Purpose: The purpose of this study was to develop antimicrobial packaging films using olive leaf extract as an antimicrobial agent and investigate their effectiveness against foodborne pathogens.
Methods: Olive leaf extract (OLE) was made from fresh olive leaves using an alcohol extraction method followed by vacuum-freeze-drying. Commercial OLE powders were also used to compare the effectiveness compared of the laboratory-prepared OLE. Antimicrobial (AM) film was developed by mixing 6% OLE, 6% chitosan, and 2% organic acid and then drying the mixture for 24 h. The antimicrobial efficiency of AM film samples was evaluated in peptone water and apple juice (ratio of 0.5 g OLE per each 10 ml liquid sample), which were inoculated with Escherichia coli K-12 (surrogate of E. coli O157:H7) and Listeria innocua (surrogate of Listeria monocytogenes). The surviving microbial populations were determined at 24 h and 48 h after film treatments.
Results: In peptone water, the AM film reduced E. coli and L. innocua populations from 8.2 and 7.8 CFU/g, respectively, to <1 log/g after 24 h. No bacterial cells were detected after 48 h. In apple juice, the AM film reduced E. coli populations from 7 to <1 log/g after 24 h and reduced L. innocua populations from 7 to 1.5 CFU/g at 24 h and <1 CFU/g after 48 h. There were no significant (P>0.05) differences in antimicrobial efficiency between the commercial and laboratory-prepared OLE samples.
Significance: The results showed that AM films with OLE were highly effective against both gram-positive and gram-negative bacteria in liquid products and that the films have the potential to reduce pathogenic contaminants in solid food products.