Conditioning of Grain

the treatment of grain with water and heat before grinding in order to change its structural and biochemical properties. Conditioning improves the milling qualities of grain because the coats become more viscous and elastic than the endosperm and thereby may be removed more easily. It also improves the bread-baking properties of flour, owing to the action of heat on the protein complex of the moistened grain. In addition, the gluten becomes more pliable, and enzyme activity increases—a beneficial factor in the fermentation of dough.

Conditioning of grain, known as “soaking grain,” was introduced in Russian mills in the early 19th century. In this process water acts as a regulator of grain toughness, affecting its various parts differently. For the coats, rich in capillaries and containing large amounts of cellulose and hemicellulose, water acts as a plasticizer, helping to intensify deformation caused by increased toughness. For the endosperm, water acts to decrease toughness, helping to reduce resistance to grinding. Heat accelerates all the conditioning processes and regulates the flow of moisture in grain in the necessary direction, thus helping to alter its physicochemical properties.

In practice, cold and hot conditioning are both used. Cold conditioning—the manual processing of grain—involves optimum moistening (different for each variety) and then keeping the grain in soaking bins until it is permeated with moisture. Hot conditioning—the hydrothermal machine processing of grain in a conditioner—includes not only moistening and soaking but also intermediate treatment of grain with heat. The method of conditioning varies with grain species and variety—its structure and the quality of its gluten. The moisture content of wheat is raised to 16–20 percent (the lower limit for soft wheat and the upper for durum wheat), and the grain is heated to 41°-60°C (the lower limit for durum wheat and the upper for soft wheat). The procedure lasts from 45 minutes to 1½ hours. In cold conditioning, the soaking time ranges from 12 to 16 hours (the lower limit for soft mealy wheat and the upper for durum wheat). In hot conditioning, the soaking time is shortened three- to four-fold.

Effective conditioning improves the structure of grain, reduces the ash content of the flour, improves the color, and increases the amount of bread obtained. Conditioned grain is more easily ground, and the flour can be sifted better, which makes it easier for machines to process the grain after conditioning.