Nitrogen -free Exirad — Carhohydrates 75 



enous bodies of less importance are not so "well known, 

 as, for instance, such uncommon sugars as mannose 

 and galactose, and their mother substances, mannan 

 and galactan. 



The manufacture of beers and liquors and many of 

 the ordinary phenomena of cooking operations, are based 

 upon the chemical properties of the starches and sugars. 

 To the presence of these and related bodies is due many 

 of the agreeable flavors and appetizing characteristics of 

 certain foods, as, for instance, the sweetness or acidity 

 of fruits, and flavors produced in grain foods under the 

 influence of heat. 



The most prominent and important members of the 

 nitrogen -free extract group are known as carbohy- 

 drates, the significance of this term being that these 

 compounds contain carbon united with hydrogen and 

 oxygen in the proportions in which these two elements 

 exist in water. 



A common and convenient classification of the car- 

 bohydrates, though not strictly rational from the stand- 

 point of chemical constitution, is the following: 1. The 

 starches, such as corn and potato starch and those 

 bodies similar in elementary composition, including cel- 

 lulose, inulin, glycogen, the dextrin s, pectin and the 

 gums. 2. The sugars, of which there are two main 

 classes, the glucoses and the sucroses, the main sugar 

 of "corn syrup" being a familiar example of the former 

 class, and the ordinary crystallized sugar of commerce 

 the most prominent member of the latter. 



The starches. — Starch is a widely distributed and 

 abundant constituent of vegetable tissue. Food plants, 



