372 PRINCIPLES OF AGRICULTURAL CHEMISTRY 



When heated to a temperature above 120 C., starch is changed 

 to dextrin. This takes place in the browning of flour, prepara- 

 tion of toast, and some other processes of cooking. 



When starch paste is treated with malt (this is best done at a 

 temperature of about 65 ), it is converted into maltose and dextrin, 

 and goes into a solution, which may be fermented. Advantage is 

 taken of this property in the manufacture of alcohol or alcoholic 

 beverages from materials containing starch, such as corn, rye, 

 barley, etc. The grain is ground, heated with water, treated with 

 malt, and to the aqueous solution yeast is added to cause fer- 

 mentation. If alcohol or whiskey is desired, the fermented 

 material is distilled. The residue from the treatment with 

 malt is dried and used for cattle food (brewers' grains), or 

 it may be fed without drying. 



Malt is partly sprouted barley, the sprouts being rubbed off. It 

 contains an enzyme known as diastase, which acts upon starch as 

 stated above. 



Manufacture of Starch. Starch is made from potatoes, corn, 

 arrow-root, cassava, and other materials rich in it. The prepara- 

 tion of starch from potatoes is a simple mechanical operation. 

 The potatoes are washed and grated to a pulp to break the cell 

 walls. The starch is washed out of the pulped mass on sieves. It 

 is allowed to settle and dry. With some other materials such 

 as wheat and rice, the proteids which accompany the starch must 

 be brought into solution by fermentation or by means of caustic 

 soda. 



Inulin, C 6 H 10 O 5 , is found dissolved, in a pasty condition in 

 many plants of the Compositae family, and in these plants plays 

 the part that starch does in most others. It is obtained from the 

 dahlia tubers. It is a white powder, composed of small crystals, 

 easily soluble in warm water, being slowly precipitated on cool- 

 ing, but readily by alcohol. It is not colored by iodine, hardly 

 affected by diastase, and is much more easily hydrolized by dilute 

 acids than starch. Since it yields only fructose, it is used for the 

 preparation of pure fructose. 



Glycogen, C G H 10 O r> . is a starch-like carbohydrate found in 



