Presence of microorganisms in flavoured extra-virgin olive oil

The paper reports a study on the presence of microorganisms in the flavoured extra-virgin olive oils. The microbiological analysis of the commercial extra-virgin olive oils flavoured with lemon, oregano, garlic and red chilli pepper indicated the presence of a different type of microflora according to the ingredient. Moulds were present in all of the types of commercial flavoured olive oils, yeasts were only found in the oil enriched with oregano, while bacteria were only occasionally observed. The trials performed in laboratory using experimental extra-virgin olive oil, flavoured with the same ingredients, at zero concentration (control), 1, 5 and 10% (w/v), confirmed the survival of the microorganisms in the flavoured olive oil in a different way according to the type and concentration of the ingredients. In fact, after 40 days of storage, yeasts were present in the olive oil flavoured with 1% of oregano; moulds were widespread in all of the samples of oil flavoured with lemon, oregano and red chilli pepper, while bacteria were only observed in the oil enriched with 5 and 10% of red chilli pepper. The results obtained from both of the trials demonstrated that microorganisms are capable of surviving in the flavoured extra-virgin olive oils, but the ingredients condition the life of the microbes in the oil in a selective way according to their chemical characteristics.