2 BULLETIN" 1010, U. S. DEPARTMENT OF AGRICULTURE. 



removing the albuminous :ancjl coloring matter by treating the oil 

 with caustic; 3 (2) bleaching the oil by heating with fuller's earth 

 or decolorizing carbons, or both; and (3) deodorizing the oil by 

 treating it with steam under reduced pressure at a high temperature, 

 which also effects a further bleaching. 



This general procedure is followed, in the main, by most refiners of 

 corn oil, but considerable difference of opinion exists regarding the 

 technical details of the process. Consequently, it was thought 

 advisable to make a thorough study of the preparation of an edible 

 oil from the crude product with a view to clarifying some of the details 

 in dispute. 



This bulletin includes a discussion of experiments on the refining 

 of corn oil under various modifications of the usual methods, a com- 

 parison of the economics of the methods proposed, and detailed 

 plans of a commercial refining plant. 



SMALL-QUANTITY EXPERIMENTS ON METHODS OF REFINING CORN OIL. 



TREATMENT WITH CAUSTIC. 



The technique involved in treating an oil with alkali varies accord- 

 ing to the character of the oil and the individual opinion and expe- 

 rience of the operator. Oil obtained from the average quality of 

 corn germs does not as a rule contain much more than 2 per cent of 

 free fatty acids, and in many cases its acidity is as low as 1 per cent. 

 If a good grade of corn is used the oil produced varies but slightly 

 during the season with regard to acidity and color. It is possible, 

 therefore, to refine many batches of such an oil with only slight, if 

 any, changes in the process. 



The oil used for the experimental work herein described was pro- 

 duced in a hominy mill and contained 1.76 per cent of free fatty acids. 

 Method 1 was the so-called official method 4 used in control labora- 

 tories for grading cottonseed oils except that the maximum* tempera- 

 ture was 55° C. instead of 45° C. In this method the quantity of 

 caustic solution added is equal to 10 per cent of the weight of the oil. 

 In method 2 only sufficient caustic solution is added to neutralize 

 the free fatty acids present plus an additional quantity to remove the 

 color and extraneous matter, the excess quantity being determined 

 by the behavior of the oil under preliminary treatment. The experi- 

 ments recorded are designed to show the proper strength of caustic 

 to use with these two methods and, in the case of method 2, the 

 quantity of excess which should be used, the two methods differing 

 only in the quantity of caustic added. The technique employed in 

 each case follows : 



3 The term "caustic" as used in this bulletin refers in all cases to sodium-hydroxid solution. 



4 Interstate Cottonseed Crushers' Association. Official methods adopted by the chemists' committee 

 and rules committee. III. Crude cottonseed oil. In Cotton Oil Press, v. 3, no. 3, p. 117. 1919. 



