Thymol is widely recognised as an antibacterial compound. However, its use in food technology is hindered by its high volatility, its light sensitivity and its low solubility in water. To overcome these drawbacks, the preparation of nanoparticles using polylactic acid (PLA) is proposed in this study. The average size of the nanoparticles and thymol encapsulation efficiency parameters were studied using different PLA and thymol concentrations. Furthermore, the morphology, the storage stability of the nanoparticles at several pHs and the in vitro thymol release profile were also studied, as well as their thermal degradation profile. Finally, their antimicrobial activity on a real food model was measured, using for this purpose apple pieces previously inoculated with E. coli. The PLA was found to be the key variable in optimizing the nanoparticle preparation, producing spherical nanoparticles with a thymol encapsulation efficiency of 60.3 +/- 8%. These nanoparticles showed a high storage stability at several pHs and improved antimicrobial properties in comparison with the non-encapsulated thymol.