Gelatin films incorporated with thymol nanoemulsions: Physical properties and antimicrobial activities

Abstract

Essential oils are natural antimicrobils and have been frequently incorporated into edible films aimed at extending shelf-life of food products. In this study, thymol nanoemulsions co-emulsified by natural emulsifiers (i.e., blend of gelatin and soy lecithin) were prepared and incorporated into gelatin films. The physical and antimicrobial properties of gelatin films were characterized. Thymol nanoemulsions incorporation increased the water vapor permeability and elongation at break of gelatin film, but decreased the moisture content and tensile strength. With nano-scale and uniform particles, the surface of films containing thymol nanoemulsions was smooth and continuous. Due to the hydrophobic property of lecithin and thymol, the water contact angle of gelatin film increased to above 90°. Moreover, sustained release of thymol from gelatin films was also observed, and these films exhibited effective inhibition activities against both Gram-positive and Gram-negative bacteria. Therefore, gelatin films containing thymol nanoemulsions co-emulsified by gelatin and lecithin may have great potentials to be applied as novel and GRAS biodegradable packaging materials to achieve the goal of extending the shelf life of food products.

Keywords: Antimicrobial and release properties; Film; Lecithin; Nanoemulsions; Thymol.