Thymol Modified Activated Carbon Nanohybrids for Chitosan/Poly-Vinyl-Alcohol Based Active Coatings

Abstract

Food waste disposal to landfills practice contributes to greenhouse problem due to the emission of gases such as methane to 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)/poly-vinyl alcohol (PVOH) matrix activated with a nanohybrid of natural thymol (TO) adsorbed in activated carbon (AC) derived from spent coffee. The results shown that, compared to the pure CS/PVOH polymeric matrix, the coating with 15% wt. TO@AC nanohybrid concentration achieved +23.5 % Young’s modulus value, +20.1% ultimate strength value, increased barrier of +50.2% for water and +74.0 % for oxygen, +69.0% antioxidant activity, increased antibacterial activity of +5.5% against Escherichia coli, +17.8% against Salmonella enterica, +42.5% against Staphylococcus aureus, and +2.5% against Listeria monocytogenes. A visual evaluation of this coating shown a delay to fresh bananas enzymatic browning and significantly decrease their weight loss. This indicates that it could be potentially used to extend the shelf-life of fresh fruits.