Micro-dispersed essential oils loaded gelatin hydrogels with antibacterial activity

Plant-based essential oils (EOs) are natural antimicrobial agents that have a relatively new application as edible coatings to extend the shelf life of foods such as meat. In this study, we developed gelatin hydrogels containing microdroplets of rosemary essential oil (REO) and orange essential oil (OEO). The microdroplets were successfully stabilized by the surfactant Tween®80. The droplet size distribution was slightly affected by the type of EO and homogenization time. The rheological properties in the linear viscoelastic range depend on the EO concentration and the Bloom number of the gelatin. The nonlinear behavior remains typical of gelatin gels, with stiffening and shear thickening at large deformation amplitudes. Escherichia coli and Bacillus cereus were sensitive to the gelatin-REO hydrogels with a minimum inhibitory concentration (MIC) of 0.5%. The gelatin-OEO hydrogels inhibited only Bacillus cereus with an MIC of 0.5%, but the gelatin-REO hydrogels showed greater cell reduction. Surprisingly, the Staphylococcus aureus strain used here was resistant to all gelatin-EO hydrogels. Our experiments show that gelatin-EO hydrogels prepared by simple emulsification have high stability and antibacterial activity suitable for potential preservation of gelatin-tolerant foods.