After decorticating, we usually have :
» 86% of meats containing 52.5% of oil, 5.6% of water and 13% of remaining hulls
» 14% of hulls used in the boiler, containing maximum 1% of oil more than the botanical oil content of the pure hulls.
The process of the sunflower seeds in order to extract the oil includes the following steps:
» Drying of the seeds till 7-8% of moisture before ensilage
» Decortication and preparation before preexpelling
» Pre-expelling giving cakes with 18 to 22% of oil
» Solvent extraction of cakes.
Direct solvent extraction is however possible but presents the following disadvantages:
» Due to the necessity to keep the hulls for the direct solvent extraction, the wear of the flakers is heavy and the extracted meal is poor in proteins
» Size of the solvent extraction unit
» A poor final residual oil content
» Meal desolventising rather difficult
» When necessary to reach higher protein content, the decorticating of the extracted meal is rather difficult.
The sunflower oil contains approximately 1.5% of lecithin (phosphatides) as main part of the unsaponifiables. Separated before neutralization, it is re-incorporated into the extracted meal.
In the unsaponifiables of the sunflower oil, the waxes also represent a big amount. Those waxes, at cold temperature, are quite insoluble in the triglycerides and have a tendency to precipitate, which gives the oil a turbidity aspect, which is detrimental to marketing even if waxes are not contrary to the intrinsic value of the oil. As the waxes come from the shells, it points out the importance of the decorticating; the latter is counterbalanced by the fact that a certain amount of shells are necessary for a good prepressing and by the oil loss through the entrained seed.
The waxes can be eliminated from the oil by winterising.
Finally the oil is bleached and deodorised.