Endogenous microflora in turbid virgin olive oils and the physicochemical characteristics of these oils

Abstract

Cloudy olive oil, the fresh olive juice, is an intermediate form before full precipitation of freshly produced olive oil. Some consumers prefer it because they consider it as more natural and less processed. The cloudy form can persist for several months. The oil is a sort of dispersion/suspension system which can be also described as a micro-emulsion/suspension. Water micro-droplets were found to have a size ranging from 1 to 5 μm. Cloudiness is due to the low water content and the presence of natural emulsifiers in the oil. The suspension is formed by solid particles (5-60 μm) deriving from the olive fruit. They are present in small amounts (12-460 mg/kg oil). In the newly produced olive oil, containing 0.17-0.49% water, a number of microorganisms of different types (bacteria, yeasts, moulds) were found to survive, but at very low concentrations (<3 log cfu/mL oil). They originate from the exterior of the fruit (epiphytic microflora) and their presence is considered natural. Their enzyme activities do not seem to affect the quality of the final product. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.