The Physical Refining process is possibly the most important step in Edible Oil Refining and is aimed at creating a fatty acid free, odourless product with a very light hue and very stable against oxidization.
The simplest and most economical way to execute physical refining is to pass the oil through a serious of compartments intermittently placed horizontally and vertically while subjecting it to steam stripping under high vacuum. This ensures all volatiles like fatty acids, aldehydes, ketones, alcohols and colouring agents are removed.
The Physical Refining process is monitored continuously through instrumentation with precise control over all variables like temperature, flow rate, vacuum and time.
Through this method, the free fatty acids are removed through the process of distillation in one stage of deodorizing. In order to come up with effective results, the crude oil should be thoroughly degummed. This is not applicable with some oil like the oil extracted from cottonseeds. All kinds of refining methods are done with the help of various equipment and machinery, and are used to refine almost all kinds of oil extracted from oil seeds like sunflower seeds, flax seeds, groundnuts, sesame seeds, and mustard seeds, etc.
Features of Physical Refining
High refinement rate; less oil loss
No waste water discharged
More FFA distilled
Especially suited for highly acidic oils, and those of low gum content
Chemical technology of edible oil refining is performed in order to remove the fatty acids from the crude oil that is extracted from the seeds. These are further neutralized with the use of caustic soda. This results in the removal of sodium soaps by batch settling or centrifugal separators. The neutral oils are then bleached and deodorized.
Features of Chemical Refining
Excellent adaptability and fewer requirements for high oil quality
The finished oil is consistent and stable
Less bleaching earth necessary compared with physical refining.