The available information on the micro-biological safety of olive oil is limited. Knowledge about the safety of olive oil has been published the last decade. There are not outbreaks of food-borne illness connecting to olive oil.
The bacteria present in olive oils is bellow the level of detection. Virgin and extra virgin olive oil, are exceptional oils, which contain water in the form of mini drops. Under microscope, micro-organisms are shown to be present in the water.
In extra virgin olive oils there are anti-microbials that are effective against micro-organisms. The anti-microbial components vary in composition, for different reasons, like the variety of the olive, the way of cultivation, maturity, weather conditions, oil extraction and storage. Extra virgin olive oil doesn’t contain food-borne pathogens.
In Greece , in a study conducted by Boskou and Triantafillou, cloudy, fresh produced olive oil, was examined for lactic acid bacteria, molds and yeasts. The result was that they range bellow the detection limits.
Olive oil differs from other edible oils, in its fatty acid content and in the presence of bio-active compounds, due to its unrefined process. The fatty acid content is the same in all olive oils and different in minor components like squalene, alcohols, tocopherols, triterpene acids, phenolic acids and poly-phenols.
The phenolic compounds in olive oil (hydroxytyrosol, tyrosol), secoiridoids (oleuropein), poly-phenols and flavonols are classified as poly-phenols.
In a study by the same researchers was determined that fresh produced olive oil, contains tiny drops of water, mixed in. Between fresh olive oil and commercially filtered olive oil, the water content was 0.17% to 0.49% for the fresh and 0.08% to 0.09% for the filtered one.
In the tiny drops of water in the freshly produced olive oil, micro-organisms are trapped. After a few weeks, more tiny drops of water accumulated. These water drops keep the availability of nutrients limited for the micro-organisms. The content of water in olive oil depends on the method of the extraction process of the oil and its storage for sedimentation.
Studies have proven that the composition of the phenolic content of olive oil, depends on the cultivar, ripeness, weather conditions and the extraction process.
Researcher Medina in 2006 studied the anti-microbial activity of edible oils and reported that extra virgin olive oil has anti-microbial properties against E. coli and Salmonella.
Aflatoxins are carcinogenic and mutagenic compounds, very dangerous to health. Ochratoxins are molds grown on plants, including olives, under humid conditions. Extra virgin olive oils and virgin olive oils are consumed without undergoing the refining process to get rid of aflatoxins. Greek olive oils were tested for aflatoxin B1 by Daradimos, Markaki and Koupparis. They found minimal levels of it.