Journal of Tea Science

Research Progress on the Volatile Compounds of Premium Roasted Green Tea

SHI Yali, ZHU Yin, MA Wanjun, YANG Gaozhong, WANG Mengqi, SHI Jiang, PENG Qunhua, LIN Zhi, LYU Haipeng

Journal of Tea Science. 2021, 41(3): 285-301. doi:10.13305/j.cnki.jts.2021.03.001

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Aroma is one of the key indicators to evaluate tea quality, and aroma quality is formed by the complex interactions between different volatile compounds. Premium roasted green teas generally have characteristics of excellent flavor quality, and are the most typical and representative Chinese green tea. In recent years, studies on their volatile compounds had increased gradually and made good progress. However, there were very few systematic explanations on the composition characteristics in aroma compounds of diverse high-quality roasted green teas. Therefore, the present study summarized the research progression in volatile compounds of premium roasted green teas in recent twenty years, enumerated the aroma compounds, illuminated the common compounds, and further discussed the key aroma compounds. These results will provide scientific evidence for the flavor evaluation and aroma quality control for the premium roasted green tea.

Identification of Alcohol Dehydrogenase Gene Family and Their Expression Analysis in the Withering Process of White Tea

GU Mengya, WANG Pengjie, CHEN Xuejin, ZHENG Yucheng, GUO Yongchun, LIN Xinying, GAO Ting, HOU Binghao, YE Naixing

Journal of Tea Science. 2021, 41(3): 302-314. doi:10.13305/j.cnki.jts.2021.03.002

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Alcohol dehydrogenase (ADH) plays an important role in the formation of tea aroma as one of the key enzymes in the synthesis of fatty acid metabolism pathway. In this study, 19 CsADH gene family members were identified from the chromosome level genome database of tea plants for the first time. Bioinformatics analysis shows that the members of ADH gene family were divided into six subfamilies. Collinearity analysis shows that there were 2, 4 and 12 pairs of collinearity between ADH gene family of Camellia sinensis and Arabidopsis thaliana, Vitis vinifera and Actinidia chinensis, respectively. The tea ADH gene family contains 1-13 exons, which encode 236-669 amino acids with molecular weight of 26.15-73.83 kDa. It is mainly located in cytoplasm and chloroplast, and only CsADH1is located in nucleus. In addition, a large number of cis-acting elements closely related to light responsive, plant growth, stress and phytohormone responsive were found in the upstream promoter region. Fluorescence quantitative detection shows that the expression of CsFDH2 was the highest at 4 h of withering. The expressions of CsADH4 and CsADH10 were the highest at 32 h of withering, which were 4.11 and 3.54 times that of the control respectively. The expression of CsADH3 reached the peak at 48 h of withering, which was slightly higher than that at 32 h of withering. The expression of CsADH-like1 reached the highest value at 40 h of withering. The highest expression of CsADH-like3 was at 24 h of withering. This study provided a reference for exploring the molecular mechanism of alcohol dehydrogenase genes acting on the formation of aliphatic aromatic substances in the withering process of white tea.

Cloning and Expression Analysis of CsCML16 in Tea Plants (Camellia sinensis) under Low Temperature Stress

CHEN Siwen, KANG Rui, GUO Zhiyuan, ZHOU Qiongqiong, FENG Jiancan

Journal of Tea Science. 2021, 41(3): 315-326. doi:10.13305/j.cnki.jts.20210514.001

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Calmodulin-like proteins (CMLs) are important calcium signaling proteins in plants, which play a pivotal role in abiotic stress. In this study, one-year-old tea cutting seedlings of ‘Longjing43’, ‘Fuding Dabai’ and ‘Huangjinya’ were used as research materials. The physiological changes of the three tea cultivars were explored to preliminarily screen the cold-resistance tea cultivar. The CsCML16 gene was cloned to analyze its expression patterns in different cold-tolerance tea cultivars under low temperature stress. The results show that ‘Longjing43’ had the highest cold tolerance under low temperature stress, followed by ‘Fuding Dabai’ and ‘Huangjinya’. CsCML16 gene was cloned from ‘Longjing43’. Sequence analysis shows that the CDS length of CsCML16 is 480 bp, encodes 160 amino acids, contains EF-hand conserved domains with molecular weight of 17.58 kDa. Subcellular localization assay indicates that CsCML16 localized in the nucleus and plasma membrane. Quantitative real-time PCR analysis reveals that CsCML16 gene was involved in the regulation of tea plants in response to low temperature stress, and its expression levels varied with tea cultivars with different cold tolerance. This study provided a basis for further study on the biological function of CsCML16 gene.

Cloning of CsCHLI Gene and Its Expression Analysis in Different Albino Tea Cultivars (Camellia sinensis)

ZHAO Yiqing, LIU Zhengjun, ZHANG Tianxin, ZHAO Yanting, XIAO Bin, GAO Yuefang

Journal of Tea Science. 2021, 41(3): 327-336. doi:10.13305/j.cnki.jts.20210224.001

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Magnesium chelatase is one of the key enzymes in the process of chlorophyll synthesis, which is closely related to the albino phenomenon of leaves. In this study, the leaves of tea cultivars Shaancha 1, Baiye 1, Jibai 1, Huangjinya and Haungjinye were used as materials to clone the full-length CDS sequences of CsCHLI (Mg-chelatase I subunit). Multi-sequence alignment shows that the two base differences (G502C, C1169T) were found in Baiye 1, which lead to the change of two amino acid residues (G168R, A390V) in the AAA⁺ and AAA lid domain. Meanwhile, there was an amino acid residue changed (R401H) in the AAA lid domain of Huangjinye, due to the difference of G1202A. Subcellular localization analyses illustrates that CsCHLI is localized in chloroplast and the differences of the bases or amino acid residues did not affect its subcellular localization. The RNA secondary structure analysis shows that base site mutations of CsCHLI would affect its stem-loop structure and the stability. Moreover, the chlorophyll contents in albino tea plants were 25%-77% of that in Shaancha 1, and the expressions of CsCHLI in albino tea plants were 24%-46% of that in Shaancha 1. The results show that the CsCHLI expression was positively correlated with chlorophyll content in tea plants. Furthermore, these results provided experimental evidences for the in-depth study of the chlorophyll metabolism in albino tea plants.

Detection of Bitterness-related Substances in Youxi Bitter Tea and Correlation Analysis with Bitterness

WEI Shasha, PENG Jing, CHEN Zhidan, SUN Weijiang, LIN Lin

Journal of Tea Science. 2021, 41(3): 337-349. doi:10.13305/j.cnki.jts.2021.03.003

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The main taste substances of 37 individuals from four regions of natural distribution of Youxi bitter tea were detected and their bitterness were also evaluated. The main evaluation group members were evaluated and screened according to the ranking method test and quantitative description ability test in food sensory analysis, and 7 panelists with high accuracy and good repeatability were obtained finally. The results of taste substances detection show that the biochemical components and bitter taste of Youxi bitter tea were diverse. The individuals of Chimu village were more bitter than the other three regions, and the contents of gallic acid, EGCG, ECG and theobromine were higher. The bitterness intensity of individuals in Guangming Village was the lowest with high content of non-gallated catechins such as EGC and EC and caffeine. The contents of lysine, cysteine and total amino acids of individuals in Qiushan village were higher. The contents of umami amino acids (aspartic acid and serine) and bitter amino acids (histidine and methionine) in non-protected areas of Chimu village were higher. The correlation analysis between bitterness intensity and the contents of taste substances shows that the contents of theobromine and valine were positively correlated with bitterness intensity, and the content of aspartic acid with sweet taste was significantly and negatively correlated with bitterness intensity.

Analysis of Characteristics of Lipid Metabolism of Different Germplasm Tea Seeds

CHEN Mingjie, DU Zhenghua, QIN Jianheng, LI Ruoyu, YU Zhaoxi, GUO Li

Journal of Tea Science. 2021, 41(3): 350-360. doi:10.13305/j.cnki.jts.2021.03.004

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The development of dual-purpose tea resource is especially important for the structural adjustment and efficiency improvement of tea industry. Thus, it is essential to comprehensively characterize the seed-related traits from current available tea germplasms, which can be used to guide dual-purpose tea genetic improvement. In this study, tea seeds of the same year were collected from 31 germplasms grown in Fujian, Yunnan, and Hunan, seed oil contents and compositions were analyzed. We found that there were more than two-fold variations in seed oil content. Ten different fatty acids were detected from tea seed oil, including palmitic acid, palmitoleic acid, 11(Z)-hexadecenoic acid, stearic acid, oleic acid, 11(Z)-octadecenoic acid, linoleic acid, linolenic acid, arachidic acid, and eicosanoid acid. Oleic acid was the dominant component of tea seed oil, which accounted for 42.1%-59.2% of the total fatty acids, followed by linoleic acid (18.9%-32.8%). Saturated fatty acid accounted for 15.9%-20.8% of the total fatty acids, with palmitic acid as the dominant component. Feature analysis of fatty acid composition indicates that there were large variations of the FAD2 and FAD3 activities among these germplasms. Based on these findings, the methods to select parent lines for dual-purpose tea breeding were discussed.

Study on the Safe Pesticides and Efficient Application Method Against Tea Lace Bug (Stephanitis chinensis Drake)

LUO Hong, CUI Qingmei, CAI Xiaoming, LUO Fengjian, ZHANG Qiang, CHEN Zongmao

Journal of Tea Science. 2021, 41(3): 361-370. doi:10.13305/j.cnki.jts.20210407.001

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In recent years, the tea lace bugs have broken out in some tea areas of China, and there is an urgent need for an efficient and safe control technology. In this paper, the safe and efficient control technology against tea lace bug was studied from aspects of application methods, types of pesticides, applied dosage and pesticide residues. The control efficiency of knapsack mist sprayer was significantly higher than that of knapsack electric sprayer, and the control efficiency was significantly increased with the increase of water consumption. Among the 8 single-dose chemical pesticides, bifenthrin, beta-cypermethrin and fenpropathrin showed good control effects on tea lace bugs with the control effects higher than 90% 7 d after application. Their dosages of active ingredients were 1.31 g·hm^-2, 22.50 g·hm^-2 and 11.25 g·hm^-2, respectively. Moreover, the pesticide residues in tea were all lower than the maximum residue limit standards from China and the European Union. The control effect of tolfenpyrad could be up to 70% 7 d after application. But the control effects of chlorfenapyr, spinetoram, indoxacarb, and buprofezin were not satisfactory. The control effect of beta-cypermethrin·pyriproxyfen was the best among the 3 compound chemical pesticides, and could reach to 89% 7 d after application. Among the 3 group botanical pesticides, the control effect of pyrethrum was the best, which could be up to 90% 7 d after application when the active ingredient was 45.00 g·hm^-2. The mixture of azadirachtin and veratrine and the mixture of azadirachtin and matrine did not show good control effects. These results indicate that the application of pyrethroids and pyrethrum through knapsack mist sprayer was an effective and safe control technology against the tea lace bugs.

Volatile Organic Compounds from Fresh Tea Leaves and Their Fumigation Antifungal Activities on Fungal Pathogens of Tea Plants

ZHI Yanan, XU Yunfei, ZHU Mingxing, WANG Chunsheng, JIN Yinli, CHEN Lijun

Journal of Tea Science. 2021, 41(3): 371-378. doi:10.13305/j.cnki.jts.2021.03.005

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In order to determine the relationship between volatile organic compounds (VOCs) from fresh tea leaves and the main fungal pathogens of tea plants, the VOCs from fresh tea leaves were extracted and analyzed by HS-SPME-GC-MS. The fumigation antifungal activities of volatile monomers from fresh tea leaves against four fungal pathogens including Botryosphaeria dothidea, Colletotrichum camelliae, Colletotrichum gloeosporioides, Pestalotiopsis theae were also studied. The results show that 28 chemical compounds were found from VOCs of fresh tea leaves, and 19 of them were characterized, accounting for 94.405% of the total VOCs. The main chemical compounds were hexanoic acid, 3-hexenyl ester, (Z)-hexanoic acid-3-hexenyl ester (18.395%), leaf acetate (16.935%), ocimene (12.615%), and cis-3-hexenyl butyrate (11.210%). Cis-3-hexenyl butyrate exhibited strong fumigation antifungal effect on the four tested fungal pathogens, and the EC₅₀ were lower than 61.29 μL·L^-1. In conclusion, cis-3-hexenyl butyrate can be used as a potential fumigant control of tea diseases.

Analysis of Metabolite Changes in the Natural Withering Process of Fu′an White Tea Based on Non-targeted Metabolomics Approach

YUE Wenjie, JIN Xinyi, CHEN Mingjie, YE Naixing, GUO Li, ZHAO Feng

Journal of Tea Science. 2021, 41(3): 379-392. doi:10.13305/j.cnki.jts.20210304.001

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In this study, Camellia sinensis cv Fu'an Dabai was used as materials to make white tea following the standard indoor natural withering procedure. Samples were collected every 3 h, and non-targeted metabolomics was used to analyze tea metabolite changes. Principal component analysis (PCA) shows that metabolite contents in fresh leaves showed regular dynamic changes during the process of indoor natural withering of white tea. Totally 109 metabolites with significant difference were identified and showed 5 major patterns. These patterns could be divided into four stages: 24 h before withering, 24-48 h during withering, 48-57 h during withering and after 57 h. According to their structure, these metabolites can be classified into 4 types. The 8 monomer catechins (Catechins) showed a downward trend during the withering process. The contents of 18 proanthocyanidins (PAs) and 5 Theasinensins (TSs) showed different trends. The galloyl containing PAs and TSs showed an upward trend, while non- galloyl containing PAs and TSs showed an opposite trend. For glycoside derivatives, 6 kaempferol glycosides, 4 Quercetin (quercetin) glycoside and 1 apigenin glycoside showed an upward trend. Their contents increased significantly after 48 h withering. In the process of withering, 5 of the 12 phenolic acids showed an upward trend. While the rest 7 showed a downward trend. All of them reached their peaks or bottom at 57-60 h. In addition, 22 different metabolites including alkaloids, amino acids, peptides, coumarins, sugars, etc. were also identified. Caffeine showed an upward trend. Their contents reached the peaks at 60 h. Theobromine decreased significantly in the mid-withering period, and slightly recovered in the latter period. The contents of 2 theanine isomer and 4 coumarins rose to the peak at 12 h. After that, there was an overall downward trend during the withering process. These data offered important insights for understanding the biosynthesis and regulation mechanism of white tea during indoor natural withering process.

The Effect of Red Light Withering on the Volatile Components of Tea Leaves and the Quality of Black Tea Product

LIN Jiazheng, TU Zheng, CHEN Lin, YE Yang, LIU Fei, WANG Yuwan, YANG Yunfei, WU Xun, LYU Haowei

Journal of Tea Science. 2021, 41(3): 393-405. doi:10.13305/j.cnki.jts.2021.03.006

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Red light withering contributes to the formation of tea aroma. However, the effect of different red light quality on the volatile components of withered tea and the quality of the black tea product after processing remains to be studied. In this study, headspace solid phase micro extraction-gas chromatography-mass spectrometry was used to detect and analyze the volatile components of withered leaves under different light treatments such as dark, red light (630 nm, 1 000 lx, 3 000 lx), natural light (260-325 lx), and the dynamic changes of the volatile components of withered leaves and red light withered differential volatile substances under different light treatments were studied. The results show that a total of 130 volatile components were detected in withered leaves at different time periods, including 26 alcohols, 33 esters, 29 hydrocarbons, 12 aldehydes, 13 ketones, and 17 others. Comparing different light withering methods, it was found that the total content of volatile components in the red light 3 000 lx group pre-mid withering period (The first 8 h) were significantly higher than that in other groups. With the increase of red light intensity, the total content of esters increased significantly (P<0.05), while the total content of ketones decreased significantly (P<0.05). Through orthogonal partial least squares discriminant analysis, the variable projection importance factor was greater than 1 and the coefficient of variation was greater than 50%, 5 volatile components were screened out with the greater response to red light, including 1,2-dimethylpropyl-2-methyl-butanoic acid ester, 1-isocyano-3-methyl-benzene, decanal, 2-methyl-2-decanol, linoleic acid ethyl ester. Among them, the coefficient of variation of decanal was as high as 133.34% under red light 1 000 lx. The results of this study could provide a scientific basis for the improvement of black tea aroma quality and targeted regulation.

The Effect of Initial Microwave Drying on Black Tea Quality

CUI Lidan, ZHANG Xianglin, XIANG Xi, LI Lanlan, QU Qingyun, XU Yangyang, WANG Jiguo, LIU Feng, GONG Zhihua, XIAO Wenjun

Journal of Tea Science. 2021, 41(3): 406-418. doi:10.13305/j.cnki.jts.2021.03.007

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Flushes of two leaves and a bud of tea cultivar ‘Bixiangzao’ were picked during late summer and early autumn as raw material. During the black tea processing, initial microwave drying was adopted instead of conventional initial air drying. Seventeen processing groups were set up with independent variables of microwave density, time duration and piled leaf depth. Sensory quality, taste compounds and aroma compounds of the black tea were investigated and considered as quality criteria. The results show that compared with conventional initial air drying, the black tea processed with microwave power density of 600 W, 3 min, and piled leaf depth of 2 cm had the best sensory quality. Meanwhile, it showed a significant increase in the contents of theaflavins, thearubigins, catechins, ester catechins, EGCG, amino acids, caffeine and soluble sugar (P<0.05), while presented a significant decrease in the contents of tea polyphenols and theabrowmines (P<0.05). The number of aroma compounds increased from 43 to 50. The relative contents of floral and fruit scent compounds such as linalool and phenylethanol increased significantly (P<0.05). Furthermore, several novel sweet and flower scent compounds including (Z)-3,7-dimethyl-2,6-octadien-1-ol, 2,6,6-trimethyl-1,3-cyclohexadiene-1-formaldehyde, 2,6,6-trimethyl-1-cyclohexene-1-formaldehyde, and eugenol were identified. In conclusion, the initial microwave drying benefits the quality of black tea.

Effects of Biochar Application on Soil Properties and Fungi Community Structure in Acidified Tea Gardens

WANG Yixiang, HUANG Jiaqing, YE Jing, LI Yanchun, LIN Yi, LIU Cenwei

Journal of Tea Science. 2021, 41(3): 419-429. doi:10.13305/j.cnki.jts.2021.03.008

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The impact of long-term biochar application on soil improvement and fungal community structure in acidified tea gardens is still unclear. Five years after biochar application, the changes of soil properties and fungi community structure in tea gardens with different biochar applications (0, 2.5, 5, 10, 20 and 40 t·hm^-2) were studied. The results show that after applying biochar for 5 years, the pH value of soil increased by 0.16 to 1.11 units, the soluble organic carbon content increased by 52.6% to 92.3%, and the contents of ammonium nitrogen and nitrate nitrogen in soils with 10 t·hm^-2 biochar application were the highest. The changes of soil properties further affected the fungi community structure. The Chao index, ACE index and Shannon index of the fungi community firstly increased and then decreased with the increase of biochar amount. The effect of biochar application on the secondary fungi (LDA value<3.50) was higher than that on dominant fungi (LDA value>3.50). In addition, the relative abundance of Mortierella, Trichoderma and Chaetomium increased after the application of biochar, but the relative abundance of Melanconiella decreased.

The Influencing Factors and Trade Efficiency of China Tea Export: Based on Stochastic Frontier Gravity Model

ZHANG Fei, GUAN Xi, ZHU Rongjun

Journal of Tea Science. 2021, 41(3): 430-438. doi:10.13305/j.cnki.jts.2021.03.009

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Based on the stochastic frontier gravity model and trade non-efficiency model, using panel data of 37 representative countries (regions) from 2001 to 2017, influencing factors and trade efficiency of China tea export were analyzed. The results show that China tea export efficiency had a rising tendency, but the overall export efficiency was at a low level and presented regional imbalance. The China tea export efficiency with the developed economies was relatively high, but the tea trade efficiency with countries along "the Belt and Road" was at a very low level. The failure to realize the full potential of China tea export efficiency mainly came from the loss of technical efficiency. The increase of domestic supply, the expansion of importing market capacity and the reduction of trade cost were all conducive to improve China tea export efficiency. To some extent, the business environment improvement of importing markets could offset the impact of trade inefficiency. Free trade agreement had not yet played a positive role in China tea export.

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