Effects of essential oil from mint (Mentha piperita) on Salmonella enteritidis and Listeria monocytogenes in model food systems at 4° and 10°C

The effect of mint ( Mentha piperita ) essential oil (0·5, 1·0, 1·5 and 2·0%, v/w) on Salmonella enteritidis and Listeria monocytogenes in a culture medium and three model foods; tzatziki (pH 4·5), taramosalata (pH 5·0) and pâté (pH 6·8), inoculated at 10⁷ cfu g^-1, at 4° and 10°C for ca 1 week was studied. In the culture medium supplemented with the essential oil, no growth was observed over 2 d at 30°C determined by a conductance method with a Malthus 2000 growth analyser. Salmonella enteritidis died in tzatziki in all treatments and declined in the other foods except for pâté at 10°C as judged with viable counts. Listeria monocytogenes populations showed a declining trend towards the end of the storage period but was increased in pâté. Mint essential oil antibacterial action depended mainly on its concentration, food pH, composition, storage temperature and the nature of the micro-organism.