• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.4
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• pp.271-282
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• 1982

The browning development, mainly through the Maillard reaction, occurring in the dried fish meat products during storage causes reduction of the nutritional value due to the loss of the essential amino acid such as available lysine as well as off -flavor resulting in the deterioration of the food quality thus shortening the shelflife. In the work, the changes in the amount of available lysine, extractable nitrogenous compounds (nonprotein-N, amino-N, trimethylamine oxide, trimethylamine, and free lysine) and development of browning were measured to assess the relationship between the shelflife and the quality loss in dried filefish under the steady state conditions (35,45, and $55^{\circ}C;a_{w}'s$ of 0.44 0.52, 0.65 and 0.75 at each temperature) and fluctuating temperature condition of $35/55^{\circ}C$ will. alternating 7 day periods at each water activity. The results indicated that the amount of available lysine and extractable nitrogenous compounds except TMA decreased rapidly with increasing temperatures and water activities while the rate of available lysine and extractable nitrogenous compounds must be involved in the initial stage of brown pigment formation. The available lysine loss of the dried filefish products stored under the fluctuating temperature conditions was greater than that stored under its fixed mean temperature, $45^{\circ}C$. The activation energies for lysine loss obtained from the Arrhenius plot ranged 6.9 to 4.4 Kcal/mol and $Q_{10}$ values at $40^{\circ}C$ were 1.4 to 1.2. The values for browning were 15.7 to 14.4 Kcal/mol and 2.2 to 2.0 respectively. Shelf-life, defined as the time to reach 0.15 O. D./g solid or the limit of off-color deterioration by browning reaction, was extented longer than the halflife of Iysine loss, actually corresponding $75\%$ loss of available lysine. This suggested that the halflife of lysine loss might not be adequate to assess the shelf-life of the food system with high potential of protein, nonproteinous nitrogen compounds, and lipids.

• Journal of the Korean Society of Food Science and Nutrition
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• v.20 no.6
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• pp.609-614
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• 1991

Thermal stability and quality change during storage of red pepper oleoresin were studied. Upon heat treatment, carotenoids in oleoresin from red pepper were more stable under nitrogen than air. In the thermal stabilities, the presence of air at $100^{\circ}C$ for 3 hours and 10 hours were 69.1% and 42.3%, respectively ; whereas, in the presence of nitrogen, 95.4% and 92.3%, respectively. In contrast, capsaicin was comparatively stable upon heat treatment in the presence of air. The retentions of capsaicin at $100^{\circ}C$ for 3 hours and 10 hours were 84.7% and 81.3% with air, those were 90.7% and 87.5% with nitrogen, respectively. Color appearance showed close relation to the stability of total carotenoids during 60 days storage at varying temperatures ; $5^{\circ}C,\;25^{\circ}C\;and\;40^{\circ}C$ were 69.4%, 48.0% and 35.1%, respectively. The degradation of total carotenoids during storage could be interpreted as a first order reaction. The activation energy obtained from the Arrhenius plot was 5.03 kcal/mole. Conversely, capsaicin was very stable under storage temperatures. More than 90% of capsaicin was remained upon completion of storage. In the mean time, pH of oleoresin was increased slightly as increasing storage temperatures.

• Journal of the Korean Society of Food Science and Nutrition
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• v.17 no.3
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• pp.226-232
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• 1988

Non-enzymatic browning is a carbohydrate dehydration reaction, accelerated thorough the interaction of amino compounds. Reaction depends on several factors including temperature, reactant concentration, pH, water activity and specific ion concentrations, and result in progressive development of brown pigments in the affected food systems. The present study was designed to utilize a kinetic approach to analyze the effect of temperature and water activity on the browning development in green ten. The green tea was controlled at aw of 0.33, 0.44, 0.52 and 0.65 using saturated salt solutions and then stored at 35,45 and $55^{\circ}C$. Author portion of the sample of which the water activities were controlled in the same manner was stored at 35 and $55^{\circ}C$ alternately with 7 days interval. Simplified kinetic models were used to obtain the various kinetic parameters for browning development in green tea subjected to accelerated shelf-life tests(ASLT). The reaction of browning development was zero order. The activation energies calculated from Arrhenius plot ranged $1.5{\sim}2.4kcal/mole$ and $Q_{10}$ values were between 1.07 and 1.12. These kinetic parameters were then used to predict browning development under the nonsteady storage. Assessed from the parameters the shelf-lives at $25^{\circ}C$, the time to reach 1.02 O.D./g solid at which severe brown color change could be detectable, ranged 57 to 113 days and showed decrease with increase in aw. The predicted shelf-lives at different water activities were a little higher than actual values.

• Clean Technology
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• v.21 no.1
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• pp.53-61
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• 2015

In this study, we have investigated the kinetics on the char-CO₂ catalytic gasification reaction. Thermogravimetric analysis (TGA) experiments were carried out for char-CO₂ catalytic gasification of an Indonesian Kideco sub-bituminous. Na₂CO₃ and K₂CO₃ were selected as catalysts which were physically mixed with coal. The char-CO₂ catalytic gasification reaction showed a rapid increase of carbon conversion rate at 850 ℃, 60 vol% CO₂, and 7 wt% Na₂CO₃. At the isothermal conditions ranging from 750 ℃ to 900 ℃, the carbon conversion rates increased as the temperature increased. Four kinetic models for gas-solid reaction including the shrinking core model (SCM), random pore model (RPM), volumetric reaction model (VRM), and modified volumetric reaction model (MVRM) were applied to the experimental data against the measured kinetic data. The gasification kinetics were suitably described by the MVRM for the Kideco sub-bituminous. The activation energies for each char mixed with Na₂CO₃ and K₂CO₃ were found 55-71 kJ/mol and 69-87 kJ/mol.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.2
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• pp.89-97
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• 2010

$Al_2O_3$, $TiO_2$, $ZrO_2$, $Al_2O_3-TiO_2$, $Al_2O_3-ZrO_2$, 및 $TiO_2-ZrO_2$ 혼합 산화물을 지지체로 한 Ni 기반 혼합 산화물을 졸-겔법으로 제조하였다. 제조된 혼합 산화물은 1173K에서 열처리 한 후 구조적 특성 변화를 전자현미경 및 X-선 회절 분석을 이용하여 관찰하였으며, 수소를 이용한 승온 환원(TPR; temperature-programmed reduction) 실험을 통하여 1173K 까지 각 시료들의 환원 피크를 비교 고찰하였다. $Al_2O_3$ 또는 $TiO_2$ 가 혼합된 시료의 경우 1173K 에서의 열처리 후 니켈 알루미네이트 또는 니켈 티타네이트와 같은 새로운 결정상의 생성이 관찰되었으나 $ZrO_2$가 혼합된 경우에는 새로운 결정상의 생성이 관찰되지 않았다. TPR 결과에 의하면, $Al_2O_3$ 또는 $TiO_2$를 혼합된 시료의 경우 벌크 NiO의 TPR 결과와는 달리 생성된 새로운 결정상에 기인한 여러 개의 환원 피크가 나타났으나 $ZrO_2$를 혼합한 경우 벌크 NiO와 비슷한 환원 피크를 보였다. TPR 결과를 기초로 Arrhenius plot 으로부터 각 혼합 산화물들의 수소 환원 활성화 에너지를 도출하였다. $ZrO_2$를 지지체로 사용하는 경우 다른 혼합 산화물들보다 지지체로서 안정한 혼합 산화물상을 형성한다는 것을 지시하듯이 상대적으로 가장 낮은 활성화 에너지를 나타냈다.