Industrial Uses for Grain Sorghum

John H. Martin, M. M. MacMasters.

Grain sorghum, which is harvested for grain on about 6 1/2 million acres in the United States, exemplifies our success in putting old products to new uses. Right in the region where sorghum is grown, sorghum starch now is used as an ingredient of drilling muds for oil wells.

The average production of grain sorghum in recent years has been 120 million bushels. It is grown chiefly in the drier sections of Texas, Oklahoma, Kansas, and adjacent States.

Before the Second World War, it was used largely for feed. Since 1945, American-grown grain sorghum has found wide use as food for people in India and other war-stricken countries. People of southern Europe, who were unaccustomed to eating grain sorghum, nevertheless consumed a great deal of our crop as flour that was blended with wheat flour before shipment. A common blend was one part of sorghum flour to four of wheat flour.

Because grain sorghum had been regarded as a feed crop, it received little attention, until recently, from industrial processors or from the research laboratories.

Grain sorghum has long been a potential source of industrial raw material. It contains more protein ( 11.5 to 16.5 percent) than does the corn grain. The protein and oil from grain sorghum should find uses similar to those from corn. The starch content of grain sorghum (63 to 73 percent) is about the same as that of corn, and the starch is like cornstarch in general.

Waxy varieties of grain sorghum have been used for special food delicacies in China for several centuries. Natives of Africa have made beer from grain sorghum since prehistoric times. Varieties with a brown or red seed coat or subcoat are used for making the native beers, because the tanninlike substances in colored grains supply the bitterness that in European and American beers is derived from hops. African natives reserve the palatable white and yellow varieties for food.

Grain sorghum nearly always is cheaper than corn on the open market. The heavy-producing area in the Southwest, particularly along the Gulf Coast, is favored by transportation advantages in reaching important domestic and foreign seaboard markets, as compared with corn from the central Corn Belt. Products from grain sorghum should be able to replace sugars, oils, starches, and waxes that have been shipped into the South and Southwest from other areas. Large amounts of those products are regularly imported. Industrial utilization of grain sorghum should permit the crop to replace some of the wheat and cotton which must seek foreign markets when they are in oversupply. Research on grain sorghum thus helps producers of other crops.

With the outbreak of the Second World War, several new and improved dwarf varieties of grain sorghum came into extensive production. The scarcity of labor forced some cotton growers to shift to sorghum, which had become a profitable mechanized crop. The mobile brigade of custom combines moved into the area to harvest the grain, because the number of local combines was inadequate for the large acreage. At about the same time the southwestern corn borer advanced eastward to devastate the corn crop of the southern Great Plains States, and much of the corn in central and western Kansas was replaced by the new resistant combine grain sorghums. Processing plants that depended on corn from the region sought a new raw material. Shortage of corn on the cash market during and after the war caused industrial users of corn to seek additional sources of supply. Eyes turned toward grain sorghum.

The investigation of grain sorghum as a possible source of industrial material was begun at the Iowa Agricultural Experiment Station about 1936. Shortly thereafter the Kansas Agricultural Experiment Station took up the problem. Intensive research financed by the Corn Products Refining Co. was begun at the company's laboratories and at the Midwest Research Institute in Kansas City, Mo. Additional research was conducted by the General Foods Corp., the Kansas and Nebraska Agricultural Experiment Stations, the Northern Regional Research Laboratory, and various distillers and brewers. Sorghum breeders of the Bureau of Plant Industry, Soils, and Agricultural Engineering cooperated with the State agricultural experiment stations of Nebraska, Kansas, Oklahoma, and Texas in expanding their activities. The experiment stations received support from industrial concerns for this new work. Varieties better suited to industrial processing were needed.

It was necessary to develop modifications of wet- and dry-milling methods that would be adapted to grain sorghum. That was done first in the laboratory and then in a pilot plant. Finally, large-scale milling of grain sorghum was carried out in a corn wet mill. New varieties were analyzed to determine their chemical properties. The suitability of grain sorghum products for various purposes had to be determined. Possible markets for the products were explored. Byproduct protein feeds were tested for palatability and nutritive value.

Research at the Kansas Agricultural Experiment Station revealed that the seed coat of grain sorghum contains a wax that is similar to carnauba wax, which is extracted from the leaves of the carnauba palm of the Tropics and is used for making polishes for furniture and shoes, carbon paper, sealing wax, electrical insulators, and other products. One ton of sorghum grain yields 5 pounds or more of a wax which may replace much of the imported carnauba wax. The wax is present in the seed coat of all varieties, whether or not the endosperm contains the waxy starch. The possibility of obtaining wax as a byproduct tends to offset the disadvantage of the lower oil content in grain sorghum, as compared to corn.

Sorghum breeders had developed several dwarf disease-resistant varieties now widely cultivated. More recently they developed several new white-seeded, combine-type varieties of kafir and milo, which can be processed at a lower cost than can the colored varieties. Some of the white-seeded grain sorghums, including the Cody waxy variety, are entirely free from pigments that stain the starch. White-seeded varieties also yield more palatable gluten feeds than are obtained from deeply colored varieties.

Combined research efforts brought quick results. Grain sorghum was accepted as a source of grain alcohol and some 30 million pounds was used for that purpose in 1942. The alcohol industries in 1945 used more than 2 billion pounds, nearly half of which went into industrial alcohol. Smaller quantities have been used since that time. However, some 560 million pounds was used by the distilling and malt-beverage industries in 1946. The manufacture of butyl alcohol from grain sorghum was begun in 1944. Butyl alcohol, when combined with certain organic acids, forms butyl esters, which are used as lacquer solvents and in the manufacture of 2,4 D weed killers.