Grades Of Tea Research Articles

Gas chromatographic Analysis of Organic Acids in Japanese Green Tea Leaves.

Herein, gas chromatography is used to determine and quantify organic acids in Japanese green tea leaves, and the established method is employed to profile the acid components of Matcha, Gyokuro, Sencha green teas, and green tea varieties and thus acquire data needed to ensure the high quality and safety of green tea. The tea leaves were esterified with 10 vol% sulfuric acid in 1-butanol at 100℃ for 2 h. Oxalic acid contents were high in Asatsuyu and Okuyutaka samples and were low in Sofu, increasing in the order of Sencha < Gyokuro < Matcha, while citric acid content increased in the order of Sencha < Matcha < Gyokuro. Moreover, the oxalic acid content of Gyokuro only slightly increased with increasing tea grade. The relative contents of the different fatty acids did not strongly vary between the different green tea varieties. However, the n-3 to n-6 ratio was found to be low in Sofu. The progressing maturity increased the n-3 to n-6 ratio of Yabukita. The n-3 to n-6 ratio was low in high-grade Matcha, Gyokuro, Sencha green teas, and was related to the green tea quality. The developed method was concluded to be suitable for the evaluation of green tea quality.

Detection of bitterness and astringency of green tea with different taste by electronic nose and tongue.

An electronic nose was used to evaluate the bitterness and astringency of green tea, and the possible application of the sensor was assessed for the evaluation of different tasting green tea samples. Three different grades of green tea were measured with the electronic nose and electronic tongue. The sensor array of the E-nose was optimized by correlation analysis. The relationship between the signal of the optimized sensor array and the bitterness and astringency of green tea was developed using multiple linear regression (MLR), partial least squares regression (PLSR), and back propagation neural network (BPNN). BPNN is a multilayer feedforward neural network trained by an error propagation algorithm. The results showed that the BPNN model possessed good ability to predict the bitterness and astringency of green tea, with high correlation coefficients (R = 0.98 for bitterness and R = 0.96 for astringency) and relatively lower root mean square errors (RMSE) (0.25 for bitterness and 0.32 for astringency) for the calibration set. The R value is 0.92 and 0.87, and the RMSE is 0.34 and 0.55, for bitterness and astringency, respectively, of the prediction set. These results indicate that the electronic nose could be used as a feasible and reliable method to evaluate the taste of green tea. These results can provide a theoretical reference for rapid detection of the bitter and astringent taste of green tea using volatile odor information.

EFFECT OF WHITE TEA EXTRACT IN VITRO AGAINST CARIOGENIC AND PERIODONTAL BACTERIA

Objective: This work aimed to evaluate the in vitro antimicrobial properties of white tea maceration extract against pathogenic oral bacteriaStreptococcus mutans (serotype F), Porphyromonas gingivalis (strain ATCC 33277), and Actinobacillus actinomycetemcomitans (phenotype A); theproperties of this product were also tested against non-pathogenic Streptococcus sanguis (ATCC 10556) for comparison.Methods: A maceration extract was made from white tea collected from West Java, and the infusion was prepared at concentrations of 5–80%. Theselected strains of each microbial species were cultured under anaerobic conditions, and equalized standard dilutions of the cultured bacteria wereused for testing. Dilution and diffusion tests were conducted to quantify the antimicrobial properties of white tea extract (WTE) against the bacteria.Results: The dilution test results showed a minimum inhibitory concentration of 40% of WTE against S. mutans, P. gingivalis, andA. actinomycetemcomitans and 80% against S. sanguis. The minimum bactericidal concentration was 80% for all tested bacterial strains.Conclusion: The diffusion test results showed higher inhibition with increasing extract concentration; however, the difference between concentrationsof 40% and 80% was small or negligible, except for A. actinomycetemcomitans. These results imply the clear, acute antimicrobial effect of WTE againstthe tested oral anaerobic pathogens in vitro. Considering that these effects were concentration dependent and that white tea has the highest contentof antimicrobial phenolic compounds among all grades of (green) tea, white tea or WTE may be useful for inhibiting the growth of pathogens involvedin the development of caries and/or periodontal disease.

Non-targeted metabolomics reveals distinct chemical compositions among different grades of Bai Mudan white tea.

So far, the chemical quality of different grades of white tea has largely remained unexplored. The objective of this study was to establish a model for quality evaluation of different grades of Bai Mudan white tea. We applied non-targeted ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry in combination with multivariate analysis and analyzed four different grades of Bai Mudan white tea. We found that the metabolite composition from the super-grade and the first-grade shared higher similarity compared to the second-grade or the third-grade white tea, and the Partial Least Square-Discriminant Analysis model showed high capability to explain the sample variation (R2Y = 0.998, Q2 = 0.95 in negative ionization modes). In total, 93 metabolites were structurally identified, wherein 21 low abundant metabolites showed distinct changes in abundance that were closely correlated with tea grade variation. These findings suggested their potential as markers to discriminate different grades of Bai Mudan white tea.

Effect of altitude, shooting period, and tea grade on the catechins, caffeine, theaflavin, and thearubigin of Turkish black tea

The effect of altitude, shooting period, and tea grade on the catechins and caffeine contents of Turkish black tea was investigated. The experimental factors significantly affected all of the parameters analyzed. Epigallocatechin gallate was the major catechin of black tea (0.719-1.007 g 100 g-1 dm) followed by epigallocatechin (0.627-0.791 g 100 g-1 dm). Additionally, caffeine (1.810-2.175 g 100 g-1 dm), theaflavin (3.201-6.000 μmol g-1), and thearubigin (8.577-12.635 g 100 g-1 dm) contents were determined. Samples of tea grown at high altitude generally produced a considerably greater amount of the catechins that improve tea quality. Shooting period, which is specific to tea cultivation in Turkey, significantly affected almost all of the quality parameters of black tea. Tea produced in the first shooting period contained more catechins than the samples plucked in the following shooting periods. Dust and orange pekoe 1 contained the most catechins of the tea grades analyzed.

Black tea classification employing feature fusion of E-Nose and E-Tongue responses

In this article, wavelet energy feature (WEF) has been extracted from the responses of e-nose and e-tongue for the classification of different grades of Indian black tea. For WEF, different decomposition levels of wavelet packet transform have been tested for both the systems and performance is evaluated with K- Nearest Neighbors classifier. Energy features of the best-suited decomposition level for e-nose and e-tongue have been calculated and fused to get a combined sensor response. Results confirm that the clustering nature (PCA plot) and classification accuracy (10-fold cross-validated based on KNN) have improved (accuracy 99.75%) with the applied method on the combined data. Moreover, this method is compared with some benchmark classification methods namely PLS-DA and Sammon's projection method which exhibits the superiority of the WEF extraction method combining the responses of multi sensory system.

Indonesian Black Tea Classification Using Fourier-Transform Near-Infrared Spectroscopy and a Principal Component Analysis

Indonesian black tea (Camellia sinensis) is processed based on several standard methods to achieve a certain grade. There are more than 25 grades produced including Dust one (D1), Fanning’s (FANN) and Pekoe Fanning’s (PF). In general, the physical appearances are similar to each other, which makes it difficult to be differentiated from visual observations by non-experts. During the packaging process, a tea grade can easily be packed using a bag with a different label of the grade. In the global market, such a mistake should be avoided before shipping. Since shipping usually involves a large number of bags, then rapid, accurate, and nondestructive methods are critical. This paper discusses a method for classifying tea grades rapidly, accurately and nondestructively using Fourier-transform near-infrared spectroscopy (FT-NIRS) and a principal component analysis (PCA). Sixty-nine tea samples from grade Dust one (D1), Fanning’s (FANN) and Pekoe Fanning’s (PF) were separated into two groups; 46 samples were used for the training sets and 30 samples for the validation sets. The analysis successfully differentiated that of 3 different grades, indicating that the method is a potential alternative for tea classification in quality control processes.

A Novel Low-Cost Hand-Held Tea Flavor Estimation System

This paper describes a method for developing a novel, low-cost, hand-held electronic nose (E-Nose) for black tea flavor estimation using metal–oxide–semiconductor gas sensors. In this research, a first-level experimentation has been conducted with a computer-assisted-technology-based system for sensor selection and validation. In the second level, a novel hand-held E-Nose is designed and developed for generation of tea aroma, capturing the response patterns and signal processing in a microcontroller (PIC 18F45K22) for tea flavor grading. The results of the first-level experimentation provide the sensor selection, where only four out of 12 sensors were selected based on their performance. Moreover, the classification network was predetermined for implementation in the microcontroller. Experiments conducted on the developed hand-held E-Nose show the classification on eight different grades of tea (each with ten samples) varying from 70% to 100%, revealing an average classification efficiency of 90%. The repeatability of the system was also found to be 80%. The developed system also overcomes the problem of heating the tea sample, since the volatile organic compounds of tea are generated due to the emitted heat of the sensors in the proposed system.

An emerging strategy for evaluating the grades of Keemun black tea by combinatory liquid chromatography-Orbitrap mass spectrometry-based untargeted metabolomics and inhibition effects on α-glucosidase and α-amylase

Quantitative analysis and untargeted liquid chromatography mass spectrum (LC–MS) based metabolomics of different grades of Keemun black tea (KBT) were conducted. Quantitative analysis did not show tight correlation between tea grades and contents of polyphenols, but untargeted metabolomics analysis revealed that high-grades KBT were distinguished from the low-grades. S-plot and Variable Importance (VIP) analysis gave 28 marker compounds responsible for the discrimination of different grades of KBT. The inhibitory effects of KBT on α-amylase and α-glucosidase were positively correlated to tea grades, and the correlation coefficient between each marker compound and inhibitory rate were calculated. Thirteen compounds were positively related to the anti-glycemic activity, and theasinensin A, afzelechin gallate and kaempferol-glucoside were confirmed as grade-related bioactive marker compounds by chemical and bioassay in effective fractions. This study suggested that combinatory metabolomics and bioactivities assay provided a new strategy for the classification of tea grades.

차 품질관리향상 연구

This study aimed to improve quality control of tea through quality evaluation of tea, and for methods of quality control, it inquired into subjects such as cultivation management, storage management, hygiene management and quality control. The purpose of quality evaluation of tea lies in producing fine-quality tea through improvement of tea manufacturing process and securing stable consumer market by providing good-quality tea for consumers. Furthermore, quality evaluation of tea aims to contribute to promoting smooth development of production and consumption of tea, by establishing order in the distribution market based on the indication system of objective quality and grade of tea. Quality evaluation of tea is divided into physiochemical quality evaluation and sensory quality evaluation. This study focused on sensory quality evaluation, which is the method of quality measurement in terms&#x0D; of appearance evaluation (shape, color, gloss) and internal quality evaluation (solution color, aroma, flavor). For practical example of quality evaluation of tea, it referred to Premium Tea Selection Festival of the 41stBoseongDahyangFestivalof2015. The improvement plan for quality control can be proposed as follows: Firstly, it is necessary to establish quality system of tea production. Secondly, it is required to seek development of new quality control. Thirdly, once quality control standards are proposed according to use adequacy of customers, it will be directly applied to quality improvement of tea. Fourthly, the degree of evaluation can improve in terms of precision, fairness and reliability when sensory quality evaluation is carried out in company with physiochemical quality evaluation. Furthermore, quality control through quality evaluation of tea must be followed. In the process of cultivation management, it is essential to achieve mechanization and organized system of facilities not only for reduction of production cost but also for massive production of tea leaves of uniform quality. As for storage management, the optimum storage condition is -10℃ with anaerobic treatment on the grounds that this condition does not bring about decrease of color, aroma and flavor of tea. Regarding hygiene management and quality control, it is necessary to analyze hazard factors in the entire processes of manufacturing, distribution, sales and consumption of tea and&#x0D; prepare an efficient management to improve quality control.

Development of a New Three-Dimensional Fluorescence Spectroscopy Method Coupling with Multilinear Pattern Recognition to Discriminate the Variety and Grade of Green Tea

According to the different types and contents of amino acids in green tea, a new method was proposed for green tea classification and quality evaluation based on excitation-emission matrix (EEM) fluorescence spectroscopy coupled with multilinear pattern recognition in this work. Amino acids in green tea samples were first derived with formaldehyde and acetyl acetone solution. Derivatives of green teas were then scanned with a three-dimensional fluorescence spectrometry. Multilinear pattern recognition methods, including multilinear principal component analysis (M-PCA), self-weight alternative trilinear decomposition (SWATLD), and multilinear partial least squares discriminant analysis (N-PLS-DA) methods, were used to decompose the EEM data sets. All of these multilinear pattern recognition methods showed the clustering tendency for five different kinds of green tea. Compared with the other two methods, N-PLS-DA got more accurate and reliable classification result because it made full use of all the fluorescence information of the derivative green tea samples. At the same time, this method also revealed the possibility of evaluating the grade of green tea.

Antidiabetic mellitus activity of low grade black tea in alloxan induced male albino mice

Tea (Camellia sinensis [L]) has a very potential character of quality and biological activities. Potential activity of black tea such as antidiabetic been proven by several studies. Grade of black tea was classified based on colour, shape, size and density of particles. Â This study aims to evaluate the most optimal antidiabetic activity of low grade black teas;BT II, DUST III, BBL and BTL in alloxan induced male albino mice. The results showed that liquor of black tea grade DUST III has blood glucose lowering activity with the most optimal percentage reduction 49.07% with a significant difference in the positive control group (p &lt;0.05).

COMBINED MULTIVARIATE DATA ANALYSIS OF GC/MS AND SENSORY EVALUATION FOR AROMA QUALITY PREDICTION MODEL OF ORTHODOX BLACK TEA GRADES

Relationships between sensory aroma and the volatile composition of 04 black tea grades produced from Northern Vietnam were studied. Consumer preference test on the aroma was carried out by 80 consumers to evaluate the aroma quality of these samples. Aroma concentrate was prepared by Brewed Extraction Method (BEM) method and analyzed using GC/MS. Partial Least Squares Regression (PLSR) was used to determine the relationship between preference scores and peak area percentage data of 39 detected volatile compounds. Among these compounds, 20 identified compounds were determined to contribute significantly to the perceived aroma quality of OTD black teas. On the basis of these 20 compounds, the PLSR model was constructed to predict the aroma quality of OTD black teas. The result showed that the volatile composition by GC/MS in the profiling with sensory and multivariate data analysis should be a useful reference for aroma quality prediction of OTD black tea grades.

In vitro antibacterial activity of Sri Lankan orthodox black tea (Camellia sinensis L.) belonging to different agro-climatic elevations

Objective: To investigate the antibacterial properties of three grades of orthodox Sri Lankan black tea belonging to the three agro-climatic elevations. Methods: Methanloic extracts of orange pekoe (OP), broken orange pekoe fannings (BOPF) and Dust No. 1 belonging to three agro-climatic elevations (low, mid and high grown) were made and tested in vitro (concentration: 300 µg/disc) against Gram-positive pathogenic bacteria, Staphylococcus aureus (ATCC 25923) (S. aureus) and Bacillus cereus (ATCC 11778) (B. cereus), and two Gram-negative bacteria Pseudomonas aeruginosa (ATCC 9027) (P. aeruginosa) and Escherichia coli (ATCC 35218) (E. coli), using agar disc diffusion assay. Gentamycin (10 µg/disc) was used as the positive control and methanol as the negative control. Minimum inhibitory concentration (MIC) values were evaluated, using micro dilution method. Results: None of the tea extracts exerted an antibacterial action against P. aeruginosa and E. coli. In contrast mild to moderate antibacterial activity was exerted against S. aureus and B. cereus. Further gentamycin exhibited strong antibacterial activity against all the four bacterial species. Further low MIC values were evident for tea samples against the two Gram-positive bacteria. The order of anti-bacterial activity for tea extracts was Dust No. 1 > BOPF > OP. Conclusions: It is concluded that Sri Lankan orthodox black tea belonging to Dust No. 1, BOPF, and OP pocess in vitro antibacterial activity against S. aureus and B. cereus but not against Gram-positive bacteria P. aeruginosa and E. coli. Article history:

Chemical constituents analysis of white tea of different qualities and different storage times

Gallic acid, caffeine, catechins and amino acids in different grades of white teas and white teas under different storage times were determined in this study. The qualitative analysis was carried out on the main chemical components in white teas by ultra-performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry (UPLC-QQQ-MS/MS). A total of 29 compounds were detected in white teas. The results showed that contents of total catechins and caffeine decreased with grades reducing. The middle-grade of white tea, Gong Mei, contained the amino acids at the highest content of 53.606 mg g−1, while the low grade Shou Mei contained the lowest (14.848 mg g−1). It was observed that contents of catechins and amino acids showed a similar tendency to decrease with storage times, while gallic acid increased with storing time (from 0.770 to 1.420 mM). This study suggested that high- and low-grade white tea should not be distinguished solely based on a single characteristic component or by market price, as well as providing an important basis for changes in characteristic components in white tea of different storage times.

Characteristic of kombucha tea concentrate purified through stirred microfiltration cell (Smfc) from local green tea (Camellia sinensis (L.) O. Kuntze) as functional drink for relaxation

L-theanine is amino acid contained in tea (Camellia sp.) leaves having ability as relaxation compound. Combination of L-theanine and other compounds produced from fermentation of green tea extract by Kombucha starter generates Kombucha tea with unique taste and better relaxation functional. The concentrate of Kombucha tea as functional drink for relaxation (anti stress) was produced by purification on fermented green te extract through 0.2 µm MF membrane fitted in stirred microfiltration cell (SMFC) at stirrer rotation speed of 200 rpm and 400 rpm, and pressure of 30 psia. Purification was conducted on 4 grades of Kombucha tea from local green tea extract with rich L-theanine, such as Pekoe, Dewata, Arraca Kiara and Arraca Yabukita as a result of purification by MF module. Kombucha tea produced through fermentation at 1 part of permeate and 1 part of water ratio using Kombucha (5%, v/v) starter riched by sucrose of 10% (w/v) under room temperature for 7 days. Based on the best L-theanine concentration, the result of experiment showed that SMFC at stirrer rotation speed of 400 rpm was able to retain L-theanine in retentate from Kombucha tea of Arraca Kiara, Arraca Yabukita, Dewata, and Pekoe grades, subsequent 29.1, 96,53, 44.62 and 71.54% (w/v) from prior to process as feed. In other words, optimization condition was reached at Kombucha tea of Arraca Yabukita grade producing retentate or concentrate of Kom­bucha tea with L-theanine, total poly­phenol, reducing sugar, total solids, and total of titratable acids of 2.5605% (w/w), 3.4314% (w/w), 14 mg/mL, 4.8947% (w/w), and 0.2195% (v/v) respectively.

210Ро in black and green teas

The 210Ро content in various grades of tea sold in St. Petersburg shops was determined, and the effective annual dose of internal irradiation from 210Ро at daily tea drinking was estimated. As shown by α-ray spectrometry, the activity concentration of 210Ро in tea leaves varies from 1.1 to 25 Bq kg–1. The 210Po content in black teas is, on the average, 1.7 times higher than in green teas. This difference is accounted for by specific features of processes for the production of black and green teas. From 1.5 to 56% of 210Ро passes into aqueous extracts. Despite higher polonium content in black teas, the amount of 210Po extracted from green teas is, on the average, 6.3 times higher than that extracted from black teas. This effect may be associated with the formation of water-soluble organic polonium compounds on the surface of tea leaves in the course of tea processing. The effective annual dose of internal irradiation from polonium at daily use of 10 g of dry tea is estimated at 0.8–9.5 μSv year–1 depending on the tea grade, or 0.5–5.8% of the average annual dose of irradiation of the Russian Federation population from the sum of the nuclides (210Pb, 210Po, 228Rа, 226Rа, etc., except 40K) getting into a human body with food and water.

Dynamics of production and export in transformation of tea plantation sector in India

The study was based on secondary published data with effect from 1971 to 2011 with an objective to examine the trends of production and export of tea and growth in India. It was observed that tea sector plays an important role contributing more than 200 crores to the GNP of the country. The major three producing regions are Darjeeling, Assam and Nilgiri. In the recent years, the sector has witnessed a stiff competition in the international export market affecting domestic production. It was observed that China produces 39.00% of world tea followed by India sharing 24.55% with an annual change of 2.87% during 1971–81 to 3.06% during 2001–11. Production of tea in the country was mainly due to increase of area and productivity. Replanted and replacement area could not influence the production of tea significantly. Number of tea estates was found to increase in between 1991–01 at the rate of 74.09% due to inclusion of small tea gardens and it declined from 5.29% to 3.64% during 1961 to 2011. Productivity change was higher in Assam, Tripura, Tamil Nadu and Kerala with high production change during the decades. The area growth during the decades was low. Production share of tea grades like CTC, Darjeeling and Green tea declined over years while share of Orthodox tea increased over years. The country witnessed high annual change of area of tea bushes under the age group of 5 to 10 years followed by below 5 years due to more area put under the small tea estates in the recent years. The export of tea bags as value added tea grew faster from 1971–72 to 2011–12 in terms of quantity and value followed by packet tea. Auction sale in the country declined. Employment generated per estate varied from 191 in Karnataka to 1011 in West Bengal in 2011. The emerging small tea sector has contributed from 5% in early 90’s to 31% during current year and is expected to touch 50% within next few years. It can be concluded that area could influence the production and it needs to be increased under replanting and replacement planting. Steps should also be taken to increase the export of value added tea in the country. The small tea sector should be organised and regulated to make it more productive.

Electrochemical Sensing of Tea Polyphenols by Chloramine-T Modified Electrodes: A New Approach

Antioxidant activities of tea samples vary depending on its polyphenolic content. This paper presents an electrochemical sensing system for fast detection of polyphenols in tea infusion using a redox reagent, chloramine-T. Three different transducers namely, screen-printed electrode (SPE), glassy carbon (GCE) and platinum (PtE) electrodes were used. The electrochemical reactions included oxidation of polyphenols (>C-OH) to o-quinone (>C=O) and reduction of chloramine-T to p-toluene sulfonamide (p-TSA). An IR band at 1636 cm−1 (stretching of carbonyl group, >C=O) of the reaction product confirmed reduction of chloramine-T. The oxidation potential was obtained from cyclic voltammetry on three different electrode systems. Amperometric measurements were conducted at optimum anodic potential. The disposable SPE exhibited the lowest detection limit of 0.674 mgL−1 with coefficient of variation less than 2.3%, recovery range of 98–103% and excellent selectivity against interfering compounds. The results compared very well with observations through high performance liquid chromatography (HPLC). A distinct concentration pattern was observed when varieties of tea were tested for polyphenols content. The sensor could be utilized to assess the quality of different grades of tea and pricing.

Fast two-dimensional fluorescence correlation spectroscopy technique for tea quality detection.

A fast two-dimensional fluorescence correlation spectroscopy technique based on light emitting diodes is developed, which uses light intensity and excitation wavelength as quickly changeable and easily controllable external perturbations. A compact and automatic system is set up to detect tea quality. A partial least square regression method is used to create predictive models for tea grades. Compared to the traditional fluorescence spectroscopy method, this convenient two-dimensional correlation spectroscopy technique is more accurate according to our experimental results and is promising for practical applications.