Oil obtained from pressing the seeds is suitable for human consumption.  However, there are some impurities that may need to be removed from the oil before it becomes suitable for human consumption.  Each type of oil has different levels of impurities and some may contain unique impurities.  Typical impurities present in crude oils include Meal Particles, Moisture, Gums, Free-Fatty Acid, Color, Smell, Waxes, and other Impurities. 

The main impurity that limits use of crude oil for cooking is Gums.  Gums are emulsifiers and tend to create foaming when the oil comes in contact with water and heat, making it impossible to cook. 

Therefore, at a minimum, all oils must be degummed to remove gums.  Gums can be removed by treating with water at a certain temperature for a certain amount of time.  The gums are allowed to settle and drained.  The oil is heated under vacuum to remove residual moisture.