Multilayer antimicrobial films based on starch and PLA with superficially incorporated ferulic or cinnamic acids for active food packaging purposes

Active packaging based on biodegradable polymers with naturally occurring active compounds, such as ferulic (F) and cinnamic (C) acids, have been studied to reduce the environmental impact of food packaging while prolonging food shelf-life. Three-layered films PLA/starch/PLA (PSP) were designed based on the complementary barrier properties of the polymers, and film systems with improved barrier properties were obtained. To promote the compound release, superficial incorporation of F or C through two coating methods was tested: film spraying with 5% ethanolic solutions of F or C and electrospinning of solutions containing PLA and active compound. Electrospinning was effective at producing fibre mats encapsulating the acids while the film spraying produced firmly attached crystalline formations of active compounds on the surface. Films coated by both electrospinning and pulverisation showed effective growth inhibition of E. coli and L. innocua. Listeria was more sensitive to both active compounds while C showed greater antibacterial activity. Electrospun films were more effective than pulverised, suggesting a greater ability to release the active compounds. Therefore, PSP laminates with surface-loaded ferulic or cinnamic acid are good materials for active food packaging, contributing to extending the food shelf life.