Quality evaluation on green tea

Horie, Hideki; Fukatsu, Shuichi; Mukai, Toshihiro; Goto, Tetsuhisa; Kawanaka, Michio; Shimohara, Tohru

doi:10.1016/0925-4005(93)85424-9

Cited by 15 publications

(10 citation statements)

References 4 publications

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“…As demonstrated by the FIA system, cold water steeping is effective for extracting amino acids, thus, astringency can be suppressed (Table 3). The experimental result is consistent with that obtained by a quality evaluation of green tea study (Horie et al, 1993), which showed that the major components extracted by boiling and cold water differed. This study determined that extraction efficiency for amino acids was better than that for tannin using cold water for <1 h. Therefore, tea prepared using the cold-brew method can generate a superior taste due to the reduction of astringent components (tannin) and increase in umami (amino acids), demonstrating the potential of the proposed system to optimise steeping time.…”

Section: Taste Quality Assessment Of Green Tea and Partially Fermentesupporting

confidence: 93%

Sequential determination of tannin and total amino acid contents in tea for taste assessment by a fluorescent flow-injection analytical system

Hung

Chen

et al. 2010

Food Chemistry

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Section: Taste Quality Assessment Of Green Tea and Partially Fermentesupporting

confidence: 93%

Sequential determination of tannin and total amino acid contents in tea for taste assessment by a fluorescent flow-injection analytical system

Hung

Chen

et al. 2010

Food Chemistry

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“…On the other hand, green tea is obtained without oxidation but with little processing stage (Pongsuwan et al 2007 ). As a result, type of tea processing has significant effect on the composition of the phyto constitutes and hence quality and bioactivity of the beverage (Kuroda and Hara 1999 ; Horie et al 1993 ). Apart from the effect of processing on the composition and quality of tea leaves, the cultivar differences and environmental effects have meticulous contribution to the overall quality and composition of the metabolites.…”

Section: Introductionmentioning

confidence: 99%

Determination of some selected secondary metabolites and their invitro antioxidant activity in commercially available Ethiopian tea (Camellia sinensis)

2016

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Eight brands of tea (Camellia sinensis),which are cultivated and commercially available in Ethiopian market, were analyzed for estimation of their total secondary metabolites (polyphenols, flavonoids and tannins) content and free radical scavenging activity which is expressed on dry weight basis. In this present study, the total polyphenols, tannin and flavonoid contents were studied spectrophotometrically using Folin–Dennis, Folin–Dennis/protein precipitation and aluminium chloride methods respectively. The free radical scavenging activity was determined by using DPPH radical assay. Results of the analysis revealed that the total polyphenol content varied from 21.3 ± 0.24 to 31.6 ± 0.31 mg of gallic acid equivalent/g of dry matter. Total flavonoids content in the tea samples varied from 8.17 ± 0.68 to 23.2 ± 0.68 mg of catechin equivalent/g of dry weight and tannin content varied from 5.64 ± 0.39 7.45 ± 0.27 mg tannic acid equivalent/g of dry weight basis. The free radical scavenging activity among the tea brand samples ranged from 28.8 ± 1.86 to 80.0 ± 0.63 mg ascorbic acid equivalent/g and the half maximal inhibitory concentration (IC50%) values varied from 7.3 ± 1.35 to 64.0 ± 2.81 µg/mL of extract. The correlation between the antioxidant activity with total polyphenol content (R = 0.91325), with flavonoids (R = 0.80658) and with tannin (R = 0.73125) was calculated and maximum correlation value was found between polyphenol content and the free radical scavenging activity of the tea samples. The results in this study also revealed that green tea had the higher polyphenolic content and found to have the most promising antioxidant activity. This study further confirmed that Ethiopia tea is reach in phenolic compounds as compared to some overseas tea cultivars/varieties.

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“…The characteristic fragrance of tea, the 'aroma' of either in fused leaf or the tea liquor, is one of the most significant parameters for evaluation of its quality [1][2][3]. The aro ma indicates that the tea comprises at least one of a certain number of odours that are desirable and are h ighly valued in 'good quality tea'.…”

Section: Introductionmentioning

confidence: 99%

Neural network based electronic nose for classification of tea aroma

Borah

Hines

Leeson

et al. 2007

Sens. & Instrumen. Food Qual.

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This paper describes an investigation into the performance of a Neural Net work (NN) based Electronic Nose (EN) system, which can discriminate the aroma of different tea grades. The EN system comprising of an array of four tin-o xide gas sensors was used to sniff thirteen randomly selected tea grades, which were exemp lars of eight categories in terms of aroma profiles. The mean and peak of the transient signals generated by the gas sensors, as a result of aro ma sniffing, were treated as the feature vectors for the analysis. Principal Co mponent Analysis (PCA) was used to visualise the different categories of aro ma profiles. In addition, K-means and Kohonen's Self Organising Map (SOM) cluster analysis indicated there were eight clusters in the dataset. Data classification was performed using supervised NN classifiers; namely the Multi-Layer Perceptron (MLP) network, Radial Basis Function (RBF) network, and Constructive Probabilistic Neural Network (CPNN) were used for aroma classification. The results were that the three NNs performed as follows: 90.77, 92.31, and 93.85%, respectively in terms of classificat ion accuracy. Hence the performance of the proposed method of aro ma analysis demonstrates that it is possible to use NN based EN to assist with the tea quality monitoring procedure during the tea grading process. In addition the results indicate the possibility for standardization of the tea aro ma in nu meric terms. Keywords Tea aro ma _ Electronic nose _ Neural network IntroductionThe characteristic fragrance of tea, the 'aroma' of either in fused leaf or the tea liquor, is one of the most significant parameters for evaluation of its quality [1][2][3]. The aro ma indicates that the tea comprises at least one of a certain number of odours that are desirable and are h ighly valued in 'good quality tea'. This odour is also known by the 'tea tasters' as the 'nose' or 'fragrance' and is one of the three attributes of the tea flavour relating to the smell of the tea, and is utilized for the assessment of tea quality in the tea industry. The other two flavour attributes are senses of taste and astringency, which are perceived within the taster's mouth. The source of the tea aroma is attributed to various volatile organic compounds (VOCs) present in tea. These VOCs are formed as a result of significant lip id degradations during the course of the various tea processing stages [4]. For example, the majo rity of the aro ma compounds are formed fro m amino acids, fatty acids, carotenoids and glycosides [5]. On the other hand, the variation of aroma in different teas is attributed to the variation of these VOCs, and their ratios, as pres ent in tea. There are many reasons for such variations in aroma profile of which one of the main reasons is due to tea being made fro m different varieties of 'tea clones' [6]. Moreover, the processing techniques, the pruning and the pruning time also have a major impact on the variations in VOCs; thus affecting the aroma profiles [7][8][9]. Du ring quality evaluation, exp...

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Quality evaluation on green tea

Cited by 15 publications

References 4 publications

Sequential determination of tannin and total amino acid contents in tea for taste assessment by a fluorescent flow-injection analytical system

Sequential determination of tannin and total amino acid contents in tea for taste assessment by a fluorescent flow-injection analytical system

Determination of some selected secondary metabolites and their invitro antioxidant activity in commercially available Ethiopian tea (Camellia sinensis)

Neural network based electronic nose for classification of tea aroma

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