The use of disc stack centrifuge in the virgin olive oil industry

Abstract

The disc stack centrifuge (DSC) in the virgin olive oil (VOO) industry is widely used for oil purification at a final stage of extraction process. The obtained oil should be commercialized directly as turbid or sent to settling and/or filtration. Despite technology is strongly consolidated, few literature is available on the effect of DSC on efficiency and quality of VOO, specially compared with alternative methods. Alternative technologies to DSC like settling or direct filtration are suitable only for very small production scale. Application of advanced technology already available for DSC like hermetic design is applicable also to VOO but more research is necessary to establish effect on quality and cost/benefit ratio. Improvement of installation module and a more appropriate use of DSC on VOO industry are recommended to reduce water consumption and consequent loss of VOO quality. IntroductionDr Gustaf de Laval was granted the patent of The Centrifuge for the separation of cream from milk in June 1878. The introduction of centrifuge generates a revolution in a wide range of industrial application and currently the technology is applied throughout many manufacturing industries with different centrifuge designs adapted to particular uses (Beveridge, 2000). Disc stack sedimentation centrifuge (DSC) with radial solids-ejecting are the commonest, and today the most important applications are production of milk, wine, other beverage and purification of vegetable oil, olive oil, fuel and lube oil on ships (Axelsson and Madsen, 2012). The use of centrifugal technology in the virgin olive oil (VOO) industry was introduced for the first time by Alfa Laval in 1927 (Alfa Laval, 1928). The DSC was introduced to purify oil must come from hydraulic press in alternative to the traditional static sedimentation which is a slow process where the oil is in contact with vegetable water and residual solids with consequent contamination. By the use of DSC, the purification becomes a continuous and fast operation with a consequently significant improving of quality of final oil (Frezzotti, 1928). After thirty years from the first introduction, the DSC was extended to most of press traditional mills and was considered and integrated as key technology also in all alternative processing methods proposed at that time as Sinolea, SIMA-Baglioni, Elettrolia, Veraci-Primolia, Dieffenbach and Veraci-Olier (Carole et al., 1964). However, mentioned extraction system not received success on the market due to different problem like oil yield or cost. Once again, the alternative to the press traditional mills was definitively developed by Alfa Laval with the introduction of the new process extraction line named Centriolive. New process extraction line includes the steps of washing, crushing, malaxing and two successive centrifugation steps: the decanter extraction for centrifugation of olive paste in three phases and the DSC used both for final oil purification and for oil recover from black water (Valleggi, 1966;Vitagliano and Radogna, 1...

The Oil:Water Ratio in the Vertical Centrifuge Separator and Its Influence in Phenolic Compounds in the Virgin Olive Oil and the Olive Mill Wastewater (Alpechín)

“…Although a vertical centrifuge forced decanting system may be a source of oxidation reactions, loss of substances of interest due to the use of warm water, and high water consumption, there exist no alternatives. It is the most efficient, with several functional advantages, and its disadvantages are more readily assumable than those of the other options that have been studied [26]. The system consists of a centrifuge with plates at a determined inclination, which rotates at high speed (6500-8000 rpm), and which, with the addition of warm water, quickly removes a large amount of impurities, and practically all of the vegetation water together with the water added in the process.…”

“…Factors such as water quantity and effluent temperature are critical for the presence of compounds such as phenols that are of nutritional and quality interest [26][27][28][29], as well as for the equipment's correct functioning. The amount of water usually added to the vertical centrifuge is highly variable.…”

Effect of Clarification System on the Conservation of Virgin Olive Oil during Its Storage

“…VOO clarification is carried out by two different systems: vertical centrifugal separators (VCS), or/and natural settling in conical bottom settling tanks (CBST). [ 10,24–27 ] Vertical centrifugation is the most used clarification method since it is faster, requires little labor, and lets to separate impurities effectively. However, normally this system involves lukewarm water addition, from 1:1 to 1.5:1 v/v water/oil ratio.…”

“…The content of this suspended matter in clarified VOOs is variable and it is significantly influenced by the clarification system and its conditions. [ 23 ] Suspended solids can be present until a 0.2% in clarified oils by VCS [ 25,26,27,33 ] and between 0.01% and 0.03% for clarified oils by CBST. [ 25 ] Water can be present about 0.5% in VCS oils, although have been described values over 1%, [ 25,26,34 ] and between 0.65% and 1.03%, and 0.53% and 0.58% in clarified VOOs by settling after 24 and 48 h, respectively.…”

Development of a new washing machine in olive oil extraction plant: A first application of usability-based approach

“…The production of quality EVOO's is influenced by the optimal management of unit operations leading to its production, such as, harvesting, removing leaves and twigs, washing, olive milling, malaxing, centrifugation and filtration processes (Beghi et al, 2017). Certain steps of EVOO production, such as, post-harvest (Beghi et al, 2013), malaxing (Tamborrino et al, 2017), centrifugation (Boncinelli et al, 2009) and filtration (Costagli, 2018;Guerrini et al, 2015), were main topics of scientific research in the last few years, allowing a significant enhancement of the finished products' quality. The washing stage has been slightly neglected or leastwise, did not experience the same involvement, regarding experimental research efforts, despite representing one of the crucial steps for the quality of the finished product and for the reduction of the environmental impact.…”