Engineering Active PET Packaging via Corona Treatment and Natural Biocide Coating: Carvacrol and Trans-Cinnamaldehyde for Food Preservation

The food packaging industry requires sustainable solutions to reduce plastic waste and replace synthetic additives. This study addresses the need for scalable methods to transform conventional polyethylene terephthalate (PET) packaging into active food preservation systems using natural biocides. Commercial PET packaging was surface-activated using industrial-scale corona treatment, followed by coating with natural biocides—carvacrol (CV) and trans-cinnamaldehyde (tCN). The resulting active packaging materials (PET-CV and PET-tCN) were characterized using XRD, FTIR, SEM, AFM, and desorption kinetics. Packaging properties including mechanical strength, oxygen barrier, antioxidant (DPPH), and antibacterial activity (against S. aureus and E. coli) were evaluated. Real-food preservation tests were conducted using fresh minced pork (4 °C, 6 days) and table olives (23 °C, 21 days), monitoring microbiological (TVC), colorimetric (CIE L*a*b*), and pH changes. Corona treatment successfully anchored both biocides through physical adsorption, with tCN exhibiting stronger surface interaction (desorption energy: 128.0 kJ/mol). Both coatings significantly improved oxygen barrier properties (61% reduction for PET-CV, 80% for PET-tCN). PET-tCN demonstrated superior antibacterial activity (inhibition zones: 15.0 mm against E. coli). In pork preservation, PET-tCN achieved a 2-log reduction in TVC, maintained meat redness (a*: 12.80 vs. 5.10 for control), and stabilized pH. For olives, PET-tCN reduced TVC by 2.35 log cycles and preserved green color. This corona-assisted coating approach, demonstrated here at laboratory scale, successfully transforms inert PET into multi-functional active packaging with potent antimicrobial, antioxidant, and barrier properties, significantly extending food shelf-life and offering a sustainable solution for reducing food waste.