Pressing (also known as trituration) and purification (or filtration) represent the two main stages in the production of oil from oilseeds, such as rapeseed.
Two methods of pressing exist: cold pressing or industrial pressing.
- Cold pressing in a screw press: no solvent is used to extract the oil. The solid residue, the meal, has a high nutritional quality because it is rich in fatty acids,an asset for the farmer and his cattle
- Industrial pressing: oil extraction is more efficient because solvents are used but the meals are of lower nutritional quality
From one tonne of rapeseed, cold pressing produces about 300 kg of oil and 700 kg of oilcake, while the industrial method produces 400 kg of oil and 600 kg of oilcake.
The purification of the oil is conventionally carried out in two ways:
- Simple filtration: the oil passes through a plate filter which retains the particles
- Decantation and filtration: the particles contained in the oil are decanted and removed, the oil then passes through a plate and/or cartridge filter
Use of the oil
Vegetable oils from rapeseed, sunflower, maize, etc. can of course be consumed in food. Other more marginal uses are possible:
- Pure vegetable oil used in cogeneration or as fuel in suitable tractors
- Bio-based products: biolubricants, biosurfactants…