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A key challenge in the actual context of fossil sources rarefaction, global warming, and of increase of the world global population, is to promote the use of molecules derived from renewable sources such as plants. Among these molecules, lipids and proteins are targets of interest. Plant lipids from oilseeds are attractive substitutes to the use of fossil oil. Till the beginning of the 20th century, numerous products used in the daily life were derived from natural renewable products. For instance, plant oil was commonly used as fuel for vehicles and was entering in the composition of paintings, lubricants etc. Unfortunately, natural oils have been progressively replaced by cheaper fossil oil in the fabrication of these products. Nowadays, fossil oils are becoming increasingly expensive being a finite comodity. It is thus important to reduce our dependence from fossil oil and develop substitution industries. Oilseeds contain important amounts of proteins which are mainly used in feed. As several kilograms of plant protein are needed to obtain one kilogram of animal protein, the interest toward using plant protein in food is reinforced. The developments of the use of plant lipids, as well as proteins are a major stakes for the competitiveness of European agriculture and industry, as well as for sustainable development. Extraction of oil and proteins from rapeseed has a significant cost, in term of energy and solvent uses, and finally affects the ultimate quality of the products (protein digestibility). In order to quantitatively extract seed reserves under mild conditions, it will be necessary to limit the amount of energy needed, and avoid any use of solvents. Ideally, seeds should be processed in a bio refinery. In this paper, we will describe how oilseeds store their reserves, and roadblocks for improving actual oilseed extraction processes. A continuum of research projects aimed at answering targeted questions will be presented, with selected results obtained.

The outermost mucilaginous layer of the seed is a major, valuable component of flaxseed, but it induces a rapid thickening of the medium when the seeds are immersed in water, reducing the efficiency of oil body extraction. Ultrasound can be used to extract this mucilage rapidly before the seeds are ground in water. This makes it possible to extract the oil bodies as an emulsion, with the proteins present acting as dispersing and stabilizing agents. This emulsion is a thick fluid displaying shear-thinning and predominantly elastic behavior. This phase can be valorized directly due to its high concentration in polyunsaturated fatty acids, high content of valuable sterols, and high arginine content of its proteins.

Seed oil bodies are intracellular particles to store lipids as food reserves in oleaginous plants. Description of oil body-associated proteins of Arabidopsis thaliana has been recently reported whereas only few data are available in the case of rapeseed. Oil bodies have been prepared from two double-low varieties of Brassica napus seeds, a standard variety (Explus) and an oleic variety (Cabriolet). Oil bodies have been purified using floatation technique in the successive presence of high salt concentration, detergent or urea in order to remove non-specifically trapped proteins. The integrity of the oil bodies has been verified and their size estimated. Their protein and fatty acid contents have been determined. The proteins composing these organelles were extracted, separated by denaturing gel electrophoresis, digested by trypsin and their peptides were subsequently analyzed by liquid chromatography-tandem mass spectrometry. Protein identification was performed using Arabidopsis thaliana protein sequence database and a collection of Expressed Sequence Tag (EST) of Brassica napus generated from the framework of the French plant genomics programme “Genoplante”. This led to the identification of a limited number of proteins: eight oleosins showing a high similarity each other and representing up to 75% of oil body proteins, a 11 β hydroxysteroid dehydrogenase-like protein highly homologous to the same protein from A. thaliana, and only few contaminating proteins associated with myrosinase activity.