In this process no attempt is made to recover the wheat germ. In the wet milling of corn the steeped grain is degerminated and the germ is processed for corn oil. Wheat contains less than half as much oil as does corn and a much smaller proportion of the wheat oil is concentrated in the germ. The small size of the wheat germ makes its separation from the ground grain very difficult. For these reasons it does not seem practical to recover the wheat germ. During the milling operations the bulk of the wheat oil stays with the gluten and some of it remains in the fibers, but fortunately it does not contaminate the starch. Except for minor losses, all of the oil appears in the byproduct feed.

The starch produced by this process is of excellent quality; on the average it contains 0.25 percent protein, whereas cornstarch contains 0.35 percent. From a 60-pound bushel of soft winter wheat containing 60 percent starch, the yield of commercial starch, containing 12 percent moisture, amounts to 33 pounds. In the wet milling of corn, the yield of commercial starch averages 34 pounds per 56-pound bushel. In the wet milling of wheat the yield of commercial feed, containing 12 percent moisture, is approximately 22 pounds per 60-pound bushel; that in the commercial wet milling of corn averages 16.7 pounds per 56-pound bushel. This type of feed has sold for about 2 cents a pound.

In the Corn Belt, where the price of wheat exceeds that of corn, the wet milling of wheat has been conducted only during periods of acute shortages of cash corn. In the summer of 1945 a corn wet-milling company processed approximately 2 million bushels of wheat for the production of glucose sirup. Careful study of both processes revealed that only minor changes are required in plant equipment and operating methods in order to utilize wheat in a corn wet-milling plant. The objection to the change arises from the fact that the capacity of the plant is greatly reduced. In order to obtain wheat starch of high quality it is necessary that the density of the mill starch to the tables should not be greater than 6 Baume. The volumetric rate of feed to a given table is the same in both instances; hence the table capacity in a corn wet-milling plant will be reduced by approximately 50 percent. Because the quantity of wheat that can be processed in such a plant is limited by the tables available, the remaining equipment will not be used to full capacity. If a plant were being designed specifically for the utilization of wheat the condition obviously would not obtain.

Both processes that have been described contributed materially to our war effort, and undoubtedly their use will continue in suitably located plants. The batter process appears to be ideally adaptable as an adjunct to beet-sugar factories. The wet-milling process will probably continue to be used in areas where the price of wheat is normally less than that of corn.

Advantageous use of the batter process can be made in beet-sugar factories and sugar refineries to produce starch for conversion into sweetening agents. At such sites equipment is available for processing the saccharified starch liquor into sirup or sugar. Because beet-sugar factories operate on a seasonal basis, the production of sweetening agents from starch could be carried out during the off season. Such a scheme would keep the plants and labor force occupied throughout the year. Some installations of the process have been made in beet-sugar factories.

In the Pacific Northwest, where the price of soft white wheat is relatively low and, in normal times, is invariably lower than that of corn at Chicago, the wet-milling process appears to be economically feasible. For a small plant with a capacity of 10,000 bushels a day, the total cost of processing is estimated to be 23 cents a bushel. Assuming a price of $1 a bushel for soft wheat, the cost of raw material and processing amounts to $1.23. With no credit for oil, the only byproduct credit is that for feed, amounting to 44 cents a bushel. Thus the net production cost for 33 pounds of marketable starch is 79 cents or an average cost of 2.39 cents a pound. That figure probably exceeds the production cost of cornstarch, but it is much lower than the 1947 market price of wheat starch and is considerably less than the market price of cornstarch.

THE AUTHORS

Cecil T. Langford is head of the Engineering and Development Division of the Northern Regional Research Laboratory, Peoria, Ill., one of the laboratories of the Bureau of Agricultural and Industrial Chemistry. His work is concerned with the development, on a pilot-plant scale, of processes that show industrial possibilities after the fundamental research has been concluded in other divisions of the laboratory. Dr. Langford holds degrees from the University of Oklahoma and the University of California.

Carl E. Rist is acting head of the Starch and Dextrose Division of the Northern Regional Research Laboratory. He joined the Department in 1929 as a member of the Fixed Nitrogen Research Laboratory. His work involves the development of processes for the production of starch and sirups and the development of industrial products derived from starch and dextrose.