Analytical spectroscopic characterization of green chitosan/copper nanocomposites for food packaging applications

INTRODUCTION

Reducing agrifood waste has become an important goal, considering that up to 50% of total production is lost due to contamination by harmful microorganisms. In this context, controlling the interface between food products and the external environment can be a powerful tool to prevent waste. The aim of this study was to produce a bio-based and biodegradable food packaging material loaded with copper particles, which act as a reservoir of cupric ions.

METHODS

A green one-pot approach was used to synthesize copper particles using poly(N-vinylpyrrolidone) (PVP) as a capping agent (Cu@PVP), preventing aggregation through steric hindrance and eliminating the need for an inert atmosphere. The influence of PVP and reductant concentrations, as well as reaction time, on the oxidation state of copper phase, synthesis kinetics, and particle size was investigated by varying each of these parameters individually. Optimal conditions were identified to obtain an average particle diameter above 200 nm, while minimizing reagent and time consumption, to prevent nano-cytotoxicity effects. After a purification step, the Cu@PVP particles were suspended in ethanol and embedded in a chitosan (CS) polymeric matrix.

RESULTS

Composite films were obtained by solvent casting. The polymer solution concentration was adjusted to maintain good rheological properties even in the presence of inorganic particles. Torsional rheology and water uptake measurements were performed to assess the mechanical behavior of the self-standing films obtained after solvent evaporation. The antimicrobial capabilities were demonstrated by ionic Cu²⁺ release kinetics, and in vitro by growth inhibition of three different model fungi responsible for agrifood spoilage.

CONCLUSIONS

This innovative material could be used for the production of biodegradable bags and envelopes destined for the storage of fruits and vegetables, extending the shelf-life of these horticultural products.