【作者】 王然；

【导师】 周江；

【作者基本信息】 吉林大学 ， 农业机械化工程， 2023， 博士

【摘要】 Pickering乳液是一类以固体颗粒作为乳化剂作用于油水界面而稳定的乳液。相比于传统的以分子乳化剂稳定的乳液,Pickering乳液具有颗粒用量少、稳定性好、无化学污染、后续易分离以及环境友好等优势。淀粉作为初级农产品,其来源广泛、价格低廉、易于改性,并具有良好的生物相容性和加工适应性。本文以玉米淀粉为原料,对其进行改性制备纳米淀粉基颗粒乳化剂,并研究不同方式制备的纳米淀粉基颗粒乳化剂的性质及其对Pickering乳液物理稳定性和氧化稳定性的影响,最终通过调控纳米淀粉基颗粒乳化剂构建食品级Pickering乳液递送体系。主要研究结果如下:(1)研究辛烯基琥珀酸酐(OSA)酯化淀粉纳米颗粒(SNPs)稳定的Pickering乳液。采用乙醇沉淀法制备SNPs,并使用OSA对SNPs进行酯化改性,制成了OSA酯化淀粉纳米颗粒(OSA-SNPs)。通过微纳尺寸形态学、粒度分布统计学结合光谱学等多种方式对纳米淀粉基颗粒乳化剂及其稳定的水包油(O/W)型Pickering乳液进行表征,证实了经OSA酯化改性后SNPs表面Zeta电位绝对值增加,并且其与水相的界面接触角增大,说明OSA-SNPs疏水性增强;其稳定的Pickering乳液的性质受体系颗粒乳化剂质量浓度、p H值和离子强度的影响:通过调节体系p H至酸性或碱性以及添加KCl提高体系的离子强度,则会导致乳液的平均粒径增加、乳化指数(EI)下降,乳液失去稳定性而表现为油水相分离;在中性p H和没有添加KCl的条件下,通过增加体系中OSASNPs的浓度会使乳液的平均粒径减小、EI值提高;采用荧光显微镜(FM)观察发现,质量浓度为2%的OSA-SNPs能够附着在油水界面并形成物理屏障,抑制分散相油滴的聚结,保持乳液物理稳定。(2)基于传统乳化剂酪蛋白酸钠(SC)在油水界面的吸附特性,设计在SC溶液中添加微量的OSA-SNPs,研究传统乳化剂SC和颗粒乳化剂OSA-SNPs的作用关系以及其对Pickering乳液性质的影响。研究结果表明:随着OSASNPs质量浓度的增加,其与SC的混合液的流体动力学直径增加,混合液表面Zeta电位绝对值以及其与油相的界面接触角和界面张力均减小。SC和OSASNPs共同稳定的Pickering乳液随着OSA-SNPs浓度的增加,乳液界面蛋白浓度、脂肪部分聚结率和平均粒径均呈现先增加再减小的趋势,试验结果证明浓度为0.04 g/100 m L的OSA-SNPs能促进SC在油水界面的吸附行为,共同维持乳液的稳定。(3)具有抗氧化功能的纳米淀粉基颗粒乳化剂及其稳定的食品级Pickering乳液的构建。在蜡质玉米淀粉(WMS)中添加天然抗氧化剂—茶多酚(TPs),并采用乙醇沉淀法制备WMS/TP纳米颗粒,考察TPs添加量对WMS/TP纳米颗粒理化性质和乳化性质的影响,并分析WMS/TP纳米颗粒浓度和不同TPs添加量的WMS/TP纳米颗粒对Pickering乳液物理稳定性和氧化稳定性的影响。研究结果表明:随着WMS纳米颗粒中TPs添加量从5%增加至15%,颗粒的形貌和尺寸发生明显的变化,颗粒由球形逐渐变为棒状和拉伸条带的混合物,说明TPs具有连接淀粉分子的功能。通过傅里叶红外光谱(FT-IR)分析发现,TPs与淀粉之间存在氢键相互作用。与WMS纳米颗粒相比,WMS/TP纳米颗粒与水相的接触角增大,与油相的接触角减小,说明添加TPs改善了WMS纳米颗粒的疏水性。通过激光共聚焦荧光显微镜(CLSM)分析发现,不同TPs添加量的WMS/TP纳米颗粒能够吸附在乳液的油水界面,随着体系中WMS/TP纳米颗粒浓度的增加,乳液的平均粒径减小。此外,随着WMS/TP纳米颗粒中TPs添加量的增加,其稳定的Pickering乳液的黏弹性和EI值增加。乳液在15 d贮藏期能够保持物理稳定。通过加速氧化试验分析发现,与WMS纳米颗粒稳定的乳液相比,由WMS/TP纳米颗粒稳定的乳液在贮藏中其初级氧化产物(POV)和次级氧化产物(TBARS)明显减少,说明乳液的氧化稳定性增强。(4)基于OSA酯化淀粉(OSS)的界面性质及其与TPs的相互作用,采用乙醇沉淀法制备具有抗氧化功能的OSS/TP纳米颗粒,用于构建Pickering乳液生物活性物质递送体系。研究结果表明:随着OSS/TP纳米颗粒中TPs添加量从5%增加至20%,OSS/TP纳米颗粒的平均粒径增加,颗粒表面Zeta电位绝对值下降,颗粒与水相接触角减小,说明其乳化性能有所减弱。随着OSS/TP纳米颗粒浓度的增加,其稳定的乳液的平均粒径明显减小;OSS/TP纳米颗粒(TPs添加量为10%)稳定的乳液形成了油滴紧密堆积的界面结构,能够抑制油滴迁移并保持乳液稳定。与其他乳液样品相比,OSS/TP纳米颗粒稳定的乳液在15 d贮藏期的POV明显减小,其荷载的白藜芦醇的稳定性明显提高;通过体外模拟消化试验分析发现,OSS/TP纳米颗粒稳定的乳液能够减小消化环境对其荷载的白藜芦醇的侵蚀,延缓白藜芦醇的释放,说明OSS/TP纳米颗粒稳定的乳液能够作为递送载体,提高生物活性物质的稳定性和生物利用率。更多还原

【Abstract】 Pickering emulsions refer to the emulsions that are stabilized by using solid colloidal particles as emulsifiers to work at oil/water interface of emulsions.Compared with traditional emulsions stabilized by molecular emulsifiers,Pickering emulsions have advantages of less particle dosage,excellent stability,no chemical pollution,easy subsequent separation and environmental friendliness.Starch,as a kind of primary agricultural product,has a wide source,lower price,easy to modify,and good biocompatibility and processing adaptability.In this paper,maize starch was used as raw material with modification to prepare nano-starch-based particle emulsifiers.The properties of the nano-starch-based particle emulsifiers prepared by various means were studied and their influences on physical stability and oxidative stability of the Pickering emulsions were investigated.Finally,the food-grade Pickering emulsion delivery vehicles were fabricated through regulating the nano-starch-based particle emulsifiers.(1)Preparation of Pickering emulsions stabilized by starch nanoparticles modifying with octenyl succinic anhydride(OSA).Starch nanoparticles(SNPs)prepared through ethanol precipitation were esterified by OSA to make OSA modified starch nanoparticles(OSA-SNPs).Characteristics of nano-starch-based particle emulsifiers and their stabilized oil-in-water(O/W)Pickering emulsions were determined by various means including morphology,particle size distributions,spectroscopy and so on.The results showed that the absolute value of surface Zeta potentials of the SNPs increased after OSA esterification.In addition,water contact angle of the OSA-SNPs raised,indicating their enhanced hydrophobicity.The stability of the Pickering emulsions stabilized by the OSA-SNPs was influenced by particle mass concentrations,p H and ionic strength.Adjusting p H to the acidic or alkaline,or adding KCl to improve the ionic strength of emulsions could induce the increase of emulsion droplet mean size and decrease of emulsified index(EI),thus leading to the instability of the emulsions for oil/water phase separation.The emulsion droplet size decreased with the increasing concentration of the OSA-SNPs under neutral p H and without KCl in emulsions.While EI of emulsions increased under that of conditions.Fluorescence microscopy showed that OSA-SNPs of 2%(w/v)could absorb at oil/water interface of the Pickering emulsions to form a physical barrier which inhibited the coalescence of dispersed oil droplets,thus keeping physical stability of the Pickering emulsions.(2)Sodium caseinate(SC),as traditional emulsifier,can adsorb at the oil/water interface of the emulsions.The interactions between traditional emulsifier(SC)and particle emulsifier(OSA-SNPs)and their influences on the properties of Pickering emulsions were studied by adding a small number of the OSA-SNPs into SC dispersions.The results showed that hydrodynamic diameters of the mixture increased with the increase of OSA-SNPs concentrations.Moreover,the absolute values of surface Zeta potential of the mixture decreased as the increasing the OSA-SNPs contents,and also the oil contact angles and interfacial tension of the mixture.Concentrations of interfacial protein,fat partial coalescence rate and mean particle size of the emulsions stabilized by the mixture of the SC and the OSA-SNPs increased firstly and then decreased with the increasing concentrations of the OSA-SNPs.It was proved that the OSA-SNPs of 0.04 g/100 m L could promote the adsorption of SC at the oil/water interface,which was in favor of the stability of the Pickering emulsions.(3)The nano-starch-based particle emulsifiers with antioxidant capacity and their stabilized food-grade Pickering emulsions were fabricated.Natural antioxidant tea polyphenol(TPs)and waxy maize starch(WMS)were combined to prepare WMS/TP nanoparticles through ethanol precipitation.Effect of TP additions on the physicochemical properties and emulsifying capacity of the WMS/TP nanoparticles were investigated.The physical stability and oxidation stability of the Pickering emulsions stabilized by the WMS/TP nanoparticles with different additions of TPs and with various particle concentrations were analyzed.The results showed that morphology and size of the WMS/TP nanoparticles changed obviously as increasing the additions of TPs in the WMS nanoparticles from 5% to 15%.Morphologies of the WMS/TP nanoparticles transformed from spherical to the mixture of rod-like and stretched strips,indicating the bridge functions of TPs among starch molecular chains.The hydrogen bond interactions between TPs and starches were proved by Fourier transform infrared spectroscopy(FT-IR).Compared with the WMS nanoparticles,the water contact angles of the WMS/TP nanoparticles increased and the oil contact angles decreased,suggesting that the addition of TPs enhanced the hydrophobicity of the WMS nanoparticles.Laser confocal fluorescence microscopy(CLSM)showed that the WMS/TP nanoparticles with different TP additions can adsorb to the oil/water interface of the emulsions,and the droplet mean sizes of emulsions decreased with the increasing concentrations of the WMS/TP nanoparticles.Moreover,the viscoelasticity and EI values of Pickering emulsions stabilized by the WMS/TP nanoparticles increased when increased the added TPs.Emulsions stabilized by the WMS/TP nanoparticles could keep the physical stability during 15 d of storage.Accelerated oxidation test showed that compared with the emulsions stabilized by the WMS nanoparticles,the primary oxidative products(POV)and secondary oxidative products(TBARS)of the emulsions stabilized by the WMS/TP nanoparticles decreased significantly during storage,indicating the oxidative stability of emulsions was enhanced.(4)Based on the interfacial property of the OSA esterified starch(OSS)and its interactions with TPs,OSS/TP nanoparticles with antioxidant function were prepared through ethanol precipitation to fabricate Pickering emulsion delivery system for bioactive substances.The results showed that the mean particle size of the OSS/TP nanoparticles increased with increasing the addition of TPs(from 5% to 20%),and the absolute values of surface Zeta potential and water contact angles of the OSS/TP nanoparticles decreased,suggesting their reduced emulsifying capacity.Mean droplet size of emulsions decreased with the increasing concentration of the OSS/TP nanoparticles.Interfacial structure with oil droplets close-packed was formed in the Pickering emulsions stabilized by the OSS/TP nanoparticles with TP additions of 10%,which could inhibit the migration of emulsion droplets and keep the stability of the Pickering emulsions.Compared with other emulsion samples,the POV of the Pickering emulsions stabilized by the OSS/TP nanoparticles decreased after 15 d of storage.In addition,the stability of resveratrol encapsulated in Pickering emulsions improved obviously.In vitro digestion model showed that encapsulated in Pickering emulsions stabilized by the OSS/TP nanoparticles,the resveratrol was not eroded in digestive environment,so it delaying the release of the resveratrol.These facts indicated that the Pickering emulsions stabilized by the OSS/TP nanoparticles can be used as a delivery carrier to improve the stability and bioavailability of bioactive substances.更多还原