Purpose: The study was aimed to evaluate antimicrobial and synergistic potential of essential oil emulsions against E. coli (ATCC 25922), E. coli (ATCC 700927), L. monocytogenes (ATCC 19115), L. innocua (ATCC 33090) and S. Typhimurium(ATCC 19585).
Methods: Cinnamon, oregano, clove, thyme, rosemary, sage, bergamot, nutmeg, lemon grass, bay and also t-cinnamaldehyde, euganol and carvacrol emulsions were formulated using ultrasonication and tween 80 as an emulsifier. Antimicrobial efficacy and synergistic potential of t-cinnamaldehyde emulsion was evaluated against the test strains using broth-dilution test and checkerboard assay. To determine the antimicrobial efficacy of the selected essential oils and their combinations in a food model, chicken samples were treated and inoculated. They were stored at 4°C and analyzed on day 0, day1, day3 and day6 for bacterial growth.
Results: Cinnamon showed the highest antimicrobial efficacy against all test organisms at 312.5 ppm. Oregano had the second highest efficacy at 625 ppm, while the other oils did not exhibit high antimicrobial activities. The only synergism observed was between cinnamon and oregano against E. coli (ATCC700927) and L. innocua (ATCC 33090) and also between cinnamon and clove towards L. innocua (ATCC 33090). All other combinations were additive or indifferent in nature to the test organisms. Cinnamon in comparison to control showed Log reduction of E. coli (ATCC25922), E. coli (ATCC 700927), L. monocytogenes (ATCC 19115), L. innocua (ATCC 33090) and S. Typhimurium (ATCC19585) by 2.885, 3.39, 3.275, 4.29 and 3.06 in the chicken samples. While oregano reduced E. coli (ATCC25922) and E. coli(ATCC700927) by 3.21 and 3.53 Log.
Significance: Antimicrobial emulsion of select essential oils and their combinations have the potential to be used as alternative antimicrobial agents for enhancing food safety.