Oils can be extracted by a great many methods. Sometimes the method used depends on the oil. Cooking oils are often extracted using a solvent like hexane, while aromatic oils are extracted with various oil extraction methods including steam distillation and the traditional cold pressing method. In all of these options, the goal is to produce a pure oil free from contaminants and traces of the original plant material.
One of the latest oil extraction methods is through chemical extraction, making the use of solvent extracts that creates higher yields and is faster and cheap. The best solvent is the petroleum derived hexane. Well this method is used for the most new industrial oil like corn oils and soybean. The other method is the physical extraction that does not make the use of the solvent extracts. This method is used to produce more of traditional oils like olive etc.
Cold pressing requires a rind, so it can only be used with citrus fruits and certain seeds. The rind is ground into small pieces and then pressed. Under the pressure, the oil will be squeezed out along with trace amounts of the rind. The oil is then allowed to separate and harvested.
With the method of steam distillation, the plant substance is placed in a still, where pressurized steam is used to separate the oil and carry it away as vapor. This vapor is then cooled back down to a liquid, and the oil that was recovered floats to the top, where it is skimmed off. This method produces a pure oil, but takes time and a large quantity of the plant being used.
