Sustainability assessment of active packaging incorporating nanomaterials

Abstract

Packaging plays an important role in ensuring food safety and quality. The development antimicrobial packaging enables actively inhibiting/killing the spoilage microorganisms, and thus extending food product’s shelf life. Generally, 50% shelf life extension is possible. The interest for using metallic nanoparticles in active packaging derives from its superior antimicrobial efficacy and no negative impact on the food sensory properties. In this thesis, the packaging material of concern is a PLA (Polylactic Acid) coated paper incorporating zinc oxide nanoparticles (ZnO NPs) in the coating layer. The material was characterized and its antimicrobial activity was evaluated. The SEM images show that the nanoparticles were homogenously distributed across the surface thanks to its surface modification. Antimicrobial assay indicates that the active material was effective in inactivating E. coli and S. aureus. Furthermore, E. coli was found to be more susceptible to this type of agent, showing 3.14 log reduction for 0.5 wt% agent loading in the PLA coating layer. This result was compared across the publications using the same agent for treating both Gram- positive and Gram-negative microorganisms. The discrepancy between the results can be explained by the fact that ZnO nanoparticles have multiple action mechanisms, and different antimicrobial testing methods may activate part of the action mechanisms. On the other hand, recyclability is regarded as an important attribute for paper- based packaging material, as it enables to conserve the resources and reduce the environmental impacts. Accordingly, when it comes to the nano-enabled paper packaging material, recyclability should be maintained. In this case, a recyclability test was carried out in a lab-scale paper recycling line. The protocol was based on a method adapted from the ATICELCA MC501-13, which enabled to recover over 99% of the solids material. The mass balance result indicates that 86%-91% zinc oxide nanoparticles ended up in the rejected material stream, mostly embedded within the polymer coating; whereas 7%-16% nanoparticles ended up in the accepted material stream. Besides, the tensile strength of the recycled handsheets suggests that the nano-enabled coating had no negative impacts on the recovered fibre quality. Active packaging plays a positive role in reducing food losses. If food and packaging are considered as a whole system, its overall environmental impact can be justified by incorporating the food loss reduction due to the application of active packaging. The LCA calculation shows that a breakeven point can be easily achieved for the case of red meat products of high environmental impact.