Active sprayable coatings based on cellulose acetate/chitosan with cypress essential oil and anthocyanins: A novel combination for sardine fillet preservation.

Abstract

Sprayable coatings represent one of the most effective strategies to preserve freshness and extend the shelf life of highly perishable seafood products, which are prone to rapid deterioration leading to economic losses and health risks for consumers. This study aimed to exploit the properties of cypress essential oil (Cyp) and anthocyanin extract (Ant) to develop active coatings based on a cellulose acetate (CA) and chitosan (CS) blend. The physicochemical and antibacterial properties of the elaborated CA-CS-Cyp-Ant coatings, as well as their preservation effects on sardine fillets stored at 4 °C, were evaluated. Results showed a reduction in the viscosity of film-forming solutions in the presence of EO and Ant in CA-CS matrix due to hydrogen-bonding interactions. This result has been supported by in silico analysis, which revealed strong binding affinities (-3.9 kcal/mol for Ant-CA and - 3.8 kcal/mol for Ant-CS). This low viscosity suggests its use to a film-forming solution, thus making it suitable as a sprayable coating for food products. The CA-CS-Cyp-Ant films exhibited a pink coloration and increased thickness with Ant addition. FTIR confirmed interactions between the bioactive compounds and the CA-CS matrix, while XRD indicated reduced crystallinity (from 46.48% in CA-CS to 17.29% in CA-CS-Cyp-Ant). This amorphous character also influenced film morphology, making the surface smoother and more compact. Mechanical properties were improved, with a better balance between tensile strength and ductility observed in CA-CS-Cyp-0.5Ant films. Furthermore, CA-CS-Cyp-Ant films displayed strong antibacterial activity against E. coli (35 ± 1.4 mm) and S. aureus (36 ± 0.9 mm). When applied as sprayable coatings, they effectively preserved sardine fillets by reducing pH, maintaining color, and delaying lipid and protein oxidation, thereby extending shelf life. These findings highlight the potential of CA-C