12 



BULLETIN 1610, TJ-. S. DEPARTMENT OF AGRICULTURE. 



the oil at the desired temperature. After the oil is steamed for the 

 necessary length of time the steam is turned off and the oil cooled 

 under the reduced pressure to ordinary temperature. 



In the experimental work on this process conducted in the labora- 

 tory, the oil was heated in a round-bottom glass flask on a sand bath 

 by means of gas burners to 105° C. under a vacuum of 25 inches; 

 the steam was then admitted and the heating continued to the 

 desired temperature. All the experiments were conducted in a 

 darkened room in order to avoid any possible bleaching effect of the 

 light. 



Two principal determinations were sought in this experimental 

 work: (1) The proper temperature to be maintained and (2) the 

 length of time necessary to give the best product. In determining 

 the results obtained two qualities were considered: (1) The extent 

 of the deodorization as indicated by the taste, odor, and acidity 

 and (2) the bleaching effect obtained. In the first experiment 

 samples of corn oil, previously neutralized and bleached with fuller's 

 earth, were deodorized at 150°, 200°, and 300° C, respectively, the 

 time of treatment varying from 15 to 120 minutes. The samples 

 treated at 200° C. (392° F!) were uniformly of a very acceptable 

 quality, even the one treated for only 15 minutes being entirety 

 devoid of the peculiar cereal odor and taste of the untreated oil. The 

 samples deodorized at 150° C. (302° F.) were practically the same in 

 this respect. Those treated at 300° C. (572° F.) appeared to possess 

 a slightly charred odor. 



Table 6 shows the eifect of the treatment on the percentage of 

 free fatty acids. 



Table 6. — Percentage of free fatty acids in corn oil deodorized under various conditions. 





Temperature. 



Percenta 



ie of free fatty acids a after treating for the number of minutes 

 specified. 





15 



30 



45 



60 



75 



90 



120 



150° C 



0.055 



.07 

 .057 





0.03 

 .05 

 .045 







0.027 





200° C 



0.046 



0.047 



0.032 



.023 



0.024 



300° C . . . 



.025 -- 















a The sample of corn oil used contained before the treatment 0.061 per cent of free fatty acids. 



Before being deodorized by the foregoing method the oils gave a 

 positive reaction for aldehydes by the Kreis test, 7 but after the de- 

 odorization the reaction was negative in all cases. 



The treatment as described had a very marked bleaching effect. 

 Figure 5 illustrates the extent to which bleaching was effected at 

 the several temperatures. 



7 Kerr, Robert H. Chemical tests for the detection of rancidity. In Jour. Indus. Engin. Chem., v. 10, 

 no. 6, p. 471-475. 1918. 



