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The Effect of Drying Temperature upon the Nutritive Value and Commercial Grade of Corn¹

Nebraska Agricultural Experiment Station

Abstract

Mature ear corn was reduced in kernel moisture content from 27 percent or more to a safe storage value of about 14 percent by heated air under forced draft at temperatures ranging from 240° to 120° F. in four to 49 hours.

The market grade of corn was not affected by drying temperatures up to 180° F. Drying at 200° F. and 240° F. in one year 1946 lowered the grade to four and five respectively, because of heat damage. In two other years, 1947 and 1948, a 240° F. temperature lowered the grade to sample and grade 4 as a result of heat damage.

Drying at seven different temperatures ranging from 80° to 240° F. did not materially affect the proportion of the various feed constituents of corn on a comparable moisture basis. The nutritive value of the protein, however, was affected adversely at 160° F. or more as evidenced by reductions of 18 to 32 percent in the weight gain of rats fed individually for eight weeks with especially designed rations in which the corn was the only source of protein. These higher temperatures also reduced the amount of feed consumed an average of 5 percent under that of the check dried naturally at 80° F. There was a corresponding reduction of 18 percent in the amount of gain per unit feed consumed.

When corn dried at various temperatures was tested as a source of energy in special rations fed to rats, its energy value was significantly reduced by 140° F. or higher temperatures. This amounted to 8 percent less gain after eight weeks of feeding. A corresponding non-significant reduction in the amount of feed consumed averaged 5 percent. Grain dried at the higher temperatures was apparently somewhat less palatable, although the gain in weight per unit feed consumed was but slightly affected as compared with the naturally dried check.

As a general practice, drying corn at temperatures above 140° F. would be objectionable from the standpoint of reduced nutritive value. This reduced feeding value may not be apparent in the feeding of hogs when a protein-mineral-vitamin supplement is added to the ration or in the feeding of the mature ruminant which has the ability to utilize less desirable feeds due to the microorganisms of the digestive tract. However, since over-heating corn lowers its market grade and impairs its milling quality in addition to reducing its intrinsic nutritive value, excessive drying temperatures should be avoided.

¹ Published with the approval of the Director as paper No. 548 Journal Series, Nebraska Agricultural Experiment Station.

² Associate Professor of Dairy Husbandry, Research Engineer and Professor of Agronomy, respectively, Nebraska Agricultural Experiment Station.