• Bulletin of the Korean Chemical Society
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• v.26 no.5
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• pp.747-754
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• 2005

Liquid chromatographic methods with UV and fluorescence detection have been used to determine the levels of (+)-catechin, (-)-epicatechin, (-)-epicatechin gallate, and (-)-epigallocatechin gallate in Korean green tea infusions. The extracts of Korean green tea leaves or powders in water at various temperatures (100 ${^{\circ}C}$, 80 ${^{\circ}C}$, 60 ${^{\circ}C}$) and time, were washed with chloroform and re-extracted to ethyl acetate. The ethyl acetate phase was dried and re-dissolved in methanol and analyzed. Five catechin compounds were separated by gradient elution. The flavonoids were found decomposed on prolonged extraction, thus exhaustive extraction by a Soxhlet apparatus was found useless for green tea. Some unknown components were found in the extracts at 100 ${^{\circ}C}$. When the green tea was filtered and re-extracted with new fresh water, still some flavonoids were extracted. However, the contents of flavonoids in the third extract were found negligible. The flavonoid extraction rate of green tea powders was higher than that of green tea leaves, but flavonoid decomposition of green tea powders was also faster than that of green tea leaves. The traditional way of drinking green tea was found appropriate in view of flavonoids intake.

• Nutritional Sciences
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• v.9 no.2
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• pp.61-67
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• 2006

Green tea has attracted attention with respect to its potential for preventing and treating neurodegenerative disease. The neurotoxin, 6-hydroxydopamine (6-OHDA), was used to produce experimental Parkinson's disease (PD) model. The purpose of this study was to investigate the effects of green tea diet on behavioral changes, striatal dopamine content, and hepatic antioxidant parameters of PD model rats. In this study, we used male Sprague-Dawley rats weighing $200\sim220g$ and injected 6-OHDA into the right substantia nigra and medial forebrain bundle of the brain. The supply of green tea diet was started at 2 weeks before 6-OHDA lesion and continually supplied during 0, 2, and 4 weeks after 6-OHDA lesion (GT-0, GT-2, GT-4). Behavioral disturbance was measured by the stepping and d-amphetamine drug-induced rotation tests. Then, we assayed the striatal dopamine content and the hepatic malondialdehyde (MDA), hydrogen peroxide $(H_2O_2)$, and superoxide dismutase (SOD) activity. The percentage of lesioned forepaw to non-lesioned forepaw step scores was the highest in GT-4 group among all groups at both 3 and 4 weeks after 6-OHDA lesion. At 4 weeks after 6-OHDA lesion, the rotation score was the lowest in GT-2 group (p<0.05). However, increasing rate of the rotation score from 2 to 4 weeks after 6-OHDA lesion was the lowest in GT-4 group. The striatal dopamine content was not significantly different among four groups by green tea diet. The hepatic MDA level was the lowest in GT-4 group among four groups. The hepatic SOD activity was increased with the prolongation of green tea diet period These results suggest that green tea diet affects behavioral changes in rats of PD model. It seems that continuous green tea supplementation has an influence on the reduction of behavioral disturbance and the hepatic MDA level. Accordingly, continuous green tea supplementation was recommended for the prevention and treatment of PD. However, further studies are needed to investigate the mechanisms and efficacy of green tea in PD.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.7
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• pp.1021-1025
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• 2003

The study was to investigate the quality of wet noodle added with the powder green tea. The wet noodles were prepared to the ratio of 1, 2, 3, 5, 7.5 and 10% (w/w) of the powder green tea based on a flour weight. The initial pasting temperature in an amylograph was increased as the increase of the powder green tea, while peak and final viscosity as the increase decreased. The weight and volume of cooked noodles were decreased, and turbidity of soup was increased with the addition of the powder green tea. L and a values of wet noodles were decreased with the addition of the powder green tea, and b value was increased. Texture profile analysis of cooked noodle showed a increase of hardness, cohesiveness, springiness, chewiness up to 2% powder green tea, but decreased from 3% power green tea. However, adhesiveness decreased as the increase of the powder green tea. From the sensory evaluation, the wet noodles included 1% powder green tea were similarly evaluated as the noodle used whole wheat flour.

• The Korean Journal of Food And Nutrition
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• v.31 no.3
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• pp.416-424
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• 2018

The physiologically advantageous aspects of green tea have been identified recently and green tea has been a favorite drink of many people. Due to the increased awareness of green tea's positive effects on human health, the demand for foods containing green tea has increased. This has led to the development of diverse green tea-related beverages; thereby many companies in Korea have put a wide variety of manufactured green tea beverages on the market. However, the components within green tea beverages have not been examined in Korea yet. In this study, we investigated the contents of the physiologically functional materials found in green tea, such as catechin, catechin gallate, epicatechin, epicatechin gallate, epigallocatecin gallate, gallocatechin gallate and caffeine. Fifty-six green tea products purchased from the local grocery stores and cafes were analyzed using high performance liquid chromatography (HPLC) analysis. As a result, all tested products contained catechin and caffeine, although the amount of each component was largely different. The total amount of catechin derivatives in the manufactured green tea beverages purchased from cafes was 263.17 mg/L, while they were 61.99 mg/L in the beverages purchased from the local grocery stores. And, to the almost samples the amount of caffeine was proportional to the amount of catechin.

• Journal of the East Asian Society of Dietary Life
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• v.9 no.4
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• pp.501-513
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• 1999

In order to investigate consumption pattern and image of beverage, this study was performed by using questionnaire based on stratified random sampling about 200 students from September 6, 1999 to September 18, 1999. The result was as followings: 1. For the reasons of each beverage consumption, coke, soda pop and sport drinks were for quenching thirst. And coffee and juices were for dessert and milk.yoghurts, dietary beverages, green tea and ginseng tea were for health. 2. For the priority in selecting each beverage, trademark was dominant factor for choosing coke. And the dominant factor of choosing milk.yoghurts and ginseng tea was nutrition and in case of other beverages taste was the first factor. 3. For the place of taking beverages, coffee, coke and sport drinks were mainly consumed in school and milk.yoghurt and juices in home. 4. The college students loved or liked milk.yoghurt and juices, and they liked or enjoyed coke, soda pop, sport drinks and green tea moderately, and enjoyed ginseng tea and black tea moderately or disliked them. 5. For the frequency of each beverage, many of them consumed coffee and milk.yoghurt once or twice a day. and consumed coke. soda pop. sport drinks and juices once or twice a week. And they answered that they did not consume dietary beverages, green tea, ginseng tea and black tea so often. 6. There was significant correlation with frequency of drinking and preference score of beverage. 7. For the consumption of the Korean traditional beverages, more than 50% of the subjects had no experience in taking sangwha tea, omiza tea, and Kugiza tea. Among them, many answered that they would try the Korean traditional beverages, if they had an opportunity, and that their price was moderate. 8. The results from the analysis of the image of those beverages were as followings; \circled1 Coffee, coke, sport drinks and dietary beverages had a modern image and green tea, ginseng tea and black tea had a traditional image. \circled2 Coke, sport drinks and ginseng tea had a manly image and juices, dietary beverages, green tea and black tea had a womanlike image. \circled3 The students recognized coffee, coke, milkㆍyoghurt, sport drinks, juices, dietary beverages and green tea to be daily and catholic. \circled4 Milkㆍyoghurt, juices, dietary beverages, green tea, ginseng tea and black tea were recognized to be good for health and coffee and coke bad for health. \circled5 Coffee, coke, soda pop, sport drinks, juices and green tea were slightly concerned with a change. \circled6 Coke, soda pop and sport drinks had a dynamic image and coffee, juices. green tea, ginseng tea and black tea had a little static image.

• Journal of the East Asian Society of Dietary Life
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• v.14 no.2
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• pp.156-160
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• 2004

This study was carried out to examine the changes of chlorophyll a and b contents by the extraction temperatures and the number of soaking using five kinds of Korean green teas(3 kinds of green tea and 2 kinds of tea bag) which were obtained from a local market in Daegu city, Korea. The chlorophylls were extracted with 80% acetone, and determined by a visible spectrophotometer. The concentration of chlorophyll in Sulrok(tea bag) were the highest among all kinds of teas when they were extracted at 60, and decreased with the number of soaking increased. On the other hand, the chlorophyll content of green teas was the highest at 80, and decreased with the increase of the number of soaking as the tea bag did. It was found that the Korean tea bag contained more chlorophyll than green teas did, and green teas contained significantly more chlorophyll b than chlorophyll a.

• Food Science and Biotechnology
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• v.17 no.2
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• pp.349-356
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• 2008

The green tea market is rapidly growing and identifying the driving factors of consumers' liking for the green tea is important in the tea industries. The objectives of this study were to investigate the effects of manufacturing conditions of the green tea on its sensory characteristics, to elucidate its relationship with the consumer liking. A descriptive analysis and consumer acceptability test were conducted for various green tea samples. The samples differed with regard to the source of the tea, the amino acid content, and the processing methods including the roasting temperature. Partial least square regressions (PLS-R) were performed to establish the relationship between the descriptive data and the consumer acceptability data. The PLS-R results showed that the majority of the consumers liked a green tea which has a stronger 'sweet taste' and roasting-related flavors such as 'roasted barley' and 'burnt leaf'. Such sensory characteristics were produced when a sample made of tea leaves mixed with the tea stem was roasted at a high temperature ($250^{\circ}C$) in this study.

• Korean journal of food and cookery science
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• v.15 no.2
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• pp.95-101
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• 1999

This study was carried out to prepare green teas by traditional roasting manufacturing process, Ku Geung Ku Po and to determine the quality charateristics of the green teas by examining the change of their main components induced during this roasting process. The content of total sugars in unroasted tea leaves was 7.82%. Its content of roasted teas was decreased by increasing the number of roasting and there was significantly differences between samples. The content of total sugars in 9th roasted green tea was 3.98%. The total nitrogen contents of green teas produced by this process were 4.96∼6.38%. The more the number of roasting and the less content of tannin in green teas. And the ratio of total nitrogen and tannin in tea leaves 21.97 but its ratio in 9th roasted tea was increased to 45.54. The ascorbic acid in tea leaves consisted in 1,820.3 mg/100g but its content was decreased by increasing the number of roasting process. Whereas the content of caffeine in green teas was not reduced significantly by this traditional method. Of all amino acids, green tea produced by Ku Jeung Ku Po was rich glutamic acid, lysine and aspartic acid. And especially, phenylalanine, which was rarely found in other green teas, was abundant in these green teas. The compositions of glutamic acid and methionine were increased as increasing the number of roasting process but those of aspartic acid and arginine decreased by these processing. The main fatty acids of Ku Jeung Ku Po green tea were linolenic acid, linoleic acid and palmitic acid and the contents of unsaturated fatty acid in green teas were composed over 70% of total fatty acid. And the fatty acid contents in green teas were not affected during Ku Jeung Ku Po's process. The contents of minerals in these teas was rich in the oder of potassuim. magnessuim and calciumim, and these contents were not observed the prominant change during the process.

• Journal of Nutrition and Health
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• v.31 no.6
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• pp.999-1005
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• 1998

This study was conducted to investigate the effect of late-harvested green tea extract on serum and tissue lipid contents and Ca absorption. Sprague-Dawley male rats weighing 200g were fed high fit diets containing no tea(control), 0.5%(0.5LG), 1.0% late-harvested green tea extract(1.0LG), and 1.0% early-harvested green tea extract(1.0EG) for 4 weeks. Though daily food intake of experimental groups showed no significant difference from that of control group, daily body weight gain and food efficiency ratio were lower in all groups fed green tea extract. The contents of serum triglyceride of 1.0LG and 1.0EG groups and the content of serum total cholesterol of 1.0LG group were significantly lower than those of control group. The values of serum HDL-cholesterol in groups fed green tea extract were higher than that in the control group. LDL-cholesterol and atherogenic indices of all groups fed green tea extract were significantly lower than those of the control group. The contents of total lipid and triglyceride in liver were significantly lower in only 1.0LG group. For epididymal fit pad, the contents of total lipid and triglyceride in 1.0LG and 1.0EG groups were lower than those in the control group. The contents of total lipid excreted in feces were higher in groups fed diets of 1.0% green tea extract. There was no significant difference among experimental groups in Ca absorption. These results suggest that the administration of late-harvested green tea extract decreases the contents of fat in the body without reducing Ca absorption. (Korean J Nutrition 31(6) : 999-1005, 1998)

• Applied Biological Chemistry
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• v.31 no.3
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• pp.284-291
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• 1988

To establish the evaluation method of Korean green tea, the correlation between physicochemical characteristics and sensory scores by the expert panels were investigated using 15 kinds of green tea manufactured in 1985 from Korea, Taiwan and Japan. Tannin, caffeine and total free amino acid contents of Korean green tea are higher than foreign ones, but the chlorophyll content is the highest in Japanese high grade green tea. Sixteen free amino acids including theanine were identified, and theanine, glutamic acid, aspartic acid and arginine contents which affect the brothy taste of green tea infusion were highest in Korean green tea. Sensory score for the color of Korean green tea infusion were lower than Japanese tea, but the flavor and taste were the best. In multiple regression analysis, the quality affecting factors of the green tea were elucidated as the caffeine$(X_1)$, chlorophyll b$(X_2)$, total free amino acid contents$(X_3)$, and L value$(X_4)$ of green tea infusion. The regression equation was expressed as $Y=-21.5820+2.1691X_1+0.0130X_2+0.2314X_3-0.0001X_4$ and then $R^2$ was 0.8919.