expellerpress

An expeller press, or screw press, is a mechanical method for extracting oil from oil-bearing seeds and nuts. It operates by feeding the material into a rotating screw within a tapered barrel. As the screw turns, the seeds are crushed and compressed, and the oil is expelled through a perforated plate while the solid residue exits as a dry cake. The process generates heat from friction, and many modern presses include temperature controls or cooling systems to manage heat and improve quality.

Expeller pressing can be performed as a cold-press or a hot-press operation. Cold pressing maintains relatively low processing temperatures to preserve heat-sensitive nutrients and flavors, often at the expense of throughput and total oil yield. Hot pressing allows higher temperatures, which can improve oil yield and reduce viscous viscosity but may degrade certain nutrients and aromas.

Equipment varies from single-screw to twin-screw designs. Twin-screw presses generally offer higher throughput and more uniform extraction, while single-screw units are common in smaller facilities. Compared with solvent extraction, expeller pressing typically yields less total oil from a given batch, and the resulting oil cake retains more residual oil. The press cake is commonly used as animal feed or as an input for further processing.

Common inputs include seeds such as sunflower, soybean, canola, sesame, peanut, cottonseed, and palm kernel. The method is favored for small- to medium-scale production, for products labeled as “cold-pressed,” or when chemical solvents are discouraged or unavailable. See also solvent extraction and cold pressing for related oil extraction methods.