2 BULLETIN 330, U. S. DEPARTMENT OF AGRICULTURE. 



briefly these processes and the machinery employed, and to consider 

 each operation in the light of its effect on the chemical and mechani- 

 cal qualities of the finished products. It is hoped that in so doing 

 it may be possible to correct some of the popular misunderstandings 

 of the various grades and finishes of rice now found on the market. 



STRUCTURE OF THE RICE GRAIN. 



A brief description of the physical and microscopic structure of 

 the rice grain is of such value in understanding the milling processes 

 that it is presented here. Prior to 1914 about half of the rice grown in 

 the United States was of the Honduras type and nearly all the remain- 



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Fig. 1. — Outline map of the United States, showing the relative importance of various rice- 

 producing areas in 1914 ; each dot represents 50,000 bushels. 



der was of the Japan type, each deriving its name from the country 

 from which it was originally imported. 1 The grain of the Honduras 

 type of rice is long and slender, that of the Japan type distinctly 

 smaller and more nearly round, but from the viewpoint of the struc- 

 ture of the grain the two are virtually the same. 



The rice grain as it leaves the farm thrasher and enters the mill 

 is covered with a hard, siliceous hull, or palet, which is loosely at- 

 tached to the edible grain within. The germ, or embryo, is dis- 

 tinctly visible near the base of the hulled grain. Directly beneath 

 the hull, but separate from it and firmly attached to the starchy body 

 of the grain itself, is a light-brown bran coat. A careful study of 

 this coat with the microscope reveals seven types of cells arranged 

 in layers and enveloping the starchy interior of the grain. Figure 



1 In 1914 the rice known commercially as " Blue Rose " was first widely grown through- 

 out the rice belt. In shape and size the grains of Blue Rose rice are intermediate between 

 those of the Honduras and the Japan types. 



