本文選題：飽和同酸偶數(shù)碳甘油三酯 + 熔化行為　； 參考：《天津科技大學(xué)》2016年碩士論文

【摘要】：人們的日常生活和經(jīng)濟(jì)領(lǐng)域中,油脂及其相關(guān)產(chǎn)品都占據(jù)著重要的地位。可可脂作為油脂的一種,被廣泛應(yīng)用于巧克力的生產(chǎn)過程中。然而,存在于可可脂中的脂肪酸及甘油三酯,在溫度波動(dòng)下會(huì)形成結(jié)晶,并可能出現(xiàn)同質(zhì)多晶現(xiàn)象,即出現(xiàn)巧克力"起霜"現(xiàn)象,這在很大程度上會(huì)影響巧克力的感官品質(zhì)。據(jù)統(tǒng)計(jì),在巧克力食品品質(zhì)諸多問題中,起霜問題占65%-80%,成為影響巧克力工業(yè)的一大難題,尚未得到有效解決。本課題選用在糖果工業(yè)中經(jīng)常使用的、同屬于飽和同酸偶數(shù)碳甘油三酯系列的月桂酸甘油三酯、棕櫚酸甘油三酯以及硬脂酸甘油三酯,對(duì)其熔化/凝固行為、同質(zhì)多晶型轉(zhuǎn)變以及晶體形貌進(jìn)行調(diào)查,試圖尋找出該系列甘油三酯結(jié)晶行為的相關(guān)規(guī)律。取得的主要研究成果如下:1.采用差示掃描量熱儀(DSC)分別測(cè)定這3種飽和同酸偶數(shù)碳甘油三酯的結(jié)晶、熔化行為的熱力學(xué)性質(zhì),結(jié)果表明:升溫過程中,該系列甘油三酯樣品分別在接近熔點(diǎn)時(shí)形成一個(gè)明顯的熔融峰,且隨著甘油骨架上所連接的脂肪酸鏈長(zhǎng)增加,該熔融峰的峰值溫度不斷向較高溫度偏移。這可能是由于碳鏈延長(zhǎng),物質(zhì)內(nèi)部分子間相互作用力加強(qiáng),各分子間相互連接得越緊密,由穩(wěn)定晶型構(gòu)成的甘油三酯固態(tài)結(jié)構(gòu)越不容易被破壞,將其完全轉(zhuǎn)化為液態(tài)(即熔化過程)所需要吸收的能量越高。另外,在相同且極為緩慢的升溫速率(1℃/min)下,3者均在熔融峰出現(xiàn)之前形成1個(gè)很微弱的吸熱峰,推測(cè)此時(shí)該類別甘油三酯發(fā)生了同質(zhì)多晶型轉(zhuǎn)變,形成了較不穩(wěn)定的β'型。2.通過X-射線粉末衍射(XRD)對(duì)以上3種甘油三酯同質(zhì)多晶型物的晶體結(jié)構(gòu)進(jìn)行確定,結(jié)果表明:常溫下,該系列甘油三酯均形成了穩(wěn)定的β型結(jié)晶。3.通過傅里葉紅外吸收光譜(FT-IR),我們得到了飽和同酸偶數(shù)碳甘油三酯形成不同晶型時(shí)的特征紅外吸收峰。結(jié)果顯示:常溫下,3種測(cè)試甘油三酯樣品均在717cm-1前后出現(xiàn)了單譜帶,這與該類甘油三酯形成穩(wěn)定晶型(β晶型)時(shí)的特征紅外光譜帶(717cm-1)是非常一致的,因此證明了以上3種甘油三酯在常溫下會(huì)形成穩(wěn)定的β晶型。此外,棕櫚酸甘油三酯(PPP)控溫MIR測(cè)試顯示:控溫條件下,棕櫚酸甘油三酯中紅外吸收光譜在59℃前后出現(xiàn)了新的吸收譜帶(位于272.01cm-1處),這有別于常溫下其MIR吸收峰,表明在溫度上升至59℃過程中,棕櫚酸甘油三酯形成了新的晶型,且有別于常溫下形成的穩(wěn)定晶型。4.最后,通過掃描電子顯微鏡(SEM),對(duì)這3種甘油三酯在常溫下的晶體表觀形態(tài)進(jìn)行研究。掃描結(jié)果顯示:我們所選取的3種甘油三酯雖然屬于同一系列,但是它們?cè)谖⒂^形態(tài)上呈現(xiàn)出較大差異:LaLaLa呈現(xiàn)長(zhǎng)方形、片狀形態(tài),表面粗糙且伴有稀疏的針孔狀凹陷;PPP呈平行四邊形、片狀結(jié)構(gòu),且片層之間存在不規(guī)則疊加;StStSt則是由尺寸各異的不規(guī)則晶體碎片聚集而成的圓球狀。
[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，

本文編號(hào)：1816023