Improving active packaging functions of PLA films

There has been a marked increase in the use of biopolymer-based active packaging film, which can improve the shelf life of food. However, poly(lactic acid) (PLA) packaging suffers from poor gas barrier as wenn as poor antibacterial und UV barrier properties. To address this issue, researchers have applied a coating technology to improve the active packaging functions of PLA film. In this study, inspired by super adhesion and versatility of catechol groups based on mussel bionics, catechol-functionalised layered clay (LDHs@QUE-Cu) was first synthesised through adsorption and complexation of natural active polyphenol quercetin (QUE) with copper ions on the surface of layered double hydroxides (LDHs). PLA active multilayer composite films were developed by incorporating LDHs@QUE-Cu (0.5–5 wt%) into chitosan (CS)/poly(vinyl alcohol) (PVA) coatings.

Good transparency and mechanical properties

With the addition of LDHs@QUE-Cu, the maximum antibacterial rate against Escherichia coli of PLA active multilayer composite films reached 87.8 %. Even compared with the control sample (PLA film coated by pure PVA), the oxygen transmission rate of PLA active multilayer composite films was still reduced by 77.5 %. Compared with PLA film, the UV absorption (at 280 nm) of PLA active multilayer composite films was increased by up to 39.8 %. Still, all films maintained good transparency (higher than 88.0 %) and mechanical properties. Therefore, the multilayer composite films obtained by waterborne multifunctional coatings on the surface of PLA film can be applied potentially in active food packaging application.

The study has been published in Progress in Organic Coatings, Volume 170, September 2022.