The most common vegetables oils used in food preparation come primarily from soybeans, rapeseed, sunflower seed, corn, cotton seed, and safflower seeds.
Depending on the products oil extraction ranges from simple, inexpensive, small scale techniques o complex capital-intensive methods. The oils are usually removed from plant tissues by three methods.
In the first method, cells containing oil are ruptured by heat and mechanical methods. To maximize extraction efficiency, oil seeds are usually ‘crushed’ thus decreasing particle size and lowering the mass transfer resistance of oil removal.
A second method is called expeller method. This method involves squeezing the seeds at very high pressures, which may generate some heat. The oil still retains most of their flavor, color, aroma and nutrients.
The third method involves solvent extraction using petroleum hydrocarbons at 60 – 70 degree Celsius. Solvent extraction is a more recent method. This method, which is a continuous one, has a capacity of processing of hundreds of tons of oil per day.
The by-products of these methods are proteins, which are used in animal feeds.
Seed extraction is achieved by pressing and/or extraction with hexane. Oils such as palm and olive, on the other hand, are pressed out of the soft fruit or endosperm.
Expeller methods are typically used for edible products such as nutrients and food oils, whereas solvent extraction is for more modern oil application.
Plant oils extraction