电场下乙醇对玉米醇溶蛋白膜性质的影响

Effects of Ethyl Alcohol Concentrations on Properties of Zein Films Produced by Casting under Electric Field

在浇铸法成膜过程中引入电场处理玉米醇溶蛋白溶液,在不同乙醇浓度溶剂下,得到了质地柔软、形状完整的玉米醇溶蛋白膜,克服了纯玉米醇溶蛋白膜易碎裂、耐水性差的缺点。通过对薄膜性质的测定,研究了乙醇浓度与电场协同作用对玉米醇溶蛋白膜性质的影响。结果表明:电场处理可改善玉米醇溶蛋白膜性质,在电场与乙醇浓度协同作用下,玉米醇溶蛋白分子有序排列形成均匀的网络状结构,提高了薄膜的均一性;随着乙醇浓度的增大,玉米醇溶蛋白膜表面疏水性增强;电场处理后薄膜热特性改变,变性温度增大。当乙醇体积分数为90%时,薄膜理化性质最佳,拉伸强度、断裂伸长率分别为73.41 MPa、9.54%;水蒸气透过率为2.54×10-8g·m/(m2·h·Pa);SEM观察显示薄膜表面粗糙度明显降低,断面无孔隙;静态接触角测试为62.46°,变性温度为116.52℃,熔融热为56.61 J/g;Raman结果显示C=O双键断裂,β-折叠含量增加。通过调节溶剂浓度可得到具有一定机械强度,同时具有疏水特性的薄膜,为开发可食性食品包装材料提供了理论基础。

Coupled with the paralleled uniform electric field,the soft zein films with complete shape were obtained by casting. Effect of the electric field force on mechanical properties of zein film prepared for different alcohol concentrations was studied. As the tertiary structure of zein molecules was destroyed by electric field force,charged polar residues（ amino groups and carboxyl groups,etc） exposed and directionally moved along the electric field lines. The stable state of micelle-like structured zein molecules was seesawed until the molecules found some new levels of equilibrium. It was demonstrated that at the initial phase,tensile strength,breaking elongation and contact angle of films were increased with the increase of the concentrations of ethanol solution,and reached the maximum value（ 73. 41 MPa,9. 54%and 62. 46°,respectively）; water vapour permeability（ WVP） reached the minimum value of 2. 54 ×10- 8g·m /（ m2·h·Pa）. The changes of C=O and β-sheet vibrating peaks of Raman analysis indicated denaturation of protein partly. Observations under scanning electron microscope（ SEM） of surface and cross section revealed that the presence of uniform electric field helped to improve the properties of zein films. In conclusion,the findings of the synergistic effect of ethanol and the paralleled uniform electricfield on zein films may contribute to develop edible food packaging material with ideal surface morphology and hydrophobicity.