Antimicrobial Activity of Selected Essential Oils on Pseudomonas Species Associated with Spoilage of Fish with Emphasis on Cinnamon Essential Oil

Eight plant essential oils (cardamom, cinnamon, clove, eucalyptus, lemongrass, lime, nutmeg and rosemary) were evaluated for their antimicrobial activity against threePseudomonasspecies associated with microbial spoilage of refrigerated tilapia.In vitrotest of the essential oils, using disc-diffusion method, showed various degrees of antimicrobial activity against thePseudomonasspecies. Cinnamon essential oil (CEO) had the highest antimicrobial activity, followed by clove essential oil. The remaining essential oils showed consistently weak activity. The antimicrobial efficiency of CEO against thePseudomonasspecies was confirmed by potential minimum inhibitory concentration and minimum bactericidal concentration values, ranging between 0.125 and 0.375 mu L/mL and 0.250-0.500 mu L/mL, respectively. The anti-Pseudomonasactivity of CEO was also tested in fish extract model at refrigeration temperature. The essential oil reduced thePseudomonasviable count in fish extract but to a lesser extent than when it was applied at the same concentrations in culture medium. The chemical composition of CEO showed that the oil contained 79.1% cinnamaldehyde, which was suggested to be responsible for its antimicrobial activity. These results revealed the potential of CEO as a promising natural antimicrobial agent that could efficiently contribute to the control of spoilage bacteria and retard microbial spoilage of fresh fish.