Soap Manufacturing > 4. Raw Materials Treatments
The Raw Materials used in Soap Manufacturing can be saponified as they are in nature, but the major part of time they undergo treatments for many reasons:
- removal of impurities and free fatty acids
- color changing
- removal of bad odor
The Oil Refining is composed by three processes:
- Refining (chemical or physical)
- Bleaching (physical)
The oil is mixed with caustic soda (NaOH, sodium hydroxide). The mixture is heated, stirred, then separated. This process removes free fatty acids in form of soap stock, but also removes phospholipids, minerals and impurities. For removal of alkali traces, oil is washed with hot water.
Physical refining is a modern process to refine palm oil by distillation at higher temperature and under vacuum. This process replaces chemical refining.
The free fatty acids, in form of palm fatty acid distillate (PFAD), is a by-product that is removed from refined oil during the physical refining process.