Physical and antibacterial properties of PLA electrospun mats loaded with carvacrol and nisin

Abstract

Functional, biopolymeric electrospun structures for the controlled release of antimicrobial agents are gaining increasing interest in food packaging applications. In this study, the physical and antibacterial performances of ternary systems composed of polylactic acid (PLA) electrospun mats loaded with 20 wt% of different relative amounts of carvacrol (CRV) and a commercial nisin formulation (Nis) were assessed. Scanning electron micrographs displayed micro-scaled fibers with different diameter size distributions depending on the relative concentrations of the additives. The PLA/CRV/Nis membranes’ wettability was affected by the relative amount of CRV and Nis loaded, switching from hydrophobic to hydrophilic at the highest Nis concentrations. Thermal and tensile tests assessed the plasticizer action of CRV on PLA, while the Nis formulation was found to modify the mechanical behavior of the membranes from ductile to brittle. The release profiles of CRV and Nis from PLA/CRV/Nis structures, assessed via spectroscopical measurements and fitted with a power-law model, permitted to investigate of the different release mechanisms of the additives as a function of their relative concentration. The determination of the antibacterial activity of the electrospun material clearly indicated that the most effective inhibition of food-borne pathogenic bacteria was registered with PLA containing 20% of CRV.