expeller

An expeller, in the context of oil processing, is a mechanical press used to extract oil from oil-bearing seeds and nuts by applying pressure and friction. The device is commonly referred to as an oil expeller or screw press.

The core of an expeller is a rotating screw (or two screws in a twin-screw design) inside a perforated barrel. As material is fed in, the screw conveys it forward while compressing it, rupturing cell walls and releasing oil. The oil drains away, while the remaining solid material—the cake— is discharged.

Expellers are used in small- to mid-scale operations and in traditional processing facilities. Common inputs include soybeans, sunflower seeds, canola (rapeseed), cottonseed, sesame, peanuts, coconut kernels, and palm kernels. Oils produced by expellers are often labeled as expeller-pressed, though some heat is generated by friction, which can affect flavor and stability; cold-press methods minimize heat.

Variants include single-screw and twin-screw configurations, hydraulic or mechanical drives, and designs optimized for low-temperature or high-efficiency operation. By-products, known as oil cake or meal, can be used as animal feed or for further processing. Compared with solvent extraction, expeller pressing generally requires less chemical use and is favored for certain edible oils and artisan products.

See also: screw press; oil extraction; oil cake.