CHAPTER XXXIII 

 Roots, Tubers, and Fruits 



423. General Composition. Roots, tubers, and fruits 

 contain a large amount of water and a small amount of 

 dry matter. The dry matter is composed mainly of non- 

 nitrogenous compounds as starch and sugar. These foods 

 all contain small amounts of nitrogenous compounds of 

 which the larger portion is in amide and non-proteid 

 forms. Organic acids in small amounts and essential 

 oils are characteristic features. 



424. Potatoes contain about 75 per cent, of water. 

 The dry matter is largely starch. About half of the 

 nitrogen is present as proteids of which the larger portion 



IS Protein. 



I Indigestible. 



Fig. 92. Composition of potatoes. 



is in the form of soluble albumin. The amount of fat is 

 small, less than a tenth of i per cent. Potatoes contain 

 but little cellulose. Tartaric and other organic acids, 



