12 
BULLETIN 1010, U. 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 entirely 
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 effect of the treatment on the. percentage of 
free fatty acids. 
Table 6. — Percentag 
e of free fatty acids in corn oil deodorized under various co 
nditions. 
Temperature. 
Percentage 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 
.023 
.025 
200° C. 
0.046 
0.047 
0.032 
0.024 
300° C 

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. 
