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題 名 | 亞麻油酸存在下膽固醇受熱時自氧化動力學模式=Kinetic Model of Cholesterol Autoxidation in the Presence of Linoleic Acid during Heating during Heating |
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作 者 | 王惠珍; 戴志全; 林方宜; 陳炳輝; 陳炯堂; | 書刊名 | 食品科學 |
卷 期 | 25:1 1998.02[民87.02] |
頁 次 | 頁82-93 |
分類號 | 341.91 |
關鍵詞 | 膽固醇; 自氧化; 動力學; 自由基; 加熱; Cholesterol; Autoxidation; Kinetics; Free radicals; Heating; |
語 文 | 中文(Chinese) |
中文摘要 | 膽固醇氧化物(Cholesterol Oxidation Products,COPs)為膽固醇受熱自氧化所產生的物質,若與油脂共同存在時其機制複雜,有必要進一步確立其自氧化動力學以便了解熱加工時COPs的生成。研究採用膽固醇標準品中添加亞麻油酸(Linoleic aid,LA)(添加量為:實驗 I:20%,w/w及實驗Ⅱ:50%,w/w),於充分氧及150℃下加熱,再以Thin Layer Chromatography (TLC)及High Performance Liquid Chromatography (HPLC)分析COPs。結果顯示COPs濃度會隨加熱時間而增加,膽固醇在 15 min已降解73.3%,w/w((實驗Ⅰ)及 50.1%, w/w(實驗Ⅱ)。膽固醇初期自氧化可分為二個途徑,分別為碳七氧化與環氧化。經統計非線性迴歸程序分析發現,自氧化動力學模式除了 7-hydroperoxycholesterol (7-OOH)及5,6-epoxycholesterol(5,6-EP)之生成為二級反應之外,其他皆符合一級反應。 LA的添加量愈高,其自氧化及裂解反應的速率常數也愈大。這顯示添加LA於膽固醇中會誘導膽固醇自氧化並加速其反應。在固定LA添加量下,各反應速率常數依序為:環氧化反應>自由基連銷反應>脫水反應>還原反應>脫氫反應。以上各方程式迴歸分析之r2,除了實驗Ⅰ中 7-Keto之生成(γ2=0.71)及實驗Ⅱ中 7-OOH之生成(γ2=0.82)較低之外,其餘皆大於0.94,顯示本研究所提動力學方程式可預測 150℃加熱膽固醇時,COPs濃度之變化。 |
英文摘要 | The formation of cholesterol oxidation products (COPs) during heating of cholesterol at 150 ℃ for various times was kinetically studied using non-linear regression models. Due to the complexity of its autoxidation in the presence of fatty acids, it is necessary to establish its kinetic models to rationize the formation of COPs during thermal processing. Cholesterol in the presence of linoleic acid (LA) (experiment I: 20%, w/w and II: 50%, w/w) was used as a model system in this study. The various COPs were analyzed by means of thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). Results showed that the COP concentration increased with increasing heating time, and that the cholesterol loss reached 73.3 %, w/w (experiment I) and 50.1% (experiment II) after 15 rain of heating. In the earlier stages, the autoxidation of cholesterol includes two pathways: C-7 oxidation and epoxidation. The analysis of non-linear regression showed that the reactions for the formation of 7-hydroxylcholesteroI (7-OOH) and 5,6-epoxy- cholesterol (5,6-EP) fitted the second orders while the others fitted the first orders. All the rate constants of cholesterol autoxidation increased with increases of LA. This implied that addition of LA in cholesterol promoted its autoxidation. In the earlier stages, the highest rate constant (h-1) was observed in the reaction of epoxidation, followed by 7-OOH formation, dehydration, reduction, and dehydrogenation. The correlation coefficient (r2) for each reaction was higher than 0.94, with the exceptions of 0.71 for dehydration in experiment I and 0.82 for 7-OOH formation in experiment II. This indicated that the kinetic models developed in this study can be used to predict the concentration changes of COPs during heating of cholesterol at 150 ℃. |
本系統中英文摘要資訊取自各篇刊載內容。