不同硬脂酸添加量下大豆分离蛋白/海藻酸钠膜特性研究

为改善大豆分离蛋白/海藻酸钠复合膜的耐水性，通过添加不同添加量（0、2%、4%、6%、8%、10%）硬脂酸制备大豆分离蛋白/海藻酸钠/硬脂酸三元复合膜，探究硬脂酸对大豆分离蛋白/海藻酸钠复合膜的机械性能、阻水性能和微观结构的影响，最终明确不同硬脂酸添加量对耐水性变化的影响规律。结果表明：与大豆分离蛋白/海藻酸钠二元复合膜相比，添加6%和8%硬脂酸后，复合膜的断裂伸长率、水蒸气透过率显著下降，并且对其含水率及水溶性也有显著影响。当硬脂酸添加量为8%时，三元复合膜的水蒸气渗透性最低，水蒸气透过系数为（2.95±0.49） g·mm/（m²·h·kPa）,接触角最大，为91.68°±9.02°。通过傅里叶变换红外光谱和扫描电子显微镜分析可知，大豆分离蛋白和海藻酸钠通过共价交联形成网络结构，加入的硬脂酸则分布在网络结构的缝隙中，当硬脂酸添加量为8%时，膜的表面较为光滑平整，内部结构致密，能够形成良好的网络结构，键与键之间结合较强，能有效提高复合膜的阻水性能。

Effect of Stearic Acid on Properties of Soy Protein Isolate/Sodium Alginate Films

Soy protein isolate/sodium alginate composite films were prepared with stearic acid to improve the water resistance of soy protein isolate/sodium alginate composite films. Effects of different stearic acid additions (0, 2%, 4%, 6%, 8%, 10%) on composite films were evaluated by measuring mechanical properties, water resistance and microstructure of composite films. The results showed that with the 6% and 8% stearic acid addition, elongation at break and water vapor transmittance was significantly decreased, and water content and water solubility were also greatly affected compared with that of the composite film without stearic acid. When the adding amount was 8%, ternary composite films had the lowest water vapor permeability value ((2.95±0.49)g·mm/(m2·h·kPa)) and highest contact angle value (91.68°±9.02°). Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis showed that soy protein isolate and sodium alginate formed the network structure through covalent crosslinking, and stearic acid was distributed in the gaps of the network structure. Therefore, when 8% stearic acid was added, the formation of a good network structure made the molecular structure of the composite films denser, and imparted smother surfaces and flatter cross-sections to the composite films, which can improve the water-resistance performance of the composite films. These results showed that the water resistance of soy protein isolate/sodium alginate composite films can be improved by using appropriate stearic acid effectively, which would have important implications in the development of biopolymer-based packaging materials with moisture barrier properties.