【作者】 刘峰；

【导师】 王正武；

【作者基本信息】 江南大学 ， 应用化学， 2010， 博士

【摘要】 许多脂溶性食品功能因子都具有多种有益于人类健康的生理功能。但这些功能因子存在不溶于水,易被氧化,不稳定等缺点,处于纳米态的表面活性剂聚集体(微乳液、液晶、自发囊泡等)作为食品功能因子载体具有性能稳定、制备简单、成本低等显著优点。本文分别制备了α-亚麻酸,共轭亚油酸,姜黄素三种食品功能因子的微乳液体系,利用动态光散射、透射电镜、核磁共振、流变学方法等手段,对微乳液体系的粒径、分散度、包封位置、稳定性、动态流变性质,以及体系的相态进行了研究。并进一步用小角X射线散射、流变学方法等,对α-亚麻酸,共轭亚油酸与非离子表面活性剂/水体系中溶致液晶的形成、微观结构、动态流变学性质展开了研究。主要研究结果如下:(1)总结了食品功能因子载体领域的研究热点和发展方向,包括环糊精、脂质体、无机纳米材料、表面活性剂自聚集体等;进一步分析了表面活性剂聚集体在食品功能因子载体领域的研究现状。制备了全反式维甲酸阴阳离子复配自发囊泡体系。这些聚集体能同时具有不同亲脂/亲水性能的微环境,但宏观上却是均匀的多相体系,从而在改变液体食品的外观、品质、功效等方面有重要的应用价值。(2)以α-亚麻酸(ALA)为油相,以非离子表面活性剂失水山梨醇单油酸酯(Span80)、蓖麻油聚氧乙烯(35)醚(EL-35)为乳化剂,首次制备了无助表面活性剂的ALA微乳液。研究了此四元体系的相形为,pH值对微乳液区域的影响;用电导率法测定出O/W微乳液区;动态光散射及负染色透射电法研究了微乳液的粒径及稳定性;并通过利用核磁共振的测量,推断出ALA在O/W微乳液中的包封位置;同时研究了微乳液的动态流变行为;并将此微乳液体系加入到几种常见饮料中,研究了ALA微乳对饮料稳定性的影响。结果表明,微乳液为粒径为20-40 nm的球状结构;浓度较低时,ALA会增溶在微乳液的内核,但随着ALA浓度的增大,ALA会进入到微乳液亲水层内;微乳液稳态剪切流变的测量显示,体系有两次剪切变稀的过程,分析表明,这两次过程分别为聚集体扭曲、变形和结构破坏重组的过程;微乳液在两个月的存储时间内,粒径无明显变化,稳定性较好,其在各种饮料中也非常稳定,基本不会破坏饮料原有结构及稳定性。(3)以共轭亚油酸(CLA)为油相,以非离子表面活性剂聚氧乙烯山梨醇酐单油酸酯(Tween80)、EL-35为乳化剂,乙醇,正辛醇为助表面活性剂,制备了CLA微乳液;并用Tween80和Span80制备了CLA多重乳状液。研究表明,微乳液粒径随表面活性剂浓度的增大而减小,但CLA浓度增加,粒径会发生明显增大。微乳液粒径在30天的存储时间内,粒径无明显变化,稳定性较好。随着存储时间的延长,CLA在微乳液中的浓度会明显下降,对比相同存储环境下,CLA在微乳液中比在乙醇溶液中明显稳定。多重乳状液结果显示:单一乳化剂体系中,相同条件下以Tween80作亲水乳化剂制备的CLA多重乳状液体系稳定性较好。当M(内水相)∶M(油相)∶M(外水相)=1.0∶5.0∶1.3, M(Span80)∶M(Tween80)=9.0,乳化剂含量为9.7%时,多重乳液相对体积达到93%。复合乳化剂在第一相的HLB值为7.4,外水相中Tween80占4.9%,第一相中M(复合乳化剂)∶M(Tween80)=9.0,乳化剂在在第一相中的质量分数为6.7%时,多重乳液相对体积达到94%,稳定性较好。(4)以Tween80为乳化剂,乙醇为助表面活性剂,乙酸异戊酯(IA)为油相,制备了Tween80/乙醇/IA/水四元体系的微乳液,将其作为姜黄素载体,测定了体系对姜黄素的最大包封量、包封率及缓释效果。动态光散射结果表明,姜黄素的加入,会明显增大微乳液粒径,但粒径并不随姜黄素浓度的增加而增大;在实验周期内,微乳液粒径随时间略有增大,但变化并不明显,溶液始终澄清、透明,稳定性较好。1H NMR结果表明,姜黄素被包封在O/W微乳液的栅栏层内。微乳液不仅对姜黄素有明显的增溶效果,而且能提高其稳定性。体外透析实验表明,微乳液包封后的姜黄素溶液有更加明显的缓释效果,同时微乳液中姜黄素浓度的增加,可加快透析速率。(5)首次制备了以ALA为油相的,双连续立方相Ia3d和层状溶致液晶,并研究了EL-35/ALA/H2O三元体系的相形为。SAXS法研究了体系溶致液晶的微观结构,结果表明,随着体系含水量的增加,立方相液晶的晶胞参数及水通道的半径r依次增大,而疏水/亲水界面上表面活性剂分子的截面积aS并没有明显变化;层状液晶重复间距d增大,而疏水层半径和aS并没有明显变化,ALA主要增溶在胶束内核,ALA浓度增加,层状相中非极性区域的厚度增大。动态流变性质的测量表明,体系液晶样品的储能模量G’都大于损耗模量G’’,一定浓度ALA的加入,对液晶的结构有稳定作用。立方相液晶在44°C时结构开始转变,并在49°C后完全破坏成为O/W微乳液,在温度高于43°C后层状液晶结构被破坏。(6)研究了EL-35/AEO2/CLA/H2O体系的拟三元相图,开展了其层状液晶微观结构参数的计算和流变性质的研究。SAXS研究表明,固定表面活性剂相与油相的比例,随着体系含水量的增加,层状相重复间距d,表面活性剂分子在胶束疏水/亲水界面上的有效截面积aS,线性增加,CLA主要增溶在层状相的疏水内核。动态流变性质显示,体系液晶以弹性为主,随着体系含水量的增加,液晶内部的交联度增大,空间结构强度增大,温度扫描结果表明,随着含水量的增加,液晶相转变温度也随之升高。AEO表面活性剂中氧乙烯链的长度增加,界面层排列变疏松,液晶结构强度和形成弹性网络结构的频率依次减小。更多还原

【Abstract】 Epidemiologic and experimental data have provided evidence for a beneficial effect of water insoluble functional food factors. However, these factors are water-insoluble, especially sensitive to light, temperature and easily to be oxidized. Self-assemblies of surfactants (such as microemulsion, liquid crystal and vesicle) possess several advantages over their solvent-based counterparts, which are thermodynamically stable, nanoscale droplets, easy to prepare and low cost. In this paper,α-Linolenic Acid (ALA), conjugated linoleic acid (CLA), and curcumin microemulsions were prepared. The particle diameter, polydispersity index, encapsulation position, stability and rheological properties of these systems have been observed by dynamic light scattering (DLS), TEM, 1H NMR spectroscopy and rheological techniques. And the microstructures and dynamic rheological properties of lyotropic liquid crystal phases have been studied with the aid of small angle X-ray scattering (SAXS) and rheological techniques for the systems of ALA, CLA with nonionic surfactants and water. In details, the results of the researches as following:(1) The most attractive researches in the field of functional food factor carriers, such as cyclodextrin, lipidosome, inorganic nanophase materials and self-assemblies of surfactants, have been summarized. Furthermore, progress in food delivery system study of surfactant aggregates has been intensively analyzed. Spontaneous vesicle systems which were used as all-trans retinoic acid (ATRA) delivery systems were prepared. These nanophase delivery systems will be of great importance in food appearance, quality, and efficacy.(2) A novel ALA-in-water microemulsion composed of ALA as the continuous oil phase, water as the dispersed phase, and a mixture of EL-35 / Span80 as the emulsifiers were prepared and investigated as potential food delivery systems. The influences of pH on the microemulsion region were considered. The microstructure and characterization of microemulsion were determined by dynamic light scattering, negative-staining TEM and rheological behavior. The location of ALA molecules in the microemulsion formulations was determined by 1H NMR spectroscopy. The results show that the size of O/W microemulsion droplets depends strongly on the contents of ALA, and the diameter ranges from 22.1 to 42.1 nm. All samples keep a remarkable stability in the experiments of 60 days. The results of DLS and 1H NMR confirmed that the ALA molecules are solubilized in oil core of the O/W microemulsions drops in low ALA concentration. With the addition of ALA, they are solubilized in the hydrophilic shells of the microemulsion. The rheological results showed that the flow behaviour of microemulsion follows shear thinning. All microemulsion samples exhibit two Newtonian regions, and in low shear-rate region, the flow behavior can be described by the Carreau model. Centrifugation and storage experiments were used to test the stability of beverage samples with microemulsion system. The results showed that ALA could be added into juice, coke and sports beverage under a certain conditions.(3) CLA-in-water microemulsion based on Tween80, EL-35, ethanol and n-octanol was investigated as potential food delivery systems. The size of O/W microemulsion droplets depends strongly on the contents of surfactants and CLA, and the diameter ranges from 22.1 to 30.7 nm and from 18.3 to 32.8 nm respectively. All samples keep a remarkable stability in the experiments of 30 days. The stability of CLA in microemulsion and ethanol solution was determined by UV-vis spectrophotometry, the results revealed that the stability of the CLA in the microemulsion was increased remarkably. The stability of multiple emulsions showed that the optimum conditions for solo emulsifier system are: M (Span80)∶M (Tween80) =9.0, the mass fraction of the emulsifier in the emulsion is 9.7%, the oil to water mass ratio is 5.0 in first phase, and the mass ratio of first phase to second phase is 6.0∶1.3. The optimum conditions for complex emulsifiers system are: HLB of the emulsifier in the first phase is 7.4, M (mult-emulsifiers)∶M (Tween80)=9.0, and the mass fraction in the emulsion is 6.7%.(4) The ternary phase diagram of a curcumin-encapsulated O/W microemulsion system using food-acceptable components, Tween 80 as the surfactants, ethanol as the cosurfactant and isoamyl acetate as the oil phase was constructed. The stability and characterisation of curcumin in microemulsion were investigated. The results indicated that the diameter of microemlsions increased with the addition of curcumin. 1H NMR confirmed that the curcumin molecules are solubilized in palisade layer of the O/W microemulsions drops. microemulsion can significantly increase the solubility of curcumin in water. A permeation study for testing the penetration effect of various curcumin loading in the microemulsions in different dialysates was also performed and discussed.(5) The bicontinuous cubic (Ia3d) and lamellar liquid crystals were approved in EL-35/ALA/H2O system. The results of SAXS show that the lattice parameter and water channels radius (r) of cubic phase and the repeated distance (d) of lamellar phase get increased with the increase of water contents, and the area per surfactant at the hydrophobic/hydrophilic interface (aS) has no significant change. ALA is solubilized in the core of the micelle. The storage moduli are bigger than loss moduli for all samples. A certain concentration participation of ALA will stabilize the structure of liquid crystal. The cubic and lamellar phases were discharged into O/W microemulsion at 49 and 43°C, respectively.(6) The phase diagram of EL-35/AEO2/CLA/H2O system was prepared. The microstructure and rheological properties were researched by SAXS and rheological technique. The results of SAXS show that the repeated distance (d) and the area per surfactant at the hydrophobic/hydrophilic interface (aS) of lamellar phase get increased with the increase of water contents. CLA is solubilized in the core of the micelle. The dynamic rheology results show that the strength of lamellar phase network and the phase transition temperature are increasing with the increase of water contents. The different in the EO units among the AEO surfactants has an obvious effect on the lamellar phase. The interface layer arranged is looser, the strength of phase network and the crossover frequency decreases with the increase of EO units.更多还原