饱和同酸偶数碳甘油三酯结晶行为的研究

发布时间：2018-04-28 16:25

  本文选题：饱和同酸偶数碳甘油三酯 + 熔化行为　； 参考：《天津科技大学》2016年硕士论文

【摘要】：人们的日常生活和经济领域中,油脂及其相关产品都占据着重要的地位。可可脂作为油脂的一种,被广泛应用于巧克力的生产过程中。然而,存在于可可脂中的脂肪酸及甘油三酯,在温度波动下会形成结晶,并可能出现同质多晶现象,即出现巧克力"起霜"现象,这在很大程度上会影响巧克力的感官品质。据统计,在巧克力食品品质诸多问题中,起霜问题占65%-80%,成为影响巧克力工业的一大难题,尚未得到有效解决。本课题选用在糖果工业中经常使用的、同属于饱和同酸偶数碳甘油三酯系列的月桂酸甘油三酯、棕榈酸甘油三酯以及硬脂酸甘油三酯,对其熔化/凝固行为、同质多晶型转变以及晶体形貌进行调查,试图寻找出该系列甘油三酯结晶行为的相关规律。取得的主要研究成果如下:1.采用差示扫描量热仪(DSC)分别测定这3种饱和同酸偶数碳甘油三酯的结晶、熔化行为的热力学性质,结果表明:升温过程中,该系列甘油三酯样品分别在接近熔点时形成一个明显的熔融峰,且随着甘油骨架上所连接的脂肪酸链长增加,该熔融峰的峰值温度不断向较高温度偏移。这可能是由于碳链延长,物质内部分子间相互作用力加强,各分子间相互连接得越紧密,由稳定晶型构成的甘油三酯固态结构越不容易被破坏,将其完全转化为液态(即熔化过程)所需要吸收的能量越高。另外,在相同且极为缓慢的升温速率(1℃/min)下,3者均在熔融峰出现之前形成1个很微弱的吸热峰,推测此时该类别甘油三酯发生了同质多晶型转变,形成了较不稳定的β'型。2.通过X-射线粉末衍射(XRD)对以上3种甘油三酯同质多晶型物的晶体结构进行确定,结果表明:常温下,该系列甘油三酯均形成了稳定的β型结晶。3.通过傅里叶红外吸收光谱(FT-IR),我们得到了饱和同酸偶数碳甘油三酯形成不同晶型时的特征红外吸收峰。结果显示:常温下,3种测试甘油三酯样品均在717cm-1前后出现了单谱带,这与该类甘油三酯形成稳定晶型(β晶型)时的特征红外光谱带(717cm-1)是非常一致的,因此证明了以上3种甘油三酯在常温下会形成稳定的β晶型。此外,棕榈酸甘油三酯(PPP)控温MIR测试显示:控温条件下,棕榈酸甘油三酯中红外吸收光谱在59℃前后出现了新的吸收谱带(位于272.01cm-1处),这有别于常温下其MIR吸收峰,表明在温度上升至59℃过程中,棕榈酸甘油三酯形成了新的晶型,且有别于常温下形成的稳定晶型。4.最后,通过扫描电子显微镜(SEM),对这3种甘油三酯在常温下的晶体表观形态进行研究。扫描结果显示:我们所选取的3种甘油三酯虽然属于同一系列,但是它们在微观形态上呈现出较大差异:LaLaLa呈现长方形、片状形态,表面粗糙且伴有稀疏的针孔状凹陷;PPP呈平行四边形、片状结构,且片层之间存在不规则叠加;StStSt则是由尺寸各异的不规则晶体碎片聚集而成的圆球状。
[Abstract]:Oil and its related products occupy an important position in people's daily life and economic field. Cocoa butter, as a kind of grease, is widely used in the production of chocolate. However, the presence of fatty acids and triglycerides in cocoa butter may lead to the formation of crystallization under temperature fluctuation, and may lead to homogeneous polycrystalline phenomena, that is, "frosting" phenomenon of chocolate, which to a large extent will affect the sensory quality of chocolate. According to statistics, among the many problems of chocolate food quality, frosting accounts for 65-80, which has become a major problem affecting the chocolate industry and has not yet been effectively solved. In this paper, the melting / solidification behavior of triglycerides lauric acid, triglycerides palmitate and triglycerides stearate, which are often used in the confectionery industry and belong to the series of saturated even carbon triglycerides, is selected. The homogenous polycrystalline transformation and crystal morphology were investigated in order to find out the related laws of the crystallization behavior of the series of triglycerides. The main research results are as follows: 1. Differential scanning calorimetry (DSC) was used to determine the thermodynamic properties of the crystallization and melting behavior of the three saturated triglycerides. This series of triglyceride samples formed an obvious melting peak at close to the melting point, and the peak temperature of the melting peak shifted to a higher temperature with the increase of the chain length of fatty acids attached to the glycerol skeleton. This may be due to the prolongation of the carbon chain, the stronger the intermolecular interaction within the substance, the closer the interconnections between the molecules, the less likely the solid structure of triglycerides, which is composed of stable crystalline forms, will be destroyed. The higher the energy needed to convert it completely into a liquid (that is, the melting process). In addition, at the same and extremely slow heating rate of 1 鈩，

本文编号：1816023