Active TPS/PBAT Blown Films Incorporating Sodium Lactate for Improved Oxygen Barrier, Antimicrobial Activity, and Cheese Preservation

Biodegradable active packaging that incorporates food-grade additives offers a promising solution for extending shelf life and minimizing food waste. This study investigates the development of functional packaging films for cheese applications by blending thermoplastic starch (TPS) and poly (butylene adipate-co-terephthalate) (PBAT) in a 60/40 (<i>w</i>/<i>w</i>) ratio with various concentrations of sodium lactate (SL; 1-7% <i>w</i>/<i>w</i>) using blown-film extrusion. Spectroscopic analyses, including ¹H NMR and FTIR, confirmed the presence of hydrogen-bonding and ionic interactions between the hydroxyl (-OH) groups of thermoplastic starch (TPS) and the carboxylate (-COO^-) groups of sodium lactate, which enhanced interfacial compatibility and produced smoother, more compact film morphologies. SL acted as a multifunctional plasticizer and compatibilizer, improving film flexibility while slightly reducing tensile strength. Notably, SL incorporation increased water vapor permeability and surface wettability but significantly decreased oxygen permeability to below 1 cc·mm/m²·day·atm. At moderate concentrations (≥ 3% <i>w</i>/<i>w</i>), SL also exhibited antimicrobial activity against Staphylococcus aureus. When applied to cheese packaging, SL-modified films effectively maintained color stability for up to 9 days under refrigerated storage. Notably, cheeses packaged with films containing 3-7% (<i>w</i>/<i>w</i>) SL exhibited significantly lower hardness values than the control on day 3, indicating improved moisture retention and texture preservation, although these differences were no longer significant by day 9. These findings demonstrate that sodium lactate can simultaneously enhance interfacial miscibility, oxygen barrier performance, and antimicrobial functionality in sustainable, biodegradable active packaging systems.