• 한국식품과학회지
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• 제54권3호
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• pp.272-279
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• 2022

본 연구에서는 감광제에 의한 폴리페놀의 갈변 정도 및 폴리페놀 함량의 변화와 산화방지활성과 ROS 생성을 분석하였다. 그 결과 감광제에 의해 갈산과 타닌산의 자동산화가 현저히 가속화 되었으며, 타닌산에서 그 효과가 더욱 두드러졌다. 폴리페놀 함량은 산화가 진행됨에 따라 유의적으로 감소하였으나, 감광제에 농도에 의한 유의적인 차이는 EB에 의해서만 나타났으며, ABTS 라디칼 소거능 변화에서도 유사한 양상을 보였다. 갈산과 타닌산에서 ROS 생성의 증가는 명소에서 감광제 존재 하에 농도 유의적으로 증가하였다. 본 연구 결과는 폴리페놀이 감광제와 함께 빛에 노출 시 폴리페놀의 산화를 촉진시키며, 식품의 가공 및 저장 시 이들의 상호작용을 통한 품질저하 및 생리활성 변화에 주의할 필요가 있음을 시사한다.

• 융합정보논문지
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• 제11권5호
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• pp.223-231
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• 2021

유산균에 의한 감국 추출물(CIL)의 항산화능의 변화를 알아보기 위해 64%, 80% ethanol 로 추출한 농도별 CIL를 발효시켜 total phenolic contents (TPC), flavonoid, 2,2-diphenyl-1-picrylhydrazyl (DPPH), reducing power (RP), linoleic acid 자동산화 저해활성의 변화를 확인해 보았다. TPC의 경우 3109, 3237에서 증가하였으며, flavonoid에서는 모든 균주에서 감소를 나타냈다. DPPH 측정에서는 64% CIL 발효 후 3074, 3109에서 증가하였으며, 80% CIL 발효에서는 모든 균주가 증가를 나타냈다. RP측정에서는 64%, 80% CIL에서 모든 균주에서 증가를 보였으며, linoleic acid 자동산화 저해활성에서는 모든 균주에서 감소를 나타냈다. 특히 3109 항산화능을 평가하는 DPPH와 RP 측정에서 다른 균주에 비해 전반적으로 높게 측정이 되었다. 결과적으로 4종의 유산균 중에서 3109가 발효과정을 통해서 CIL의 항산화 효능을 효과적으로 증대하는 것을 확인할 수 있었다.

• 대한화장품학회지
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• 제31권2호
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• pp.153-159
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• 2005

본 연구는 한방제제의 구성 약재인 마황이라는 천연한방소재로부터 미백효과가 있는 화장품 원료를 개발하고자 하였다. 본 실험에서 마황추출물의 tyrosinase 억제 효과를 확인하고 마황추출 과정을 세분화하여 methylene chloride 및 물분획물을 얻었으며 이들을 가지고 다시 tyrosinase 억제 실험을 실시하였다. 그 결과 수층부분에서만 $0.2\%$ 농도에서 $60.6\%$의 tyrosinase 억제 효과를 보여주었으며 이후 수층부분만을 농축하여 L-DOPA 산화억제 실험 및 B-16 melanoma를 이용한 미백 실험을 실시하였다. 그 결과 마황추출물 $0.5\%$ 농도에서 $87\%$의 L-DOPA 산화억제 효과를 보여주었으며, $0.75\%$에서는 $98.8\%$의 억제효과를 보여주었다. 또한 B-16 melanoma에서는 $0.05\%$에서 $70.2\%$, $0.075\%$에서는 $79.9\%$의 억제효과를 보여주었다. 그리고 수층부분만을 농축한 마황추출물의 in vivo상에서의 미백 효과를 검증하기 위하여 마황추출물 $0.5\%$를 함유한 제형으로 미백 임상실험을 실시하였다. 그 결과 마황추출물을 함유한 제형에서 10주 경과 후에 육안 및 기기평가 모두에서 미백효과를 보여주었으며 통계적으로도 유의한 차이(p<0.05)를 보여주었다.

• 한국자동차공학회논문집
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• 제17권3호
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• pp.81-89
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• 2009

In this experimental study, the effects of clean alternative fuels compatible with diesel combustion on nano-sized particle emission characteristics were investigated in a 0.5L auto-ignited single-cylinder engine with a compression ratio of 15. Because the number concentration of nano-sized particles emitted by automotive engine, that are suspected of being hazardous to human health and environment, might increase with engine fuel considerably and recently attracted attention. So a ultra-low sulfur diesel(ULSD), BD100(100% bio-diesel) and Di-Methyl Ether(DME) fuels used for this study. And, as a particle measuring instrument, a fast-response particle spectrometer (DMS 500) with heated sample line was used for continuous measurement of the particle size and number distribution in the size range of 5 to 1000nm (aerodynamic diameter). As this research results, we found that this measurements involving the large proportion of particles under size order of 300nm and number concentration of $4{\times}10^9$ allowed a single or bi-modal distribution to be found at different engine load conditions. Also the influence of oxygen content in fuel and the catalyst could be a dominant factor in controlling the nano-sized particle emissions in auto-ignited engine.

• Tribology and Lubricants
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• 제31권6호
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• pp.258-263
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• 2015

Biodiesel is an environmentally-friendly fuel with low smoke emission because it contains about 10% oxygen. Biodiesel fuel prepared by transesterification of vegetable oil or animal fats is susceptible to auto-oxidation. The rate of auto-oxidation depends on the number of methylene double bonds contained within the fatty acid methyl or ethyl ester groups. Biodiesel may be easily oxidized under several conditions, i.e., upon exposure to sunlight, temperature, oxygen environment. Maintenance of the fuel quality of biodiesel requires the development of technologies to increase the resistance of biodiesel to oxidation. Treatment with antioxidants is a promising approach for extending the shelf-life or storage time of biodiesel. The chemical properties of various amine-based antioxidants were evaluated after synthesis of the antioxidants by condensation of phenylenediamine with alkylamines at room temperature. In general, the oxidative stability can be assessed based on various experimental parameters. Such parameters may include temperature, pressure, and the flow rate of air through the samples. The Rancimat method (EN14112) was selected because it is a rapid technique that requires very little sample and provides good precision for oxidative degradation analysis. Specifically, the EN 14112 technique provides enhanced efficiency for oxidative stability evaluation when a larger ester head group is utilized. Therefore, this technique was employed for evaluation of the oxidation stability of biodiesel by the Rancimat method (EN14112).

• Food Science and Biotechnology
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• 제16권6호
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• pp.981-987
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• 2007

Effects of lignan compounds (sesamol, sesamin, and sesamolin) extracted from roasted sesame oil on the autoxidation at $60^{\circ}C$ for 7 days and thermal oxidation at $180^{\circ}C$ for 10 hr of sunflower oil were studied by determining conjugated dienoic acid (CDA) contents, p-anisidine values (PAV), and fatty acid composition. Contents of lignan compounds during the oxidations were also monitored. ${\alpha}$-Tocopherol was used as a reference antioxidant. Addition of lignan compounds decreased CDA contents and PAY of the oils during oxidation at $60^{\circ}C$ or heating at $180^{\circ}C$, which indicated that sesame oil lignans lowered the autoxidation and thermal oxidation of sunflower oil. Sesamol was the most effective in decreasing CDA formation and hydroperoxide decomposition in the auto- and thermo-oxidation of oil, and its antioxidant activity was significantly higher than that of ${\alpha}$-tocopherol. Sesamol, sesamin, and sesamolin added to sunflower oil were degraded during the oxidations of oils, with the fastest degradation of sesamol. Degradation of sesamin and sesamolin during the oxidations of the oil were lower than that of ${\alpha}$-tocopherol. The results strongly indicate that the oxidative stability of sunflower oil can be improved by the addition of sesamol, sesamin, or sesamolin extracted from roasted sesame oil.

• 한국식품과학회지
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• 제43권3호
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• pp.255-262
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• 2011

본 연구에서는 비발아들깨와 12, 36, 48시간 발아시킨 들깨로 부터 유지를 추출한 후 $60^{\circ}C$의 빛이 차단된 상태 또는 빛의 존재 하에 4일 동안 저장하면서 가속조건에서의 유지 산화 및 토코페롤 안정성을 평가하였다. 들깨유의 과산화물값과 공액이중산 값은 저장기간이 증가함에 따라 유의하게 증가하였으며, 비발아 들깨유에 비해 발아들깨유에서 낮은 경향을 보였다. 또한 빛이 차단된 조건에 비해 빛 존재 하에서 들깨유의 산화와 토코페롤 분해가 더 많이, 더 빨리 진행되었다. 들깨유 중 12시간 발아시킨 들깨로부터 추출한 들깨유는 유의하게 낮은 공액이중산값과 토코페롤의 낮은 분해속도 등에 기인하여 가장 높은 자동산화, 광산화 안정성을 보여주었다.

• 한국응용과학기술학회지
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• 제40권5호
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• pp.1163-1175
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• 2023

Cholesterol is prone to oxidation, which results in the formation of cholesterol oxidation products (COPs). This occurs because it is a monounsaturated lipid with a double bond on C-5 position. Cholesterol in foods is mostly non-enzymatically oxidized by reactive oxygen species (ROS)-mediated auto-oxidative reaction. The COPs are found in many common foods of animal-origin and are formed during their manufacture process. The formation of COPs is mainly related to the temperature and the heating time the food is processed, storage condition, light exposure and level of activator present such as free radical. The level of COPs in processed foods could reach up to 1-10 % of the total cholesterol depending on the foods. The most predominant COPs in foods including meat, eggs, dairy products as well as other foods of animal origin were 7-ketocholesterol, 7 α-hydroxycholesterol (7α-OH), 7β-hydroxycholesterol (7β-OH), 5,6α-epoxycholesterol (5,6α-EP), 5,6β-epoxycholesterol (5,6β-EP), 25-hydoxycholesterol (25-OH), 20-hydroxycholesterol (20-OH) and cholestanetriol (triol). They are mainly formed non-enzymatically by cholesterol autoxidation. The COPs are known to be potentially more hazardous to human health than pure cholesterol. The procedure to block cholesterol oxidation in foods should be similar to that of lipid oxidation inhibition since both cholesterol and lipid oxidation go through the same free radical mechanism. The formation of COPs in foods can be stopped by decreasing heating time and temperature, controlling storage condition as well as adding antioxidants into food products. This review aims to present, discuss and respond to articles and studies published on the topics of the formation and inhibition of COPs in foods and key factors that might affect cholesterol oxidation. This review may be used as a basic guide to control the formation of COPs in the food industry.

• 방사성폐기물학회지
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• 제16권4호
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• pp.411-420
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• 2018

공기 분위기하 $UO_2$의 독특한 산화거동을 모사하기 위해 기존 Crackling Core Model (CCM)을 개선하였다. $UO_2$가 $U_3O_8$으로 전환될 때 시간-전환율 곡선에서 나타나는 실험적 sigmoid 거동을 근사하게 재현할 수 있도록 모델 개선에 파편화 효과로 인한 반응 표면적 증대 및 결정립 가변 전환시간 개념을 고려하였다. $UO_2$는 $U_3O_7$을 거쳐 $U_3O_8$으로 전환되며 최종 결정립 산화소요 시간은 초기 결정립 산화 소요 시간의 10배에 해당한다는 가정을 도입했을 때, 개선된 모델은 599 - 674 K에서의 $UO_2$ 구형 입자의 실험적 산화거동과 근사한 계산결과를 나타내었으며 핵종성장모델(Nucleation and Growth Model) 및 자촉매반응모델(AutoCatalytic Reaction Model)과 비교할 때 가장 작은 오차를 보여주었다. 개선된 모델을 통해 $U_3O_8$으로의 100% 전환시 계산된 활성화에너지값은 $57.6kJ{\cdot}mol^{-1}$로 자촉매반응모델로 계산된 값인 $48.6kJ{\cdot}mol^{-1}$보다 크며, 외삽에 의해 결정된 실험값에 더 근사함이 밝혀졌다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
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• pp.64-68
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• 2005

Methane reforming processes to obtain hydrogen were investigated experimentally by using atmospheric plasma source. Among possible reforming processes, such as a $CO_2$ reforming(dry reforming), a partial oxidation (POx), a steam reforming(SR), and a steam reforming with oxygen(SRO or auto-thermal reforming), partial oxidation and the steam reforming with oxygen were considered. We choose a rotating arc plasma as an atmospheric plasma source, since it shows the best performances in our preliminary tests in terms of a methane conversion, a hydrogen production, and a power consumption. Then, the effects of a feeding flow-rate, an electrical power input to a plasma reaction, an $O_2/C$ ratio and a steam to carbon ratio in the case of SRO on the reforming characteristics were observed systematically. As results, at a certain condition almost 100% of methane conversion was obtained and we could achieve the same hydrogen production rate by consuming a half of electrical power which was used by the best results for other researchers.