10.13305/j.cnki.jts.2024.01.010

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Tea, as a natural beverage, is highly favored due to its clear health benefits. With in-depth research on the active ingredients of tea in recent years, it has been confirmed that natural components can have positive effects on various disease models. Acne is an inflammatory skin disease with a high prevalence and recurrence rate. In addition to traditional clinical diagnosis and treatment, complementary and alternative therapies represented by patches, skin care, and dietary improvement are also popular. In the market, more and more acne control products claim to add tea active ingredients to the raw materials. Natural components such as tea polyphenols, caffeine, theanine and tea saponins have shown great potential in alleviating acne. In this paper, the effects and molecular mechanisms of different functional components of tea on inhibiting sebum secretion, alleviating acne, improving skin microbial imbalance, and alleviating skin focal inflammation were reviewed, in order to provide reference for the research and development of tea natural products.

Selection and Validation of Internal Reference Genes for qRT-PCR Analysis under Fluoride Stress in Camellia sinensis Leaves

LI Qinghui, LI Rui, WEN Xiaoju, NI Dejiang, WANG Mingle, CHEN Yuqiong

Journal of Tea Science. 2024, 44(1): 27-36. doi:10.13305/j.cnki.jts.2024.01.001

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In order to screen the internal reference genes for quantitative real-time PCR analysis in tea leaves under fluoride stress, the low-fluoride cultivar ‘Fuding Dabaicha’ and the high-fluoride cultivar ‘Jinguanyin’ were used as experimental materials according to the fluoride evaluation results in these tea cultivars previously. The qRT-PCR technology combined with three Excel-based algorithms (geNorm, NormFinder and BestKeeper) were used to analyze the expression stabilities of eight candidate reference genes (CsACTIN, CsEF-1α, CseIF-4α, CsGAPDH, CsPP2A, CsTBP, CsTIP41 and CsUBC) in tea leaves (shoots and old leaves) under fluoride treatment (0.42 mmol·L^-1 NaF) for different time periods (0, 1, 3, 7 d). The results indicate that under fluoride stress, the optimal combination of reference genes in tea shoots was CsEF-1α, CsTIP41, CsTBP and CsACTIN and the optimal combination of reference genes in old leaves was CsPP2A and CsUBC. Moreover, to further confirm the stability of the selected reference genes, the expression levels of CsFEX in tea shoots and old leaves were analyzed using their corresponding optimal internal reference gene combinations. The expression profiles of CsFEX in tea shoots or old leaves between the two cultivars were consistent, indicating that the combinations of four and two internal reference genes were sufficient for normalizing the target gene expression in tea shoots and old leaves under fluoride stress, respectively.

Risk Assessment and Source Analysis of Heavy Metal Pollution in Chinese Tea Gardens in 2000-2022 Based on Meta-analysis

YANG Yanhu, CHEN Xiaohan, ZHANG Xiaoqing, REN Dajun, ZHANG Shuqin, CHEN Wangsheng

Journal of Tea Science. 2024, 44(1): 37-52. doi:10.13305/j.cnki.jts.2024.01.002

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Heavy metal pollution is one of the important factors affecting the ecological environment of tea gardens and the safety of tea products. This study collected literature on heavy metal (Cu, Pb, As, Hg, Cd, Cr, Zn, Ni) pollutions in tea garden soils in major tea producing areas in China, including Hubei, Hunan, Fujian, Yunnan, Guizhou and Sichuan. The weight of a single study was obtained using meta-analysis method to obtain the weighted average of heavy metal concentrations in tea garden soils in each province and across the country. The potential ecological risk index method and geological accumulation index method were used for ecological risk assessment, and source analysis using the APCS-MLR model was applied. The results show that compared with the background values, all 8 heavy metals were enriched to a certain extent, with Hg and Cd pollutions being more severe. The moderate and above risks of Hg were mainly distributed in inland provinces such as Guizhou, Shaanxi, Sichuan and Anhui. The moderate and above risks of Cd were mainly distributed in coastal provinces such as Guangdong, Fujian, Zhejiang, Jiangsu, Shandong, Hainan, etc. The two heavy metals show mild to moderate risks. Compared with other countries in the world, tea gardens or agricultural land in developing countries generally have higher levels of heavy metals, with Cd and Hg being the elements with more severe pollution levels. The source analysis results show that the first, second, third, and fourth principal components are natural sources, industrial activity pollution sources, traffic exhaust pollution sources, and agricultural activity pollution sources, respectively. Industrial and agricultural activities are the main pollution factors, with Hg mainly coming from industrial activities and Cd mainly coming from agricultural activities.

Effects of Foliar Application of Different Concentrations of Organic-based Biostimulant Formulas on Yield and Quality of Tea (Camellia sinensis L.) in Red Soil Regions

WANG Limin, CHEN Shiping, HUANG Dongfeng

Journal of Tea Science. 2024, 44(1): 53-61. doi:10.13305/j.cnki.jts.2024.01.007

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The purpose of this study was to evaluate the effect of different concentrations of organic-based biostimulant formulas (OBFs) on the yield and quality of tea (Camellia sinensis L.) in red soil regions. A field experiment was therefore conducted to investigate the nutrient uptake, yield, and quality of tea under different fertilization treatments. On the basis of conventional fertilization, foliar applications with the volume percentage concentration of OBFs including 0 (T₀), 0.33% (T₁), 0.66% (T₂), 0.99% (T₃), 1.32% (T₄), and 1.65% (T₅) were set up. The results show that foliar application of OBFs improved agronomic characteristics, enhanced nutrient uptake of tea plants and improved the tea yield and quality. Compared with the T₀ treatment, tea yield in the T₁, T₂, T₃, T₄ and T₅ treatments increased by 1.4, 1.4, 1.3, 2.1 and 2.4 times, respectively (P<0.05). In addition, as the concentrations of OBFs increased, the contents of total alkaloid, caffeine, and amino acids were first increased and then decreased. The contents of total alkaloid in the T₁ and T₂ treatments increased by 9.6% and 9.3%, caffeine increased by 9.3% and 11.4%, and amino acids increased by 5.0% and 12.4% in comparison with the T₀ treatment, respectively (P<0.05). Meanwhile, under T₁ and T₂ treatments, nitrogen (N) uptake of tea leaves increased by 5.5% and 6.1%, phosphorus (P) increased by 19.9% and 13.3% and potassium (K) increased by 20.9% and 10.0%, respectively (P<0.05). Under T₁ treatment, silicon (Si) increased by 14.8%. Furthermore, tea yield was positively correlated with bud density, 100-bud weight, leaf area and chlorophyll content. Meanwhile, the contents of total alkaloid and caffeine were positively related to N, P, K and Si contents in tea leaves, respectively. Similarly, there was a significant and positive relationship between N, P and K contents in tea leaves and the contents of amino acids and essential amino acids. Overall, foliar application with 1.65% OBFs could increase tea yield, while foliar application with 0.33% and 0.66% OBFs could promote N, P, K and Si uptake in tea leaves, improve agronomic characteristics, which is beneficial for tea yield and quality.

A Grading Identification Method for Tea Buds Based on Improved YOLOv7-tiny

HONG Konglin, WU Minghui, GAO Bo, FENG Yening

Journal of Tea Science. 2024, 44(1): 62-74. doi:10.13305/j.cnki.jts.2024.01.006

Abstract ( 361 )

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The intelligent grading and recognition of tea buds in a natural environment are fundamental for the automation of premium tea harvesting. To address the problems of low recognition accuracy and limited robustness caused by complex environmental factors like lighting, obstruction, and dense foliage, we propose an enhanced model based on YOLOv7-tiny. Firstly, a CBAM module was added into the small object detection layer of the YOLOv7-tiny model to enhance the model's ability to focus on small object features and reduce the interference of complex environments on tea bud recognition. We adjusted the spatial pyramid pooling structure to lower computational costs and improve detection speed. Additionally, we utilized a loss function combining IoU and NWD to further enhance the model's robustness in small object detection by addressing the sensitivity of the IoU mechanism to position deviations. Experimental results demonstrate that the proposed model achieves a detection accuracy of 91.15%, a recall rate of 88.54%, and a mean average precision of 92.66%. The model's size is 12.4 MB. Compared to the original model, this represents an improvement of 2.83%, 2.00%, and 1.47% in accuracy, recall rate, and mean average precision, respectively, with a significant increase of 0.1 MB in model size. Comparative experiments with different models show that our model exhibits fewer false negatives and false positives in multiple scenarios, along with higher confidence scores. The improved model can be applied to the bud grading and recognition process of premium tea harvesting robots.

Experimental Study on High-quality Tea Plucking by Robot

LI Yatao, ZHOU Yujie, WANG Shaoqing, CHEN Jianneng, HE Leiying, JIA Jiangming, WU Chuanyu

Journal of Tea Science. 2024, 44(1): 75-83. doi:10.13305/j.cnki.jts.2024.01.003

Abstract ( 332 )

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This study evaluated the performance of a newly developed track-type tea plucking robot on Longjing tea picking, including its detection accuracy, localization accuracy, end effector plucking accuracy, time consumption across each stage. The results show that the detection success rate of the developed robot was 88.54%, the localization success rate was 84.07%, the end effector plucking success rate was 87.22%, and the overall plucking success rate was 61.30%. The plucked tea leaves met the requirements of middle-grade Longjing tea. The single tea shoot plucking time was approximately 1.51 s, and the machine could pluck over 2 000 tea shoots per hour, basically achieving the picking efficiency of one machine replacing one worker.

Study on the Glycosidically Bound Volatiles and Aroma Constituents in the Processing of Wuyi Rougui

WU Zongjie, OU Xiaoxi, LIN Hongzheng, YU Xinru, CHEN Shouyue, WU Qingyang, LI Xinlei, SUN Yun

Journal of Tea Science. 2024, 44(1): 84-100. doi:10.13305/j.cnki.jts.2024.01.005

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‘Rougui’, the main cultivar of Wuyi rock tea, is characterized by a rich floral and pungent cinnamon aroma. To elucidate the contribution of key aroma constituents and glycosidically bound volatiles (GBVs) to Wuyi Rougui rock tea, this study employed ultra-high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF/MS) and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) to investigate the dynamic changes of GBVs and aroma constituents during the processing of Wuyi Rougui rock tea. The results reveal that a total of 276 aroma constituents were identified from 11 different processing stages of Wuyi Rougui rock tea. These aroma constituents belong to various chemical classes, including esters, alcohols, heterocyclic constituents, ketones, aldehydes and terpenes, with heterocyclic constituents, esters, terpenes and alcohols being the predominant aroma components. Orthogonal partial least squares-discriminant analysis (OPLS-DA) identified 35 characteristic aroma constituents in Wuyi Rougui rock tea, as indicated by their Variable Importance in Projection (VIP) values and Odor Activity Values (OAV) greater than 1. Notably, the contents of constituents associated with green and grassy flavor, such as (Z)-3-hexen-1-ol, (E)-2-nonenal and hexanal, exhibited decreasing trends during the processing, while aroma constituents associated with floral or fruity aromas, like linalool, benzyl alcohol, benzaldehyde, eugenol and β-ocimene, displayed increasing trends. Furthermore, in fresh leaves of Wuyi Rougui rock tea, aroma constituents including linalool, benzyl alcohol, benzaldehyde, 2-ethoxy-3-methylpyrazine and (E,E)-3,5-octadien-2-one exhibited ACI values greater than 1, suggesting they are key aroma constituents during the processing of Wuyi Rougui rock tea. Constituents such as dehydrocinnamyl alcohol and α-ionone contributed to the characteristic cinnamon aroma of Wuyi Rougui rock tea. In addition, ten GBVs were identified. During the processing, the contents of glucosides showed an upward trend, while primeveroside showed trend. The total contents of GBVs remained relatively stable. During the late stages of fermentation, both GBVs demonstrated declining trends, particularly constituents like benzyl primeveroside, 2-phenylethyl primeveroside, geranyl glucoside, linayl primeveroside and benzyl glucoside. The results indicate that GBVs were involved in the development of the faint scent and floral-fruity notes of Wuyi Rougui rock tea. This study clarified the role of characteristic aroma constituents and GBVs in the aroma formation of Wuyi Rougui rock tea, in order to better improve the aroma quality of Wuyi Rougui rock tea.

Analysis of the Major Characteristic Aroma Compounds in Different Grades of Jingshan Tea

ZHANG Huiyuan, MA Kuan, GAO Jing, JIN Yugu, WANG Yujie, SU Zhucheng, NING Jingming, CHEN Hongping, HOU Zhiwei

Journal of Tea Science. 2024, 44(1): 101-118. doi:10.13305/j.cnki.jts.2024.01.009

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To characterize the difference of odorants among different grades of Jingshan tea, we investigated the super grade, the first grade, the second grade and the third grade of Jingshan tea by stir bar sorptive extraction gas chromatography-mass spectrometry (SBSE-GC-MS), headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and gas chromatography-olfactometry (GC-O) analysis. Herein, we detected and identified 161 volatile organic compounds. The differences between the four grades of Jingshan tea were revealed by principal component analysis (PCA) and hierarchical cluster analysis (HCA). The variable importance in projection (VIP) of the orthogonal partial least squares discriminant analysis (OPLS-DA) was used to determine candidate differential volatile compounds among tea samples of different grades and further screening of differential compounds was carried out through analysis of relative odor activity value (ROAV) and GC-O analysis. A total of 18 volatile compounds were identified as key odorants for the discrimination of different grades of Jingshan tea, including linalool, geraniol, indole, (Z)-jasmone, dimethyl sulfide, etc. Among them, the contents of hoterienol, methyl jasmonate, and indole in the super grade Jingshan tea were significantly higher than those in other grades, and together with (Z)-jasmone, δ-decalactone, and 1-octen-3-ol and other aroma-active compounds constitute the characteristic floral aroma of super grade Jingshan tea samples. This study revealed significant differences in the characteristic volatile compounds among different grades of Jingshan tea, providing a reference for distinguishing the grades of green teas by chemometrics combined with multivariate statistical analysis.

Inductive Effect and Mechanism of EGCG on Beiging of White Adipose Tissue in High-fat Diet-fed GK Rats

WAN Liwei, ZENG Hongzhe, PENG Liyuan, WEN Shuai, LIU Changwei, BAO Sudu, AN Qin, HUANG Jian'an, LIU Zhonghua

Journal of Tea Science. 2024, 44(1): 119-132. doi:10.13305/j.cnki.jts.2024.01.008

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The types of adipose tissue are closely related to human metabolism. Transforming white adipocytes into thermogenic beige adipocytes through dietary or nutritional interventions is a safe strategy to reduce fat accumulation and regulate metabolism. Currently, research on the role of white adipose tissue beiging has mainly focused on obese populations. To explore the effect of EGCG on promoting the beiging of white adipose tissue in non-obese individuals with metabolic disorders and its related mechanisms, this study used non-obese, spontaneously diabetic type 2 GK rats. These rats were fed a high-fat diet and received 40 mg·kg^-1 and 80 mg·kg^-1 EGCG daily by gavage. In this study, we assessed body weight, food intake, cellular morphology of adipose tissue, gene expression levels associated with beiging, and protein expression levels of UCP1 in GK rats. Additionally, transcriptome sequencing was also performed on epididymal white adipose tissue. The results show that gavage intervention with 80 mg·kg^-1 EGCG has no significant effect on the food intake and body weight of GK rats. It induced a trend of beiging in adipocytes towards a multilocular phenotype transformation, characterized by a decrease in cell size and an increase in cell number. Moreover, it significantly upregulated the expression levels of beiging-related genes Pparg, Ppargc1a, Ucp1 and the protein expression level of UCP1.This demonstrates the inducing effect of EGCG on the beiging of visceral epididymal white adipose tissue in high-fat diet-fed GK rats, indicating its potential in the regulation of lipid metabolism. Combined with transcriptome analysis, the results suggest that the induction mechanism of EGCG on the beiging of white adipose tissue in high-fat diet-fed GK rats may be associated with the PPAR signaling pathway, PI3K/Akt, and MAPK signaling pathway.

Establishment of Lu'an Guapian Green Tea Brewing Control Chart

ZHAO Xiaoyi, CHEN Aini, JIANG Qing, ZHAO Lei, QIU Tong, FANG Wanxin, LIANG Chuyun, SHARIPOVA Alina, DAI Qianying

Journal of Tea Science. 2024, 44(1): 133-148. doi:10.13305/j.cnki.jts.2024.01.012

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The Coffee Brewing Control Chart is widely used in the coffee industry. According to the evaluation indices of coffee, this study applied extraction yield (EY) and total dissolved solids (TDS), which represent flavor balance and strength respectively, as quality indices to evaluate Lu'an Guapian green tea (LAGP) infusion. The optimum range of EY and TDS which yielded the maximum consumer acceptance were estimated by survival analysis. EY ranged from 2.53% to 4.57%, and TDS ranged from 0.14% to 0.28%. The LAGP Brewing Control Chart was established regarding the optimum range as the “ideal” zone. The chart was verified by both consumers and experts. This study indicates that when tea to water ratios (g∶mL) ranged from 1∶30 to 1∶15, brewing temperature ranged from 85 ℃ to 100 ℃, regulating brewing time of the first, second and third infusion less than 33 s, 15 s and 13 s, respectively, the ideal infusion can be gained. The study scientifically provided theory basis for guiding green tea brewing like LAGP.

Study on the Spatiotemporal Evolution and Spatial Differentiation Pattern of Carbon Sink in China’s Tea Industry

YUAN Liwen, ZHANG Junbiao, QIN Jiangnan

Journal of Tea Science. 2024, 44(1): 149-160. doi:10.13305/j.cnki.jts.2024.01.011

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The tea garden ecosystem has an important carbon storage function. Analyzing and evaluating the carbon sink level during the production and planting process of tea gardens is of great significance for scientifically evaluating the potential ecological value of tea gardens and promoting the green and low-carbon development of the tea industry. This paper selected data from 16 major tea producing provinces in China from 1978 to 2020, used biomass models of tea plant growth cycles and soil carbon content models to calculate and evaluate the basic situation of carbon sinks in China’s tea industry. The center of gravity fitting model was used to analyze the spatiotemporal evolution of carbon sinks in the tea industry, and the driving factors of spatial differentiation were explored in conjunction with geographic detector models. The results show that: (1) The total carbon sink of China’s tea industry had shown a phased growth trend, reaching 735.311 million tons in 2020, and the accumulation of soil carbon sink was higher than that of plant carbon sink. The carbon sink intensity showed a “rise-decrease-rise” characteristic. (2) There were significant differences in carbon sink intensity among different provinces in the tea industry. High-intensity provinces were concentrated in the eastern coastal and western regions of China, and the carbon sink gravity center had long been located within Hunan province, but there was a slight trend of westward displacement. (3) The agricultural subsidies and the development level of agricultural economy were important driving forces that affect the spatial distribution pattern of carbon sinks in China’s tea industry, but there were differences in the dominant factors for the spatial differentiation of carbon sinks in different regions. Based on this, this paper proposed relevant suggestions from the management and operation of carbon sinks in the tea industry, as well as the formulation of industrial policies.

Research on the Path to Realize the Value of Tea Agricultural Cultural Heritage: Empirical Analysis Based on 31 Typical Cases

MA Jie, YE Chaoyang, MAO Liyu

Journal of Tea Science. 2024, 44(1): 161-174. doi:10.13305/j.cnki.jts.2024.01.013

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The realization of the value of tea agricultural cultural heritage (TACH) is an important way for its protection and sustainable development. Based on the technology-organization-environment framework (TOE), this study explored the configuration effects of TOE condition variables on TACH value realization, as well as the linkage matching relationship among different elements. Based on 31 typical cases of TACH as research samples, the Fuzzy-sets qualitative comparative analysis (FsQCA) method was applied to explore the influencing factors and driving paths of TACH value realization. This study found that: (1) the realization of the value of TACH is the result of the combined action of necessary and sufficient conditions. (2) the realization of the value of high-level TACH is the result of the combination of core conditions and marginal conditions, with three typical models: "Collaborative Organizational Environment Type", "Social Resource Driven Type " and "Comprehensive Coupling Type". (3) The driving combination for the realization of non-high-level and high-level TACH value is asymmetric. Therefore, different paths could be chosen based on one's own resource endowment and external factors, in order to promote TACH value realization.

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