Variations in flavour precursor compounds of tea leaves (Camellia sinensis), planted in Northern Vietnam by cultivars and plucking time

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1 Academia Journal of Agricultural Research 6(6): , June 2018 DOI: /ajar ISSN: Academia Publishing Research Paper Variations in flavour precursor compounds of tea leaves (Camellia sinensis), planted in Northern Vietnam by cultivars and plucking time Accepted 15 th June, 2018 ABSTRACT Hoang Quoc Tuan* and Nguyen Thi Minh Tu Hanoi University of Science and Technology, School of Biotechnology and Food Technology, Department of Quality Management, No 1 Dai Co Viet Street, Hai Ba Trung Dist, Hanoi 10000, Vietnam. *Corresponding author. tuanhqibft@gmail.com, tuan.hoangquoc@hust.edu.vn. Amino acids (a.a), carotenoids and fatty acids in tea leaves are important flavour precursors which play important role on aroma quality of final teas products. In this study, 16 amino acids, 16 fatty acids, -carotene, and zeaxanthin contents in fresh green tea leaves of three cultivars (Shan Chat Tien, Trung Du and Phu Ho 11) plucked in June, September 2014 and March 2015 which coresponding to Summer, Autumn and Spring season of harvest were analyzed by HPLC and GC/MS. The results showed that the profiles of amino acids, fatty acids, zeaxanthin and - carotene were different among cultivars and plucking time. Amino acid content of sample plucked in March was highest for Trung Du and Phu Ho 11, while for Shan Chat Tien amino acid was found highest when collected in September. Fatty acids profile showed that C16:0, C18:2, C18:1, C18:0 and C18:3 were the most abundantly. In particular, total saturated fatty acid in the tea leaves plucked in June and September was higher than total unsaturated fatty acid and vice versa for sample plucked in March. Total carotenoid in all 3 samples was observed highest in June. Moreover, -carotene and zeaxanthin were found highest for Trung Du sample at 31.6 and 34.4 mg/100 g dry basic in June and March, respectively. These data demonstrated tht cultivars and plucking time significantly influenced qualitatively and quantitatively the flavour precursors in tea leaves. Key words: Tea flavour, precursors, amino acids, carotenoids, fatty acids. INTRODUCTION Statistically tea leaves (Camellia sinensis) contain % caffeine, % theaflavins, 1-3% a.a, 2-4% sugars, less than 1% carotenoids and about 5% minerals (Dalluge and Nelson, 2000; Lin et al., 1996; Collier and Mallows, 1971; Burghahen, 2004). Tea processing, depending on the type of tea products, that is, white tea, black tea or green tea, involves different degree of oxidation of the leaves: stopping the oxidation and forming the flavour (Ravichandran, 2002; Senthil et al., 2013). In the case of clonal black tea reported by Owuor in 2008, its aroma composed of volatile flavour compounds (VFC) generated during tea processing, such as aldehyde, alcohol, terpend etc.. These VFC can be divided into two groups. The Group I compounds are mainly the products of lipid breakdown, which develop an undesirable grassy odour. However, the Group II compounds, which impart a sweet flavour aroma to black tea, are mainly derived from carotenoids and amino acids. Moreover, the flavour of made tea depends on the ratio of Group II to Group I, which is expressed as flavour index or VFC index (Owuor et al., 2008). Senthil et al. (2013) reported that amino acids, fatty acids and carotenoids constituents of tea leaves are affected by several factors, such as geological location, fertilizers use, irrigation water, climatic conditions and more importantly by processing and packaging of tea leaves. Related to a.a, Maillard reaction products are found in green tea, as well as in black tea but only in a small amount. Pyrrole derivatives, one of Maillard reaction products, are primarily responsible for the roasted, nutty,

2 Academia Journal of Agricultural Research; Tuan and Tu. 182 and popcorn-like flavours in tea infusion. Pyrazines have been found to be important constituents in black tea and oolong tea (Ho et al., 2015). On other hand, carotenoid in enzymatic oxidative degradation is catalyzed by dioxygenases and often happens during fermentation. During processing, at first, carotenoids are cleaved by dioxygenases, forming primary oxidation products, then the enzymatic transformation of oxidation products produces aroma precursors, followed by acid hydrolysis to liberate volatile compounds which mainly are -ionone, - damascenone and theaspirone (Ho et al., 2015). In case of fatty acid, poly-unsaturated fatty acids such as -linolenic acid, linoleic acid, oleic acid, and palmitoleic acid, are precursors for 6 to 10 carbon volatile aroma compounds, such as (E)-2-hexanal, (E)-2-hexanol, and (Z)-3-hexanol, which contribute fresh and greenish odours in tea infusion (Ho et al., 2015; Takeo and Tsushida, 1980). Thus, a.a, fatty acids and carotenoids emerge as an important area for research and quality control of tea. The precursors both of positive and negative flavours in tea are a subject of great interest to the tea industry. In Vietnam, up to date, there are no any data published related to tea flavour precursors. Therefore, the aims of this study are to determine the distribution of those precursors in the tea leaves at different plucking times collected from 3 major tea cultivars of Northern Vietnam: Shan chat tien, Trung du and Phu Ho 11. EXPERIMENTAL Samples Tea leaves of cultivars Trung Du (TD), Shan Chat Tien (SH) and Phu Ho 11 (PH11), representing the genetically diverse Northern Vietnam cultivars, were harvested from the Phu Tho, Vietnam, in June and September 2014, and March in the next year. Amino acid analysis Preparation of tea infusion: Following the nethod of Wang et al. (2010), 0.5 g of tea powder was diluted with 30 ml of distilled water, then ultrasound-assisted extraction for 30 min. After cooling to room temperature, it was made up to 50 ml with distilled water and filtered through a 0.45 µm filter membrane (Wang et al., 2010). Precolumn derivatisation with OPA: The derivatisation with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) reagent was carried out according to the method reported with some modifications (Bosch et al., 2006). Briefly, a 10 μl aliquot of tea infusion or standard amino acid solution was mixed with 70 μl of AccQ.FluorBorate buffer and vortexed for 10 s. Then, 20 μl of AQC solution was added and vortexed for 10 s, and incubated at 55 C for exactly 10 min. Thereafter, the reaction mixture was immediately used for HPLC analysis. HPLC- fluorescence analysis: The determination of amino acids was performed using an HPLC system of Waters, U.S.A. The separation was completed on a Phenomenex Phenyl-Hexyl, U.S.A-C18 column (250 mm 4.6 mm 5 μm). The temperature of column oven was set at 37 C. The mobile phase consisted of acetonitrile/water (60/40, B) and buffer Waters AccQ.Tag (A). Elution was performed with linear gradient. The flow rate was 1.0 ml m -1. The derivatives were detected by programmable fluorometer with excitation ( ex) and emission ( em) wavelengths at 250 and 395 nm, respectively. Carotenoid analysis Carotenoid extraction: This was carried out as described by Rodriguez-Amaya et al. (2001): About 0.50 g of tea leaves was extracted with 20 ml ethanol: petroleum ether (4:3 v/v) and 0.05 gram MgCO 3. The mixed sample was ultrasounded at low temperature for 10 min and then centrifuged at 5000 rpm for 10 min. The upper layer was pooled. The extraction step was repeated at least three times until the residue was colourless. Added were 10 ml ethanol, 20 ml saturated sodium chloride solution and 50 ml H 2O to the ethanol: petroleum ether extracts and mixed carefully. The ethanol aqueous phase was decanted and the upper petroleum ether phase was transferred through anhydrous sodium sulphate and then concentrated to dryness under vacuum. The residue was transferred to a brown glass vial using portions of 1 ml of mobile phase (acetonitrile: methanol: dichloromethane 75:20:5) for further analysis (Rodriguez-Amaya, 2001; Hart and Scott, 1995). High performance liquid chromatography (HPLC): HPLC Agilent 1200 equipment with an ultraviolet and visible light variable wavelength detector was used for analysis. Solvents were HPLC grade. The mobile phase was a ternary mixture of acetonitrile: methanol: dichloromethane (75:20:5 v/v/v) to which 0.1% BHT was added. The column was a Waters Sunfire C18 column, 3.5 m, mm. The column was kept at room temperature and the follow rate was 1 ml min -1. The wavelength was adjusted to 450 nm (Hart and Scott, 1995). Fatty acid analysis Lipids were extracted from green tea leaves using chloroform-methanol 2: 1 (v/v) and centrifuged at 3000 rpm for 10 min. Fatty acids were converted to fatty acid

3 Academia Journal of Agricultural Research; Tuan and Tu. 183 Table 1: Amino acids content in tea leaves of different cultivars and at different plucking times. June September March Amino acids TD SH PH11 TD SH PH11 TD SH PH11 mg/100 g dry basis Aspartic acid , Serine Glutamic acid Glycine Histidine Arginine Threonine Alanine Tyrosine Valine Methionine Lysine Isoleucine Leucine Phenylalnine Theanine Total amino acid MAT 0 C THS, h MAP, mm MAT: Monthly Average Temperatures; THS: Total number of hours of sunshine; MAP:Monthly Average Precipitation. methyl ester (FAME) by dissolving in hexane and 0.5N methanolic NaOH. The fatty acid composition was identified in triplicate by separating the FAME on a GC- MS/MS (model GC 7890A/GCMS 7000 triple quad-agilent, USA) equipment with DB1 column (30 m 0.25 mm 0.25 µm). The temperature program was 0.5 min at 50 C and then it was increased to 200 C with 15 C/min and thereafter, increased to 250 C with 3 C/min, held for 5 min. The injection temperature was 250 C, interface temperature was 280 C, and split flow (ml/m) was 1 and the split ration was 10:1 (Ravichandran and Parthiban, 2000). Statistical analysis Statistical comparisons of the mean values for each experiment were performed by one-way analysis of variance (ANOVA) using SPSS 11.5 for Windows software. Significance was declared at P Principal component analysis (PCA) was performed by SPAD 5.5 software. RESULTS AND DISCUSSION Profile of amino acid (a.a) of various cultivars at different plucking times Amino acid contents in fresh tea leaves of different cultivars plucked at different times is presented in Table 1. It shows that the total a.a content was lowest in June and it was increasing in the next season with increase in temperature. Thus, it is clear that climatic factors have an impact on amino acid synthesis. In the samples of June, the highest a.a contents were obtained in Shan Chat Tien cultivar, that is, mg/100g d.b, whereas the PH11 cultivar gave the lowest content ( mg/100g d.b) of amino acid. In samples of September, the a.a contents in tea leaves were at peak in Shan Chat Tien and Trung Du cultivars, that is, and mg/100 g g.b, respectively, while the amino acid content of PH11 cultivar showed the lowest content in this plucking time, that is, mg/100g d.b. For samples plucked in March, the highest amount of a.a contents was obtained in Trung Du cultivar ( mg/100g d.b), followed by PH11 cultivar ( mg/100g d.b), and Shan Chat Tien cultivar as lowest. In general, the present study showed that the amino acids content of tea leaves increased as environmental temperature decreases. The results obtained in the present study are similar to some previous studies. Previous studies (Wang et al., 2010; Bosch et al., 2006) showed that the α-a.a in tea leaves material will undergo Strecker degradation to form corresponding aldehydes in the presence of oxidizing tea flavanols (Ho et al., 2015; Sanderson and Grahamm, 1973). In principle, all free amino acids should have their corresponding Strecker aldehydes. However, only amino acids, such as glycine, alanine, valine, leucine, phenylalanine, isoleucine and

4 Academia Journal of Agricultural Research; Tuan and Tu. 184 Figure 1: Score plot between the first 2 PCs. Thu13: Samples plucked on September; Xuan14: Samples plucked on March; Ha13: Samples plucked on June. methionine, have their Strecker aldehydes, and their corresponding Strecker aldehydes are formaldehyde, acetaldehyde, isobutyraldehyde, isovaleraldehyde, phenylalacetaldehyde, 2-methylbutanal and methional, respectively. One reason is that non-volatile products are generated instead of volatile aldehydes. The other possibility is that some Strecker aldehydes are so unstable that they readily decompose into other volatiles by cyclization, coupling, or dehydration (Ho et al., 2015; Sanderson and Grahamm, 1973). In this study, for all cultivars and plucking time, alanine was the most abundant free-form amino acids among the detected precursor of Strecker aldehydes, followed by phenylalnine, valine, isoleucine and leucine, while methionine showed the lowest content. The content of seven precursor of Strecker aldehydes was highest in samples plucked in September, followed by June s samples and, the content was lowest in March. This can partially explained why high levels free amino acids are essential for taste quality of green tea and aroma quality of black tea (Senthil et al., 2013; Nair, 2010). Those data also explored by PCA and the score and variables obtained were plotted in Figures 1 and 2. Profile of carotenoids of various cultivars at different plucking times Carotenoids included β-carotene and zeaxanthin which accounted for approximately 85% of the total carotenoid content in leaves and they have been identified as precursors for many green and black tea flavours, and play key roles in deciding the quality of tea (Ho et al., 2015). In this study, -carotene and zeaxanthin contents in tea leaves are different among cultivars and harvested time. In the samples of June, the β-carotene was not significantly different between Trung du and PH11 cultivar (31.6 and 31.0 mg/100g d.b, respectively), while it was lowest in the Shan Chat Tien, that is, 10.2 (mg/100 g d.b). This profile was also similar to the case of zeaxanthin, which was 23.0, 22.2 and 5.1 (mg/100 g d.b) for Trung du, PH11, Shan Chat Tien, respectively. In September, tβ-carotene was observed to decrease as compared with June s sample. The highest amount of each of β-carotene and zeaxanthin was obtained in Trung du cultivar (13.8 and 43.7 mg/100 g d.b, respectively), and the lowest was in PH11cultivar (7.3 and 16.9 mg/100g d.b, respectively). Interestingly, the zeaxanthin content in tea leaves plucked in March was found to be approximately 2-4-fold higher than in tea leaves plucked in June, especially in the case of Shan Chat Tien cultivars. However, the β- carotene content in March s samples was determined to be nearly 2-fold lower than June samples, except Shan Chat Tien cultivar. Table 2 also shows that the three cultivars studied differed significantly in their carotenoid content, which was higher in tea leaves plucked in June and September, except Shan Chat Tien cultivar. The results here are

5 Academia Journal of Agricultural Research; Tuan and Tu. 185 Figure 2: Variables plot between the first 2 PCs. Table 2: Carotenoid content in tea leaves of different cultivars and plucking time. June September March Compounds TD SH PH11 TD SH PH11 TD SH PH11 mg/100 g dry basis β-carotene zeaxanthin Total carotenoids MAT 0 C, THS, h MAP, mm consistent with some previous studies reported on the influence of temperature and light intensity to the concentration of amino acids and carotenoids of tea leaves. When environmental temperature is below 20 C, the development of chloroplast from etioplast and the accumulation of chlorophylls a and b including biosynthesis process of carotenoid are blocked, but protein biosynthesis prevails, therefore tea leaves have high concentration of amino acids. However, this phenomenon disappears when the temperature is above 20 C, resulting in sharp decrease in amino acids level and increase in total carotenoid content (Wang et al., 2013; Du et al., 2008). After identification and qualification of amino acid and two carotenoid compounds in tea leaves, the data matrix of relative contents was preprocessed through generalized log transformation and pareto scaling. In exploratory data analysis, principal component analysis (PCA) was employed to screen cluster of sampling and amino acid and two carotenoid compounds distribution in three group. The PC1 versus PC2 as plotted in Figure 1 account for 69.17% of data variance and shows a distinct discrimination among the cultivars. From the sample score plot obtained from PCA in Figure 1, nine tea leaves samples from three cultivars and plucking times were clearly classified into three group as samples which were plucked in the same month were close to each others and may be combined as a group, except tea leaves samples plucked in September. This indicates significant differences among the three cultivars plucked at that time. Figure 2 shows the variables plot between the first 2 PCs. More importantly, the results showed that the fatty acids distribution in three groups in this figure is as follows: (a) the tea leaves plucked in March had relatively high content of zeaxanthin, theanine, tyrosine, threonine and lysine; (b) the tea leaves plucked in June had relatively high content of β-carotene; (c) the tea leaves plucked on September had relatively high content of

6 Academia Journal of Agricultural Research; Tuan and Tu. 186 Table 3: Variation in the fatty acid composition (relative content) with plucking time and cultivars. March June September Fatty acids TD SH PH11 TD SH PH11 TD SH PH11 % C8:0 nd nd nd nd C10:0 nd 0.58 nd 0.34 nd C11:0 nd nd nd nd nd 11.9 nd nd 0.38 C12: nd nd C14:1 nd nd nd nd 1.68 nd nd C14: C16:1c nd 1.29 nd C16: C18:2n nd C18:3n nd nd nd nd nd nd C18:1c nd nd C18: C18:1t nd nd nd nd 0.41 nd nd C20:0 nd nd nd nd C22: nd 1.54 nd nd C24:0 nd nd nd nd nd nd nd nd 0.84 Total saturated FA Total unsaturated FA Total lipid* MAT, o C THS, h MAP, mm MAT: Monthly Average Temperatures; THS: Total number of hours of sunshine; MAP:Monthly Average Precipitation; TD: Trung du cultivar; SH: Shan Chat Tien cultivars; PH11; FA: fatty acid.* g/100 g, alanine, leucine. Profile of fatty acids of various cultivars at different plucking times The fatty acid compounds contribute to the flavour of tea leaves and tea products. There have been many efforts to establish genotypical, plucking standard, process variables in lipid and fatty acid composition of plants (Senthil et al., 2013; Ravichandran and Parthiban, 2000; Ravichandran and Parthiban, 1998). Variation in fatty acids could play an important role in the selection of cultivars with improved tea-making potential but not found any data for Vietnamese tea. In this study, five fatty acids found abundantly, including linoleic acid, linolenic acid, palmitic acid, oleic acid and stearic acid, were detected (Table 3), while C8:0 to C12:0 and C20:0 to C24:0 were found low in all samples. Total fatty acid content was highest in March s sample ( g/100 g), followed by September s ( g/100 g), and lowest in June s sample ( ). Variations in proportions of unsaturated and saturated fatty acids due to plucking time and cultivars were observed. In general, a high content of polyunsaturated fatty acid in samples was plucked in March and vice versa for June and September s samples. The high content of polyunsaturated fatty acid is know as the `Pacha Taint problem which causes off- flavour in black tea on storage, and its dominance in south tea industries has been reported to be due to poor lipid metabolism (Senthil et al., 2013). In total, 14 fatty acids were identified in Trung du cultivar in general. For plucking in March, the content of C16:0 was determined as the most abundant fatty acid; its concentration was 22.64%, followed by C18:3 (22.58%), and next were C18:1 and C18:2 (17.07 and 16.42%, respectively). The lowest fatty acid content was identified that are C8:0 (0.29%) and C12:0 (0.38%). In Shan Chat Tien cultivar, a total of 14 fatty acids were determined, C16:0 was also the most abundant (29.8%), followed by C18:1 (23.30%), and in lower concentration were C20:1 (0.52%), C10:0 (0.58%) and C16:1t (0.47%). For Phu Ho 11 cultivar, the order was: C18:2 (39.04%), followed by C18:3, C18:1 and C16:0 (19.22, and 15.03%, respectively). In term of season unsaturated and total fatty acid was decreasing from Spring to Summer then increasing from Summer to Autumn, while for saturated fatty acid the peak amount reached in June s sample, where 9, 5 and 10 fatty acids were identified in Trung du, Shan Chat Tien, Phu Ho 11, respectively. In Trung Du s tea leaves, the C18:0 was determined at the highest content (49.8%), followed by C16:0 (15.3%) and C18:2 (14.37%); in Shan Chat Tien, C16:0 (34.98%), C20:0 (33.08%), C18:0 (23.05%) were the most abundant; and in tea leaves of Phu Ho 11 cultivar the highest content is C18:0 (41.12%), C18:1 (16.47%) and C16:0 (16.39%).

7 Academia Journal of Agricultural Research; Tuan and Tu. 187 Figure 3: Score plot between the first 2 PCs. Figure 4: Variables plot between the first 2 PCs. Twelve fatty acids were identified in Trung du cultivar which was plucked in September. Thus the fatty acids with high content were C18:1c (25.25%), C14:0 (18.42%) and C16:0 (24.3%). While, 13 fatty acids were found in Shan Chat Tien cultivar with the same time plucking; thus C16:0 (25.90%) and C18:1c (21.90%) were the most abundant, followed by C18:2 (10.5%), C14:0 (9.67%) and C18:0 (9.5%). 11 fatty acids was identified in PH11 cultivar; thus C16:0 (32.41%) and C18:1c (29.90%) were the two fatty acid with high content, while C20:0 and C22:0 had very low (0.55 and 0.56%, respectively). In exploratory data analysis, principal component analysis (PCA) was employed to screen cluster of sampling and fatty acid distribution in three group. From the sample score plot obtained from PCA in Figure 3, nine tea leaves samples from three cultivars and plucking times were clearly classified into three group, in that, samples which were plucked in the same month are close to each others and may be combined as a group. Figure 4 shows the variables plot between the first 2 PCs. More importantly,

8 Academia Journal of Agricultural Research; Tuan and Tu. 188 the results showed that the fatty acids distribution in three groups as shown in this figure is as follows: (a) the tea leaves plucked on March, relatively high content of C18:2, C18:1t and C18:3; (b) the tea leaves plucked on June, relatively high content of C20:0, C22:0, C18:0 and C11:0; (c) the tea leaves plucked on September, relatively high content of C18:1c, C16:1c, C8:0 and C10:0. CONCLUSION This study shows that amino acids, carotenoids and fatty acids composition of tea leaves varies depending on the cultivars and plucking times.. The results showed that amino acid content of sample plucked in March had higher than in sample plucked at June and September, except cultivar Shan Chat Tien. In fatty acid profile, the most abundant in all samples were C18:1, C18:2 and C18:3. The lipid content tends to be higher in dry season and decrease in rainy season. While, total carotenoids content in sample plucked in March was lower than in sample plucked in June and September. In particular, zeaxanthin and -carotene were different among cultivars and plucking time. -Carotene content in green tea leaves plucked in June and September was higher than in sample plucked in March and vice versa for zeaxanthine content. Takeo T, Tsushida T (1980). Changes in lipoxygenase activity in relation to lipid degradation in plucked tea shoots. Phytochemistry. 19(12): Wang L et al (2010). Analysis of free amino acids in Chinese teas and flower of tea plant by high performance liquid chromatography combined with solid-phase extraction. Food Chem. 123(4): Bosch L, Alegria A, Farre R (2006). Application of the 6-aminoquinolyl-Nhydroxysccinimidyl carbamate (AQC) reagent to the RP-HPLC determination of amino acids in infant foods. J. Chromatogr. B Analyt. Technol. Biomed. Life Sci. 831(1-2): Rodriguez-Amaya DB (2001). A Guide to Carotenoid Analysis in Foods. Printed in the United States of America. Hart DJ, Scott KJ (1995). Development and evaluation of an HPLC method for the analysis of carotenoids in foods, and the measurement of the carotenoid content of vegetables and fruits commonly consumed in the UK. Food Chem. 54(1): Ravichandran R, Parthiban R (2000). Lipid occurrence, distribution and degradation to flavour volatiles during tea processing. Food Chem. 68(1): Sanderson GW, Grahamm HN (1973). Formation of black tea aroma. J. Agric. Food Chem. 21(4): Nair KPP (2010). 9 - Tea (Camellia sinensis L.), in The Agronomy and Economy of Important Tree Crops of the Developing World, K.P.P. Nair, Editor. Elsevier: London. Pp Wang KR et al (2013). Effect of sunlight shielding on leaf structure and amino acids concentration of light sensitive albino tea plant. African J. Biotechnol. 12(36): Du YY et al (2008). Effect of temperature on accumulation of chlorophylls and leaf ultrastructure of low temperature induced albino tea plant. African J. Biotechnol. 7(12): Ravichandran R, Parthiban R (1998). Occurrence and distribution of lipoxygenase in Camellia sinensis (L) O Kuntze and their changes during CTC black tea manufacture under southern Indian conditions. J. Sci. Food and Agric. 78(1): ACKNOWLEDGMENT The authors would like to thank the Ministry of Education and Training of Vietnam for providing the financial support for project B REFERENCES Dalluge JJ, Nelson BC (2000). Determination of tea catechins. J. Chromatogr. A. 881(1 2): Lin YL, et al (1996). Composition of Polyphenols in Fresh Tea Leaves and Associations of Their Oxygen-Radical-Absorbing Capacity with Antiproliferative Actions in Fibroblast Cells. J. Agric. Food Chem. 44(6): Collier PD, Mallows R (1971). The estimation of flavanols in tea by hare Gas chromatography of their trimethylsilyl derivatives. J. Chromatogr. A. 57: Burghahen M (2004). Coffee Tea and Cococa, in Food Chemistry, H.-D. Belitz, Werner Grosch, and P. Schieberle, Editors Ravichandran R (2002). Carotenoid composition, distribution and degradation to flavour volatiles during black tea manufacture and the effect of carotenoid supplementation on tea quality and aroma. Food Chemistry. 78(1): Senthil KRS et al (2013). Chapter 4 - Black Tea: The Plants, Processing/Manufacturing and Production, in Tea in Health and Disease Prevention. Academic Press. pp Owuor PO et al (2008). Influence of region of production on clonal black tea chemical characteristics. Food Chem. 108(1): Ho CT, Zheng X, Li S (2015). Tea aroma formation. Food Science and Human Wellness. 4(1): Cite this article as: Tuan HQ, Tu NTM (2018). Variations in flavour precursor compounds of tea leaves (Camellia sinensis), planted in Northern Vietnam by cultivars and plucking time. Acad. J. Agric. Res. 6(6): Submit your manuscript at