Food packaging has become an essential tool in food manufacturing since it protects them against contamination, preserving their nutritional and sensory properties, and extending the product's shelf life. Polylactic acid (PLA) is one of the most attractive bio-based and biodegradable polymers used for food packaging. However, its use has been limited because of the poor barrier properties. Various strategies have been adopted to improve the properties of biopolymers, such as the creation of multilayer systems.

In the present study, layers of cellulose nanocrystals (CNC) and chitosan (Ch) were applied on PLA film to enhance the barrier properties and antimicrobial activity. Packages composed by functionalized PLA were made to store a cured semi-skimmed cheese at refrigerated conditions. Shelf-life parameters were monitored through the performance of physicochemical (moisture, pH, acidity, texture profile analysis, and colour determination) and microbiological analyses (total mesophilic and total mould/yeast). The tests were carried out in parallel with unpackaged cheese samples (control) and cheese samples packaged in low-density polyethylene (LDPE) film.

Unpackaged cheese samples presented the worst values in terms of moisture, colour and hardness from the first week, while the PLA multilayer film functionalized with Ch-CNC presented physicochemical properties similar to LDPE and better results in microbiological tests. Therefore, this active packaging can be used to improve the shelf-life of cheese.

Acknowledgments: A. Lestido-Cardama is grateful for her grant “Margarita Salas grants for the training of young doctors” (Ministry of Universities, Spain). A. I. Bourbon acknowledges funding by FCT, through the individual scientific employment program contract (2020.03447.CEECIND).