• Journal of Food Hygiene and Safety
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• v.5 no.4
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• pp.213-217
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• 1990

A simple and practical method for the determination of caffeine in coffee, black tea and green tea was studied. The analysis of caffeine was performed by reverse phase high perfomance liquid chromatography using a ${\mu}-Bondapak$ C18 column at isocratic condition with methanol-acetic acid-water (20: 1: 79) on UV detector at 280 nm. The extraction and clean-up of caffeine in sample is based on combing a simple pretreatment with the use of a Sep-Pak Alumina A cartridge. The average recoveries of caffeine from several samples were 95.2 -101.3%, the relative standard deviation for the whole procedure was 0.10 ~ 0.62%, and the detection limit of caffeine in sample solution was about $0.1\;\mu\textrm{g}\;per\;ml$.

• Proceedings of the Korea Contents Association Conference
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• 2004.05a
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• pp.473-477
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• 2004

Cotton fabric was treated with Cationon UK(tertiary ammonium salt) to improve the dyeability to black tea colorants. In order to investigate the efficacy of Cationon UK for improving dyeing properties of cotton fabric, the effect of Cationon UK treatment conditions and dyeing conditions on dye uptake of the cotton fabrics treated with Cationon UK were examined and the colorfastness to washing, perspiration, rubbing and light was also evaluated for practical uses. Cationized cotton treated with Cationon UK showed high dye uptake at lower dyeing concentration and shorter dyeing time, compared with untreated. Dyeing temperature did not affect significantly dye uptake and the maximum dye uptake was obtained at pH 5. Most colorfastness was relatively good, showing 4/5∼5 rating.

• Journal of Life Science
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• v.6 no.1
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• pp.56-65
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• 1996

Black tea extractbsupplemented with 10% sucrose was fermented by fungus at 30$\circ$C. A pellicle thick as 7$\sim$8 mm covered entire surface of the medium and the wxtract converted to acidic beverage(abbreviated below as fermented black tea) by 14 days of fermentation. It was a kind of acetic acid fermentation depending on symbiotic microorganisms. During the fermentation strains of yeasts(Saccharomyces cerevisiae and Eeniella sp.)and bacteria(Bacillus subtilis, Kurthia zopfii, Gluconobacter oxydans and Deinicoccus sp.) were isolated from aqueous layer. Contrastly to it, a bacterial strain(Acetobacter aceti) was isolated from thick pellicle. The bacteria grew as a viscouse cluster on solid agar medium differently from usual strains of A. aceti. Fermented black tea had sweet-sour taste and sweet smell.

• Food Science and Preservation
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• v.16 no.2
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• pp.230-237
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• 2009

The phenolic contents, antioxidant effects, and acetylcholinesterase inhibitory activities of hot water extracts prepared from various Korean commercial teas(green tea, puer tea, oolong tea, and black tea) were investigated. Total phenolic contents were in the range 72.03-85.62 mg/g. Flavonol contents of hot water extracts from green tea, puer tea, oolong tea, and black tea were 350.96, 254.17, 334.48, and 240.23 mg/100 g, respectively. Catechin contents were 2,920.35 mg/100 g in green tea, 1,016.23 mg/100 g in puer tea, 2,824.22 mg/100 g in oolong tea, and 1,006.51 mg/100 g in black tea. The highest caffeine content was in the green tea extract. All four extracts scavenged $ABTS^{{\cdot}+}$ radicals in a concentration-dependent manner, and the green tea extract was the most potent in this regard. The highest reducing power was observed in the green tea extract. All four extracts exhibited considerable antioxidative activities in linoleic acid autoxidation, $\beta$-carotene bleaching, and acetylcholinesterase inhibition assays; the effects were concentration-dependent and decreased in the order green tea > oolong tea > puer tea > black tea.

• Journal of Food Hygiene and Safety
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• v.32 no.6
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• pp.460-469
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• 2017

The aim of this work was to study the comparison of anti-oxidative activity in a single serving size of commercial coffees and teas. Commercial regular coffees and teas, including, brand regular coffees ($BC_A$, $BC_B$, $BC_C$, $BC_D$, and $BC_E$), green tea ($GT_A$, $GT_B$, $GT_C$, and $GT_D$), black tea ($BT_A$, $BT_B$, and $BT_C$), pu-erh tea ($PT_A$, $PT_B$, and $PT_C$), chamomile tea ($CT_A$, $CT_B$, and $CT_C$), peppermint tea ($P_A$, $P_B$, and $P_C$), polygonatum odoratum tea ($POT_A$, $POT_B$, and $POT_C$), and jujube tea ($JT_A$, $JT_B$, and $JT_C$) were assayed for the levels of ascorbic acid, caffeine, total content of polyphenols and flavonoids, and ability to scavenge free radicals, using two in vitro antioxidant assays. The scavenging abilities of $BC_A$ and $BC_C$ were $664.91{\pm}48.87mg$ ascorbic acid equivalent/serving size and $624.36{\pm}16.18mg$ ascorbic acid equivalent/serving size, respectively. The four beverage samples ($BC_A$, $BC_C$, $GT_D$, and $BT_A$) significantly reduced the production of reactive oxygen species (ROS) and intracellular oxidative stress induced by $H_2O_2$. These results suggest that the beverages possess significant radical scavenging ability, which may be due to the presence of antioxidants. Furthermore, the significant reducing level of ROS evidences the potential antioxidant effects of these beverages in human cells.

• 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.31 no.2
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• pp.273-279
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• 1999

Forty plants used as tea materials were chosen for determining the contents of total phenolics, selenium (Se), ${\beta}-carotene$, ${\alpha}-tocopherol$ and ascorbate. Total phenolics and ascorbate contents were analyzed colorimetrically. The Se contents were measured by hydride-atomic absorption spectrometry. The contents of ${\beta}-carotene$ and ${\alpha}-tocopherol$ were simultaneously determined by high performance liquid chromatography using separate detectors, UV for ${\beta}-carotene$ and FL for ${\alpha}-tocopherol$ analyses. The contents of these antioxidants were as follows (per 100 g dry plant); Contents of total phenolics in green tea leaf, black tea leaf, oolong tea leaf and instant coffee were about 7 g and the Se contents in corni fructus and arrowroot were found to be about $4{\mu}g$, which were the highest among all plants used. Contents of ${\beta}-carotene$ in eucommiae cortex, persimmon leaf and green tea leaf were 8587, 6222 and $3652\;{\mu}g$ respectively. The persimon leaf contained the highest ${\alpha}-tocopherol$ content (33 mg) and then followed by eucommiae cortex (26 mg), green tea leaf (16 mg) and black tea leaf (13 mg) in order. Ascorbate contents were found to be high in green tea leaf (199 mg) and black tea leaf (117 mg).

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.1
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• pp.66-71
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• 2008

This study was conducted to predict optimum leaching conditions for functional components of black tea. Two variables were used to determine the optimum leaching temperature and leaching time with a five-level central composite design and response surface methodology. Soluble solid, reducing sugar, total phenolics, and total flavonoid contents increased as leaching temperature and time increased. The ranges of maximum leaching conditions for these components were $78.28{\sim}87.08^{\circ}C$ and $3.97{\sim}4.27min$. Vitamin C level was maximal at $61.29^{\circ}C$ and 2.68 min. Electron donating ability showed the highest values at $68.30^{\circ}C$ and 0.54 min. Based upon the superimposed results, it was predicted that the optimal ranges of leaching conditions for some functional components from black tea were $63{\sim}79^{\circ}C$ for $1.5{\sim}2.1$ min.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.9
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• pp.1134-1139
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• 2007

This study was conducted to investigate the effects of four kinds of tea (Camellia sinensis) extracts on the antioxidant defense systems as well as the activities of alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) in ethanol administered ICR mice. According to the results, treatment with puerh tea significantly increased the superoxide dismutase activity and glutathion reductase activity in liver. In addition, the group treated with oolong tea exhibited higher superoxide dismutase activity and glutathion reductase activity in serum than those of puerh tea, green tea and black tea treated groups. The oolong tea and puerh tea also reduced malondealdehyde contents in both liver and serum. These results suggested that puerh tea and oolong tea were the most effective against alcohol-induced oxidative damage among the Camellia sinensis teas. On the other hand, in the measurement of alcohol break-down enzyme activities, the group treated with green tea exhibited the highest hepatic ADH and ALDH activities, suggesting that the group treated with green tea might be useful for alcohol down-regulation.

• Journal of Food Hygiene and Safety
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• v.38 no.6
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• pp.442-448
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• 2023

This study aimed to prepare kombucha, a fermented tea beverage, containing Dendropanax morbiferus (DM) leaves and roots, and analyze its antioxidant and intracellular activities. We compared the pH change, total acidity, radical scavenging activity, and oxygen radical absorbance capacity (ORAC) of kombucha fermented with black tea alone and that with added DM leaves or roots during fermentation. Using RAW 264.7, we evaluated the effects of kombucha containing different DM parts on nitric oxide (NO) production and inflammation-related cytokine content in cells. Kombucha containing ethanol extracts of DM leaves (BTK-E-DML) and roots (BTK-E-DMR) showed higher radical scavenging activity and ORAC 3 d after fermentation than that prepared from black tea alone (BTK-Ori). In an in vitro experiment using RAW 264.7, samples were treated with 8 mg/mL kombucha considering cytotoxicity; the lipopolysaccharide (LPS)-induced NO content significantly reduced after BTK-E-DML and BTK-EDMR treatments compared with that after BTK-Ori treatment. Additionally, the levels of interleukin-6 and tumor necrosis factor-alpha, which were LPS-stimulated inflammatory cytokines, significantly decreased in cells treated with BTK-E-DML and BTK-E-DMR 15 d after fermentation compared with those treated with BTK-Ori. In conclusion, these results demonstrate that kombucha fermented with the leaves and roots of DM increases antioxidant activity and can significantly regulate inflammatory responses at the cellular level.