Bioinspired hydrophobic chitosan-based films for monitoring the visual freshness of pork

This study used chitosan (CS) as the film matrix and curcumin (Cur) as the indicator (CC). Inspired by the adhesion of mussels, a hydrophobic indicator film was prepared by fixing a hydrophobic layer formed by rice bran wax (RW) and hydrophobic SiO 2 onto the CS matrix via dopamine self-polymerization. The results showed that the CS film with RW and SiO 2 coatings (CC-R-S) presented hierarchical micro- and nanostructures, significantly increasing the hydrophobicity and stability compared with those of CC. The water contact angle (WCA) increased from 84.28° to 130.43°. Even after mechanical abrasion, the WCA remained above 118°, and after chemical corrosion, the WCA stabilized at approximately 120°. The excellent durability enabled CC-R-S films to be applicable to the internal surfaces of various food packages to decrease the amount of liquid food remaining as much as possible. Moreover, after being sprayed with RW-SiO 2 , the elongation at break increased by 1.73 times, whereas the water vapor permeability decreased by 0.19 times. The CC-R-S film also displayed good pH responsiveness and NH 3 sensitivity. When monitoring the freshness and preservation of pork at different temperatures, the CC-R-S film clearly varied in color from yellow to red but also extended the shelf life of pork by 2 days at 25 °C and 4 °C. Therefore, this study holds enormous potential for the application of smart food packaging to monitor meat quality changes.