• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.2
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• pp.293-298
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• 1995

Antimicrobial effect of tea extracts from green tea(steamed, roasted), oolong tea and black tea was investigated. Minimal inhibitory concentration(MIC) of tea extraxcts against 9 well known strains of foodborne pathogenic bacteria such as the Gram positive and Gram negative bacteria was determined at 37$^{\circ}C$. Significant antimicrobial activity was observed in the steamed green tea and the roasted green tea of the water-soluble fraciton, and the steamed green tea of the methanol-soluble fraction, and the steamed green tea, roasted green tea and the oolong tea of the crude catechin fraction. The MIC of these extracts against B. subtillis were 700$\mu\textrm{g}$/ml, 500$\mu\textrm{g}$/ml and 120 $\mu\textrm{g}$/ml, respectively. The crude catechin fraction possessed greater antimicrobial activity than did the other fractions. Among tea extracts, extracts of steamed green tea, roasted green tea and oolong tea showed higher antimicrobial activity than them of black tea. The MIC of the crude catechin fraction obtained from tea extracts against Gram-positive bacteria such as M. Iuteus, B. subtillis and S. mutans were 30~50$\mu\textrm{g}$/ml, 120~240$\mu\textrm{g}$/ml and 120~180$\mu\textrm{g}$/ml, and against Gram-negative bacteri such as e. aerogenes and V. parahaemolyticus were 50~60$\mu\textrm{g}$/ml and 60~70$\mu\textrm{g}$/ml in the broth medium, respectively. Especially, the MIC to Streptococcus mutans which has known as a causative bacteria of a decayed tooth were 120$\mu\textrm{g}$/ml, 140$\mu\textrm{g}$/ml, 180$\mu\textrm{g}$/ml and above 1,000$\mu\textrm{g}$/ml in steamed green tea, roasted green tea, oolong tea and black tea, respectively. Tea extracts had strong growth inhibition activity against foodborne pathogenic and dental bacteria.

• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.2
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• pp.299-304
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• 1995

Antioxidative effect of tea extracts from green tea(steamed, roasted), oolong tea and black tea was investigated. Antioxidative activities of the crude catechin fraction were the most effective in oolong tea which contained the highest level of (-)-epigallocatechin gallate(EGCg). The water-soluble fraction obtained from oolong tea exhibited binding with more ferrous than copper ions. It showed a synergistic effect when used with an antioxidant such as BHT(0.5mg) and $\alpha$-tocopherol(2mg). Especially, this synergistic effect was exhibited more with BHT than with $\alpha$-tocopherol. Also steamed green tea, roasted green tea and oolong tea showed remarkable free radical scavenging action. The SC50(the concentration of a water-soluble fraction which is required to scavenge 50% of 100$\mu$M 1, 1-diphenyl-2-picryl hydrazyl radicals) of steamed and roasted green tea, oolong tea and black tea extracts were 11.3$\mu\textrm{g}$/ml, 11.4$\mu\textrm{g}$/ml, 12.7 $\mu\textrm{g}$/ml and 14.9$\mu\textrm{g}$/ml, respectively. It is assumed that the antioxidative activity of tea extracts is due to inhibition of peroxidation free radical scavenging and binding action of ferrous ions by mainly tea polyphenol compounds.

• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.1
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• pp.154-159
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• 1995

Inhibition of xanthine oxidase by tea extracts obtained from non-fermented tea(steamed green tea and roasted green tea), semi-fermented tea(oolong tea) and fermented tea(black tea) were investigated. The crude catechin fraciton had a hgher inhibitory effect against xanthine oxidase, and the effect was increased with the addition of tea extracts. Their inhibitory effect were hardly influenced until extracted three times with hot water. According to the investigation of catechins in the crude catechin fraction obtained from tea extracts, (-)-epicatechin-(EC), (-)-epicatechin gallate(ECg). (-)-epigallocatechin(EGC) and (-)-epigallocatechin gallate(EGCg) were 80.1$\mu\textrm{g}$/mg 113.5$\mu\textrm{g}$ /mg, 186.3$\mu\textrm{g}$/mg and 367.7$\mu\textrm{g}$/mg in steamed green tea, and 75.6$\mu\textrm{g}$/mg, 114.7$\mu\textrm{g}$/mg, 193.7 $\mu\textrm{g}$/mg and 381.9$\mu\textrm{g}$/mg in roasted green tea, and 69.4$\mu\textrm{g}$/mg, 110.0$\mu\textrm{g}$/mg, 127.1$\mu\textrm{g}$.mg and 464.9$\mu\textrm{g}$/mg in oolong tea, and 78.1$\mu\textrm{g}$/mg, 171.8$\mu\textrm{g}$/mg, 80.7$\mu\textrm{g}$/mg and 51.4$\mu\textrm{g}$/mg in black tea, respectively. Order of the content of these catechins was (-)-EGCg>(-)-EGC>(-)-ECg>(-)-EC in steamed green tea, roasted green tea and oolong tea, and was (-)-ECg>(-)-EGC>(-)-EC>(-)-EGCg in black tea. Also the concentration of catechins was hardly influeced until extracted three times. The inhibition ratio of xanthine oxidase by autherntic catechins was hardly influenced until extracted three times. The inhibition ratio of xanthine oxidase by authentic catechins was 94.9% and 87.6% by addition of 5.0$\mu\textrm{g}$/ml of (-)-EGCg and (-)-ECg, respectively. the inhibitors of xanthine oxidase were supposed to be due to (-)-ECg and (-)-EGCg in tea polyphenol compounds.

• Korean journal of food and cookery science
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• v.15 no.5
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• pp.475-482
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• 1999

This study was carried out to prepare green tea by traditional roasting process, Kujeungkupo, and to determine its sensory characteristics. The carotenoid content in green tea was increased by roasting and reached 1,317 mg/100 g by Kujeungkupo. Of all carotenoids, the contents of lutein and $\beta$-carotene were 1,170 mg/100 g and 111.1 mg/100 g, respectively. The total cathechin content in green tea was 14.57 g/100 g after 9th roasting. The more the number of roasting the little contents of cathechin in green teas. Of all cathechin, epigallocathechingallate was the highest(6.80g/100 g) followed by epicathechingallte and epicathechin. total cholrophyll content was 141 mg/100 g of green tea. The free sugar content in Kujeungkupo green tea wet 2.18 g/100 g, of which sucrose comprised 46% (1.01 g/100 g). The color value ($\Delta$E) of Kujeungkupo green tea was 16.25. In sensory evaluation, sweet taste was the highest in green tea roasted 3 times and the flavor was best in that roasted 5 times. The sweet and astringent tastes of green tea had negative relationships with a and b values. The content of cathechin in green tea had a negative relationship with sweet taste and a positive relationship with astringent taste.

• 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.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.4
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• pp.518-524
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• 1995

In this study physicochemical characteristics such as crude lipid, crude protein and total sugar contents have been analyzed with samples taken at different developing stages and growing sites, Bongsan-ri(steam-roasted green tea) and Buchun-ri(roasted green tea) area. Leaf area of new leaf was larger in Buchun-ri(7.23cm$^2$) than in Bongsan-ri(6.93cm$^2$). Variation of leaf area by the developing stages was the largest at between stage II (May 5) and stage III(May 18). Dry matters ratio of tea leaf were 26.3% in Bongsan-ri and 26.6% in Buchun-ri. Water content, ash, water-soluble matters, total sugar content of green tea sampled in Bongsan-ri and Buchun-ri were 5.6, 6.1, 33.1, 4.6 and 6.2, 5.8, 35.2, 2.8%, respectivley. Crude lipid, total nitrogen and water-soluble protein, inorganic matters content of green tea sampled in Bongsan-ri and Buchun-ri were 2.8, 5.1, 1.1, 2.56 and 2.2, 5.7, 1.0, 2.34%, respectively. At the later developing stages crude lipid, total sugar contents were increased, whereas total nitrogen had low content. Vitamin C, Vitamin E and Vitamin A content of green tea produced in Bongsan-ri and Buchun-ri area were 413mg%, 71.8mg%, 32.15IU and 311mg%, 52.3mg%, 25.68IU, respectively. Vitamin C and Vitamin E content were increased toward the later sampling stages. Water-soluble matters and water-soluble protein content of green tea prepared by the steam-roasted method and the roasted method were increased by 0.11, 0.13 and 0.09, 0.08%, respectively, compared to unroasted check. Crude lipid content of green tea prepared by the steam-roasted method and the roasted method were decreased by 0.13 and 0.24%, respectively. Total nitrogen content of green tea prepared by the steam-roasted method and the roasted method was changed 0.019 and 0.036%, respectively and total nitrogen content showed minute different between two methods.

• 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.

• Journal of Life Science
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• v.17 no.8 s.88
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• pp.1111-1114
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• 2007

The volatile flavor components of buckwheat (Fagopyrum esculentum Moench)-green tea were analyzed and identified. To make tea having good flavor and functional property, parched buckwheat (50%) was mixed with green tea (50%). The extraction of volatile flavor compounds of buckwheat-green tea was accomplished by a simultaneous distillation and extraction method using a Likens and Nickerson's extraction apparatus. The concentrated extract was analyzed and identified by gas chromatography and GC-mass spectrometry. The main volatile flavor components of buckwheat-green tea were compounds that originated from parched buckwheat and the green tea. The former were 15 pyrazines having roasted and nutty aroma and methylbutanals and furfural having sweet-aroma. The latter were nerolidol, linalool, indole, ${\beta}-ionone$ and geraniol etc having flower-like odor in green tea.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.6
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• pp.775-781
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• 1995

This study was conducted to find out the variation in some medicinal components of Korean green tea by processing recipe and harvesting time in Bongsan-ri(steamroasted green tea) and Buchun-ri(roasted green tea) area. Total chlorophyll content of green tea grown at Bongsan-ri and Buchun-ri was 293mg% and 275mg% and ratio of chlorophyll a to chlorophyll b was 70:30 and 67:33 respectively. The later harvested one had the higher chlorophyll content but the chlorophyll content of the last harvested green tea at Buchun-ri decreased more sharply. Water-soluble pectin of green tea produced at Bongsan-ri and Buchun-ri was 2.05% and 1.84%, respectively. It also increased at the later harvested ones. Total amino acids content of Bongsan-ri and Buchun-ri tea was 2,156mg% and 1,723mg%, respectively. The later harvested tea showed the remarkably decreased. Caffein and catechins of Bongsan-ri and Buchun-ri tea were 2.03%, 11.52% and 2.62%, 14.05%, respectively, Total free catechins content of Bongsan-ri and Buchun-ri tea was 35.59% and 42.73%, and ester type was 58.09% and 44.47%, respectively. Extracted catechins and caffeins of green tea were increased when extracting water temperature was raised from $65^{\circ}C$ to 85$^{\circ}C$ and leaching time was lengthened from 3min. to 9min. About 89% catechins and 97% caffeins of green tea was extracted by nine minutes soaking in 85$^{\circ}C$ water.

• 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.