The  crude oil  whether  expelled or  solvent extracted  contains gummy matters,  pigments,  slimes and  other  impurities in  addition to free fatty acids.

The  object of  refining  is to  eliminate all  these impurities almost completely thus making an oil fit for Edible purpose.

 Neutralization  process  is the  chemical  process  in which free fatty acids  are  reacted with  sodium  hydroxide  solution  making insoluble soap,  which  is  called  soap-stock,  Soap-Stock  thus  formed settles down  along with  impurities  it  also  absorbs  major  portion of color pigments  present  in crude  oil making light  color  oil.  When  crude oil  contains   considerable   amount  of  gums,  caustic  refining  is preceded  with  chemical  pre-treatment  process  specially for removing gums. When the Neutralization process is over, the soap stock so formed is allowed  to settle  in the  cone of  Neutralizer  vessel for 6 House depending upon the  nature and  quality of  soap-stock.  After settling period, Soap-stock is drained and the contents of the vessel are washed with  boiling water repeatedly to wash out the fine particles of soap-stock remained unsettled.

 While setting in the cone, some oil also remains  trapped and is washed in the soap-stock when draining. The object of the operator must always be to maneuver the refining process according to the quality and nature of the  crude oil,  so that minimum oil is wasted. After water washing, the oil  is practically  free from Soap  particles and is ready for the following process which is called Bleaching Process.

The  Neutralized  oil free of soap  particles  is then  charged  into a cylindrical vertical vessel called Bleacher. Before  charging the oil into vessel it is evacuated by means of vacuum equipments to  expel  the  air  from  the  vessel thus eliminating the chances of oxidizing the oil under process. When  charge is over,  agitator is put on the oil is heated by steam in heating  coils,  during heating  process,  moisture  from  the  oil is removed  in  the  Barometer  through  fat  trap  when  the  moisture is completely removed moisture  of activated  carbon and activated fillers earth  is sucked in the quantity of mixture and carbon  earth ratio are determined  prior to  dozing  into  the  Bleacher  depending  upon  the quality and degree of bleached oil desired.

 After  taking  in  carbon  and  earth,  the  mixture is stirred for 30 minuets, thereafter the  contents of bleacher are cooled and  filtered to remove carbon and earth.

Process of  Neutralization  and Bleaching remove gums, pigments, slimes other  impurities and  free of fatty acids. These  two processes do not remove the  odor if aerosol  materials  which  oils  possess  to varying amount according to the nature of the oils. 

In addition to this natural odor,  Neutralization  and Bleaching  process  also add up to process odor.

 Deodorize  process  is simple  in heating Neutralized and Bleached oil  in deodorize  to high temperature (about 180 to 230 degree C) under high  vacuum with open  steam. Stripping  steam  leaves the deodorizer carrying with it  the odouriferous materials from the oils. The process is continued till the sample drawn is completely  odorless.  The oil is then cooled in separate cooler under vacuum and then filtered and packed in tin.