A Study of Quality in Potatoes. 



223 



Cortical layer and skin . . 

 External medullary area 

 Internal medullary area. 



Starch 

 per cent. 



15.784 

 17.324 

 12.75 



Protein 

 per cent. 



2.173 

 2.291 

 2.457 



Water 

 per cent. 



76.57 

 78.43 

 81.13 



In three samples we found the specific gravity of each of these 

 portions to be as follows, each pair of samples as numbered being 

 taken from the same tuber: 



External medullary area 



(1) 1.1156 



(2) 1.0960 



(3) 1.0578 

 Average 1.0898 



Internal medullary area 



(1) 1.0716 



(2) 1.0219 



(3) 1.0513 

 Average 1.04826 



If, as stated, the starch grains expand when boiled in water, it 

 would seem that a cooked tuber ought to be greater in volume than 

 a raw one, but this is not the case to any marked extent. The 

 boiled tuber contains about the same percentage of water as a raw 

 one. In order to determine this point, two trials were made with 

 results as follows: 



Doe's Pride. 



Original weight of tuber 

 Weight of tuber peeled 

 Loss of weight in peeling 

 Weight of tuber cooked 

 Loss of weight by cooking 

 Per cent, loss 



184 . 78 grams 



148 . 1 grams 



36 . 68 grams 



144 . 64 grams 



3 . 46 grams 



1 . 87 grams 



This tuber was of decidedly poor quality (immature), remaining 

 soggy and retaining its form after cooking. Not all of the loss was 

 due to the difference in water content, however, as some solids were 

 extracted in boiling. 



