【作者】 张海洋；

【导师】 张晓鸣；

【作者基本信息】 江南大学 ， 食品科学， 2010， 硕士

【摘要】 复合凝聚微法具有有效载量高、可控制释放及缓释等优点。目前的复合凝聚微胶囊多以明胶和阿拉伯胶为壁材,阿拉伯胶价格昂贵且性质不稳定。微胶囊的交联固化通常采用有毒的甲醛,严重限制了产品的应用范围。寻找价格低廉的新型复合凝聚微胶囊壁材,以及开发安全无毒的可食用固化剂意义重大。本论文研究了明胶/羧甲基纤维素(CMC)复合凝聚法制备球形多核微胶囊的工艺,以及以安全无毒的茶多酚作为微胶囊固化剂进行固化条件优化,并对植物多酚的固化机理进行了研究。研究结果如下:以明胶和CMC为壁材制备肉桂醛微胶囊时,最佳工艺参数如下:明胶/CMC比例9:1,pH 4.6,壁材浓度1%,芯壁比2:1。在此条件下制备得到的微胶囊球形较好,表面光滑,粒径均一,微胶囊的产率、效率可达97.01%和86.55%。热重释放曲线表明芯材肉桂醛经微胶囊化之后在150℃的释放速率大大降低,在高温下具有很好的稳定性;随着芯壁比的上升,微胶囊释放芯材的速度加快。在以茶多酚为交联剂的固化过程中,反应pH、反应时间、茶多酚添加量都对固化效果有着显著的影响。固化条件优化的结果为:在pH 10.0、反应时间12 h、茶多酚添加量0.1 g/g明胶条件下,微胶囊的固化效果较好。机理研究实验的结果表明:多酚需要氧化为醌才可以与蛋白发生反应;反应没有特定的位点,几乎所有的N末端氨基酸都会参与交联反应。对不同壁材(明胶/CMC与明胶/阿拉伯胶)制备的微胶囊的性质以及不同固化剂(茶多酚,甲醛和谷氨酰胺转氨酶(TG))的固化效果进行了比较研究,实验结果如下:明胶/CMC微胶囊与明胶/阿拉伯胶微胶囊相比,形态相似,包埋率提高,耐热性好于后者,而壁材成本大大降低。80℃热水中的稳定性实验与TG热释放实验结果显示茶多酚与甲醛和TG固化效果相近,能够很好地替代它们作为复合凝聚微胶囊的固化剂。对喷雾干燥微胶囊产品的理化性质进行了研究。喷干后微胶囊水分含量为3.32%,易于保存;休止角为38.2°,流动性较好;有效载量为40.74%。扫描电子显微镜观察结果表明微胶囊干燥后结构完整,囊壁没有破坏。热重实验的结果表明喷雾干燥法制备的微胶囊产品具有良好的热稳定性。更多还原

【Abstract】 Complex coacervation has many advantages such as the high payloads achievable, the controlled release and sustained release possibilities, etc. The most commonly used microcapsule wall materials are gelatin & gum arabic, however, gum arabic is expensive and its quality is irregular. Usually adopted toxic crosslinking agent formaldehyde limited extensive application of microcapsule products. It is of great importance to develop low-cost coacervation wall materials and non-toxic crosslinking agents. Preparation method of spherical multinuclear microcapsules by gelatin/carboxymethyl cellulose (CMC) coacervation was investigated. Cross-linking parameters in the process of tea polyphenols-hardened microcapsules were optimized. Mechanism of polyphenols crosslinking proteins was also studied. The results were as follows:The optimal technical parameters for preparation of cinnamaldehyde microcapsules by coacervation of gelatin/CMC were as follows: gelatin/CMC ratio 9:1, pH4.6, wall material concentration 1%, core/wall ratio 2:1. Microcapsules made under these parameters have nice spherical shape and uniform particle size. The encapsulation yield and efficiency were 97.01% and 86.55%, respectively. The heat-stability of microcapsules was investigated, TGA curves showed that at 150°C, the release rate of cinnamaldehyde decreased dramatically after microencapsulation, which has direct ratio relations of the core/wall ratio.The hardening effectiveness was significantly affected by the change of the hardening pH, time and tea polyphenols concentration. The optimum hardening parameters were as follows: hardening pH 10.0, hardening time 12 h, tea polypenols concentration 0.1 g/g gelatin. The mechanism research showed that polyphenols can only react with proteins after they were oxidized to polyquinones, there were no specific reaction sites and almost all N-terminal amino acid participated in the crosslinking reaction.Properties of microcapsules made of different wall materials (gelatin/CMC and gelatin/gum arabic) and the hardening effect of different crosslinking agents (polypenols, formaldehyde and transglutaminase (TG)) were compared. Comparing with gelatin/gum arabic microcapsules, gelatin/CMC microcapsules have similar morphology, better embedding effect, thermal stability, and much lower cost. The result of 80℃water-bath and TGA showed that compared with formaldehyde and TG, tea polyphenols exhibited similar hardening effectiveness, and can replace them as crosslinking agent of coacervation microcapsules.Physical and chemical properties of sprydried microcapsules were studied. The moisture was 3.32% and fit for storage; the repose angle was 38.2°, and the fluid was good; The loading of microcapsules was 40.74%. The microstructure valued by scanning electron microscope showed that microcapsules were integral and the surface was not destroyed through sprydrying. TGA curves showed that microcapsules made by sprydrying have fine thermal stability.更多还原