Removing undesirable elements When processing edible vegetable oils and animal fats, it is crucially important to remove any undesirable compounds that can affect flavour, odour, stability and colour.
Deodorization is a vacuum steam distillation process in which steam is passed through such oils at very low pressure and relatively high temperature in order to remove any such substances still present after the preceding processing stages.
Essential for top-quality fats and oils processing
Beginning with deaeration Before heating the oil, air must be removed under vacuum (deaeration) in order to protect the quality of the product by preventing oxidation.
After leaving the deaerator, the oil is regeneratively heated in a special heat exchanger, the economizer, by the hot oil leaving the deodorization column. This ensures that as much heat as possible is recovered from the hot oil.
The oil then proceeds to a final heater where it is brought up to the exact temperature required for deodorization, normally using high-pressure steam.
Stripping and retention When the oil has reached the designated temperature, it is fed to the deodorization column, which is the main component used for deodorizing edible fats and oils. Such a column can consist of a stripping section and a retention section.
When the oil passes through the stripping section, it is exposed to a combination of vacuum and steam that removes volatiles – including free fatty acids (FFAs) – that have a higher vapour pressure than the oil itself. If present, these volatile impurities affect the flavour, odour and stability of edible oil.
The oil is then held in a retention section for a certain amount of time for thermal treatment – known as heat bleaching – that deals with undesirable pigments and ensures the stability of the final product.
The length of time the oil is kept in the retention section depends heavily on the desired product specifications.
Condensing removed impurities The volatile impurities that have been removed from the oil are condensed in a so-called scrubber unit, using recirculated and cooled distillate. The scrubber is either placed on top of the stripping section or built as a separate vessel.
Finally the oil is cooled in two stages. First in the economizer, and then to the specified final temperature. It then undergoes polish filtration and is transferred to subsequent processes, storage or packaging.