FIELD CROPS 461 



sideration is, then what are the factors which influence, or deter- 

 mine, the milling qualities of wheat. 



The first factor in determining the milling quality of wheat is 

 the chemical composition of the wheat itself. For the purposes of 

 chemical analyses, and to aid in estimating the food value of the ma- 

 terial, the constituents of grains are commonly divided into five 

 groups, or classes; namely, moisture, ash, crude protein, fats, car- 

 bohydrates. These are not five separate and distinct bodies or things, 

 but are groups of substances having very similar properties and 

 food values Thus, for example, crude protein is the name for a 

 general class of nitrogenous bodies, of wnich the albumen or white 

 of eggs, the mucin or lean meat of animal bodies, the gluten of 

 flour, etc., are common examples. Again, carbohydrates is a gen- 

 eral term including a large number of substances, such as starches, 

 sugars, certain vegetable gums, and the like. Now, since it is the 

 substances belonging to the protein group in the wheat which gives 

 rise to the gluten in the flour, and the carbohydrates of the wheat 

 which yield the starch of the flour, it is obvious that the percentages 

 of these constituents in the wheat is one of the determining factors 

 in its milling qualities. 



The percentages of the constituents may vary greatly in any 

 given breed or variety of wheat. It is believed that variations are 

 due to differences in the length of ripening period of the grain. 

 Most authorities are now fairly well agreed that the ripening of 

 grain is merely a process of desiccation or "drying up. Hence, 

 conditions favorable to rapid drying produce rapid ripening and 

 harder grain. The one climatic factor which would, therefore, have 

 the chief influence in changing the composition or type of grain is 

 that known as "evaporation-coefficient." Several factors or condi- 

 tions cause changes in the rate of evaporation of water at any given 

 time or place, such as temperature, relative humidity of the air, 

 wind velocity, etc., etc., but the combination of these is without 

 doubt the influence which is the chief determining factor in the ra- 

 pidity of ripening of the grain and this, in turn, determines the 

 "hardness" or type of wheat. 



The second factor influencing the milling quality of wheat is 

 the percentage of each of the several mill products which it will 

 yield. While each of these products, namely, bran, shorts, mid- 

 dlings, and the several grades of flour, has a considerable food value, 

 and a definite market price, the flour is the product which commands 

 the highest price. Therefore, the greater the yield of flour per 

 given weight of grain, the larger will be the money return for it. 

 This factor, however, is too well known and too generally recognized 

 to need further discussion. 



The third factor is the distribution of the valuable constituents 

 of the wheat to the several mill-products. Wheat of high milling 

 Cjuality must not only possess largo amounts of the desirable chem- 

 ical constituents, but they must be so distributed in the grain that 

 they will appear chiefly in the flour when the grain is milled. If 

 they go elsewhere, into the bran for example, the latter will have a 



