Carvacrol@ZnO and trans-Cinnamaldehyde@ZnO Nanohybrids for Poly-Lactide/tri-Ethyl Citrate-Based Active Packaging Films

The growing demand for sustainable food packaging has driven the development of active packaging systems using biopolymers like poly(lactic acid) (PLA) and natural antimicrobials. This study focuses on creating novel nanohybrids by loading carvacrol (CV) and <i>trans</i>-cinnamaldehyde (<i>t</i>CN) onto ZnO nanorods for incorporation into PLA/triethyl citrate (TEC) films. The CV@ZnO and <i>t</i>CN@ZnO nanohybrids were synthesized and characterized using XRD, FTIR, desorption kinetics, and by assessing their antioxidant and antibacterial properties. These nanohybrids were then integrated into PLA/TEC films via extrusion. The resulting active films were evaluated for their physicochemical, mechanical, barrier, antioxidant, and antibacterial properties. The <i>t</i>CN@ZnO nanohybrid exhibited a stronger interaction with the ZnO surface and a slower release rate compared to CV@ZnO. While this strong interaction limited its direct antioxidant activity, it proved highly beneficial for the final film's performance. Films containing 10% <i>t</i>CN@ZnO demonstrated the strongest antibacterial efficacy in vitro against <i>Listeria monocytogenes</i> and <i>Escherichia coli</i> and functioned as potent mechanical reinforcement fillers. Crucially, in a practical application, the PLA/TEC/10<i>t</i>CN@ZnO film significantly extended the shelf-life of fresh minced pork during 6 days of refrigerated storage. It effectively suppressed microbial growth (TVC), delayed lipid oxidation (lower TBARS values), and preserved the meat's colour and nutritional quality (higher heme iron content) compared to control packaging. The developed <i>t</i>CN@ZnO nanohybrid is confirmed to be a highly effective active agent for creating PLA/TEC-based packaging that can enhance the preservation of perishable foods.