Extraction aqueuse et athermique de l'huile de lin assistée par décharges électriques de haute tension

The modern society recently became aware of the need to reduce pollutant emission in the environment and to have a sustainable development i.e. which meets the needs of the present without compromising the ability of future generations to meet their own needs. The substitution of fossil origin molecules by molecules from vegetables (biodegradable and renewable) could help to solve this problem at least in part : this would also limit our energy and/or material dependence. The lubricants, currently used in automobile industry, are mainly obtained from oil and pollute soils and water. Also, their substitution by bio-lubricants seems of a particu- lar importance. Vegetable oils are the main products likely to find industrial applications as alternative to petroleum products. However, the physicochemical properties (oxida- tion, temperature stability) of these natural substances are not yet competitive compared to those of usual lubricants. Nevertheless the linseed oil, once modified, could present interesting technical properties associated to a biodegradable character. To produce the oil initially contained in the seed cells, the oil industry developed around various pretreatments (mechanic, thermic, enzymatic) aiming at enhancing oil extraction, and expression as a central operation. A solvent extraction is then applied on the produced presscake. The objective of this study is to propose a new process for efficient oil extraction. This process had to be deprived of organic solvent (ecological aspect) and excessive heat treatment in order to preserve the various components of seed (economic aspect). First, we studied the effect of the seed crushing on expression. An optimal crushing allows to recover 70 % of the initial oil, which is comparable to industrial yield obtai- ned after crushing, cooking and expression. The study of seed maturity on expression highlights the need to have mature and dry seeds. An enzymatic preprocessing allows to discover a technological bolt due to the presence of mucilage (polysaccharides mixture) in the cuticule of seed. In order to extract mucilage, we propose an original solution based on the application of high voltage electric discharges (HVED) in water. In the second time, we sought to understand the phenomena during the electric discharge and calculate the energy consumption. After modeling of damped oscillations, recorded once the electric arc is created, we calculated the useful energy for the creation of the shock waves : the totality of the energy contained in the condenser is released during the discharge. It’s noticebale that only 25 % of this energy are used to generate shock waves. This treatment was then applied to the presscake produced after optimal crushing and expression. The mixture of presscake powder and water is treated by HVED then the resulting suspension is submitted to centrifugation to produce an emulsion as well as a solid residue. We then studied the effect of the pulse repetition frequency on the suspension and the produced emulsion physicochemical properties and on the composi- tion of the final products. The oil extraction kinetics and dry matter kinetics could be established and models are proposed. This process of extraction was finally optimized using an experimental design. Two successive treatments are thus applied by adjusting pH, temperature and mass of water. The total sum of applied impulses for the two treatments remaining constant and equal to 280. The oil extraction is favoured when the suspension is concentrated and the pH close to the average isoelectric pH of proteins of flax. Residues rich in oil (20 % of initial oil) and low in oil (2 % of initial oil) can be produced by adjusting the conditions of treatment. In conclusion, our study allowed us to propose a process with the following stages : crushing, expression, crushing, two treatments per electric discharge followed by centri- fugation. We propose two processes according to the results obtained with a forthcoming study concerning the separation of the produced emulsions.

Cocoa butter expression from cocoa nibs: effects of pre-treatment and process parameters on expression yield

Cocoa butter is obtained in industrial conditions from cocoa liquor using hydraulic presses with an average oil yield of 42%. Our objective was to study the extraction of cocoa butter directly from cocoa nib and to determine the influence of pressing parameters such as the type of beans (green bean (GB), roasted alkalised bean (RAB), roasted bean (RB)), temperature, and pressure on cocoa butter yield. The extraction result depends on the rheological behaviour of the cake, which can be modelised with a four component Kelvin-Voigt model. The RAB (with a yield of 39%) is easier to press than the RB (38%) and GB (13%). The global mean compressibility coefficients of the Kelvin-Voigt model are 1.4, 1.7 and 2.1 MPa respectively for RAB, RB, and GB

Extraction aqueuse d’huile végétale à partir de tourteaux de lin assistée par décharges électriques de haute tension

Industriellement le procédé de production de l’huile de lin se compose d’un broyage, d’une cuisson et d’un pressage suivi éventuellement d’une extraction par solvant. Dans une démarche s’inscrivant dans le développement de biolubrifiants et afin de préserver l’ensemble des constituants biochimiques de la graine, nous cherchons à développer un procédé d’extraction aqueuse sans utiliser de solvants organiques et avec traitement thermique minimal. Pour cela, nous utilisons un générateur de décharges électriques de haute tension (DEHT) pour créer un arc électrique dans une chambre cylindrique contenant la suspension eau/tourteau à traiter. Cette suspension est traitée une première fois puis centrifugée. Un second traitement est réalisé sur le résidu solide ainsi obtenu. Cette partie du procédé est optimisée en utilisant la méthodologie des plans d’expériences pour 4 facteurs (température, pH, ratio eau/tourteau, durée du premier traitement). A l’issue du procédé, nous obtenons deux émulsions O/W (huile dans eau) de compositions différentes et un résidu solide dépourvu de mucilage qui pourra subir un traitement enzymatique complémentaire pour y récupérer l’huile résiduelle. Deux procédés sont proposés : l’un produisant un résidu pauvre en huile, l’autre un résidu riche en huile. Le choix entre ces deux procédés se fera au regard des performances du rendement en huile obtenu après déstabilisation et séparation des émulsions

Application of high-voltage electrical discharges for aqueous extraction from oilseeds and others plants

Aqueous extraction is a traditional operation unit used to recover from food plants various products such as sugar, oil, or proteins. The yields of extraction are generally low. To enhance aqueous extraction different treatments may be applied before and/or during extraction. Application of high-voltage electrical discharges in water leads to original phenomena such as shock waves or active species creation. Steps of creation and required material are presented. High-voltage electrical discharges in water are interesting for different applications especially for extraction

Aqueous extraction and separation of linseed press-cake components enhanced by high voltage electrical discharges

Industrially oil is produced from seeds after crushing, cooking, solid-liquid expression and eventually a solvent extraction step. The objective of this study is to extract the oil from linseed (40 % oil) with an aqueous process in which organic solvent use would be excluded. After solid-liquid expression, the press-cake was crushed and mixed with demineralized water in cake/water ratio of 1/10. High voltage electrical discharges (HVED) (40 kV, 10 kA, 3 µs) were applied to this mixture at a frequency of 0.5 Hertz. The HVED consumed energy was calculated from electrical voltage and current curves. The measurements of electrical conductivity, Brix, pH and viscosity of the liquid phase allowed to characterize the kinetic of cake extraction at different intensities of electric field

Towards an Alternative Extraction Process for Linseed Oil

Industrial linseed oil is obtained after crushing, cooking, expression and solvent extraction. Our objective was to develop an extraction process in which solvent use was excluded or minimized. In addition to that, in order to preserve the functionalities of cake proteins, a maximum temperature of 50°C was imposed throughout the process. As these two restrictive conditions decrease dramatically the oil yield, enzymatic and electric treatments were considered. Oil yields similar to those obtained by expression at 100°C were achieved by optimizing the crushing conditions. Alternatively, with expression, a high-efficiency enzymatic treatment was tested on crushed and humidified seeds. By this enzymatic liquefaction, an extremely stable emulsion was produced due to the mucilage present in the seeds, which is a good natural emulsifier. In order to separate oil from water, it is necessary to eliminate the mucilage before the enzymatic treatment. Two methods of aqueous extraction were tested: one at 34°C under agitation and the other enhanced by high voltage electrical discharges. The second process proved to be of greater efficiency. To sum up, the new process comprises the following stages: crushing, expression, demucilagination by electric discharges, centrifugal separation of mucilage and solid residue, enzymatic or electric treatment of this residue and final separation of oil, water and solid fractions

How to improve apple juice extraction and quality by pulsed electric field on an industrial scale

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