526 THE POTATO 



sometimes hears the statement made that potatoes 

 are indigestible on account of the large quantities 

 of cellulose which they contain. In reality there is 

 as much or more in almost all the cereals and other 

 vegetable foods, and such a criticism of the po- 

 tato has no warrant of fact. 



"The bulk of the carbohydrates which the 

 potato stores for future use is in the form of starch, 

 which is, of course, insoluble in cold water, and 

 small quantities of such soluble carbohydrates as 

 dextrose, sugar, etc. In young tubers there is a 

 larger proportion of sugars and less starch than 

 when they have become mature. As the tuber 

 lies in the ground the starch content increases. 

 When it begins to sprout, however, part of the 

 starch is converted by a ferment in the tuber into 

 soluble glucose. Thus, young or early potatoes 

 and old ones both have a smaller proportion of 

 starch and more soluble sugars than well-grown but 

 still fresh tubers. If the grated potato is mixed 

 with water, starch falls out from the broken cells and 

 settles to the bottom of the vessel, and may be 

 removed in the form of a white deposit. Starch 

 is manufactured to a large extent from potatoes 

 by methods which are similar to the above in 

 principle. 



''Other carbohydrates in the potato are the so- 

 called pectose bodies, the substances which cause 

 fruit jellies to stiffen, and when the tubers are 

 large and pulpy pectoses may make up 4 per 

 cent, of the tuber, though they usually occur in 

 much smaller quantities. They are believed to 

 have about the same food value as starch. 



"Fat, or ether extract, appears in such small 

 quantities in potatoes that it may be practically 

 neglected in discussing their food value, especially 



