【作者】 仇丹；

【导师】 李浩然； 陈志荣；

【作者基本信息】 浙江大学 ， 化学工程， 2008， 博士

【摘要】 本文以β-胡萝卜素为例,首先建立了对β-胡萝卜素行之有效的HPLC分析方法;然后深入研究了其在微胶囊制备过程中固体状态、溶剂溶解状态和高温油溶状态的稳定性;最后本文利用量子化学方法对β-胡萝卜素可能的反应机理进行了理论探索,建立了反应网络。通过本文的研究工作,类胡萝卜素微胶囊化过程中不同阶段的样品都能得到准确的检测;利用C₃₀-HPLC方法,实现对β-胡萝卜素八种异构体的定性分析。关于β-胡萝卜素在微胶囊制备过程中的稳定性研究表明:β-胡萝卜素在固体状态时,保持环境无氧比降低储存温度更有效,严格充氮保护下的结晶样品即使在高温下也是非常稳定的;在正常加热温度下,β-胡萝卜素在溶解度好的溶剂（二氯甲烷和四氢呋喃）中更稳定,溶剂充氮会抑制异构化反应并有助于提高β-胡萝卜素的稳定性,添加单一抗氧化剂能显著影响除异构化反应外的其它副反应的进程;在140℃～180℃的高温油脂中,β-胡萝卜素的异构化反应主要发生在反应的前2～4小时,其后虽然保留率的自然对数与时间呈线性相关,却无法用一个简单的一级反应动力学模型来描述β-胡萝卜素的变化规律,β-胡萝卜素的稳定性随温度的升高而降低,同时减少高温油脂中的氧分压不一定能有助于提高β-胡萝卜素的稳定性,β-胡萝卜素在油脂中的稳定性随着油脂不饱和度的增加而得到提高,抗氧化剂只在较低的温度下才起积极作用。最后本文又研究了β-胡萝卜素熔融过程异构化反应的反应机理,认为当不存在其它外界因素时,三重态是主要的异构化反应的中间态;然后就以全反式β-胡萝卜素作为主要的反应起始物,建立了反应网络,从中发现:1)β-胡萝卜素分子在有氧环境中更容易被引发为三重态;2)三重态发生异构化、聚合和氧化等副反应都是很容易的;3)由对氧化过程的分析得到的副产物的结构很好地吻合了第四章的实验结果;4)不同溶剂对链引发和副反应的作用是不同的,第五章的部分实验现象在此反应网络中都得到了解释。更多还原

【Abstract】 In this paper,the HPLC analysis method ofβ-carotene was firstly established.Then the stabilities ofβ-carotene of solid state,in solution and in thermal oils were studied, and the reaction mechanism ofβ-carotene was investigated by quantum chemistry methods,while a network was founded as a result.Different samples during microencapsulation of earotenoids could be well analyzed in this paper,and qualitative analysis of eight.isomers was well studied by C₃₀-HPLC.High stabilities were found during heating of nitrogen-protectingβ-carotene of storage.β-Carotene was more stable in THF and dichloromethane,and the isomedzation was inhibited in nitrogen-bubbled solvent,while a simple antioxidant could affect side-reactions except isomerization.In thermally treated oils,the isomerization took place before 2～4 hours.Though linear dependence was found between the natural logarithm of retention ofβ-carotene and time,the one-order kinetics was impossible to explain the reaction ofβ-carotene.Higher stabilities were found in lower heating temperature,lower oxygen-pressure and oils of larger iodine value.Additionally,the antioxidant would protectβ-carotene at lower temperature.Finally the mechanism of thermal isomerization ofβ-carotene was investigated, with a result that the triplet-excitedβ-earotene is a main intermediate of isomerization under mild conditions.As the network was established,it could be found that the triplet-excitedβ-carotene was more easily formed in environment oxygen,with thereby the isomerization,polymerization,and oxidation of the triplet-excitedβ-carotene would easily happen.The functional groups of byproducts were deduced, and the results were in good agreement with the former results.The effect of solvent on network was also calculated,and the phenomenon of solution could be well explained based on these results.更多还原