• Journal of the Korean Society of Food Culture
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• v.15 no.5
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• pp.398-412
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• 2000

The purposes of this study are : (a) to investigate the attitude to various coffee and tea of women, (b) to analyze the characteristics of each classified group according to eating frequency, and (c) to abstract the factors which can influence the consumption of coffee and tea. Questionnaires were hand delivered to 1,200 women residing in Seoul. A total of 1012 was usable: resulting in 84% response rate. Statistical data analysis was completed using SAS Package program for the one way-analysis of variance(ANOVA), Duncan's multiple comparison test, factor analysis and analysis of covariance (ANOCOVA). (a) Instant coffee was most consumed(22.1 times a month), green tea in tea bag(8.7), Donggulre tea(8.3), Coffee (72) in order of frequency. Among Korean traditional tea Donggulre tea(8.3) and Yuja tea (2.0) were most prefered but still a minute quantity of Korean traditional tea was enjoyed. (b) Coffee and Black tea was regarded unhealthful but habitual, delicious and familiar beverage. Green tea was regarded good for health but not so habitual, practical and familiar. The consumer awareness can be grouped into 3 clases : Healthy factor, Habitual Practical factor, Familiar factor. (c) The sociodemographic characteristics of women influenced the beverage consumption. Women in their 30s and 40s consumed much of instant coffee and coffee. 10s and 20s consumed much of canned coffee. Working women drank much of instant coffee and green tea in tea bag. Women in highest income group$({\geq}\;4,000,000\;won/month)$ consumed much of coffee. (d) The factors which influenced the eating frquency of those beverages were various. The eating frequency of instant coffee was influenced by the age, familiar factor and habitual practical factor. And coffee were influenced by income level, habitual practical factor. The frequency of green tea in tea bag was influenced by habitual practical factor and familiar factor, green tea was influenced by healthy factor and habitual practical factor, Donggulre tea was influenced by habitual practical factor.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.2
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• pp.148-157
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• 2005

This study was investigated to determine antimicrobial activity of the water and ethanol extracts of Korean wild green tea, semi-fermented tea, and fermented tea. Antimicrobial activity was examined against 8 kinds of several microorganisms. The minimum inhibitory concentration (MIC) of the water and ethanol extracts of green tea showed the most active antimicrobial activity against B. subtilis 0.2 mg/mL in Gram positive bacteria and P. fluorescens 0.3∼0.5 mg/mL in Gram negative bacteria. But the extracts did not show antimicrobial activity against lactic acid bacteria and yeast at the level of less than 1 mg/mL. Antimicrobial activity got lower as tea got more fermented. Antimicrobial activity of ethanol extracts from green tea, semifermented tea, and fermented tea was stronger than that of water extracts. Antimicrobial activity of the water and ethanol extracts of green tea, semi-fermented tea, and fermented tea was not destroyed at 50∼121$^{\circ}C$, and pH 3∼11, which proved to be very stable when given over heat, acid & alkali treatment. The ethanol extract of green tea, semi-fermented tea, and fermented tea was fractionated in the order of hexane, diethyl ether, ethyl acetate and water fraction. The highest antimicrobial activity was found in the water fraction, but not found in hexane fraction, while antimicrobial activity of fermented tea was not found in ether fraction.

• Journal of the korean academy of Pediatric Dentistry
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• v.44 no.4
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• pp.437-445
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• 2017

The aim of this study was to investigate the effects of green tea, black tea, barley tea and roasted corn tea used in South Korea to make tea on the formation of Streptococcus mutans biofilm. The aqueous samples of 4 types of tea were extracted from commercial tea bags using cold water ($7^{\circ}C$) or hot water ($72^{\circ}C$). S. mutans UA 159 was introduced into 96-well plates which contained the tea samples and 1% sucrose media. Crystal violet staining was used to assess the effects of teas on S. mutans biofilm formation. In both groups of green tea and black tea, the biofilm significantly decreased with the solution of $50{\mu}L$ aqueous sample in $200{\mu}L$ media and $100{\mu}L$ aqueous sample in $100{\mu}L$ media (p < 0.05). S. mutans biofilm with $25{\mu}L$ of barley tea or roasted corn tea aqueous sample in hot water ($72^{\circ}C$) for 10 minutes showed significant decrease compared of green tea or black tea (p < 0.05). In this study, green tea and black tea suppress the formation of S. mutans biofilm.

• The Korean Journal of Food And Nutrition
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• v.13 no.1
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• pp.13-20
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• 2000

This study was designed the antioxidative effect of the ethanol extract obtained Rooibos tea (Aspalathus linearis) on various kinds of oil, and examined the synergistic effect of Rooibos tea extract by addition of citric acid to the antioxidation activity and also investigate to antioxidation effect of the extract in food production and storage peroids. The antioxidative activity of 0.2mg of Rooibos tea extract was showed similar to same doses of $\alpha$-tocopherol, BHA and BHT in linolieic acid-ethanol system. The antioxidative effect of the mixture with 0.1% Rooibos tea extract on lard was more effective than that of the mixture with same doses of $\alpha$-tocopherol, BHA and BHT. The antioxidative effect of Rooibos tea extract was showed slightly effects on lard or soybean oil. Antioxidative effects of Rooiboe tea extract in addition of citric acid as synergist showed more effective in linoleic acid-ethanol system, but did not showed in the other oils. In the application of Rooibos tea extract to food prodctuction and storage period, the antioxidative effect was more effective in biscult, preparation added lard mixed with 0.1% Rooibos tea extract.

• Journal of the Korean Society of Food Science and Nutrition
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• v.28 no.1
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• pp.100-106
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• 1999

Use of chemical preservative for controlling harmful microorganisms in food products has been debated due to public concerns about food quality because of perceived toxic and carcinogenic potential. Thus, use of non toxic natural antimicrobial agents has become essential. This study was investigated to determine the antimicrobial activity of water or ethanol extract of commercially available tea, and of solvent fractionated ethanol extracts obtained from steamed green tea. Both of water and ethanol extracts of green tea(steamed or roasted), oolong tea and black tea exhibited strong antimicrobial activity against gram positive and negative bacteria, but not effective against yeast and mold. Also, antimicrobial activity of ethanol extract of 4 different kinds of tea was stronger than that of water extract. Among 4 different tea, ethanol extract of steamed green tea was further fractionated. One thousand g/disk buthanol extract had the strongest antimicrobial activity against bacteria and mold. The concentration of the antimicrobial activity of buthanol extract in tested microorganisms ranged from 125~1000 g/disk except for Rhizopus javanicus. Antimicrobial activity of buthanol extract of steamed green tea was not destroyed by heating at 100oC for 60 min and at 121oC for 15 min, which is very stable over heat treatment. The inhibitory effect of the buthanol extract on the growth of Listeria monocytogenes and Staphylococcus aureus was investigated. Growth of both strains was started in the presence of 250 and 500 g/ml after 12 and 24 hour respectively, whereas complete inactivation of both strains was occurred in the presence of 1000 g/ml.

• Journal of the Korean Society of Food Culture
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• v.19 no.2
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• pp.184-192
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• 2004

This study was conducted to investigate the perception and using behavior for the Green Tea by a survey. The subjects of this study were consisted of 43.1% of males and 56.9% of females in Daegu city and Gyeong-Sang Buk-Do Province. The main results are as follows : About 85.9% of the participants preferred the Green Tea owing to good for health but the others didn't like owing to not delicious. 51.1% of the subjects had one cup of Green Tea per day. The responses to the 13 questions of the Green Tea were measured on 5 point Likert scale. The item 'Green Tea is natural food' received the highest point but 'Green Tea is delicious' received the lowest. About one half of total subjects knew how to make the Green Tea and 40.4% of them learned the recipes from their mother. About 63.7% replied 'Increasing' prospects for the Green Tea consumption. About 53.7% said the plan should be 'made of good quality Green Tea' for the purpose of better improvement and extention of consumption.

• Journal of the Korean Society of Food Culture
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• v.24 no.3
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• pp.308-314
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• 2009

In this study, we examined the composition of catechins, theaflavins and alkaloids in leaves during processing to fermented black tea, which is produced by withering, roll breaking, and fermentation of Korean Yabukida tea plant. In addition, we determined the optimal conditions for the production of fermented black tea. The average moisture content in fresh leaves was 70.85%, which dropped to 3.07% in fermented black tea at the last stage of production. When the leaves were analyzed by HPLC, seven types of catechins, four types of theaflavins and three types of alkaloids were identified. The levels of catechins, theaflavins, and alkaloids were then evaluated after being processed into fermented tea. From these experiments, we found that the level of theaflavins, which determines the property of the tea, increased during fermentation. This effect resulted from the change in EGCG, ECG, EGC, EC during the process of fermentation. We also found that the maximal amount of theaflavins was created after 1-2 hours of fermentation. Thus, our results imply that the best condition for producing fermented black tea would be to ferment for 1-2 hours.

• Journal of the Korean Society of Food Science and Nutrition
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• v.23 no.5
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• pp.784-791
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• 1994

This study was to investigate the cadmium removal effect of Korean green tea, black tea and oolong tea beverage on Cd administered rat, tissues and their excretions. Male Sprague-Dawley rats weighing 143±3.2g were divided into control and experimental groups. The control group were fed standard diet without cadmium . The experimental groups, which were fed standard diet containing 40 ppm Cd, were divided into 4 subgroups again , which were the groups given distilled water (CD group), 5% black tea (BT group), oolong tea (OT group ) and green tea (GT group), respectively. Five days before to sacrifice the rats, all 4 cadmium fed groups were supplied 1 ml of water with 600ppm Cd and control group were fed 1 ml of distilled water without Cd under the same dietary condition. After that, their excretion were collected separately for 3 days. In rat liver and kidney, accmulation of cadmium in 4 Cd administered groups were more than in control group and that of GT group was significantly less than CD group. In bone , also, accumulation of cadmium in 4 Cd administered groups was more than in control group and that of GT, OT,BT groups were much less than that of CD group. GT group was excreted more Cd in urine than Cd group. In feces, 3 tea feeding groups (BT, OT, GT group) were excreted Cd 1.7, 2.1, 2.4 times more than that of the CD group, respectively. We conclude that cadmium accumulations of GT feeding group in rat's liver, kidney and bone were much less than CD group , and the absorption and retention rate of GT group was significantly lower than CD group.

• Journal of Biosystems Engineering
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• v.41 no.4
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• pp.365-372
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• 2016

Purpose: Tea is the most frequently consumed drink worldwide, next to water. About 75% of the total world tea production includes black tea, and withering is one of the major processing steps critical for the quality of black tea. There are two types of tea withering methods: physical and chemical withering. Withering can be achieved by using tat, tunnel, drum, and trough withering systems. Of these, the trough withering system is the most commonly used. This study focuses on the different types of withering, their effect on the various quality attributes of tea, and other aspects of withering methods that affect superior quality tea. Results: During physical withering, tea shoots loose moisture content that drops from approximately 70-80% to 60-70% (wet basis). This leads to increased sap concentration in tea leaf cells, and turgid leaves become flaccid. It also prevents tea shoots from damage during maceration or rolling. During chemical withering, complex chemical compounds break down into simpler ones volatile flavor compounds, amino acids, and simple sugars are formed. Withering increases enzymatic activities as well as the concentration of caffeine. Research indicates that about 15% of chlorophyll degradation occurs during withering. It is also reported that during withering lipids break down into simpler compounds and catechin levels decrease. Improper withering can cause adverse effects on subsequent manufacturing operations, such as maceration, rolling, fermentation, drying, and tea storage. Conclusion: Freshly harvested leaves are conditioned physically and chemically for subsequent processing. There is no specified withering duration, but 14-18 h is generally considered the optimum period. Proper and even withering of tea shoots greatly depends on the standards of plucking, handling, transportation, environmental conditions, time, and temperature. Thus, to ensure consumption of high quality tea, the withering step must be monitored carefully.

• Food Science and Biotechnology
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• v.18 no.3
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• pp.682-688
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• 2009

Changes in lipophillic pigments concentration and its relation to color of fresh green tea liquor during heat treatment were studied. The results showed liquor greenness decreased markedly with extension of incubation time at $55^{\circ}C$, while the brightness and yellowness changed a little. Significant increase in 'a' and 'b' values of tea liquor was observed at $95^{\circ}C$. Color change of liquor at $55^{\circ}C$ was accompanied by a decrease in the level of chlorophylls, lutein and neoxanthin, and an increase in the pheophytins and ${\beta}-carotene$ levels. However, all pigments except ${\beta}-carotene$ decreased with time extension at $95^{\circ}C$. Significant correlation was found between pigments and color difference index. The browning of fresh green tea liquor was attributed to vicissitudes of lipophillic pigments during heat treatment, especially to the change of chlorophylls/pheophytins ratio. Result also showed addition of $Zn^{2+}$ at 1.6 ${\mu}mol/L$ could partially alleviate the decrease in greenness during heat treatment.