• Journal of the Korean Society of Food Culture
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• v.22 no.4
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• pp.449-453
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• 2007

Using green tea(GT), oolong tea(OT), black tea(BT) and green tea bag(GTB) out of tea products in market, this study quantified polyphenol and catechins as anti-oxidant substances and analyzed their respective anti-oxidant capacities. As a result, more epigallocathechin(EGC) was found in GT and GTB as well as caffein(CAF) in GT and BT. GT contained more epigallocathechin gallate(EGCG) than other tea types. Both FRAP and ORAC, as two methods of analyzing anti-oxidant capacities, showed that GTB had highest anti-oxidant capacities, while OT had lowest of all. By brand, it was found that all the 3 brands of GT had similarly high anti-oxidant capacities, but there were differences in the anti-oxidant activities of GTB and BT depending on brand. Out of catechin components, it was found that epicatechin(EC), epicathechin gallate(ECG) and EGCG were major components affecting anti-oxidant capacities.

• 한국약용작물학회:학술대회논문집
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• 2007.05a
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• pp.163-164
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• 2007

• 한국약용작물학회:학술대회논문집
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• 2007.05a
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• pp.169-170
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• 2007

• 한국약용작물학회:학술대회논문집
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• 2007.05a
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• pp.167-168
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• 2007

• 한국약용작물학회:학술대회논문집
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• 2007.05a
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• pp.53-54
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• 2007

• Proceedings of the PSK Conference
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• 2002.04a
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• pp.159.1-159.1
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• 2002

• Journal of Life Science
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• v.10 no.2
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• pp.202-209
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• 2000

The factors affecting chemical composition of green tea (Camellia sinensis L.) during extraction process were temperatures and times. The optimum extraction conditions were measured in relation to the changes of chemical compositions from water extracts of green tea (Camellia sinensis L.) under different extraction temperatures (50, 70, 9$0^{\circ}C$) and extraction times (1, 3, 5 minute). The change of color intensity during browning reaction, flavonoid components, contents of total phenols and hydrogen donating activity (reducing activity for $\alpha$, $\alpha$'-diphenyl-$\beta$ -picryhydrazyl) of water extracts form green tea increased as extraction temperatures increased from 50 to 9$0^{\circ}C$ and extraction times prolonged from 1 to 5 min. The contents of important free sugars such as sucrose and glucose slightly increased as the extraction time was prolonged, while little difference in the content of fructose with the prolonged extraction time. Catechins contents extracted from the commercial steamed green tea were increased at higher temperature and longer extraction time. Epigallocatechin (EGC) extracted from 9$0^{\circ}C$ (extraction time 5 min). presented 99.9 mg/g in highest composition of catechin followed by epigallocatechin gallate (EGCg), epicatechin (EC), epicatechin gallate (ECg). The content of vitamin C extracted from green tea was increased about 2 times as the extraction temperature increased from 50 to 9$0^{\circ}C$ and as the extraction time increased from 1 to 5 min. with exception at 9$0^{\circ}C$(extraction time:5 min) which showed less vitamin C content than 7$0^{\circ}C$(extraction time : 3 min) probably due to possible destruction of vitamin C by high temperature.

• Food Science and Biotechnology
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• v.17 no.3
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• pp.464-469
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• 2008

In human beings, it is known that there is a correlation between the occurrence of acne and the ability to suppress sebum. Sebosuppression may be related to the inhibition of sebocyte proliferation, differentiation, and lipogenesis in sebaceous glands. To investigate the skin sebosuppressive activity of green tea extract, the in vivo effects of its flavonoid compounds on the androgen-dependent stimulation of pigmented macules in hamsters and performed in vitro experiments with human primary sebocytes were examined. Our results imply a dual activity of skin sebosuppression by green tea flavonoids; some catechins including epigallocatechin-3-gallate (EGCG) and gallocatechin-3-gallate (GCG) may reduce the differentiation of sebocytes by inhibiting PPAR-${\gamma}1$ mRNA expression, whereas some flavonol glycosides including kaempferol may inhibit lipogenesis in sebaceous glands by decreasing levels of the mature form of sterol-sensitive response elements binding protein-1c (SREBP-1c). Therefore, green tea is a potentially effective material for use in the development of health foods or cosmetics for skin sebosuppression.

• KSBB Journal
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• v.23 no.1
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• pp.96-100
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• 2008

In this work, we describes analysis of the antioxidant potential of Korean green tea phenolics using an high-performance liquid chromatography (HPLC) on-line $ABTS^{+}$ antioxidant screening method. In conjunction with the analysis of their 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS+) radical scavenging ability, the extraction of catechine compounds from Korean green tea were performed by various temperature and time. The optimum operating conditions were experimentally determined to analyze the catechine compounds in the pretreatment extracts. From the results, the extraction temperature $60^{\circ}C$, time 3 min was selected as an optimal antioxidant activity condition. The analysis by $C_{18}$ column was performed, the flow rate of mobile phase and UV wavelength was fixed at 1.0 ml/min and 254 nm, respectively. the mobile phase was composed from acetonitrile and water, and the gradient elution mode were applied.

• Food Science and Preservation
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• v.13 no.4
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• pp.421-426
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• 2006

Preservation stability of the extract from dried green tea produced in Jeju, extracted at $55^{\circ}C$ for 15 min and bottled in PET container after filtration and then settled at $4^{\circ}C$, indoor at room temperature and outdoor, respectively, was estimated. Color L-value was almost constant but color of the extract became darkened during storage, especially in indoor storage. Main catechins of green tea extract were (-)-epigallocatechin, (-)-epigallocatechin gallate, epicatechin, (+)-catechin, epicatechin gallate in order, and the content of epigallocatechin was 53.8%. Nevertheless total catechin content was not changed in cold storage, and $4.7\sim10%$ of total catechins were reduced in outdoor or indoor storage after 14 weeks. Caffeine content were increased but total polyphenols were not changed largely during storage. Election donating abilities (EDA) showed more than 60% without influence of storage conditions and periods. Nitrite scavenging abilities (NSA) showed more than 90% at pH 1.2, but those were decreased gradually as pH increased, and then disappeared at pH 6.0. Color, polyphenols, antioxidant activities of extract were not so changed for more than 3 months. Microbial growth was not shown during same periods, due to heat treatment of the extracts at $95^{\circ}C$ for 10 min.