Preparation, characterization and application of chitosan/thyme essential oil composite film

In order to prepare a chitosan-based antibacterial film with excellent mechanical properties and study its properties, the tape casting method was used to prepare the composite film from chitosan, glycerin and thyme essential oil. Through single factor test and response surface optimization test, the tensile strength and elongation at break were used as response indicators to prepare the composite film with better mechanical properties, and the physical properties, water vapor permeability, solubility and bacteriostasis of the composite film were measured, and the characterization of the microstructure of the composite films. The results showed that the optimized composite film ratio was 1.5% chitosan, 0.5% glycerol, 0.5% thyme essential oil, 18.69 MPa tensile strength, 19.01% elongation at break, 2.52 g/h·m² water vapor permeability, and 23.78% solubility. The composite film had a good antibacterial effect and increased the DPPH radical scavenging rate to 52.4%. Its overall performance was superior to that of chitosan single film. The chitosan/thyme essential oil composite film can reduce the weight loss rate, hardness loss rate and POD activity of blueberry fruits during storage. Additionally, it effectively inhibits the decline of soluble solids content, anthocyanin content, and Vc content, while slowing the increase of MDA content, thereby maintaining fruit quality and enhancing the fresh-keeping effect. Adding thyme essential oil to prepare composite film provides a reference for the fresh-keeping research of freshly cut fruits and vegetables.