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.

Changes in Physicochemical and Microbiological Parameters of Short and Long‐Lived Veiled (Cloudy) Virgin Olive Oil Upon Storage in the Dark

“…Veiled fresh virgin olive oil is a dispersion/suspension system consisting of nitrogen compounds and polymerized phenol complexes. [2,3] Some authors report diacylglycerols, monoacylglycerols, and phospholipids compounds in this olive oil, which may contribute, as natural emulsifiers, to the formation of an emulsion with a small quantity of water already present in the newly produced oil. [4][5][6] The fresh virgin olive oils are usually filtered or consumed after a "racking" process, where the product is stored in tanks to settle for a period of weeks or months to allow sediments to separate from the oil.…”

Effect of amurca on olive oil quality during storage

“…Sedimentation of amurca at the bottom of the container with time (Koidis et al 2008) is likely why there were higher total phenolic compounds near the bottom of the container. A cloudy appearance of freshly pressed olive oil with higher total phenolic compounds that disappears during storage was reported earlier (Tsimidou et al 2005).…”

“…Olive oil content of amurca varies tremendously (12-460 mg/kg oil) depending on the type of mills used to extract olive oil (Koidis et al 2008). The Jordanian specification for olive oil does not state a criterion for the maximum amount of amurca that is permitted in olive oil for local use (JISM 2009), and since the Jordanian consumer prefers the bitter taste and the aroma of amurca , olive oil produced for local consumption contains a high amount of amurca.…”

Sensory Analysis of Virgin Olive Oil

“…The filtration of newly-produced oil can avoid this phenomenon. It is known (Fregapane et al, 2006;Mendez & Falque, 2007;Lozano-Sanchez et al, 2010) that EVOO has a low amount of water, and for this reason it can be considered as a water-in-oil emulsion (Koidis et al, 2008) The orientation of phenolic compounds in the oil-water interface and the active surface of water droplets can protect against the oxidation of oil. According to some researchers (Tsimidou et al, 2004;Gómez-Caravaca et al, 2007), the stability of unfiltered samples is significantly higher than that of the corresponding filtered oils.…”