【作者】 胡莉；

【导师】 刘成圣；

【作者基本信息】 中国海洋大学 ， 海洋生物学， 2010， 硕士

【摘要】 微胶囊化(Microencapsulation)是指由天然或合成高分子材料包埋微小的固体颗粒、液滴或气体,形成的具有半透性或密封性囊膜粒子的过程。选择合适的材料作为壁材和稳定的微胶囊(Microcapsule, MC)制备工艺等一直是微胶囊化研究者探索的重点之一。鱼油中富含w-3多不饱和脂肪酸EPA和DHA,具有诸多对人体有益的生理功能。但由于鱼油不溶于水,对光、热、氧极为敏感等特点,限制了鱼油在食品工业中的广泛应用。壳聚糖(Chitosan, CS)是一种天然聚阳离子碱性多糖,而阿拉伯胶(Gum acacia, GA)是一种天然的植物胶,两种材料来源都相当广泛且食用安全。因此,以CS/GA为壁材,采用复合凝聚法制备CS/GA鱼油MC具有重要的现实意义。以分子量(Molecular weight, Mw) 1100kDa,脱乙酞度(Degree ofdeacetylation, DD)为88%的CS为原材料,采用醇酸降解法得到两种Mw的CS样品。采用乌氏粘度法测定三种CS的Mw分别为1080kDa、450kDa、230kDa,其相应的DD平均值分别为：87.8%、88.1%、87.6%。说明在CS降解过程中,CS的DD值无明显变化。保证了不同Mw的CS的DD的统一性。降解得到的两种CS样品的FTIR图谱没有峰的漂移,也无新峰的产生,糖链结构和氨基特征峰清晰可见,说明降解得到的不同分子量的CS的化学结构是稳定的。采用控制变量法,对复凝聚行为的影响因素进行研究。实验表明：CS/GA的质量比、壁材浓度、pH、离子强度等都会影响两种聚合物的凝聚产率以及平衡相的透光率。对于三种Mw的CS来说,得到较好的凝聚产率的条件分别是：GA:CS的质量比为6-8、壁材浓度为3-6%、pH3.5-5、低离子强度。在20-60℃实验温度范围内,凝聚产率随温度虽略有升高,但凝聚产率均在85%以上,说明温度(20-60℃)对复凝聚反应的影响不大。保证凝聚反应完成的时间是30min。凝聚产物的FTIR图谱表明：CS样品的-NH2、-CH-NH2吸收峰在凝聚物的红外光谱图中消失,说明CS分子上的氨基与GA分子发生了静电相互作用,形成凝聚产物。在保证获得较高的凝聚产率的实验条件下,确定了湿态CS/GA鱼油MC的制备工艺,并对湿态MC的部分理化指标进行了测试。实验结果表明：CS的Mw对GA与CS复凝聚成囊效果有较大的影响。其中Mw1080kDa的CS易与GA发生结块现象,难以成囊；Mw450kDa的CS与GA形成的MC形状不规则,囊间易发生粘连。Mw230kDa的CS能与GA形成规整的球形MC,囊间几乎无粘连现象发生。实验结果表明：Mw230kDa的CS适宜作为与GA复凝聚包埋鱼油的壁材。以Mw230kDa的CS为实验材料,与GA复凝聚制备湿态鱼油MC。高倍光学显微镜下观察发现在CS/GA壁材浓度为5%,CS:GA的比值为1：7,芯壁比为1：2,pH为4.5,反应温度为20℃,复凝聚反应时间30min的条件下,制备的湿态鱼油MC形态规整、呈球形、分布均匀,无粘连,且视野中可见的复凝聚形成的MC数量较多。故确定为实验室制备湿态CS/GA鱼油MC的制备条件。采用确定的实验室制备湿态CS/GA鱼油MC的工艺,获得的湿态CS/GA鱼油MC的平均粒径为16.3μm,鱼油的包埋率和壁材的利用率分别为75.33%和81.01%。采用确定的实验室制备湿态CS/GA鱼油MC的工艺,制备湿态CS/GA鱼油MC,经冷冻干燥后,形成干态CS/GA鱼油MC。观察SEM照片可见：干态CS/GA鱼油MC基本呈球形,表面为多孔结构,部分MC出现破壁。干态MC经复水后能恢复至冻干前的形态。通过测定干态CS/GA鱼油MC样品的表面油含量、总油含量和水分含量,计算分析得出MC的平均产率、包埋率和载油量分别为72.63%、67.53%、31.59%。干态CS/GA鱼油MC制备过程中,鱼油的POV增大,添加抗氧化剂TBHQ (250mg/kg鱼油)能有效抑制其氧化。有关CS/GA鱼油MC的更系统的研究,如干态CS/GA鱼油MC的干燥方法以及干态CS/GA鱼油MC对鱼油的保护作用等还有待研究。更多还原

【Abstract】 Microencapsulation is the process of preparing semi-permeable or sealed capsules using natural or synthetic macromolecule materials to embed solid particles, liquid drops or gas. Choosing the suitable wall-materials and effective methods to prepare stable microcapsules (MCs) have been the key target to researchers in the pharmaceutical and food industries. Fish oil is full of co-3 fatty acids such as EPA and DHA, which are functional ingredients to consumer. However, fish oil has poor solubility in water and is sensitive to light, heat and oxygen, which limits its application in food industries. Chitosan (CS) is a kind of natural alkalescency polysaccharides with polycation; and gum acacia (GA) is a kind of natural gel with carboxyl groups on molecular structure. Both CS and GA are absolutely safe to consumer as food materials, and have abundant sources. So it’s a significant task for us to prepare fish oil MCs using CS and GA as wall materials by complex coacervation through electrostatic interaction.The low molecular weight chitosan samples were prepared by the method of acid degradation in the HCl+Ethanol mixtures. Preliminary investigations indicated that the different molecular weights of chitosan were 1080kDa,450kDa and 230kDa, and the DD were 87.8%,88.1%,87.6% respectively. The FTIR spectroscopic studies showed the stability of different Mw CS(1080kDa and 230kDa) prepared by degradation and appearance of well-defined characteristic peaks of saccharide chains and the primary amino group structures.The influences of different factors on CS/GA complex coacervation were investigated. The results of experiments indicated that the yield of coacervation and transmittancy of equilibrium phase could be affected by the mass ratio of CS to GA, total concentration of CS/GA, pH value and ionic strength. The higher yield of coacervation could be obtained at the following experimental conditions:the mass ratio of CS:GA was 1:6-1:8, the concentration of CS/GA was 3-6%, pH was 3.5-5, and low ionic strength.The results indicated the reaction temperature had miner infection on CS/GA coacervation, because the coacervation yields were continuously above 85% with the increase of the reaction temperature from 20 to 60℃. The results also showed that the least reaction time of CS/GA coacervation were 30 minutes to ensure complete reaction. The FTIR spectroscopic studies showed absence of the characteristic peaks of-NH2 and-CH-NH2 in the coacervation samples, which could be suggested the electrostatic interaction performed between the amino group of CS and carboxyl of GA in the formation of coacervates.Under the experimental conditions of obtaining high coacervates yield, the better preparing processes of wet CS/GA fish oil MCs were determined and the physicochemical properties of MCs were tested. The results of experiments showed that the molecular weight of CS performed an important role in coacervation. The CS (Mw1080kDa) was easy to agglomerate with GA and hard to coacervate. The MCs prepared by CS (Mw450kDa)/GA were anomalous and reliable to conglutinate each other. The MCs prepared by CS (Mw230kDa)/GA were spherical shape with satisfactory structural integrity and no conglutination. The results of experiments showed the CS (Mw 230kDa) was suitable experimental sample as the wall material of MCs.The conditions of fish oil MCs prepared by CS (230kDa)/GA complex coacervation were the followings:the concentration of CS/GA was 3-5%, the mass ratio of CS:GA was 1:6-1:8, pH 4.0-5.0, the temperature was 20℃, and the reaction time was 30 min. The MCs prepared by coacervation were investigated by light microscopy. The results showed that the MCs were spherical shape with regular structural integrity and uniformity, no conglutination and higher yield of MCs in the following experimental conditions:the total concentration of CS/GA was 5%, the mass ratio of CS/GA was 1:7, pH 4.5, the temperature was 20℃, and the reaction time was 30 min. The mean particles size of MCs prepared under such condition was 16.3μm, the entrapment efficiency of fish oil and the availability of wall materials was 75.33%,81.01% respectively.Wet CS/GA fish oil MCs were prepared through the determined laboratory processes; then dried MCs were obtained by freeze drying. The SEM photographs showed that dried MCs were generally porous spheres, and part of them had break walls. Dried MCs could comeback their original shapes by rehydration. The mean yield, efficiency of microencapsulation, and the oil loading rate of the dried MCs were calculated by measuring the content of surface oil, total oil and moisture. The experimental results were 72.63%,67.53%,31.59% respectively.During the process of preparing dried CS/GA fish oil MCs, the POV of fish oil has been increased, while the oxidation of fish oil could be inhibited by adding antioxidant TBHQ (250mg/kg fish oil).More systematical experiment of the CS/GA fish oil MCs, such as the drying technologies and the protective functions of dried CS/GA MCs to fish oil, will be performed in future. v更多还原