Active Coatings Development Based on Chitosan/Polyvinyl Alcohol Polymeric Matrix Incorporated with Thymol Modified Activated Carbon Nanohybrids

The food waste disposal to landfill practice contributes to the greenhouse problem due to the emission of gases such as methane into the atmosphere. Shelf life extension of food products and further valorization of food wastes such as the conversion to activated carbon are tested nowadays as alternative techniques. The development and use of biobased active coatings against food oxidation/bacterial deterioration is an environmentally friendly technique. In this study, a novel food active coating was successfully developed based on a chitosan (CS)/polyvinyl alcohol (PVOH) matrix activated with a nanohybrid of natural thymol (TO) adsorbed in activated carbon (AC) derived from spent coffee. The results have shown that, compared to the pure CS/PVOH polymeric matrix, the coating with 15 wt.% TO@AC nanohybrid concentration achieved a +23.5% Young's modulus value, a +20.1% ultimate strength value, an increased barrier of +50.2% for water and +74.0% for oxygen, a +69.0% antioxidant activity, an increased antibacterial activity of +5.5% against Escherichia coli, a +17.8% against Salmonella enterica, a +42.5% against Staphylococcus aureus, and a +2.5% against Listeria monocytogenes. A visual evaluation of this coating showed a delay in fresh bananas' enzymatic browning and a significant decrease in their weight loss. This indicates the potential extension of the fresh fruits' shelf life.