壁材对微胶囊物化性质及与载体混合动态行为的影响机理

The physicochemical properties of microcapsules and mixing behavior with food vector affect the application range in the food industry. The project is based on wall material models of the molecular structure that principally cover molecular weight distribution, molecular chains and flexible/rigid grouping combined with the rheological characteristics of viscoelasticity and stress-strain relationship. The differences of molecular structure among wall material models was elucidated. The physicochemical properties of microcapsules prepared by spy-drying were studied in terms of parameters including outer topography or morphology, particle size distribution, flowability, test weight, mechanical properties and thermodynamic stability. The effect of the law of molecular structure and rheological characteristics of wall material models on the physicochemical properties of microcapsules was investigated. The mechanism of stress-strain and stress fracture of microcapsules was studied in the spy-drying process. The mixing dynamic behavior between microcapsules with food vectors was simulated by the Particle Flow Code-based discrete element method and three dimensional stem contact model. A mathematical model was established to describe the mixing dynamic behavior. The project aims to elucidate the mechanism of wall materials on the physicochemical properties of microcapsules and mixing dynamic behavior, to build and devise microcapsules according to the special needs of the food industry,to screen and develop new wall materials and formulate a scientific rationale and research approach.

微胶囊的物化性质和与食品载体的混合行为影响其在食品工业中的应用。本项目基于对不同壁材模型的分子量分布、分子链结构、分子柔性基团和刚性基团等分子结构的研究，结合不同壁材模型呈现出的粘弹性、应力-应变关系等流变特性，阐明壁材模型分子结构的差异；利用喷雾干燥技术制备微胶囊，并对微胶囊的表观形态、粒径分布、流动性、容重、机械力学和热力学稳定性等物化性质进行研究，探讨壁材分子结构及流变学特性对微胶囊物化性质影响的规律；揭示微胶囊在喷雾干燥制备过称中产生应力-形变、应力破碎的机理。应用离散元颗粒流数值模拟软件(PFC3D)，采用三维干接触模型模拟微胶囊和食品载体颗粒介质的混合动态行为，建立描述微胶囊与食品载体混合动态行为的数学模型。本项目旨在揭示壁材分子结构及流变学特性对微胶囊物化性质及与载体混合行为影响的机理，为构建和设计符合食品工业特定需要的微胶囊、为壁材筛选和开发新型壁材，提供科学理论依据。

壁材影响微胶囊的物化性质及其在食品工业中的应用。利用高效液相色谱对壁材分子量分布进行表征Mw依次为：变性淀粉3.069×105g/mol、阿拉伯胶(GA) 2.493×105g/mol、羧甲基纤维素(CMC) 1.351×105g/mol、大豆分离蛋白(SPI) 6.368×103g/mol、明胶5.526×103g/mol，多糖类壁材Mw明显大于蛋白类。壁材的乳化稳定指数（ESI）大小为：变性淀粉2706.25、GA 3898.33、SPI 23.72、明胶 2432.22、CMC 0。壁材膜机械力学特性的模糊综合评价累加加权隶属度值为：变性淀粉0.658，CMC0.5847，GA0.5047，SPI0.4818，明胶0.4008。.利用Anton Paar旋转流变仪研究壁材的表观黏度和动态流变模量，结果表明：表观黏度-剪切应力曲线符合假塑性流体的特征曲线， Herschel-Bulkley方程拟合结果表明呈现剪切稀化的现象。80℃条件下，壁材弹性模(G')和黏性模量(G'')均随着剪切频率的增大而增大，其中SPI的G'＞G''，其他壁材的G''＞G'。.用喷雾干燥法制备微胶囊，不同壁材制备的微胶囊的产率和效率大小为：GA 95.12%和90.77%，变性淀粉94.06%和89.64%，明胶92.15%和82.27%，SPI 86.09%和78.50%，CMC 77.60%和75.31%，ESI越高产率和效率也越高。不同壁材基的微胶囊的表观形态有差异：变性淀粉基的微胶囊成球形，表面光滑； GA基、明胶基和SPI基表面有凹陷； CMC基表面有褶皱。表观形态与壁材的黏弹性和分子结构存在相关性。变性淀粉基、GA基、SPI基、明胶基、CMC基微胶囊的体积平均粒径D(4,3)分别为38.31μm、 37.78μm、35.00μm、30.68μm、21.80μm(p＜0.05)，其流动性也依次减少。.以上研究表明，变性淀粉是一种性能优良且又经济的壁材，传统的OSA-starch的制备是酯化反应和酶解，本研究尝试微波制备OSA-starch， 研究表明微波处理马铃薯淀粉的分子量和动态流变模量变化规律为：微波处理0～15s期间，分子量缓慢降解， G′和G"缓慢增加，波处理15～20s，分子量、G′和G"降低明显，研究结果表明微波制备作为包埋壁材用的OSA-starch是可行的。