Journal of Tea Science

Research Progress on Colored Substances in Tea

LONG Piaopiao, SU Shengxiao, ZHANG Liang

Journal of Tea Science. 2023, 43(5): 593-606. doi:10.13305/j.cnki.jts.2023.05.010

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The color of tea leaves and infusions is an important attribute to tea flavor and quality. Colored substances contain chromophore and auxochrome groups, which contribute to producing different shades of green, yellow, and red hue in tea infusion. As the concentrations of colored substances increase, the tea infusions’ color will increase accordingly, presenting different colors such as yellowish-green, reddish-yellow and reddish-brown. Furthermore, fermentation (enzymatic oxidation) and drying stages during processing, as well as temperature, pH, and concentration in sensory evaluation, affect the color and brightness of tea infusions. This review revealed the color formation mechanisms by summarizing the chemical structures, color characteristics, coloration mechanisms and other factors of color substances in tea. It also provided a theoretical evidence for the quality improvement of tea flavor and the innovation of processing technology.

Advances in the Application of Metabolomics in the Study of Physiological and Biochemical Metabolism of Tea Plants [Camellia sinensis (L.) O. Kuntze]

MAO Chun, HE Ji, WEN Xuefeng, WU Chuanmei, YI Chengxi, LIAN Jianhong, GUO Wenmin

Journal of Tea Science. 2023, 43(5): 607-620. doi:10.13305/j.cnki.jts.2023.05.009

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Tea is a leafy perennial crop, and its physiological metabolism is significantly affected by external environmental factors. Main biochemical components such as amino acids, caffeine and tea polyphenols not only give tea unique flavor quality and health characteristics, but also are important contributors to the resistance of tea plants to biotic and abiotic stresses. Metabolomics technologies have the characteristics of high throughput, high sensitivity and systematization. They can identify and quantify tea metabolites comprehensively, accurately and quickly. The in-depth study of metabolomics provides a technical platform for the further development and utilization of tea metabolites. This paper reviewed the applications of metabolomics in the study of physiological and biochemical metabolism (photosynthesis, respiration, carbon and nitrogen metabolism) and metabolism of main quality biochemical components (flavonoids, alkaloids, amino acids, etc.) of tea plants in recent years, and prospected the future applications of metabolomics in the field of tea, so as to provide some theoretical references for further tea management, cultivar breeding and quality improvement.

Catalytic Function, Promoter Structure and Functional Analysis of CsNUDX1-cyto in Different Tea Cultivars

YANG Jihong, ZHOU Hanchen, XU Yujie

Journal of Tea Science. 2023, 43(5): 621-630. doi:10.13305/j.cnki.jts.2023.05.001

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Geraniol is an important monoterpenoid in tea plants, and its accumulation varies greatly among different tea cultivars. The recent study shows that CsNUDX1-cyto is responsible for the production of geraniol and its glycosides in tea plants. In order to explore the differences in the catalytic function and regulation of CsNUDX1-cyto in different tea cultivars, this study analyzed the differences in the accumulation of geraniol and expression patterns of CsNUDX1-cyto, and analyzed the differences in the catalytic function, promoter structure and function of CsNUDX1-cyto in seven tea cultivars. The result shows that CsNUDX1-cyto expression was positively correlated with geraniol content (r=0.805). The content of geranyl in fresh leaves of Camellia sinensis var. sinensis (CSS) was significantly higher than that in C. sinensis var. assamica (CSA) cultivars. Agrobacterium tumefaciens-mediated genetic transformation system shows that CsNUDX1-cyto of different tea cultivars could promote the biosynthesis of geraniol. Analysis of promoter activity shows that CsNUDX1-cyto promoter had the weakest activity in ‘Yunkang 10’, and the structural analysis shows that the promoter of CsNUDX1-cyto in ‘Yunkang 10’ had an 185 base sequence insertion at the transcription start site -33, making the enhancing element CAAT-box located at -133 (CAAT-boxes in other cultivars were located at -47). The results of this study indicate that CsNUDX1-cyto in different tea cultivars could promote geraniol biosynthesis, but the genetic diversity of the promoter region results in differences in its expression level.

Construction of Flavor Wheel and Quantitative Sensory Description Analysis of Pu'er Tea and Fu Brick Tea

CHEN Guohe, HU Tengfei, XIE He, FU Wenjie, ZHAI Yuke, BAO Sudou, AN Qin, WANG Chao, WANG Yingzi, LIU Zhonghua, HUANG Jian'an

Journal of Tea Science. 2023, 43(5): 631-644. doi:10.13305/j.cnki.jts.2023.05.008

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Flavor wheel is a simple and easy method to understand descriptor system, which is convenient for consumers to communicate the sensory flavor attributes of Pu'er tea and Fu brick tea. In this study, by establishing a sensory evaluation team, sensory evaluation was conducted on the flavor of Pu'er tea and Fu brick tea, and the flavor wheels of Pu'er tea and Fu brick tea were drawn from two dimensions: aroma and taste. On this basis, a vocabulary for quantitative sensory description of Pu'er tea and Fu brick tea was established by setting reference samples with different intensities for 23 typical sensory descriptions. Furthermore, using the M-value method combined with analysis of variance and multivariate statistical analysis, the main sensory descriptors that can better describe Pu'er tea and Fu brick tea were selected. A total of 7 aroma descriptors (woody, sweet aroma, herbal, ferment, glutinous, jujube and aged) and 5 flavor descriptors (sweet taste, bitter, astringent, sour and mellow and thick) were selected for Pu'er tea, and 5 aroma descriptors (woody, sweet aroma, herbal, aged and fungal floral) and 5 flavor descriptors (sweet taste, bitter, astringent, sour and mellow and thick) were identified for Fu brick tea, and these descriptors can better evaluate the sensory quality characteristics of Pu'er tea and Fu brick tea samples. The results of this study provide application value for distinguishing and evaluating the sensory flavor characteristics of Pu'er tea and Fu brick tea, as well as in the development of their products.

Exploring the Potential Mechanism of Hypoglycemic Effect of Fungus Fermented Black Tea Based on Liver Transcriptomics

ZENG Hongzhe, PENG Liyuan, WAN Liwei, LIU Changwei, FANG Wenwen, WANG Kuofei, ZHANG Xinyi, WEN Shuai, HUANG Jian'an, LIU Zhonghua

Journal of Tea Science. 2023, 43(5): 645-656. doi:10.13305/j.cnki.jts.2023.05.003

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EGCG is often regarded as the main active ingredient in tea to protect blood glucose homeostasis. The content of low molecular weight polyphenols such as EGCG in fungus fermented black tea (FFBT) is extremely low, and there are few studies on the hyperglycemic effect of FFBT. To explore the hypoglycemic effects and potential mechanisms of FFBT, GK rats with spontaneous hyperglycemic were given 280 mg·kg^-1 FFBT extract (equivalent to 9 g of FFBT for daily human consumption) by gavage intervention. The study assessed the effects of FFBT on body weight, glucose homeostasis, regulatory factors related to glucose homeostasis, diabetic complications and liver transcription profiles in hyperglycemic rats. The results indicated that FFBT could obviously reduce the fasting blood glucose level and random blood sugar level of hyperglycemic rats, improve the abnormal glucose metabolism in hyperglycemic rats, maintain glucose homeostasis and alleviate the damage caused by diabetic complications in hyperglycemic rats. In addition, transcriptome analysis revealed that the hypoglycemic properties of FFBT might be related to the regulation of gene expression in the liver, such as Gck, Pklr, Pkm. This study found that FFBT may be a potential hypoglycemic functional beverage, providing a theoretical basis for the development and utilization of fermented tea such as FFBT.

Glyphosate-stress Effects on Shikimic Acid in Tea Leaves

LIU Hongxia, LIU Yingying, CHEN Hongping, CHAI Yunfeng

Journal of Tea Science. 2023, 43(5): 657-666. doi:10.13305/j.cnki.jts.2023.05.005

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To investigate the effect of glyphosate stress on the growth and shikimic acid metabolism of tea (Camellia sinensis L.) plants, tea seedlings were cultured in nutrient solution with different concentrations of glyphosate and the visual phytotoxicity on tea leaves was observed. The non-targeted analysis of non-volatile metabolites in the leaves and quantitative determination of shikimic acid and glyphosate in the leaves were carried out by ultra-high performance liquid chromatography-quadrupole orbitrap high-resolution mass spectrometry. The results show that the tea seedlings under the high dose of glyphosate (200 mg·L^-1) treatment exhibited characteristics of pesticide damage, while the tea seedlings under the low dose of glyphosate (50 mg·L^-1) treatment and control did not show apparent pesticide damage. Mass spectrometric and statistical analysis indicates that there were significant changes in the contents of shikimic acid pathway metabolites in the leaves of glyphosate-treated tea seedlings, with shikimic acid being one of the main differential metabolites. Within 21 d, the accumulation of shikimic acid in leaves was highly positively correlated with the absorption amount and action time of glyphosate. When the absorption amount of glyphosate was larger than 28 mg·kg^-1, the shikimic acid metabolism in tea plants was significantly inhibited, resulting in a large accumulation of shikimic acid in tea leaves. Compared with the control group, the content of shikimic acid in tea leaves affected by pesticides increased about 16-fold. This study shows that shikimic acid is one of the main metabolites of tea plants in response to glyphosate stress.

Analysis of Aroma Characteristics and Volatile Components of Zhenghe White Tea with Different Storage Years

HUANG Wei, ZHANG Lingzhi, ZHANG Jialin, LIN Fuming, RONG Jiefeng, XIAO Chunyan, YUE Penghang, YU Huazhu, SUN Weijiang, HUANG Yan

Journal of Tea Science. 2023, 43(5): 667-680. doi:10.13305/j.cnki.jts.2023.05.006

Abstract ( 287 )

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In order to investigate the aroma characteristics of Zhenghe white tea with different storage years, quantitative descriptive analysis (QDA) combined with headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to analyze the aroma characteristics and volatile components of Zhenghe white peony tea stored for 0, 5, 10 and 15 years. The results show that the aroma characteristics of Zhenghe white peony tea varied significantly among different storage years. The aroma characteristics of BMD0 were mainly pekoe, fresh, sweet and floral. With the extension of storage time, the pekoe, fresh, sweet and floral weakened, while the stale flavour and woody increased. A total of 66 volatile components were detected in Zhenghe white peony tea with different storage years, mainly alcohols, esters and acids, with the highest alcohol content in BMD0 and BMD5, and the highest ester content in BMD10 and BMD15. With the extension of storage time, the total volatile components decreased significantly, and the composition and proportion of relative contents changed significantly. The Orthogonal partial least-squares discrimination analysis (OPLS-DA) model could effectively discriminate Zhenghe white peony tea with different storage years. A total of 14 volatile components were screened based on relative odor activity value (rOAV)>1, while 30 volatile components were screened based on variable importance for the projection (VIP)>1. Based on rOAV value>1 and VIP value>1, 6 major volatile components were screened, including β-ionone, α-ionone, nerolidol, benzyl alcohol, benzeneacetaldehyde, linolenic acid. This study provided a theoretical reference and basis for the scientific storage of white tea and the flavour analysis of aged white tea.

Parameter Optimization of Black Tea Fermentation Machine Based on EDEM and RSM

LIU Limin, DONG Chunwang, LIN Shuhong, SHI Yali

Journal of Tea Science. 2023, 43(5): 681-690. doi:10.13305/j.cnki.jts.2023.05.004

Abstract ( 135 )

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Fermentation is a key process for the formation of black tea quality, and the fermentation conditions are the important factors affecting the degree of fermentation. In order to optimize the parameters of a self-designed roller fermentation machine, the extended distinct element method (EDEM) was used to simulate three distinct gradients of the rotational speed of the flexible scraper, and compare the degree of uniformity. With sensory score as evaluation index, response surface method (RSM) was applied for optimizing three key factors affecting fermentation quality (fermentation temperature, fermentation time, stirring interval). The results indicate that the uniformity of fermentation was the best at a rotation speed of 36(°)·s^-1. Based on this rotational speed, the order of importance of each factor on fermentation quality was: fermentation time, fermentation temperature, stirring interval. The optimal process parameters were as follows: fermentation time, 230βmin, fermentation temperature, 28.5β℃, and stirring interval, 20βmin.

Exploratory Study on the Image Processing Technology-based Tea Shoot Identification and Leaf Area Calculation

LÜ Danyu, JIN Zijing, LU Lu, HE Weizhong, SHU Zaifa, SHAO Jingna, YE Jianhui, LIANG Yuerong

Journal of Tea Science. 2023, 43(5): 691-702. doi:10.13305/j.cnki.jts.2023.05.007

Abstract ( 167 )

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In this study, based on the picture collection of tea shoot growth in the field, we used deep learning target detection algorithm YOLOv5 to construct a model for identifying different growth stages of tea shoots, and the testing results indicate that the model had high accuracy. Furthermore, the Image-J software and the image processing methods of threshold cutting based on Gray, RGB and HSV values were applied to process tea leaf area, and the accuracy and efficiency of different methods were compared. The results show that the accuracy of HSV-based algorithm system of cutting tea leaves and automatically calculating tea leaf area was over 94%, which had better performance than RGB-based algorithm system. The research results provide technical support for the intelligent recognition model of tea growth state and information extraction algorithm of leaf traits, and also build a theoretical basis for the development of tea bud automatic recognition module of tea plucking machinery.

Study on Characteristic Flavor Substances in Tea Aroma Type Distilled Spirit Based on GC-MS and GC-O

HUANG Cui, WANG Fengli, CHEN Yaolin, YU Jiajun, WANG Wei, DU Sufeng, SONG Tao, CAI Zhongshui, XUE Jie, WU Yun

Journal of Tea Science. 2023, 43(5): 703-717. doi:10.13305/j.cnki.jts.2023.05.002

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As a further extension of the deep processing technology of tea raw materials, tea aroma type distilled spirit combines the aroma of tea and wine, and has a unique flavor. In order to clarify the changes of flavor substances of tea aroma type distilled spirit under different processes, solid-phase microextraction/gas chromatography-mass spectrometry was used to analyze the flavor components. The odor specific magnitude estimation method and Odor activity value method in liquid-liquid extraction/gas chromatography-olfactometry-mass spectrometry were used to determine the characteristic flavor substances and their contribution to the overall flavor. The results show that 76 kinds of aroma substances were detected, including 32 esters, 14 alcohols, 10 aldehydes and ketones, 4 acids, 13 terpenes and 3 other substances. Gas chromatography-olfactometry mass spectrometry analysis results show that there were 21 aroma compounds that could be smelled, and 12 key aroma compounds were identified by OAV and OSME together, including linalool (rose flowers), anisole (herbal), ethyl caprate (fruit), ethyl caproate (wine aroma) and so on. The results show that different kinds of microorganisms, fermentation methods and distillation technology significantly affected the composition and contents of flavor substances in tea aroma type distilled spirit. The results of this study have important guiding significance for the characteristic aroma characterization and quality control of tea aroma type distilled spirit.

Research on the Effect Evaluation and Dynamic Mechanism of the Integrated Development of Tea and Tourism Industry

LIN Xi, WU Qinyao, YANG Jiangfan

Journal of Tea Science. 2023, 43(5): 718-732. doi:10.13305/j.cnki.jts.2023.05.011

Abstract ( 179 )

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This study was based on the theories of industry integration, industry chain value, and coupling coordination, as well as previous research results. Taking the development level of the tea industry and tourism industry in the eight main tea-producing areas in China from 2011 to 2020 as the empirical research object, a quality evaluation index system for the development of the tea and tourism industry was constructed, and the coupling coordination model and spatial analysis method were used to evaluate and present the effect of tea tourism integration. And regression models were used to explore the driving mechanism of tea tourism integration development. The results indicate that the tea and tourism industries in the main tea-producing areas over the past decade were highly coupled, which were present in the middle to late stages of integrated development. The overall trend shows a spatial feature of "high in the middle and low on both sides", with an inverted "U" shape in the east-west direction. The high value area at the provincial level has always been Yunnan Province. The driving force mechanism is the joint influence of internal and external factors: the internal driving force is the internal coupling between the tea and tourism industries, which drives the formation of a new business model: the integration of tea and tourism. In terms of external macro environment, policy guidance and support are the leading forces, sustained economic development is the driving force, social and cultural prosperity is the pulling force, and technological innovation and application are the supporting forces. Suggestions were also made on further promoting the integrated development of tea tourism consisting of strengthening government guidance and support to improve factor protection, promoting the improvement of industry quality and efficiency to consolidate the foundation of development, digging and highlighting cultural connotations to expand the depth of development, applying technology to cultivate talents and thus strengthen development support.

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