CHEMICAL COMPOSITION AND MARKET VALUE 1 67 



The percentage of water usually ranges between 70 

 and 80 per cent., the extremes being 65 and 85 per 

 cent. Potatoes contain more dry matter than any root 

 crop. 



Per cent. 



White turnips 7 to 9 



Rutabagas 9 to 14 



Mangel-wurzels 9 to 16 



Sugar-beets 12 to 24 



Carrots 10 to 17 



Parsnips 10 to 18 



Potatoes 20 to 30 



About 85 per cent, of the matter is present in the 

 solid portion, or marc, and 15 per cent, in the juice. 

 It has been believed by many that the specific gravity 

 of the tubers varied with the percentage of dry matter, 

 and on this basis tables for ascertaining the dry matter 

 present in the tubers from the specific gravity have 

 been worked out and used considerably. From these 

 data the starch content was determined. Woods, 1 of 

 Maine, and Watson, 2 of Virginia, found that the ratio 

 existing between the specific gravity and the starch 

 content is not fixed. 



Starch is the most important constituent of the dry 

 matter of potatoes; it generally constitutes 15 to 20 

 per cent, of the fresh tubers, but may be as low as 10 

 or as high as 25 per cent. Maine-grown potatoes are 

 usually lower in their starch content than European- 

 grown potatoes. The starch content varies with the 

 variety and the locality. Northern-grown samples of 

 the same variety usually contain more starch than 

 Southern-grown samples. 3 



1 Me. Bui. 57, p. 150. 2 Va. Bui. 55, p. 102; Bui. 56, p. 144. 



Va. Bui. 56, p. 144. 



