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

Abstract

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.

Production and In Situ Modification of Bacterial Cellulose Gels in Raisin Side-Stream Extracts Using Nanostructures Carrying Thyme Oil: Their Physicochemical/Textural Characterization and Use as Antimicrobial Cheese Packaging

“…For example, in a film composed of Ch/PVOH and modified with Zt-Th, the characteristic peaks of Zt were not observed, indicating a homogeneous dispersion of modified Zt-Th in the film, which is supported by the Th molecules adsorbed on Zt [27]. Ch/PVOH films modified with AC-Th gave similar results, as the characteristic peaks of AC had almost disappeared [14]. Therefore, there is probably a higher miscibility and dispersion of modified Zt-Th and AC-Th nanostructures in BC [27].…”

“…The hybrid bioactive zeolite/thyme oil (Zt-Th) nanostructure has been incorporated into a Na-alginate-glycerol polymer matrix, chitosan-polyvinyl alcohol (Ch/PVOH), and lowdensity polyethylene (LDPE), producing promising films for AFP applications with enhanced tensile, water and oxygen barriers, and antimicrobial properties (against food pathogens such as Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Salmonella enterica), which could extend the shelf life of meat and fruit products. The incorporation of activated carbon/thyme oil (AC-Th) nanostructures in CS/PVOH and in LDPE produced similar results, increasing the shelf life of meat and fruit products by at least 2 days [13,14].…”

“…Superscript letters (a-m for HS, a-l for RFSE) in a row indicate statistical differences between treatments (p < 0.05). The statistical analysis was performed for each substrate separately and for each day of incubation (7,10,14) between the control and the corresponding nanostructure (C/Zt-Th/Zt and C/AC-Th/AC). The lowest concentration of the Zt-Th nanostructure (0.04 g/L) used in the HS medium produced a relatively lower BC yield than the control and the % increase was negative, while when used at 0.32 g/L it led to a ~9% increase in the BC yield.…”

“…Also, since there are several concerns about their safety when directly used in food, their incorporation into AFP films has gained increased attention. To overcome the disadvantage of rapid loss due to their high volatility, the incorporation of EOs into nanostructures as carriers and their subsequent incorporation into AFP polymeric matrices has been proposed [10,[12][13][14][15][16][17][18][19].…”

“…Natural Zt and AC have been used as nanocarriers for the encapsulation of thyme oil, to develop an AFP for the controlled release of thymol, one of its main constituents [13,14]. The hybrid bioactive zeolite/thyme oil (Zt-Th) nanostructure has been incorporated into a Na-alginate-glycerol polymer matrix, chitosan-polyvinyl alcohol (Ch/PVOH), and lowdensity polyethylene (LDPE), producing promising films for AFP applications with enhanced tensile, water and oxygen barriers, and antimicrobial properties (against food pathogens such as Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Salmonella enterica), which could extend the shelf life of meat and fruit products.…”