Biodegradable films based on thermoplastic corn starch (TPS) and copper particles with antimicrobial capacity were developed. Copper nanoparticles (Cu) and silica coated copper microparticles (Si-Cu) in the range of 0.25 to 5% were used. Composite films were obtained by melt-mixing and subsequent thermo-compression. Particles distribution within TPS matrix and the presence of some pores and cracks, induced by Si-Cu particles, was evaluated by SEM. The presence of both fillers gave composite films a brown pigmentation and decreased their transparency; these effects were more pronounced at higher particles concentrations. Regarding mechanical properties, copper particles at 1 and 5% acted as reinforcing agents increasing the maximum tensile strength but their presence lead to a decrease in elongation at break, affecting films ductility. Composites inhibited the growth of Gram+ and Gram- bacteria, demonstrating their antimicrobial capacity. Copper effectively migrated to a simulant of aqueous foods and naked particles concentration in the simulant medium resulted higher than the minimum inhibitory concentration for bacteria. The characteristics and properties of developed composite films make them an interesting material for food primary packaging, mainly for meat fresh products.

中文翻译：

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用铜颗粒功能化的柔性热塑性淀粉薄膜，用于食品包装

开发了基于热塑性玉米淀粉（TPS）和具有抗菌能力的铜颗粒的可生物降解薄膜。使用0.25至5％范围内的铜纳米颗粒（Cu）和二氧化硅涂覆的铜微粒（Si-Cu）。通过熔融混合和随后的热压缩获得复合膜。通过SEM评估了TPS基质内的颗粒分布以及由Si-Cu颗粒引起的一些孔和裂纹的存在。两种填料的存在都会使复合膜呈现褐色着色，并降低其透明度。这些影响在较高的颗粒浓度下更为明显。关于机械性能，铜颗粒的含量为1％和5％时，它们可作为增强剂来提高最大拉伸强度，但它们的存在会导致断裂伸长率降低，从而影响薄膜的延展性。复合材料抑制了革兰氏阳性菌和革兰氏细菌的生长，证明了它们的抗菌能力。铜有效地迁移到水性食品的模拟物中，并且模拟培养基中的裸露颗粒浓度高于对细菌的最小抑制浓度。发达的复合膜的特性和性能使其成为食品初级包装（主要是肉类新鲜产品）的有趣材料。