• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.7
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• pp.1079-1084
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• 2004

The present study was conducted to compare antioxidant activity of green teas, fermented teas and other related common teas by examining radical scavenging activity using DPPH (2,2 diphenyl l-picryl hydrazyl). Scavenging activity ($SC_{50}$/) of epigallocatechin gallate (EGCG) for 0.1 mM DPPH radical was 5.5 $\mu$M or 4.2 mg/L by weight, then catechin, 14 $\mu$M or 2.5 mg/L and vitamin C, 22 $\mu$M or 3.9 mg/L, respectively. Kyokuro tea (okro) powder of 24.2 mg/L or green tea powder of 25.2 mg/L was used to reach $SC_{50}$/ for 0.1 mM DPPH. One serving of 2 g green tea provides antioxidant activity equivalent to 109∼147 mg EGCG, 145∼185 mg catechin or 131∼168 mg vitamin C. Teas from the first harvest had the highest radical scavenging activity when compared with later harvest green teas grown in the same region, but there is virtually no difference by the harvest time. A Chinese green tea, Dragon well had the highest antioxidant activity among other green teas tested providing antioxidant capacity equivalent to 168 mg EGCG or 188 mg vitamin C per 2 g serving, but partially fermented Chinese teas had much lower antioxidant activity than any green tea tested. Black tea which is fully fermented showed as strong antioxidant activity as green teas (76.3 mg vs 86.7∼67.6 mg per tea bag). One tea bag of green teas from market provided antioxidant capacity equivalent to 52∼86 mg EGCG, 70∼105 mg catechin or 63-96 mg vitamin C. Teas made of persimmon leaf, pine needle, mulberry leaf had comparatively low anti-oxidant activity equivalent to 2.5∼4.8 mg EGCG or 15∼21 mg vitamin C per teabag. The third brewed green tea still had enough antioxidant activity, while tea from tea bag brewed for 3 min or 5 min did not have any difference in their antioxidant activity. More systemic studies are needed to clarify the relationship between tea catechins and antioxidant capacity focusing on how growing, harvest time, fermentation and other processes can influence on this.

• Food Science and Biotechnology
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• v.17 no.5
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• pp.1016-1020
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• 2008

Parameters of soluble solids, amino acids, catechins, and color difference of 24 green tea samples from China and Korea were determined. The levels of soluble solids, amino acids, total catechins, and infusion lightness in tea samples from Korea were higher than those from China. Concentrations of epigallocatechin galate and epigallocatechin in teas from China were higher than tea samples from Korea. Geographical origin of teas from the 2 countries was discriminated using parameters of infusion lightness, gallocatechin, and total catechins and applying principal component analysis.

• Microbiology and Biotechnology Letters
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• v.45 no.1
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• pp.71-80
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• 2017

Tea is the most popular beverage in the world. The three main types are green, black, and post-fermented. Post-fermented teas are produced by the microbial fermentation of sun-dried green tea leaves (Camellia sinensis). In this study, the composition of the bacterial communities involved in the production of traditional oriental post-fermented teas (Korean algacha, dancha, and Chinese pu-erh) were investigated using 16S rRNA gene analysis. The dominant microorganisms present in the post-fermented teas included the ${\alpha}$-proteobacteria Rhodobacteraceae and Sphingomonas, and the ${\gamma}$-proteobacteria Pantoea. Cluster analysis confirmed that the microbial populations present in both Korean and Chinese post-fermented teas grouped into the same class. Interestingly, the dominant microorganism present in the Korean post-fermented teas was a bacterium, while for the Chinese post-fermented tea, it was a fungus.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.5
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• pp.723-727
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• 2003

The antioxidant activities and their antioxidant compounds of a group of teas obtained in local markets were investigated. A total of 18 teas were tested for their antioxidant activities based on their ability to scavenge ABTS (2,2'-Azino-bis-3-ethylbenzothiazoline-6-sulfonic acid) cation radical and DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical. The former was expressed as mg of ascorbic acid equivalents per 1 tea bag (L-ascorbic acid equivalent antioxidant capacity, AEAC) and the latter was expressed as percentage of electron donating activity (EDA%). A good correlation of AEAC and EDA was observed between the two methods. The concentrations of total polyphenolics and flavonoids in tea extracts were measured by spectrophotometric methods. Total ascorbic acid was determined via the 2,6-dicholoroindophenol titrimetric method. According to the AEAC value and EDA, black tea, brown rice green tea, green tea, herb tea and malva tea showed relatively high antioxidant activities. Polyphenolic compounds were the major naturally occurring antioxidant compounds found in teas and the high concentrations of polyphenolic compounds were observed in black tea, green tea and herb tea. Overall, six teas out of 18 teas tested in the study showed better antioxidant activities and higher amounts of total polyphenolic compounds.

• Korean Journal of Food Science and Technology
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• v.44 no.4
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• pp.383-389
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• 2012

Green tea leaves grown in Jeju island were harvested at different times in 2010 and 2011. Green teas harvested in 2010 experienced higher effective accumulative temperature than green teas harvested in 2011. The free and bound volatile compounds in green tea were analyzed using headspace-solid phase microextraction gas chromatography (GC) and GC-mass spectrometry. All green teas contained the 6 major volatile compounds ${\alpha}$-methylbutanal, pentanal, (E)-2-hexen-1-ol, ${\beta}$-linalool, geraniol and ${\alpha}$-farnesene. After enzyme treatment, (Z)-3-hexen-1-ol, benzaldehyde, (Z)-3-hexenyl acetate, ${\beta}$-linalool and geraniol were increased in all green teas. (Z)-3-hexen-1-ol increased significantly in green tea harvested in 2010, and benzaldehyde increased widely in green tea harvested in 2011. However, the total volatile compounds in green teas harvested in 2011 were remarkably decreased in comparison to harvested in 2010. It was confirmed that free and bound volatile compounds in green tea are affected by low winter temperatures.

• The Korean Journal of Food And Nutrition
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• v.25 no.4
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• pp.807-819
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• 2012

To evaluate the functional characteristic and availability for drinking of the fermented Smilax china leaf tea by using different microbial species, various fermented leaf tea was prepared by non-fermentation (C), or the fermentation of Saccharomyces cerevisiae (S), Bacillus sp. (B), Bifidobacterium bifidus (L), Monascus pilosus (M) and Aspergilus oryzae (A), and sensory and antioxidant parameter of each brewed tea was observed. The color of the A tea was red, but the other teas were yellow in color. Furthermore, the aesthetic quality of the A and M tea was 3.95 and 3.30 point, respectively, and other teas (2.55~2.28) were similar to that of the C tea. TP of fermented tea water extract was lower than that of the C, although TF was not significantly different between the fermented and non-fermented tea. Especially, TF of the A tea was significantly lower than those of the other teas. The range of EDA ($1mg/m{\ell}$) of water and ethanol extracts of tea C and the fermented teas was 19.25~22.48%; however, tea A was only 8.04~12.49%. In addition, FRAP, FICA and LPOIA of teas were not significantly different between the fermented and non-fermented teas. On the other hand, XOIA and AOIA of tea ethanol extracts were slightly higher than those of water extracts. XOIA of water extract derived from the teas was 4.83~9.20%, while ethanol extract of these was 9.00~19.00%. However, XOIA of B and L teas water extract was not detected. Furthermore, AOIA of fermented tea water extract (30.17~48.52%) were lower than those of ethanol extract (44.09~66.93%). In this study, interestingly, antioxidant parameters, such as FRAP, FICA, LPOIA and AOIA, of the A tea water extract (0.1%) was higher than that of the other tea in spite of high decreasing rate in the contents of TP and TF. Therefore, above results imply the possibility of fermented Smilax china leaf tea as a functional food.

• Korean Journal of Food Science and Technology
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• v.41 no.1
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• pp.82-86
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• 2009

The objective of this study was to evaluate the effect of various solvents on extraction of bioactive phenolics and to analyze the antioxidant capacity and contents of individual catechins in various grades of green teas organically grown in Boseong, Korea. The organic green teas, based on their harvest seasons, were categorized into five grades such as Woo-Jeon, Se-Jak, Jung-Jak, Dae-Jak, and coarse tea. Solvents used to extract phenolics from these teas included water at $23^{\circ}C$ and $70^{\circ}C$ as well as 80% (v/v) aqueous methanol and ethanol. In general, aqueous organic solvents of methanol and ethanol led to higher extraction yields of phenolics than water at $23^{\circ}C$ and $70^{\circ}C$. Total phenolics and antioxidant capacity of the teas extracted with the aqueous organic solvents were approximately 1.5 to 3.2 and 1.8 to 3.8 times higher than those with water at $23^{\circ}C$ and $70^{\circ}C$, respectively. Coarse tea, the lowest grade of green tea, showed approximately 30-60% lower total phenolics and antioxidant capacity compared with the higher grade ones. Reversed-phase HPLC analysis was performed quantitatively to identify individual catechins, gallic acid, and caffeine in teas extracted with 80% (v/v) aqueous methanol. Based on their dry weights, the organic green teas contained about 1.7 to 2.9% of caffeine. Content (mg/g dry weight) of tea catechins decreased in the following order: Woo-Jeon (155.4) > Se-Jak (147.7) > Jung-Jak (143.2) > coarse tea (135.1) > Dae-Jak (130.5). (-)-Epigallocatechin gallate was the most abundant among the catechins analyzed. The highest grade of green tea, Woo-Jeon, had the highest amount of (-)-epigallocatechin gallate at 77.4 mg/g dry weight. Overall, the higher grade of organic green teas tended to have the higher level of antioxidant capacity and catechins.

• Journal of Nutrition and Health
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• v.12 no.3
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• pp.33-39
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• 1979

The antithiamin activity(ATA) and tannin content were determined for 10 kinds of herbal teas popular in Korea, also on the urinary thiamin excretion and growth rate of rats provided with certain of these teas replacing water. The results are summarized as follows: 1) The tea bag and IT-A had higher ATA (mg thiamin destroyed/g tea), while GT-A and Omiza-tea had lower activity. Different brands of the teas refulted in extremelw different ATA ana tannin content. 2) The body meight gain in the feeding groups of GT-B and GE-B were a little lower than that of the feeding groups of water, LT and IT-A, but these differences were not significant. 3) The food consumption, the food efficiency and the drink consumption of all groups for the total feeding term were not significant. 4) The thiamin excretion was higher in the LT, GT-B groups but lower in the If-A group -when compared to the water group, none of these results were significant.

• The Korean Journal of Food And Nutrition
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• v.16 no.4
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• pp.365-371
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• 2003

This study was analyzed to the characteristics of the Lindera obtusiloba eaf teas by various manufacture methods. Moisture content was the highest in the tea processed by air dry method, and the lowest in the tea roasted after steaming. The contents of soluble solid was higher in the fermented tea than in the others, and the lowest in the roasted tea. The content of tannin was the higher in the roasted after steaming tea than in the others, and the lowest in the fermented tea. The content of vitamin C was the higher in the roasted tea than in the others, and the lower in the steamed tea. The mineral contents of leaf teas was orderly K, Na, Mn, Ca, Fe, Mg, and Zn. The roasted after steaming tea was estimated to the most excellent in the sensory evaluation of leaf teas.

• Journal of the East Asian Society of Dietary Life
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• v.16 no.5
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• pp.550-558
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• 2006

The study investigated the serum lipid metabolism and enzyme activities of Korean teas for their preventative activity against chronic disease and obesity. Male Sprague-Dawley rats were raised for 8 weeks on four experimental diets: normal diet, hyperlipidemic diet, and hyperlipidemic diet to which green and black teas (2% each) were added. Various biological actions, including lipid metabolism and enzyme activities of the serum, were investigated. Diet-induced, hyperlipidemic rats fed with green and black teas, showed significant decrease in food efficiency ratio, triglyceride, total lipid, and phospholipid compared to control, i.e. the normal and diet-induced, hyperlipidemic rats. Total cholesterol, LDL-cholesterol, Al(atherogenic index), LHR, VLDL-cholesterol, ester-cholesterol, and free-cholesterol also showed a significant decrease. However, there was no significant difference between the tea-fed, diet-induced, hyperlipidemic dieted groups. HDL-cholesterol concentration was increased significantly in the tea-dieted and normal groups compared to the control. There was a little difference in lipase activity between the normal and control groups, although green and black tea-dieted experimental groups were both increased compared to the control. The contents of total lipid, triglycerides, and total cholesterol were decreased in the normal and experimental groups compared to the control. The GOT, GPT, ALP and LDH serum enzyme activities of the experimental groups were significantly reduced compared to those of the control groups.