Layer-by-layer chitosan-based films with middle-layer incorporated rosemary oil nanoemulsion for sustained release and minced beef preservation

Abstract The aim of this study is to develop three-layer chitosan films enriched with rosemary oil nanoemulsion (RONE) at concentrations of 0.5%, 1%, and 1.5%, to to enhance antimicrobial properties and control oil release. Gas chromatography–mass spectrometry (GC–MS) identified 1,8-Cineole (20.52%), borneol (19.6%), and α-pinene (17.57%) as the main components of rosemary essential oil (REO). RONE prepared via ultrasonic homogenization, had a particle size of 70.75 nm, a polydispersity index (PDI) of 0.299, and a zeta potential of − 8 mV. Films with RONE exhibited reduced hydrophobicity and water vapor permeability (WVP) but maintained tensile strength (TS) and elongation at break (EAB). Scanning electron microscopy (SEM) confirmed smooth and compact film structures. Films containing 1% and 1.5% RONE showed enhanced antimicrobial activity against Staphylococcus aureus and Bacillus subtilis . Minced beef stored at 4 °C for 12 days with these films demonstrated reduced growth of Pseudomonas spp. and H₂S-producing bacteria. Additionally, peroxide value (PV) and total volatile nitrogen (TVN) levels remained within acceptable limits. These results highlight the potential of RONE-enriched chitosan-based multilayer films as sustainable food packaging solutions with antimicrobial, antioxidant, and prolonged-release properties to extend shelf life.