Physical, Chemical, and Biological Characterization of Veiled Extra Virgin Olive Oil Turbidity for Degradation Risk Assessment

Abstract

Six different 300 kg batches of olive fruits are processed and the resulting six 20 kg batches of oil are collected at the end of the “decanter.” These batches of oil are subjected to four different water and solid particle separation treatments so as to obtain the following oil samples: veiled oil, filtered oil, “solid particle‐only” oil, and “water‐only” oil. The applied separation treatments show that water content has an important role in the degree of turbidity. High water content values (>0.2% w/w) are related to water activity values of >0.6 which are suitable for chemical and enzymatic reactions. The veiled oil samples are contaminated by microorganisms, but non‐proportional behavior occurs between the microbial cell count and the water and solid particle contents. Practical Applications: The results of this study recommend a multi‐approach method to characterize turbidity, based on control markers such as the degree of turbidity, water content and water activity, solid particle content, microbial contamination, and phenolic compound content. In this way, each degree of turbidity can be associated with a different level of risk of veiled extra virgin olive oil degradation during shelf life.

Filtration Scheduling: Quality Changes in Freshly Produced Virgin Olive Oil

“…Specifically, the microorganisms grown on YPD agar medium fell from 3.8 ± 0.2 log CFU/g in veiled oil samples to undetectable in filtered samples (Table 1). These results agree with those reported in the literature [20,22,31,32]. This difference was still observed after 30 days of storage.…”

“…The turbidity fell from 2642 ± 174 NTU to 18 ± 4 NTU, and the water activity (aw) decreased from 0.70 ± 0.03 to 0.42 ± 0.04. These results are also consistent with the literature [11,22,26] regarding aw values and the turbidity grade of filtered oil.…”

“…The latter is a combination of microdroplets of vegetation water and insoluble fruit solids, which are responsible for a wide spectrum of "turbidities" [20][21][22]. Veiled olive oils are rich in microflora, notably yeasts of candida species [11,16,[22][23][24][25]. The presence of these solid particles, which are rich in sugars, proteins, and water droplets, is associated with high water activity (greater than 0.6) [24].…”

Understanding Olive Oil Stability Using Filtration and High Hydrostatic Pressure

“…Veiled extra virgin olive oil (VEVOO) is described as a dispersion-suspension system, with the degree of turbidity resulting from the presence of micro-droplets of vegetation water and small solid fragments of olive skin and pulp covered by a film of water [8,9]. VEVOO is always very attractive on the global market, since for many consumers VEVOO is deemed to be of a higher quality than filtered extra virgin olive oil (FEVOO).…”

Effects of the Filtration on the Biotic Fraction of Extra Virgin Olive Oil

“…However, some microorganisms can also degrade the quality of the product by allowing the appearance of sensorial defects, oxidation of polar phenols, and triacylglycerol hydrolysis [1,[9][10][11][12]. The freshly produced EVOO, being a traditional and unprocessed food, has a higher content of suspended solids, colloids, and micro-drops of vegetation water, which are associated with the microorganisms making up the biotic fraction of the oil [13][14][15][16]. During storage of the product, part of the suspended material and microorganisms move to the bottom of the containers creating a water-rich habitat favourable for the growth of some harmful microbial species, responsible for serious sensory defects.…”