Abstract A chitosan-based pH-responsive functional film was prepared by the incorporation of alizarin and its properties were tested for active and intelligent food packaging applications. SEM and FTIR results showed that alizarin was uniformly distributed in the chitosan matrix to form a homogeneous film. The alizarin-added chitosan film showed high UV-blocking property with increased elongation at break, surface hydrophobicity, and thermal stability of the film. The release rate of alizarin from the film was dependent on the solution showing a higher release rate in a 50% ethanol solution than that in water, 10% and 95% ethanol solutions. The synergistic effect of antibacterial activity by the addition of alizarin was negligible against E. coli but slightly increased against L. monocytogenes. However, the antioxidant activity of the chitosan film was significantly increased by the addition of alizarin. The color of the composite film changed vividly from slightly yellow to purple in response to a pH change in the range of 4–10, and the composite film was very sensitive to ammonia vapor. The composite coating could indicate the onset of fish spoilage by showing color change from khaki to light brown as the pH of the packaged fish changed.

中文翻译：

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用于智能包装应用的含有茜素的 pH 响应壳聚糖基薄膜

摘要 通过掺入茜素制备了壳聚糖基pH响应功能膜，并对其性能进行了活性和智能食品包装应用测试。SEM和FTIR结果表明茜素均匀分布在壳聚糖基质中，形成均匀的薄膜。添加茜素的壳聚糖薄膜表现出较高的紫外线阻隔性能，增加了薄膜的断裂伸长率、表面疏水性和热稳定性。茜素从薄膜中的释放速率取决于溶液，在 50% 乙醇溶液中的释放速率高于在水、10% 和 95% 乙醇溶液中的释放速率。添加茜素的抗菌活性对大肠杆菌的协同作用可以忽略不计，但对单核细胞增生李斯特菌的作用略有增加。然而，茜素的加入显着提高了壳聚糖薄膜的抗氧化活性。复合膜的颜色随着 pH 值在 4-10 范围内的变化而生动地从淡黄色变为紫色，并且复合膜对氨蒸气非常敏感。随着包装鱼的 pH 值变化，复合涂层可以通过显示颜色从卡其色变为浅棕色来指示鱼变质的开始。