Journal of Tea Science

Research Progress on the Bitterness of Green Tea

MA Yuanyuan, CAO Qingqing, GAO Yizhou, LIU Yuyi, DENG Sihan, YIN Junfeng, XU Yongquan

Journal of Tea Science. 2023, 43(1): 1-16. doi:10.13305/j.cnki.jts.2023.01.001

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Tea, as a hobby drink, the flavor is its first quality attribute. The presentation of its taste is the comprehensive perception effect of the human taste organs on the flavor components in tea infusion, which is generally manifested as bitter, astringent, fresh, sweet and other sensory experiences. Among them, bitterness is the most easily perceived taste attribute, and as a crucial factor affecting the flavor quality of tea. Meanwhile, due to the bitter taste, summer and autumn tea resources are faced with the dilemma of large abandonment, resulting in a great waste of resources. Based on this, this paper reviewed the physiological basis of bitter perception and the evaluation methods of bitter taste perception. Taking green tea infusion as the main carrier, the bitter taste components of tea were systematically integrated, and the interaction effect between other taste monomers and bitter compounds, as well as the regulatory mechanism of post-treatment on the bitter taste of tea infusion were discussed. It was expected to enrich the theoretical basis of taste chemistry and clarify the flavor characteristics of bitter compounds of tea, the taste mechanism and the interaction effect between taste substances, and provide theoretical reference for promoting the high-value utilization and taste regulation of summer and autumn tea.

Effects of Acidification on Mineral Transformation and Potassium Supply Capacity of Tea Garden Soils

MA Wanzhu, ZHU Kangying, ZHUO Zhiqing

Journal of Tea Science. 2023, 43(1): 17-26. doi:10.13305/j.cnki.jts.2023.01.002

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Acidification is a common phenomenon of tea garden soils. In order to understand the long-term effects of acidification on mineral components and potassium in tea garden soils, the red soil developed from granite was selected, and the forest land of the same soil type was used as the control. Through soil analysis and simulation experiments, the changes and differences of soil minerals and soil potassium forms caused by soil acidification were compared after 20 and 50 years of continuous planting of tea trees. The results show that the acidification of tea garden soils reduced the capacity of slow available potassium and potassium containing minerals such as mica and feldspar in sand and silt fractions, promoted the transformation from 2∶1 type (Illite) minerals to 1∶1 type minerals (Kaolinite) in clay fraction, and reduced the total potassium content of the soils. With the increase of soil acidity, the proportion of mineral bound form and non-exchangeable form K in the soils decreased gradually. While the proportion of water-soluble K increased gradually. After soil acidification, the potassium applied to the soils mainly existed in water-soluble and exchangeable forms with high activity. The proportion of K in non-exchangeable form was significantly reduced, and the buffering ability of soil to external source K was gradually reduced. The application of zeolite in acidic soils could enhance the buffering ability of the soils to potassium transformation and reduce the leaching loss risk of soil potassium. The results show that soil acidification in tea gardens could significantly reduce soil potassium, weaken soil potassium supply capacity and potassium buffering ability.

Development and Application of Albinotea Plant mSNP Molecular Markers Based on Genome-wide Resequencing

LIU Haoran, ZHANG Chenyu, GONG Yang, YE Yuanyuan, CHEN Jiedan, CHEN Liang, LIU Dingding, MA Chunlei

Journal of Tea Science. 2023, 43(1): 27-39. doi:10.13305/j.cnki.jts.2023.01.003

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To explore the information of genetic variation in albino tea and the feasibility of the mSNP liquid chip in the identification of tea germplasm, we analyzed the genetic diversity and detected the mutation sites of 18 tea resources by genome resequencing. The results indicate that the 18 albino tea accessions could be divided into three groups based on genome-wide SNP markers, and the resources with genetic relationship or close geographical location tended to cluster together. Functional annotation of the resequencing data reveals 17 056 non-synonymous mutated genes in the 18 albino tea resources, of which 98 missense mutations were found in 14 chlorophyll synthesis related genes. Then, based on the genomic variation information obtained in the previous study, we developed a set of liquid chip containing 59 mSNP and 222 SNP sites for the first time, and used the liquid chip to detect the genotype information of 13 tea plants. The results show that the genetic similarity between pairs of the same cultivar was 92%-98%, and the genetic similarity between different cultivar was less than 84%, indicating that the chip could accurately identify 18 albino tea accessions. Our results laid a foundation for the application of mSNP liquid phase chip in the identification of tea germplasm resources and molecular marker-assisted breeding.

Identification of Watery Saliva Protein from Empoasca onukii and Preliminary Study on the Involvement in the Formation of “Hopperburn” Symptoms in Tea Plants

YAN Jiawei, CHEN Zongmao, LI Zhaoqun, LUO Zongxiu, BIAN Lei, CAI Xiaoming, JIN Shan

Journal of Tea Science. 2023, 43(1): 40-54. doi:10.13305/j.cnki.jts.2023.01.011

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The role of saliva protein of Empoasca onukii in the formation of “Hopperburn” symptom in tea plants has not been studied to date. In this paper, the double-layer parafilm clamping nutrient solution method and a simple self-made saliva collection device were developed to collect the watery saliva of E. onukii adults. The proteins were then extracted from the watery saliva using SDT splitting method and FASP (Filter-Aided Sample Preparation) enzymatic hydrolysis method, and then watery saliva proteins were detected by LC-MS/MS. The results showed that a total of 107 peptides and 92 proteins were identified, which could be divided into 7 groups according to their functions, including enzymes, transporter proteins, ion-binding proteins, regulatory proteins, cytoskeletal proteins, non-enzymatic proteins and uncharacterized proteins. In addition, the collected and purified salivary proteins were used to treat the mechanically damaged tea leaves and make comparison with the pure mechanically damaged leaves, the pure saliva-treated leaves, the serum protein treated leaves and E. onukii adults infested leaves. The results show that the saliva protein-treated leaves had the same trends as the leaves damaged by leafhopper, with “Hopperburn” symptoms appearing at 48 h of treatment. While no such symptoms appeared in the other treatments. This study provided some basic information for further understanding of saliva composition of E. onukii and the interaction mechanism between leafhopper saliva protein and tea plants.

Pathogenicity and Fungicide Sensitivity of Colletotrichum camelliae from Tea Plant (Camellia sinensis)

CHENG Kaixin, YANG Kaixin, DENG Yayuan, LI Xin, LIU Enbei, WANG Yuchun, LÜ Wuyun

Journal of Tea Science. 2023, 43(1): 55-66. doi:10.13305/j.cnki.jts.2023.01.004

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Colletotrichum camelliae is the dominant species causing foliar diseases of tea plants (Camellia sinensis). In this study, 65 isolates of C. camelliae were obtained from diseased leaves of tea plants in the 13 main tea-producing provinces of China. Phylogenetic analysis based on the multigene sequences was performed on all isolates, combined with their characteristics of colony and conidia, showed that all isolates clustered with C. camelliae. Pathogenicity analysis performed on detached leaves showed that all isolates of C. camelliae could infect the tea leaves, but the virulence of the isolates displayed a significant difference. The pathogenicity of 12 isolates, including YCW1180, YCW1331, YCW1382, YCW1387, YCW1419, YCW1443, YCW1451, YCW1453, YCW1454, YCW1461, YCW1613 and YCW2134, was significantly stronger than that of other isolates. By contrast, the pathogenicity of YCW1378 isolate was the weakest. The sensitivity of 65 isolates to 25% pyraclostrobin was determined by analyzing the inhibition rate of mycelial growth. The results show that the inhibition rate of pyraclostrobin on mycelial growth of YCW1436 isolate was only 36.00%, showing the worst antimicrobial effect. However, the inhibition rate of mycelial growth of most isolates was higher than 70.00%, which suggests that most isolates were highly sensitive to 25% pyraclostrobin. Microscopic observation shows that this agent mainly affected the conidial germination of C. camelliae. Overall, this study provided a solid foundation for the effective control of the diseases.

Screening and Identification of Strains against Fusarium solani Isolated from Camellia sinensis and Analysis of its Biocontrol and Growth Promotion Characteristics

DENG Xiaoxu, XIE Xia, PAN Yamei, ZHAO Fenghua, JIANG Shuangfeng, XU Wen, ZHANG Jie, SUN Runhong, XIA Mingcong, YANG Lirong

Journal of Tea Science. 2023, 43(1): 67-77. doi:10.13305/j.cnki.jts.2023.01.005

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Fusarium solani is a pathogen that could cause collar canker and dieback of Camellia sinensis. To obtain strains with strong antagonistic activity against F. solani, a total of 56 endophytic strains were isolated and purified from healthy leaves of tea trees collected from a tea garden in Xinxian, Xinyang, Henan province by dilution plate method and were screened in dual cultures with F. solani. The strain was identified based on morphological characteristics, physiological, biochemical and molecular tests. Biocontrol and growth-promoting traits and antibacterial spectrum test were also detected. The effects on the mycelial growth of F. solani were evaluated by ferment product and volatile test by buckle culture. The results show that strain YB-1476 exhibited the strongest antagonistic activity against F. solani with growth inhibition rate of 63.31% and was identified as Bacillus velezensis. Strain YB-1476 could produce siderophore, indoleacetic acid, and be able to secrete β-1,3-glucanase, cellulase and solubilize phosphorus. Furthermore, strain YB-1476 displayed strong antagonistic activity against Bipolaris sorokinana, Fusarium graminearum PH-1, Fusarium moniliforme, Fusarium oxysporum f. sp. niveum and Alternaria solani and growth inhibition rates were 65.03%, 42.32%, 51.67%, 52.33% and 63.22%, respectively. In addition, ferment products show that the growth inhibition rates of the original fermentation broth, 10-fold, and 100-fold dilutions were 66.67%, 51.85%, 18.52%, respectively and the volatile test shows that growth inhibition rate against F. solani was 53.37%. The above results demonstrate that B. velezensis YB-1476 is a strain with great application potential to control collar canker and dieback of tea trees.

Effect of Pile-up Processing Duration on Flavor Quality of White Tea

WU Shaoling, WANG Zhihui, SHANG Hu, ZHU Chensong, YE Tingting, SUN Weijiang

Journal of Tea Science. 2023, 43(1): 78-90. doi:10.13305/j.cnki.jts.2023.01.006

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The effects of different pile up durations on the flavor quality of white tea were investigated based on sensory evaluation and biochemical analysis, in which the white tea with different pile-up processing durations were used as the experimental materials. The results of biochemical analysis show that with the increase of the pile-up processing duration, the flavor of the bitterness and astringency first weakened and then strengthened, the sweetness first increased and then decreased, and mellow gradually increased. In addition, and the sweet and floral increased. The contents of tea polyphenols, flavonoids, soluble sugar, catechins, free amino acids were the main reasons for the taste difference. The contents of cis-linalool oxide (furanoid), trans-linalool oxide (furanoid), α-terpineol, decanal, β-cyclocitral, geranylacetone, β-ionone and octanal were the key factors affecting the difference of aroma. Under different pile-up processing durations, piling-up for 12 d had the best flavor quality, which was conducive to increasing the contents of free amino acids, soluble sugar and catechins, while decreasing the bitter taste index, and increasing the contents of trans-linalool oxide (furanoid), decanal, β-cyclocitral, geranylacetone, β-ionone, promoted floral and sweet fragrance of white tea. Our study provided reference for the optimization of white tea pile-up process and the improvement of flavor quality of white tea.

Effects of Key Genes of Jasmonic Acid Synthesis and Transduction Pathway in Tea Plant on Terpenoids during Oolong Tea Processing

LU Li, ZHAN Dongmei, ZHOU Chengzhe, ZHU Chen, XIE Siyi, XU Kai, TIAN Caiyun, LAI Zhongxiong, GUO Yuqiong

Journal of Tea Science. 2023, 43(1): 91-108. doi:10.13305/j.cnki.jts.2023.01.007

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In this study, we analyzed the key genes of jasmonic acid synthesis and signal transduction pathway in tea plants, explored their expression patterns and investigated their effects on the formation of terpenoids during oolong tea processing. There are 11 key gene families in this pathway, including 133 candidate genes. The analysis of cis-acting elements shows that the promoter regions of the key genes of the pathway contained a large number of cis-acting elements, including jasmonic acid response, damage response and anaerobic induction response. qRT-PCR analysis shows that most of the genes of this pathway showed an upward trend during the withering process, reached the highest in the second shaking process, significantly decreased in the fourth shaking process, and slightly increased in the process before green removal, and the key genes of this pathway could respond to various stresses during oolong tea processing. HS-SPME-GC-MS detected 73 terpenoids, mainly including linalool, geraniol and α-farnesene and other substances with flower and fruit flavor. Correlation analysis shows that CsLOX11, CsLOX12, CsAOS2, CsAOC1, CsACX4, CsACX8, CsMYC2-4, CsMYC2_15, CsMYC2_21 and β-pinene, limonene and myrcene are positively correlated, and CsOPR2, CsTPL6 and CsLUG4 are positively correlated with trans nerolidol, α-farnesene and ionone, among which CsTPL6 was significantly positively correlated with 35 terpenoids. In summary, the key genes of jasmonic acid synthesis and signal transduction pathway of tea plants are involved in regulating the formation of terpenoids during oolong tea processing, and this study laid a foundation for exploring the molecular mechanism of aroma formation during oolong tea processing.

Analysis of the Effect of Different Full Firing Methods on the Aroma of Jinmudan Congou Black Tea Based on Sensomics Characterization

WEI Hao, LAN Tianmeng, MIAO Yiwen, MENG Qing, KUN Jirui, ZHANG Yu, TONG Huarong

Journal of Tea Science. 2023, 43(1): 109-123. doi:10.13305/j.cnki.jts.2023.01.010

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To investigate the effect of different full firing methods on the aroma of black tea, four full firing methods, namely high temperature (80 ℃), low temperature (40 ℃), dehydrated hot air (heat pump) and vacuum freezing, were used to process Congou black tea samples using the fresh autumn tea leaves of ‘Jinmudan’. The samples were analyzed by gas chromatography-mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O), odor activity value (OAV), aroma character impact value (ACI) and aroma evaluation methods were used to compare the types and contents of key aroma compounds and their contribution to the aroma of black tea by different full firing methods. The results show that there were significant differences between the four full firing methods in terms of aroma type, classes and content of aroma compounds. The results of aroma evaluation show that: high temperature dried black tea showed an unpleasant sulky odor. Low temperature dried black tea showed no floral odor and a heavy grassy odor. Heat pump dried black tea showed a refreshing floral odor. Vacuum freezing dried black tea showed a harmonious odor with good retention of floral and fruit odor and no grassy odor. The contents of linalool and its oxides, which were determined as active aroma components by OAV and GC-O, were significantly lower in low temperature full-fired black tea. While the contents of active aromas such as (Z)-2-pentenol, which present a grassy aroma, were significantly higher than that of traditional high temperature full-fired black tea, and the contents of linalool and its oxides, benzaldehyde, phenylacetaldehyde, methyl salicylate, geraniol, etc., which show floral and fruit aromas in heat pump full-fired black tea, were significantly higher than that of traditional high-temperature full-fired black tea. The contents and contribution of linalool and its oxides, benzaldehyde, benzylaldehyde, methyl salicylate, geraniol and (Z)-2-pentenol, which show floral and fruity aromas, were higher in black tea full-fired by heat pump than in black tea full-fired by other full firing methods. The results of orthogonal partial least squares discriminant analysis (OPLS-DA) and variable importance in projection (VIP) show that the OPLS-DA model was reliable and 19 compounds with VIP value higher than 1 were screened. The results show that both heat pump and freeze-drying technologies can effectively reduce the sulky aroma of traditional high temperature full firing processes and can be used to improve the floral and fruit aroma of black tea. This study provided a technical reference and theoretical guidance for the improvement of aroma quality in black tea and process selection in processing practice.

Physicochemical Properties of Tannase in Tea Plants (Camellia sinensis) and Its Application on Green Tea Beverages

CHEN Yifan, KAN Xinyi, JIANG Xiaolan, GAO Liping, XIA Tao

Journal of Tea Science. 2023, 43(1): 124-134. doi:10.13305/j.cnki.jts.2023.01.009

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Galloylated catechins have an important impact on the taste of green tea, but excessive accumulation of galloylated catechins in tea plants in summer and autumn will reduce the sensory quality. A native Camellia sinensis tannase (CsTA) discovered in the previous study has the function of hydrolyzing galloylated catechins. But its physicochemical properties and whether it can play a role in the processing of green tea beverages are not clear. In this article, the CsTA was further studied on the basis of previous experimental results. The results show that the optimal temperature of the enzyme was 45 ℃, the thermal stability range was below 60 ℃, the optimal reaction pH was 7.0. Mg²⁺ had a significant activation effect on CsTA. Cu²⁺ could completely inactivate CsTA activity. Mn²⁺, Zn²⁺, Al³⁺, Fe³⁺, Fe²⁺ and Li⁺ had a certain inhibitory effect, and CsTA had a good storage stability after freeze-drying. After applying CsTA to green tea infusion, it was found that the best degradation effect of ester catechins was obtained when the added amount was 11 μg, the ratio of material to liquid was 1∶100, the reaction time was 20 min, and the temperature was 35 ℃. This study would provide a theoretical reference for using CsTA to reduce the bitterness and astringency and improve the quality of green tea processing in the future.

Research and Experiment on Profiling Method of Tea Picker Based on Fusion of 2D-LiDAR and Attitude and Heading Reference System

WU Min, HUAN Xiaolong, CHEN Jianneng, DONG Chunwang, SHAO Bokai, BIAN Xianbing, FAN Guoshuai

Journal of Tea Science. 2023, 43(1): 135-145. doi:10.13305/j.cnki.jts.2023.01.008

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In order to promote the mechanized harvesting of bulk tea and improve the harvesting efficiency and quality of fresh leaves of bulk tea, a fusion 2D-LiDAR and Attitude and heading reference system（AHRS）was proposed in view of the fact that the sensing sensor of the current profiling tea picker is easily affected by contact force, natural light or the gap between the leaves of the tea canopy. Based on the estimation method of profiling distance of cutting knife of tea picker, an accuracy verification test bench and an automatic profiling tea picker were designed and developed, indoor and field experiments were carried out respectively. The tea picker used 2D-LiDAR to measure the profiling distance at first. In order to improve the ranging accuracy and real-time performance, combined with the acceleration sensed by AHRS, a fusion of 2D-LiDAR ranging and acceleration (FLRA) was proposed. The algorithm accuracy verification platform and method were developed to verify the effectiveness of the algorithm. The indoor test results show that the mean value of the ranging error of the profiling distance before the algorithm processing was 36.53 mm, and the standard deviation was 23.21 mm. After the algorithm processing, the mean value of the profiling distance estimation error was 8.56 mm, and the standard deviation was 6.31 mm, which improved the accuracy and real-time performance of profiling distance ranging. Field tests show that the harvesting efficiency reached 180-210 kg·h^-1. The average picking rate of young shoots on the canopy covered by cutter was 92.38%. The integrity rate of bud and leaf was 85.34% and the impurity rate was 4.93%. The young shoots better than one bud and three leaves accounted for 90.72%, which meets the technical standards of bulk tea machine picking and the requirements of subsequent processing technology. Compared with the traditional ultrasonic sensing automatic profiling tea picker, the harvesting effect of bulk tea fresh leaves was improved.

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