Types of plant oils

The remaining solids, called seed cake, are either discarded or used for other purposes.

There has been recent interest in improving the design of mechanical oil presses, particularly for use in developing countries.

A press developed at MIT's D-Lab, for example, is capable of exerting 800–1,000psi to extract peanut oil.

Many expellers add heat and pressure, in order to increase the amount of oil extracted.

[5] In this process, used, for example, to extract the onion, garlic, wintergreen and bitter almond essential oil, the plant material is macerated in warm water to release the volatile compounds in the plant.