Mechanical pressing is a solvent-free oil extraction method in which oilseeds are compressed in a screw or expeller press to expel oil, yielding both a liquid oil fraction and a solid press cake suitable for feed use.
In trade practice
Operators control feed rate, barrel temperature and pressure to optimise oil yield and residual oil in the cake. For cold-pressed designations, temperature at the press head is monitored continuously and logged as evidence for buyers. A common error is running the press too fast, which raises friction heat and disqualifies the batch from cold-pressed labelling. The press cake is weighed and sampled separately, as its residual oil content affects overall extraction efficiency reported to buyers.
In a specification
A specification for mechanically pressed oil states the maximum press-head temperature permitted, the method of temperature recording and whether the resulting oil may be filtered or must remain unfiltered.