• Korean Journal of Food Science and Technology
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• v.39 no.2
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• pp.133-137
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• 2007

The 2,2-diphenyl picrylhydrazyl (DPPH) method, which can be used to predict the oxidative stability of edible oils, was previously reported by our research group. Not only free radical scavenging antioxidants but also radicals from oxidized oils are capable of reacting with DPPH radicals, thereby reducing the absorbance of DPPH. In this study, the optimum sample size of edible oils for the DPPH method was determined, and the oxidation of the edible oils was monitored via DPPH, coupled with other conventional methods. The optimum sample size was determined as 1.5 g using soybean oil. Soybean, corn, virgin olive, and refined olive oils were thermally oxidized for 3 hr at $180^{\circ}C$ and analyzed via DPPH, conjugated dienoic acid (CDA) value, and p-anisidine value (p-AV) protocols. Soybean and corn oils were found to be more sensitive to thermal oxidation than virgin and refined olive oils, on the basis of the CDA value and p-AV measurements. The DPPH method can indicate the inherent radical scavenging activity of unoxidized samples, the time required for the depletion of antioxidants, and the rate of degradation of the antioxidants. The soybean and corn oils evidenced higher levels of free radical scavenging compounds, required more time for the consumption of inherent antioxidants, and also manifested steeper antioxidant degradation rates than olive oils, based on the results of DPPH analysis. The DPPH method, accompanied by other conventional methods, may prove useful in predicting the degree of oxidation of vegetable oils.

• Journal of the Korean Society of Food Science and Nutrition
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• v.21 no.5
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• pp.551-556
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• 1992

To develop natural antioxidant from spices and control thermal oxidation of edible soybean oil, the available antioxidative compounds of various spices were extracted with edible soybean oil. The storage stability of the oil mixed with purified sardine oil and soybean oil containing that extracts at $37^{\circ}C$ were investigated. Furthermore the antioxidative activity of petroleum ether soluble fractions(PESF) obtained from rosemary on the thermal oxidation of edible soybean oil during heating at $180^{\circ}C$ were also investigated. By mixing with refined sardine oil and soybean oil extracts of rosemary, sage of herb spices and mace of seed spices, the oxidative stabilities were remarkably increased. The thermal oxidation of edible soybean oil was also supressed by the addition of 1.0%(w/w) of PESF obtained from rosemary. Rosemary extract exhibited higher antioxidative activity on thermal oxidation of edible soybean oil than butylated hydroxytoluene.

• Journal of Marine Bioscience and Biotechnology
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• v.7 no.1
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• pp.1-10
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• 2015

Bio diesel has advantages to reduce GHG(Greenhouse Gas) compare with the fossil fuel by using oil comes from plant/animal sources and even waste such as used cook oil. The diversity of energy feeds brings the positive effects to secure the national energy mix. In this circumstance, micro-algae is one of the prospective source, though some technical barriers. We analyzed the bio diesel which was derived from Dunaliella tertiolecta LB999 through the BD100 quality specifications designated by the law. From that result, it is revealed that the oxidation stability is one of the properties to be improved. In order to find the reason for low oxidation stability, we analyzed the oxidation tendency of each FAME components through some methods(EN 14111, EN14112, EN16091). In this study, we could find the higher double bond FAME portion, the more oxidative property(C18:1${\ll}C18:3$) in bio diesel and main unsaturated FAME group is acted as the key component deciding the bio diesel's oxidation stability. It is proved experimentally that C18:3 FAME are oxidized easily under the modified accelerated oxidation test. We also figure out low molecular weight hydrocarbon and FAME were founded as a result of thermal degradation. Some alcohol and aldehydes were also made by FAME oxidation. In conclusion, it is necessary to find the way to improve the micro-algal bio diesel's oxidation stability.

• Fisheries and Aquatic Sciences
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• v.18 no.1
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• pp.27-33
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• 2015

Seasoned laver Pyropia spp. is one of the most well-known Korean traditional seafoods, and is becoming more popular worldwide. Various mixed oils are used in the preparation of seasoned laver; however, there is no information available regarding the effects of the blending ratio of oils on the quality of seasoned laver. In this study, the effects of the blending ratio of corn, sesame, and perilla oils on the oxidation and sensory quality of seasoned laver were monitored and optimized using a response surface methodology. An increase in the proportion of corn and sesame oils resulted in an excellent oxidation induction time, whereas a high ratio of perilla oil reduced the thermal oxidative stability of the mixed oil. In the sensory test, the seasoned laver with the highest proportion of sesame oil was preferred. The optimal blending ratio (v/v) of corn, sesame, and perilla oils for both oxidation induction time ($Y_1$) and sensory score ($Y_2$) was 92.3, 6.0, and 1.7%. Under optimal conditions, the experimental values of $Y_1$ and $Y_2$ were $4.41{\pm}0.3h$ and $5.58{\pm}0.8$points, and were similar to the predicted values (4.34 h and 5.13 points). Our results for the monitoring and optimization of the blending ratio provide useful information for seasoned laver processing companies.

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.902-906
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• 1999

Electrically conducting composite films were prepared by a vapor phase in situ polymerization of pyrrole in the methyl cellulose film containing a copper(II) perchlorate. Methylcellulose had high affinity to pyrrole and was used as a matrix polymer. Conducting polypyrrole was embedded in the methylcellulose film forming a conducting network and the conductivity of the composite films ranged $10^{-1}$ to $10^{-7}S/cm$. The conductivities of conducting composite films were dependent on the nature of the matrix polymers, concentration of oxidant and polymerization time. In situ polymerization of pyrrole was observed in the matrix polymer and confirmed by UV-vis spectra. From the results of the thermogravimetric analysis, the chemical oxidative polymerization of pyrrole in the matrix polymers did not give any negative effects on the thermal stability of the composite films. Electron micrograph of composites indicated good penetration of PPy in the matrix polymer. DMA suggested a certain degree of incompatibility of the polypyrrole in the composites.