Colorimetric films incorporated with anthocyanins as an indicator for freshness monitoring have aroused growing interest recently. However, the application of the films is limited by the easily oxidizable nature of anthocyanins. In this work, we developed a novel colorimetric film with a barrier by coating mulberry anthocyanin (MBA) on the internal side of an ethylene-vinyl alcohol copolymer–montmorillonite (EVOH–MMT) multilayer film. A facile layer-by-layer (LBL) assembly was employed under a parallel electric field to build the EVOH–MMT multilayer structure, in which the exfoliated MMT nanosheets were well-oriented and assembled on the EVOH matrix to form a tightly stacked layer between two EVOH layers. The interlayer of MMT significantly enhanced the barrier and mechanical properties of the films (below 40 layers). The interactions between EVOH and MMT and between EVOH and MBA were confirmed to be intermolecular hydrogen bonds. The colorimetric response of (EVOH–MMT)₄₀–MBA₃ to volatile ammonia and pH was sensitive, and the color change could be easily distinguished by the naked eye. The successful application of (EVOH–MMT)₄₀–MBA₃ to shrimp-freshness monitoring confirms its high potential for the freshness monitoring of packaged food.

中文翻译：

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乙烯-乙烯醇共聚物-蒙脱石多层阻隔膜涂有桑An花色苷以监测新鲜度

最近，结合花色苷作为新鲜度监测指示剂的比色膜引起了越来越多的兴趣。然而，膜的应用受到花青素容易氧化的性质的限制。在这项工作中，我们通过在乙烯-乙烯醇共聚物-蒙脱土（EVOH-MMT）多层膜的内侧涂覆桑树花色苷（MBA），开发了一种具有阻挡层的新型比色膜。在平行电场下，采用简单的逐层（LBL）组件来构建EVOH-MMT多层结构，其中，剥落的MMT纳米片取向良好，并组装在EVOH基质上，以形成一层紧密堆叠的层两个EVOH层。MMT的中间层显着增强了薄膜的阻隔性和机械性能（低于40层）。EVOH和MMT之间以及EVOH和MBA之间的相互作用被证实是分子间氢键。（EVOH–MMT）的比色响应₄₀ –MBA ₃对挥发性氨和pH值敏感，并且肉眼可以容易地区分颜色变化。（EVOH–MMT）₄₀ –MBA ₃在虾肉新鲜度监测中的成功应用证实了其在包装食品新鲜度监测中的巨大潜力。