半纤维素/SPI可食膜IPN体系的构筑及其水分阻隔机理的研究

The difficulty in developing the traditional edible film materials mainly arises from their inherently poor strength and moisture barrier properties. In the present project, a novel kind of edible film material system exhibiting IPN microstructure will be constructed by the integration of hemicelluloses molecules coupled with soy protein isolate (SPI) with a three-dimension network structure. Such an approach is based on the theory of interpenetrating polymer networks (IPN) and the analysis of the molecular conformation and molecular segment in polysaccharide of bagasse hemicelluloses. The relationship between macroscopic properties of edible films and microstructure, strength and barrier properties will be disclosed based on the analysis of degree of polymerization, microstructure and film-forming properties. Besides, the isothermal adsorption curve and isothermal adsorption kinetics (GAB model) of hemicelluloses/SPI films material will be established based on the further investigation on moisture adsorption dynamics of edible films with hemicelluloses/SPI. By considering the O-H base vibration and absorption peak area, quantitative or qualitative studies regarding the hydrogen bonding between water molecules and edible film material will be performed, and the moisture barrier mechanism of edible film material can be disclosed. The proposed approach is capable of effectively governing the film-forming process and subsequently leading to the improved strength and moisture barrier of edible film material. The research results would contribute to the deep processing of agricultural and sideline products of sugarcane in Yunnan Province, Guangxi Province and so on. More importantly, it could considerably improve the added value of the products and promote the development of regional economy.

针对传统可食膜材料在强度和水分阻隔性等方面所存在的共性问题，以农业废弃物中的蔗渣半纤维素为基材，从微观结构设计角度出发，在对多糖分子构象和大分子链段分析的基础上，将半纤维素分子贯穿到具有三维网络结构的大豆分离蛋白（SPI）中，构筑具有互穿网络结构（IPN）的可食膜材料体系。通过对反应物大分子在成膜过程中物理聚合度、微观结构的研究，解析可食膜材料的IPN微观结构与强度及水分阻隔性能等宏观性质的相关性。建立半纤维素/SPI可食膜材料的吸附等温曲线和吸湿等温模型（GAB模型），并通过对所有 O-H 基振动信息和吸收峰面积的计算与拟合，定量或者定性研究水分子和可食用膜材料间氢键作用的种类和大小，明确可食膜材料的水分阻隔机理，进而实现从源头上对可食膜材料加工过程的调控，彻底解决其在水分阻隔性方面的问题。课题的研究对提升主要甘蔗产区的农副产品的附加值和推动区域经济发展方面具有重要的经济效益和社会意义。

强度和阻隔性差是传统可食膜存在的共性问题，对其进行微观结构设计和阻隔机理研究是解决上述问题的根本手段。本课题以农林废弃物中的蔗渣半纤维素为原料，在对半纤维素提取工艺及理化性质分析的基础上，依据互穿网络（IPN）聚合物理论，构建并解析膜材料微观结构与强度及水分阻隔性能等宏观性质的相关性，进而从源头上解决多糖类可食膜材料在强度和水分阻隔性方面的问题。本课题通过微波与酶、膨化及碱等协同预处理方式下半纤维素溶出规律及反应历程的研究，明确了反应条件与半纤维素高效提取及理化性质间的的交互性。理论计算及实践分析表明，酶或膨化处理有助于破坏或疏松纤维间的网络结构，可使半纤维素的提取效率提高30%以上，解决了传统半纤维素分离低效、低品质的根本问题。本项目还以纳米纤维素（NCC）为骨架，构建了具有网状结构的NCC-半纤维素/大豆分离蛋白（SPI）高强复合膜体系，解析了纳米纤维素与膜材料微观网络结构和宏观性质间的关联规律。研究发现，纳米纤维素不仅可以提高半纤维素基膜材料在常规环境下的强度，还能够改善其在高湿环境下的强度及阻隔性能。另外，半纤维素的酯化改性也进一步提高了半纤维素基膜材料在高湿环境下的疏水性能，但膜材料的强度性能也略有影响。本项目还通过半纤维素基膜材料在改善果蔬保鲜品质及果蔬出汁率方面的作用，获得了膜阻隔性能及微观结构与水果保鲜间的关联性规律。并通过对半纤维素基膜材料吸湿等温线的建立及吸附模型解析，明确了半纤维素基膜材料的吸附类型介于Ⅰ型和Ⅱ 型吸附之间，揭示了膜材料结构及阻隔性能间的关系。这些研究对从源头上解决可食膜材料强度及阻隔性能的基础科学问题提供了理论依据。