• Title/Summary/Keyword: Stability of oxidation

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Effect of Soybean Lecithin on the Thermal Oxidation of Tocopherol in Blended Oil (혼합유중(混合油中) Tocopherol의 열산화(熱酸化)에 미치는 대두(大豆) Lecithin의 효과(效果))

  • Chang, Hyun-Ki
    • Journal of the Korean Applied Science and Technology
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    • v.10 no.2
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    • pp.1-6
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    • 1993
  • The blended oil was prepared from cottonseed oil and palm olien. The oxidative stability of blended oil after the addition of natural tocopherol and soybean lecithin during heating was investigated and the effects of lecithin were evaluated. The result obtained were as follows: 1. When the concentration of palm olein in blended oil during heating was increased, the oxidative stability was improved. 2. By both addition of natural tocopherol and soybean lecithin during heating in blended oil, induction period was considerably increased and residual ratio of tocopherol was high. 3. The oxidative stability of potato chips prepared from blended oil was higher in the prsence of lecithin than in the absence of it.

Oxidative Stability of Tocopherols on Korean Sesame oil and chinese Sesame oil (한국산 참깨기름과 중국산 참깨기름의 토코페롤 산화안정성)

  • 신묘란;주광지
    • Journal of the East Asian Society of Dietary Life
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    • v.4 no.2
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    • pp.51-57
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    • 1994
  • Six sesame oils prepared from Korean and Chinese sesame were oxidized at 40$^{\circ}C$ for 16 weeks in a dark place. Effects of oxidative stability on tocopherols of those sesame oils were studied in related to chemical changes in the oils. All oil samples showed that the rate of tocopherol reduction was increased by the storage time. The changes of peroxide value, free fatty acid, carbonyl content were not caused in direct relation to the tocopherols oxidation. The amount of total tocopherol in the Korean sesame oil ranged from 48.7-50.3mg/100g and Chinese seseame oil ranged from 42.4-44.7 mg/100g According to the three individual tocopherols remaining content after 16weeks, ${\gamma}$-,${\alpha}$-,${\beta}$- tocopherol showed 70%, 30%, 20% of initial concentrations in the oils respectively. There was no significant difference between Korean and Chinese sesame oil except the higher total amount of the tocopherol in Korean sesame oil than that of Chinese.

Effect of Glutamic Acid and Monosodium Glutamate on Oxidative Stability of Riboflavin Photosensitized Oil-in-Water Emulsion

  • Ji-Yun Bae;Mi-Ja Kim
    • The Korean Journal of Food And Nutrition
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    • v.37 no.1
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    • pp.48-56
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    • 2024
  • Effects of glutamic acid (Glu) and monosodium glutamate (MSG) on oxidative stability of oil-in-water (O/W) emulsions with different emulsifier charges during riboflavin (RF) photosensitization were evaluated by analyzing headspace oxygen content and conjugated dienes. Cetyltrimethylammonium bromide (CTAB), Tween 20, and sodium dodecyl sulfate (SDS) were used as cationic, neutral, and anionic emulsifiers, respectively. Glu acted as an antioxidant in CTAB- and Tween-20-stabilized O/W emulsions during RF sensitization, whereas Glu acted as prooxidants in SDS-stabilized O/W emulsions in the dark. However, adding MSG did not have a constant impact on the degree of oxidation in O/W emulsions irrespective of the emulsifier charge. In RF-photosensitized O/W emulsions, the emulsifier charge had a greater influence on antioxidant properties of Glu than on those of MSG.

Effect of Cobalt Loading on the Performance and Stability of Oxygen Reduction and Evolution Reactions in Rechargeable Zinc-air Batteries

  • Sheraz Ahmed;Joongpyo Shim;Gyungse Park
    • Journal of the Korean Chemical Society
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    • v.68 no.2
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    • pp.87-92
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    • 2024
  • The commercialization of rechargeable metal-air batteries is extremely desirable but designing stable oxygen reduction reaction (ORR) catalysts with non-noble metal still has faced challenges to replace platinum-based catalysts. The nonnoble metal catalysts for ORR were prepared to improve the catalytic performance and stability by the thermal decomposition of ZIF-8 with optimum cobalt loading. The porous carbon was obtained by the calcination of ZIF-8 and different loading amounts of Co nanoparticles were anchored onto porous carbon forming a Co/PC catalyst. Co/PC composite shows a significant increase in the ORR value of current and stability (500 h) due to the good electronic conductive PCN support and optimum cobalt metal loading. The significantly improved catalytic performance is ascribed to the chemical structure, synergistic effects, porous carbon networks, and rich active sites. This method develops a new pathway for a highly active and advantageous catalyst for electrochemical devices.

Performance of Automotive Wheel Bearing Grease by Water Contents (수분함량에 따른 자동차용 휠베어링 그리스 품질특성 연구)

  • Lim, Young-Kwan;Lee, Eun-Hee;Lee, Joung-Min;Jeong, Choong-Sub
    • Tribology and Lubricants
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    • v.27 no.5
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    • pp.275-280
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    • 2011
  • Automotive wheel bearing grease helps to reduce stresses and prevent wear of wheel bearings. But it is easily contaminated by water and other contaminants. In this study, we investigated the property change of automotive wheel bearing grease under water contamination. The result showed that some properties such as dropping point, work penetration and oxidation stability were not influenced by water content. However, most of properties such as work stability, water washout characteristics, leakage tendency, oil separation, evaporation loss and rust protection became worse after water was added. This is thought that added water makes the interaction weak between thickener and base oil of grease.

Effect of Storage Conditions on Quality Stability of Dried Laver(Porphyra tenera) (건조김의 품질 안정성에 미치는 저장 조건의 영향)

  • 조길석
    • Food Science and Preservation
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    • v.10 no.1
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    • pp.32-36
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    • 2003
  • Quality stability of the dried layer Porphyra tenera depending on various light sources, water activities, packaging materials and storage temperatures were investigated by peroxide value and chlorophyll degradation. Major fatty acids of dried layer were 45.7% eicosapentaenoic acid and 13.6% palmitic acid. Quality stability was increased in order of darkness, incandescent and fluorescent increased sharply with the decrease of water activity and temperature, and also improved by the packaging material with strong barriers of water vapor, oxygen and light.

Synthesis and Characterization of Lithium Dual Complex Grease (Lithium Dual Complex 그리이스의 합성 및 특성연구)

  • 최웅수;권오관;문탁진;유영홍
    • Tribology and Lubricants
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    • v.1 no.1
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    • pp.80-87
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    • 1985
  • Lithium dual complex grease was prepared through the second continuous saponification reaction of a complex gellant system whose essential components comprised of a selected hydroxy fatty acid, lithium hydroxide monohydrate and boric acid to have a fiber structure of chemical, thermal and mechanical stability at high temperatures. An optimum amount of complex gellant was found to be 14% (NLGI #2), and an addition of castor wax of 1.5% provided an excellent performance properties, especially. The oil separation, oxidation stability, water wash-out property, shear stability, extreme pressure and wear property of thus prepared were tested by the ASTM and KS methods, and a characteristic result was obtained.

Changes of Fatty Acid Composition and Oxidation Stability of Edible Oils with Frying Number of French Fried Potatoes (감자튀김 횟수에 따른 식용유지의 산화 안정성 및 지방산 조성 변화)

  • Lee, Jin-Won;Park, Jang-Woo
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.39 no.7
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    • pp.1011-1017
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    • 2010
  • Sunflower oil (SO), canola oil (CO) and frying oil (FO) were used as edible oils in this study. According to the frying number, the extracted oils from French fried potatoes were used as experimental samples. To investigate the relationship between the change of fatty acid composition and the stability of the lipid oxidation during frying, the changes of fatty acid composition and the degree of the lipid oxidation of samples were examined. Acid values and peroxide values were evaluated as the degree of lipid oxidation. The acid values of CO and FO were increased with the frying times. The increased acid values of CO and FO were 0.20 and 0.17 on the basis of initial value at 30 times, respectively, but the acid value of SO was lower than those of CO and FO. The peroxide values of the samples were not increased uniformly with the frying number. As the number of frying times was increased, the fatty acid composition of SO and FO were changed. Namely, the oleic acid composition was decreased, whereas the linoleic acid composition was increased with the number of frying times. The benzo(a)pyrene contents of the extracted oils from French fried potatoes did not change regularly as the frying times was increased.

Comparison of the As(III) Oxidation Efficiency of the Manganese-coated Sand Prepared With Different Methods (망간코팅사 종류별 독성 3가 비소의 산화특성에 관한 비교 연구)

  • Kim, Byeong-Kwon;Lim, Jae-Woo;Chang, Yoon-Young;Yang, Jae-Kyu
    • Journal of Soil and Groundwater Environment
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    • v.13 no.2
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    • pp.62-69
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    • 2008
  • In this study physicochemical characteristics and stability of various manganese coated sands (MCS) prepared with different methods were evaluated. In addition, removal efficiencies of As(III) by each MCS were compared. Four different MCSs were used; B-MCS prepared by baking method, W&D-MCS prepared by wetting and dry method, NMCS prepared during the water treatment process and Birm which is a commercial MCS widely used for the removal iron and manganese. The manganese content in each MCS was following order: Birm (63,120 mg/kg) > N-MCS (10,400 mg/kg) >W&D-MCS (5,080 mg/kg) > B-MCS (2,220 mg/kg). Birm showed the least solubility (% basis) in acidic conditions. As(III) oxidation efficiency of B-MCS was continuously increased as the solution pH decreased. While As(III) oxidation efficiency of N-MCS and Birm was minimum around neutral pH. The increased As(III) oxidation efficiency above neutral pH for N-MCS and Birm could be due to the competitive adsorption of $Mn^{2+}$, which was produced from reduction of $MnO_2$, onto the surface of aluminum and manganese oxides.

Studies on the Variation of Physico-Chemical Characteristics During Storage and Frying (고추씨 기름의 저장 및 가열에 따른 이화학적 변화에 관한 연구)

  • Choi, Young-Jin;Ko, Young-Su
    • Korean journal of food and cookery science
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    • v.6 no.2
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    • pp.67-76
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    • 1990
  • To observe the propability as the frying oil and oxidative stability of red pepper seed oil, some physico-chemical tests of the oil were examined during 21 days storage period at 5$^{\circ}C$, 15$^{\circ}C$ and 30$^{\circ}C$, and AOM value determined and after heating the oil at 180${\pm}$5$^{\circ}C$ for 40 hours with or without antioxidants. The analysis storage stability of red pepper seed oil showed that the quality of storage group at 5$^{\circ}C$ was almost as good as fresh oil, and the storage group at 30$^{\circ}C$ showed certain degree of rancidity. Change of physico-chemical characteristic during storage were so small so that storage stability of red pepper seed oil was found to be good. AOM stability of red pepper seed oil was 7 hours which is lower than other vegetable oil, but the degree of stability grew greatly after adding phenolic antioxidants, such on TBHQ or PG. As for the chemical change after heating continuously for 40 hours, acid value, peroxide value and refractive index increased, but iodine value decreased as the heating processed. The fatty acid composition also showed the remarkable reduction of linoleic acid. The addition of antioxidants resulted in the delay of oxidation, the degree of which was greater in TBHQ than in PG.

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