Abstract: In this study, diatomite was used as an effective carrier for carvacrol to prepare an antibacterial complex, which was further incorporated into gelatin solution to obtain active composite films. The effect of the addition of the complex on the physical properties and antibacterial activity of gelatin based composite films was investigated. The results of scanning electron microscopy (SEM) and infrared spectroscopy showed that carvacrol was successfully adsorbed to the pores and surface of diatomite. With increasing content of the complex, the thickness, elongation at break, water vapor permeability, oxygen permeability, antioxidant activity and antibacterial activity increased, whereas the light transmission, moisture content, water solubility and tensile strength of the films decreased. Overall, the film with the complex added at 20% showed good performance, whose tensile strength and elongation at break were 15.13 MPa and 67.43%, respectively. The film scavenged 56.33% of 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical, and the inhibition zone diameter of the film against Staphylococcus aureus and Escherichia coli was 39.4 and 23.7 mm, respectively. More importantly, the gelatin film containing diatomite/carvacrol complex exhibited a much slower release rate of carvacrol and longer-acting antibacterial activity than the film containing the same content of carvacrol. These experimental results provide theoretical guidance and an experimental reference for using diatomite to carry carvacrol in developing antibacterial gelatin films with sustained release properties.

Key words: diatomite; carvacrol; gelatin; sustained-release; antibacterial film