• Korean Journal of Agricultural Science
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• v.38 no.2
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• pp.295-299
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• 2011

The content of hesperidin in the mixed tea, which was composed of dried orange peel, laurel leaf, mulberry leaf, silver magnolia leaf, oriental melon tap, cassia seed, and licorice root, was determined by high performance liquid chromatography (HPLC). Hesperidin was quantified by a reverse phase column with gradient solvent system (watcr:acetonitrile = 80:20 to 35:65 for 30 min) and UV/VIS detection (280 nm). The How rate was kept constant at 1.0 ml/min. The content of hesperidin in the mixed tea was measured in depending on extraction time 1, 2, 3, and 4 min (29.07, 52.39, 52.45, and 88.35 mg/g, respectively).

• 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.

• Korean Journal of Food Science and Technology
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• v.51 no.4
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• pp.356-360
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• 2019

To evaluate antioxidant capacities and total phenolic, flavonoid, and catechin contents of pure green tea packaged in tea bags, green tea bags of 10 commercial brands were purchased and analyzed. Considering commonly used infusion methods, green tea bags were extracted using 150 mL of spring water at $70^{\circ}C$ for 2 min. Ten brands of green tea showed a wide range of total phenolic content (46.3-93.9 mg gallic acid equivalents/g), total flavonoid content (10.3-21.7 mg catechin equivalents/g), and antioxidant capacities (88.8-175.6 mg and 87.9-183.5 mg vitamin C equivalents/g for DPPH and ABTS assays, respectively). Total catechin content of green tea ranged from 33.8-74.7 mg/g, which corresponded to 43.0-108.3 mg/150 mL of cup. Collectively, these results suggest that daily consumption of 3.8-12.5 cups of green tea packaged in tea bags meets the recommended daily intake of catechins in green tea extract as a health functional foods in Korea.

• Journal of Nutrition and Health
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• v.6 no.3
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• pp.17-20
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• 1973

Quantitative analysis was achieved by gas-liquid chromatographic method (GLC) with a single column system of OV-17 for 16 of free amino acids in Korean green tea and the contents of mineral in it was determined by atomic absorption flame emission. The results are summarized as follows: 1) Korean green tea contained Mn 1% or over out of the total ash content and $0.05{\sim}0.20%$ in the water extraction, as the major mineral. 2) Ba, Cr, Ni, Pb and V were analyzed also by small quantities relatively and Co, Tin and Ywere not detected in the water extraction. 3) GLC indicated the presence of 16 components in free ammo acids. 4) The quantities of free amino acids in Korean green tea were determined $2.96{\sim}6.61%$ Alanine, $1.01{\sim}l.89mg%$ Glycine, $2.07{\sim}7.81mg%$ Valine, $1.27{\sim}8.76mg%$ Leucine and Isoleucine, $94.31{\sim}316.27mg%$ Threonine, $9.10{\sim}39.91mg%$ Serine, $2.18{\sim}36.76mg%$ Hydroxyproline, $2.72{\sim}5.90mg%$ Proline, $39.64{\sim}70.02mg%$ Aspartic Acid, $25.93{\sim}101.28mg%$ Glutamic Acid and Lysine, $8.32{\sim}18.30mg%$ Phenylalanine and Tyrosine in trace amount. 5) The total free amino acid contents in Korean green tea ranged from 207.24mg% to 516.06mg% and Moo-Deoung tea contained outstandingly high, 516 mg% or over.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.1
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• pp.56-64
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• 2010

A system design has been conducted of the liquid rocket engine for Korean launch vehicle (KSLV-II, Korea Space Launch Vehicle II). The present turbopump-fed liquid rocket engine of vacuum thrust 76 ton and vacuum specific impulse 297 sec adopts gas generator cycle. The combustion pressure of the regeneratively cooled combustor is 60 bar. The propellant is LOx/kerosene. The engine is started by pyrostarter and the combustor is ignited by TEA (TriEthylAluminium). The engine system performance and the subsystems performance requirements are given through energy balance analysis. The combustion pressure, specific impulse and the engine mass are analyzed to be reasonable comparing with the published data. The startup analysis method which will be used in the future has been validated against the turbopump-gas generator coupled test. The tuning method for performance variation of the engine which is not actively controled has been prepared by mode analysis and performance deviation analysis.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.139-143
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• 2003

Study on the ignition characteristics of combustor and gas generator for LOx-kerosene liquid rocket engine was performed experimentally through a series of combustion tests of sub-scale engine combustor and gas generator. Characteristic of gas-torch ignitor based on gaseous methane and gaseous oxygen was compared with hypergolic ignition using propellant tri-ethyl-aluminium. Gas-torch ignitor showed good performance on igniting sub-scale liquid rocket engine combustor and gas generator. It was observed that the ignition delay is also affected by the extent of nitrogen in the combustion chamber.

• Journal of ILASS-Korea
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• v.9 no.4
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• pp.1-8
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• 2004

Breakup characteristics of liquid sheets formed by the impingement of two water jets, such as a breakup length and a breakup wavelength of sheet, were investigated as increasing the injection velocity up to 30m/s and the ambient gas pressure up to 4.0MPa. While round edged orifices formed a laminar sheet which has no waves on the sheet when the injection velocity is low, sharp edged orifices formed a turbulent sheet which has impact waves irrespective of the injection velocity. Thus we compared the differences of breakup characteristics between them. The results showed that the aerodynamic force significantly affects the breakup of laminar sheet when the gas based Weber number is higher than unity, It was also found that the turbulent sheets have three breakup regimes, i.e. expansion regime, wave breakup regime and catastrophic breakup regime according to the gas based Weber number.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1060-1060
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• 2017

• Journal of the East Asian Society of Dietary Life
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• v.13 no.6
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• pp.586-592
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• 2003

This research used High Performance Liquid Chromatography(HPLC) to analyze and compare the content and the pattern of chlorophyll to find the difference in quality, water temperature, and the stirring time between the three different types of Korean and Japanese powder green tea, which were currently on the market. Chlorophyll contents of Japanese-made medium quality tea (S5: 8.34mg/g), and low quality tea (S6: 8.23mg/g) were relatively high, and that of Korean-made medium quality tea (S2 ; 4.87mg/g) was lower. The water temperature of 85$^{\circ}C$ and 95$^{\circ}C$ were high except in Korean-made medium and low quality powder green tea (S2 and S3). Japanese-made powder tea required 60 seconds of stirring time and Korean-made tea required 15 seconds, but 30 seconds seem to be the ideal stirring time for both of them. Chlorophyll a, b, pheophytin a, b, and pheophorbide were confirmed from the chlorophyll pattern. There were 1.5∼2 times more of chlorophyll a in Japanese-made one compared to that of Korean-made one; also 1.5∼2 times more of pheophytin a in Korean-made one than Japanese-made one. It might be concluded that Japanese-made powder green tea was higher in quality.

• Journal of Food Hygiene and Safety
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• v.32 no.5
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• pp.389-395
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• 2017

A simultaneous determination of 5 phenolic acids (gallic acid, chlorogenic acid, caffeic acid, pcoumaric acid, trans ferulic acid) and 9 flavonoids (procyanidin b1, aspalathin, rutin, vitexin, hyperoside, isoquercitrin, luteolin, quercetin, chrysoeriol) in rooibos tea has been carried out by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). A validated analysis method in this study was applied to rooibos aqueous infusions. Rooibos tea is an antioxidant-rich tea which has anti-cancer, anti-aging, anti-inflammatory, anti-diabetic effect. Extraction yield of phenolics depends on steeping time and temperature of water. Tea infusions were prepared by placing 1 g of tea leaves or 1 tea bag in 100 mL of boiled water, and then at 3, 6 and 30 minutes intervals the infused teas were taken to carry out the analysis of phenolic contents. Another tea infusion was conducted with cold water ($25-30^{\circ}C$) for 30 minuntes. As a result, the total amount of phenolics was highest in rooibos tea steeped with hot water for 30 minutes, followed by 6 minutes, 3 minutes and cold water 30minutes and the result has statistical significance.