Novel eugenol-based antimicrobial coatings on aluminium substrates for food packaging applications

Active packaging systems, interacting directly with the enclosed food, can delay or inhibit those phenomena responsible for food quality decay, contrib-uting to the food shelf-life extension. In this work a vinyl resin-based coating containing free or loaded eugenol (EG) in Santa Barbara Amorphous (SBA)15 mesoporous silica nanoparticles is designed to coat flexible aluminium foils to obtain an antimicrobial material. Thermogravimetric analysis shows a good loading capacity of eugenol in SBA15 (48% wt/wt). SEM analysis shows a good dispersion of free EG in the hosting polymeric matrix, whereas some EG/SBA15 particles aggregations are observed in the material. Water contact angle highlights a higher hydrophobicity of the eugenol based-materials (> 90 degrees) compared to the pristine vinyl coating (85 degrees). Electrochemical imped-ance spectroscopy highlights no corrosion phenomena of the VIN/5%(EG/ SBA15(EG)) coating and corrosion phenomena of the VIN/5%EG coating after 7 days of exposure to lactic acid pH = 4. Finally, the two active coatings are studied to evaluate their antibacterial activity using the ISO 22196. Interest-ingly, results demonstrate that when eugenol is loaded in the SBA15 mesopor-ous silica nanoparticles the antimicrobial activity of the material significantly increases against both foodborne pathogens and food spoilage bacteria, achiev-ing the highest microbial growth reduction on S. aureus (R = 3.62 log).