Abstract
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.
Highlights
Food spoilage caused by microorganisms can occur in a short time unless the proper precautions are taken
The differences in particles size determined by Scanning Electron Microscopy (SEM) and laser diffraction (LD) could be mainly attributed to the good dispersion of particles achieved during laser diffraction analysis, in SEM observations particles were found as agglomerates
Active films were obtained from thermoplastic corn starch containing copper particles as antimicrobial agent at concentrations up to 5%
Summary
Food spoilage caused by microorganisms can occur in a short time unless the proper precautions are taken. Despite the processing of raw food extend their shelf life, processed food generally needs to be packaged for protection, containment, convenience and communication [1]. These packaging characteristics are considered passive since they merely act as a barrier between the packaged food and the external environment. The food industry has been tremendously changing to innovate packaging, to cope with global trends, technological advances, and consumer preferences [2]. The main strategies to achieve this capacity are: i) the inclusion of sachets/pads that contain volatile antimicrobial compounds, ii) the incorporation of volatile and nonvolatile antimicrobial compounds directly into the structure of the polymers, iii) the application of a coating or adsorbing antimicrobial compound onto the surfaces of the polymers in contact with a foodstuff, iv) the immobilization of antimicrobial agents in polymers by methods such as ion or covalent linkages, v) the application of polymers, such as chitosan, that can inherently act as antimicrobial compounds, and vi) the incorporation of antimicrobial nanoparticles/microparticles [5]
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