• The Korean Journal of Food And Nutrition
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• v.28 no.5
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• pp.766-773
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• 2015

This study analyzes the chemical composition of green tea, white tea, yellow tea, oolong tea and black tea with respect to extraction temperature and time. The optimum extraction conditions for these teas were determined by assessing the chemical composition of tea brewed at different temperature (50, 60, 70, $80^{\circ}C$) and extraction times (1, 3, 5, 10 minute). Catechins contents were the largest at 5 minutes and generally declined by 10 minutes. Green tea catechins contents were highest when brewed at $70^{\circ}C$ and besides other teas a change of the trend variation at 70 and $80^{\circ}C$. These temperatures did not extract theaflavins in green tea. Extract temperature and time did not significantly affect theaflavins content of white tea, yellow tea, and oolong tea. Black tea, however, was noticeably dependent on extract conditions, which were most effective at $70^{\circ}C$, brewed for 5 minutes. Caffeine content of green tea, yellow tea, and oolong tea was highest at 5 minutes, but temperature did not appear to affect the content. White tea and black tea caffeine content was highest when brewed at $70^{\circ}C$ for 5 minutes. Theobromine content of green tea, yellow tea, oolong tea, and black tea did not show major differences between the study times or temperature, though the content in white tea increased with higher temperatures when brewed for 5 minutes. The extraction of phenolic compounds increased until 5 minutes, and showed not further increase at 10 minutes. Antioxidant capacity of green tea, white tea, and yellow tea were maximized at $70^{\circ}C$ for 5 minutes or $80^{\circ}C$ for 3 minutes, while oolong and black tea were reached maximum antioxidants at $70^{\circ}C$ for 5 minutes. In general, to optimize the beneficial chemical content of brewed tea, a water temperature of $70^{\circ}C$ for 5 minutes is recommended.

• Journal of Haehwa Medicine
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• v.12 no.1
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• pp.11-26
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• 2003

Alzheimer's disease (AD) is characterized by amyloid deposition and associated loss of neunons in brain regions involved in learning and memory processes. Several causes of evidence support that the congnitive disturbance is closed associated with the deficit of cerebral acetylcholine neurotransmission, and the effect of carboxyl terminal 105 amino acid fragment (CT105) of the amyloid precursor protein (APP) on the gene expression of proinflammatory cytokines. We tested it on the scopolamine-induced amnesia model of the ICR mouse using the Morris water maze with repeated orally administration of 1st Green-Tea extract (200 mg/kg) and 2nd Green-Tea extract (200 mg/kg). The Green-Tea prevents impairment of learning and memory and neuronal loss in mouse models of cognitive disturbance and it demonstrated selectivity for inhibition of acetylcholinesterase (AChE). Furthermore, the repeated administration of Green-Tea, CT105-induced alzheimer's mouse model showed central cholinergic activity by ameliorates learning and memory impairment, and isolation of CD14 microglia showed significantly decreases intracellular release of the proinflammatory cytokines tumor necrosis factor-${\alpha}$, interleukin-$1{\beta}$ and reactive oxygen species (ROS). Because of its composite profile, oral therapeutic index and a prophylactic, Green-Tea is considered the better therapeutic candidate for the treatment of Alzheimer's disease.

• The Korean Journal of Food And Nutrition
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• v.13 no.1
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• pp.36-44
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• 2000

Survival of pathogenic bacteris(S. aureus, L. monocytogenes, E. coli and S. typhimurium) in tryptic soy broth containing green tea water extract(GTW), green tea ethanol extract(GTE), potassium sorbate (PS) and sodium benzoate(SB) stored at various pH was evaluated. Tryptic soy broth(TSB) containing 0∼2%(w/v) of green tea extracts and preservatives adjusted to pH 5.5, 6.0, 6.5 and 7.0 was inoculated approximately 105 CFU/ml of pathogenic bacteria and incubated at 35$^{\circ}C$ for 24∼48 hours. Survival of bacteria was determined by viable cell counts of bacterial culture at each pH. Minimum inhibitory concentration(MIC) and minimum bactericidal concentration(MBC) of green tea extracts and preservatives against pathogenic bacteria were derived from survival curves of each bacteria. Antibacterial activities of green tea extracts increased with increasing pH but those of preservatives decreased with increrasing pH. S. aureus was the most sensitive strain to GTW and GTE but the most resistant to PS and SB. The MICs of green tea extracts to S. aureus were 0.52∼0.98% at pH 5.5∼6.0 and non inhibitory at pH 7.0. S. typhimurium was the most resistant to green tea extracts while the most sensitive to SB. The MICs of green tea extracts to S. typhimurium were 0.46∼1.62% at pH 5.5∼6.0 and 2% of PS was bactericidal at pH 5.5. 1.0∼2.0% of GTE were bactericidal to all strains tested except L. m9oncytogenes at pH 7.0. GTE was most efficient at inactivating pathogenic bacteria, generally followed by GTW, PS and SB.

• Korean Journal of Food Science and Technology
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• v.28 no.1
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• pp.66-71
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• 1996

To extend shelf life of cooked rice, main putrefactive microorganism isolated from cooked rice were identified by using the API 50 CHB kit and fatty acid analysis of the cell and antimicrobial activity of water extract of green tea was tested against isolated strains and some type of strains. The growths of Bacillus subtilis ATCC 6633, Salmonella typhimurium ATCC 14028, Bacillus cereus YUFE 2004 and Staphylococcus aureus YUFE 2087 were inhibited in broth containing 500 and 1000 ppm of green tea extract. Main putrefactive microorganisms of cooked rice were identified as Bacillus subtilis RHJ-I and Bacillus subtilis RHJ-II. Green tea extract of 500 and 1000 ppm level inhibited the growth of Bacillus subtilis RHJ-I only.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.5
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• pp.774-783
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• 2013

This study investigated the quality characteristics of boiled pork with different amounts (0.5, 1, 1.5, or 2%) of green tea, oolong tea and black tea extracts. Characteristics measured included approximate composition, water holding capacity (WHC), hardness, pH, Hunter's color value, total aerobic bacterial counts, volatile basic nitrogen (VBN), 2-thiobarbituric acid reactive substances (TBARS), and sensory qualities. Green tea approximately contained 3.4%, 31.8%, 5.5%, and 57.7% of moisture, crude protein, crude ash, and carbohydrate, respectively. There were no significant differences with the type of tea. However, the crude fat content of green tea, oolong tea, and black tea were 1.6%, 1.0%, and 0.9%, respectively. Green tea had the highest content of crude fat (p<0.05). Boiled pork approximately contained 55.1%, 38.6%, 5.2% and 0.9% moisture, crude protein, crude fat and crude ash, respectively. The WHC of boiled pork, with tea extract added, significantly increased and there were no significant differences according to the type of tea. The hardness of boiled pork significantly increased as the amount of tea extract added increased (p<0.05). The pH of the boiled pork was not significantly different after storage for one day, but significantly decreased in control groups and boiled pork with 0.5% of any tea extract added during storage. However, in boiled pork with 1%, 1.5%, or 2% of any tea extract added, pH was not significantly different during storage. The Hunter's L and b values decreased in all boiled pork. The Hunter's a-values also decreased in boiled pork with green and black tea extract added, but increased in boiled pork with oolong tea extract added. In boiled pork with tea extract added, total aerobic bacterial counts significantly decreased as the amount of tea extract added increased during storage (p<0.05). The VBN values significantly increased during storage in all groups. TBARS values were significantly lower in boiled pork with green tea extract added, oolong tea added (at concentrations of 1%, 1.5%, or 2%), and black tea extract added compared to control groups on the first day. The sensory evaluation results showed that the color, flavor, and overall acceptance of boiled pork containing 1% of oolong or black tea extracts had the highest scores but there were no significant differences. However, taste scores were significantly different (p<0.05). These results indicate that boiled pork has improved quality characteristics with 1% of oolong or black tea extracts added.

• 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.

• Korean Journal of Veterinary Research
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• v.43 no.4
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• pp.633-639
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• 2003

We investigated the effect of green tea and its fractions of alcohol and polysaccharide on jejunal crypt survival, endogenous spleen colony formation, and apoptosis in jejunal crypt cells of mice irradiated with high and low dose of gamma-irradiation. Jejunal crypts were protected by pretreatment of green tea (i.p.: 50 mg/kg of body weight, at 12 and 36 hours before irradiation., p.o.: 1.25% water extract, for 7days before irradiation, p<0.01) and alcohol and polysaccharide fractions showed no significant modifying effects. Green tea and its fractions administration before irradiation (i.p. at 12 and 36hours before irradiation) resulted in an increase of the formation of endogenous spleen colony (p<0.05). The frequency of radiation-induced apoptosis in intestinal crypt cells was also reduced by pretreatment of green tea (i.p. at 12 and 36 hours before irradiation, p<0.05., p.o. for 7days before irradiation, p<0.001) and its fractions (p<0.001). These results indicated that green tea might be a useful radioprotector, especially since it is a relatively nontoxic natural product. Further studies are needed to characterize better the promotion nature of green tea and its components.

• KSBB Journal
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• v.16 no.5
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• pp.442-445
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• 2001

Catechin compounds as anticancer and antioxidant were target materials from Korean Green Tea in this work. The methodologies of solvent extraction and partition were utilized to recover catechin compounds from green tea and the optimal experimental conditions were found by comparing the degree of recovery as slovent. extraction times and operating temperatures. The extract was partitioned with chloroform, which was best fit to remove caffeine after the extraction of green tea with 80$^{\circ}C$ water for 40 min. Further, the resulting extract was partitioned in ethyl acetate layer to purify the catechin compounds of EGC, EC EGCG and ECG. This experimental result could be extended to preparative HPLC to obtain EGCG on a commercial scale.

• KSBB Journal
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• v.14 no.5
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• pp.517-522
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• 1999

A green tea used in this experiment was cultivated at Bosung (Chonnam) and purchased from a domestic market. The extract at 5$0^{\circ}C$ water from the powder of green tea partitioned with chloroform and ethyl acetate. The resulting solution was further purified with a chromatographic column (4.6$\times$250 mm, 15${\mu}{\textrm}{m}$, Lichrospher 100RP-18). Finally separation was achieved on a $\mu$-Bondapak $C_18$(3.9$\times$300mm, 10${\mu}{\textrm}{m}$) column. The elution order of the catechin compounds contained in the green tea was EGC(Epigallocatechin, C(catechin), EC(Epicatechin), EGCG(Epigallocatechin Gallate) and ECG(Epicatechin Gallate). From the experimental results the mobile phase for isolating EGCG from the extract consisted of 0.1% acetic acid in water/acetonitrile, 87/13%(v/v). The flow rate of mobile phase was 1.0 $m\ell$/min, and UV wavelength was fixed at 280 nm. 121.3 mg of EGCG, higher than 98% of purity, was obtained from 5 g of dry green tea.

• Food Science and Preservation
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• v.15 no.3
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• pp.450-455
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• 2008

Previously, we have shown that green tea extract lowers the intestinal absorption of cholesterol, fat, and other fat-soluble compounds. We conducted this study to determine whether green tea extract affects the rate of $^{14}C$-oleic acid esterification into various lipids in the intestinal mucosa of rats. Male Sprague-Dawley ruts were had free access to a nutritionally adequate AIN-93G diet and deionized water. Initially, the rat's mucosal content of total lipids was measured following 1 mL olive oil administration with (green tea group) or without (control group) 100 mg green tea extract powder. At 1 h and 5 h, intestinal segments were extracted for total lipid analysis. Secondly, to measure mucosal esterification rates of lipids, an abdominal incision was made along the midline, and a 10-cm long jejunal segment of the small intestine was ligated in situ. Then, micellar solutions with or without green tea extract were injected into the ligated jejunal segments and incubated for 10 mill. The micellar solution contained $200.0\;{\mu}$ Ci $^{14}C$-oleic acid, $200.1\;{\mu}mol$ unlabelled oleic acid, $66.7\;{\mu}mol$ 2-monooleoylglycerol, $66.7\;{\mu}mol$ palmitoyl-sn-glycero-3-phosphocholine, 2.2 mmol glucose, $50.0\;{\mu}mol$ albumin, and 16.5 mmol Na-taurocholate per L of phosphate buffered saline (pH, 6.3) with or without 8.87 g green tea extract powder. At 10 min, each rat was sacrificed by cervical dislocation under anesthesia and the segment was removed for lipid analysis. Significant differences were observed in mucosal triglyceride content at 1 h and 5 h in ruts given green tea extract. Significant differences in the rate of $^{14}C$-oleic acid esterification into triglycerides and phospholipids fractions were observed between control and green tea groups. However, There were no significant differences in other lipid fractions. These results indicate that the lowered esterification rates of $^{14}C$-oleic acid into triglycerides and phospholipids fractions is attributable to presence of green tea extract. This may be associated with an inhibitory effect of green tea catechin on the mucosal processes of lipids, leading to the inhibition of intestinal absorption of lipids.