Contents lists available at ScienceDirect Industrial Crops & Products journal homepage: www.elsevier.com/locate/indcrop Impact of pretreatments on the solid/liquid expression behavior of canola seeds based on the simplified computational method Laurine Bogaert, Houcine Mhemdi ⁎ , Eugène Vorobiev Sorbonne Universités, Université de Technologie de Compiègne, Laboratoire Transformations Intégrées de la Matière Renouvelable (UTC/ESCOM, EA 4297 TIMR), Centre de Recherche de Royallieu, CS 60319, 60203 Compiègne Cedex, France ARTICLE INFO Keywords: Consolidation Expression Modeling Flaking Dehulling Cooking ABSTRACT The impacts of expression parameters (pressure and temperature) and pretreatments (dehulling, flaking, cooking and their combination) on the consolidation behaviour of canola seeds were studied using a laboratory hydraulic press. It was demonstrated that the expression kinetics of treated seeds follows filtration-consolidation beha- viour. For these samples, the simplified computational method used in this work allowed the determination of the filtration diffusivity (consolidation coefficient b). Results showed that flaking and cooking enhance the ex- pression kinetics and increase the consolidation coefficient. However, dehulling reduces the pressing perfor- mance. Model adjustment showed that experimental data coincide reasonably well with the model for ν < 2.85 demonstrating the co-existence of primary and secondary consolidation. 1. Introduction Vegetable oil is a triglyceride extracted from plants and used since ancient times. Nowadays vegetable oils are used in foods, paints and for the production of renewable fuels. Mechanical expression (pressing) and organic solvent extraction are the most used technologies for oil extraction. For canola seeds, the in- dustrial process used for oil recovery is multistage (Bredeson, 1983). Seeds are first pressed using a screw press to obtain an oil of high quality and a press cake (meal) with high residual oil content (20–25%). The cake is then subjected to hexane extraction to recover the residual oil. Each technique of extraction has its benefits and drawbacks as far as operating cost, capital cost, yield and quality of the extracts are concerned. Mechanical expression (pressing) is the oldest and the cheapest extraction technique (Khan and Hanna, 1983). It gives oil of out- standing quality but the oil yield is unsatisfying adversely affecting the economical profitability of the crushing process. Organic solvent ex- traction is very efficient for oil recovery. However, concerns about the solvent residues in the oleoresin products, the new regulations of vo- latile organic solvent emissions in the air, and the extent of further refining that is required after the extraction step restrain the use of this technology. In order to improve the pressing efficiency, different pretreatments are usually applied before oil expression (Daun et al., 1993). In fact, oil is stored in small vesicles called oleosomes and enclosed in the in- tracellular medium (Lanoisellé, 1995). Cell rupture is necessary to fa- cilitate oil expression. Oleosomes denaturation deeply facilitates oil releasing in the extracellular medium. Industrially, different pretreat- ments (e.g. flaking, dehulling, moisture conditioning, cooking) may be employed to damage oilseed structure and increase oil availability. These pretreatments can be applied separately or in combination (Carré et al., 2016; Savoire et al., 2013; Zheng et al., 2003). Oil expression efficiency depends on oilseeds variety, pretreatment methods and pressing conditions (pressure, temperature, duration). The impacts of these parameters on the extraction yield were intensively studied in the literature (Ward, 1984; Savoire et al., 2013). However, just a few stu- dies have focused on the modeling of pressing behavior according to the applied pretreatment methods. Currently, most articles dealing with the simulation of mechanical expression from cellular materials adopt the filtration–consolidation theory initially developed for soils (Terzaghi, 1925; Suklje, 1969) and mineral filter cakes (Shirato et al., 1970, 1971, 1980, 1986). This theory provides a comprehensive approach for the description of liquid flow in compressible matrix of individually in- compressible particles. In fact, the mechanism of solid–liquid expres- sion from agro-food materials is very complex and the cellular materials structure is different from soils. Indeed, the biological tissues are compressible and they are often considered as triphasic systems where solid, liquid and gas phases (air) are present. The air is located between particles. The dissipation of the air and the cells damage during https://doi.org/10.1016/j.indcrop.2017.12.053 Received 8 July 2017; Received in revised form 11 November 2017; Accepted 20 December 2017 ⁎ Corresponding author at: Université de Technologie de Compiègne, Département de Génie des Procédés Industriels, Laboratoire Transformations Intégrées de la Matière Renouvelable (UTC/ESCOM, EA 4297 TIMR), Centre de Recherche de Royallieu, CS 60319, 60203 Compiègne Cedex, France. E-mail addresses: h.mhemdi@escom.fr, h.mhemdi@live.fr (H. Mhemdi). Industrial Crops & Products 113 (2018) 135–141 0926-6690/ © 2017 Elsevier B.V. All rights reserved. T