Antimicrobial activity of chitosan-based films including spices’ essential oils and functional extracts

Abstract

Essential oils (EOs) and functional extracts (EXs) from cumin (Cuminum cyminum L.), clove (Eugenia caryohyllata), and elecampane (Inula helenium L.) were used as antimicrobial ingredients for the elaboration of edible films. EOs were extracted by hydrodistillation and EXs were obtained by co-hydrodistillation using fatty acid ethyl esters (E6 and E7) as co-solvents. Antimicrobial activities of EOs and EXs were evaluated by the determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Escherichia coli O157:H7, Salmonella Typhimurium, Bacillus cereus, Staphylococcus aureus, and Listeria monocytogenes (ATCC strains). Based on the MIC/MBC results, EOs and EXs were selected to prepare edible films based on chitosan polymeric structure. The antibacterial effect of the edible films prepared was further evaluated by zone of growth inhibition against the same foodborne pathogens. Results showed that the EOs and EXs with best MIC results were: cumin (750 mg/L), clove (500 mg/L), cumin–E7 (750 mg/L), clove–E7 (500 mg/L), and elecampane–E6 (500 mg/L). Concentrations of 0–2% of EOs and EXs were used to prepare the chitosan plastic films, and the best results in growth inhibition were presented by chitosan films added with clove and clove–E7 at 2% concentration. The addition of EOs and EXs of clove to chitosan can be an alternative to produce edible films that can be used in food preservation.