Vertical centrifugation of virgin olive oil under inert gas
Virgin olive oil vertical centrifugation under inert gas (IVC) was compared with conventional vertical centrifugation in contact with air (CVC). IVC gives a strong reduction of the oil oxygenation in terms of
reduced dissolved oxygen concentration and oxidative indexes (peroxide values and K232). Minor
compounds (chlorophyll and total phenols) and volatile compounds were not affected by the treatment.
Practical applications: A technical implementation of inertized vertical separators appears a practicable
solution to preserve virgin olive oil quality traits. This can be easily implemented both by the mill
owner with homemade adjustment of the existing machines and by plant industrial manufacturers.
Available from: Lorenzo Cecchi
- "This way of working reduces the machinery purchase costs and could improve the olive oil quality. In fact, initial works have established that using a vertical centrifuge after decanting causes a marked increase in dissolved oxygen, and this oxidation shortens the shelf life of VOOs    . However, the olive oils produced in this way have more humidity and more suspended solids than the usual continuous process . "
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ABSTRACT: This study evaluates the effect of filter press filtration on the shelf life of extra virgin olive oil (EVOO). Olives were harvested and processed on the same day by a continuous industrial plant equipped with a hammer crusher, a vertical malaxator, and a decanter. One part of the oil obtained was bottled in 0.5 liter dark-green bottles with headspace representing a quarter of the bottle's volume (cloudy oil). The other part was filtered (using a filter press) directly after decanting and manually bottled using the same procedure (filtered oil). All samples were stored in a purpose-built chamber and periodically analyzed. Samples were characterized by their water content, free acidity, peroxide value, specific extinction coefficients (K232 and K268), total chlorophyll, tocopherols, total phenolic compounds, HPLC phenolic profile, volatile compounds, fatty acid composition and sensory analysis.
Immediately after filtration, the only differences that could be detected were related to turbidity and total solids. In the subsequent analyses, filtered oil retained superior nutritional and sensory characteristics than cloudy oil. More importantly, the filtered oil remained at the standard required for categorization as “extra-virgin olive oil” for longer.
Available from: Alessandro Leone
- "Recent research has been conducted on decanters to determine the best machine parameters to maximize extraction efficiency   . Other studies have investigated the liquid–liquid separation operation to evaluate the influence of vertical centrifugation on extra virgin olive oil quality   and on olive oil storage operation to define plant and olive oil quality aspects  . A crucial step of virgin olive oil extraction is the crushing operation. "
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ABSTRACT: The purpose of this study is to evaluate the effects of the mechanical components on pits and oil droplet fractionation. The olive pastes obtained using four different crushing systems were compared. Analyses of the pit particle size distribution and oil drop aggregation were performed. The analysis of the experimental data shows that different crushing machines produce different pit and oil drop fragmentation, and the trends confirm that increased pit fragmentation corresponds to increased droplet fragmentation. Therefore, the results confirm that the partial de-pitter and hammer crusher yielded the greatest enhancement in emulsification of oil droplets, and the stone mill and disc crusher yielded the greatest aggregation of oil droplets.Practical application: The practical application of this work includes understanding the effects of four different crushers on oil drops and pit fragmentation. The experimental data could be useful to define the best malaxation time and to gain a better understanding of the minor components distribution in olive oil. The results obtained could be used to construct a guideline for the design and sizing of crushing machines.
Available from: Giovanni Carlo Di Renzo
- "terpenes (À46.1%) and hexanal (À89.5%); fatty acids composition seems not to be affected) and loss of stability of the final product (increase of peroxide value (þ49%) and decrease of polyphenols content (À1.8%)) (Di Giovacchino et al., 1994; Masella et al., 2009) due to oil heating (increased processing temperature (þ2.4%)) and to increased amount of dissolved oxygen (increased peroxides value and decreased polyphenols content) (Masella et al., 2012; Parenti et al., 2007). The sedimentation significantly lowers (À28.6%) the systosterol content of the oily must, also decreasing its oxidation level (decreased peroxide value (À15.4%), "
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ABSTRACT: Olive oil extraction is mainly carried out using continuous extraction by decanter centrifuge with efficiency of approximately 80–90%. After centrifugal extraction, olive oil is generally cleaned using a vertical disc stack centrifuge separator, which is suspected of being the major cause of decreased final olive oil quality. Experiments were carried out at industrial scale to compare the olive oil properties after improved processes of sedimentation (Sedoil) or centrifugation (Cenoil) with respect to raw olive oil obtained at the decanter exit (Control). Peroxide, polyphenol, chlorophyll, carotenoid, turbidity and K232 average values were significantly different between Sedoil and Cenoil, which confirmed that the use of disc stack centrifuges represents an important source of oxidative reactions. Analysis showed that storage time dramatically affects the oxidation level of the olive oil. All parameters used to monitor the oxidation level (i.e., free acidity, peroxide value and K232) increased after 180 d of storage, and the content of natural antioxidants and pigments decreased as expected. The residual presence of water during long-term storage represented the most important source of oxidation, and an effective cleaning operation is necessary to preserve oil quality during its storage life. The analyses performed using 1H and 13C NMR showed that Sedoil was more similar in composition to Control than to Cenoil. The use of sedimentation plant allows the employment of the disk stack centrifuge to be reduced improving both energy saving and the quality of clean olive oil.
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