14 MASS. EXPERIMENT STATION BULLETIN 390 



were stored in covered and uncovered dishes in home electric refrigerators at a 

 temperature of 40°-42° F. After two days mashed potatoes had lost 40 percent 

 of their vitamin C in covered dishes and 50 percent in uncovered dishes. After 

 four days they had lost 90 percent of their vitamin C in both covered and un- 

 covered dishes. The loss of moisture was negligible in covered dishes and in- 

 creased regularly with the length of storage in uncovered dishes. These results 

 indicate the advisability of keeping mashed potatoes and other vegetables in 

 covered dishes when stored in a refrigerator in order to conserve their vitamin C 

 and to prevent them from drying out. 



Other Effects of Cooking on Potatoes 



, Weibull (53) found no appreciable loss of minerals and solids when white 

 potatoes were cooked in the peel, but there was a definite loss when potatoes were 

 peeled before boiling. Griebel and Miermeister (16) conducted similar experi- 

 ments on boiling and steaming whole and peeled potatoes. The smallest loss in 

 mineral matter occurred in the steaming of whole potatoes. The losses in total 

 mineral matter were: — from steaming, whole potatoes 1.4 and peeled potatoes 

 7.1; from boiling, whole potatoes 5.8 and peeled potatoes 17.0 percent. When 

 peeled potatoes were boiled in salted water the mineral loss was reduced to about 

 10 percent. Hill (19) reported that in discarding the water in which peeled 

 potatoes are cooked about 70 percent of the minerals and antiscorbutic constit- 

 uents were lost. These losses of water-soluble constituents of the potato during 

 cooking are due to the leaching action of the cooking water. For this reason it is 

 to be recommended that potatoes be boiled or steamed with their skins on, 

 baked, or fried in order to prevent an excessive loss of minerals. 



In discussing physicochemical changes produced by the cooking of potatoes, 

 Sweetman (47) reported that cooking is characterized by partial gelatinization 

 of the starch, solution of some of the pectin substance, increased digestibility of 

 the cellulose, coagulation of most of the protein, and more or less caramelization 

 of the sugar. 



Diemair (11) reported that the flavor of baked or roasted foods is largely due 

 to the formation of histidine bases from the decomposition of proteins. With 

 baked potatoes the optimum temperature for the formation of these flavoring 

 constituents was 175° C. (347° F.) 



THE PLACE OF POTATOES IN THE AMERICAN DIET 



From the above discussion on the composition and nutritive value of potatoes 

 it is evident that they are a particularly good source of certain of the essential 

 nutritive elements of the diet. This is particularly true in the case of low-cost 

 diets where potatoes enjoy a prominent position. Potatoes are primarily important 

 as a source of energy, vitamin Bi, vitamin C, and iron. Their low cost and the 

 relatively large amount eaten make potatoes a very economical source of these 

 elements. 



In classifying winter vegetables as sources of vitamin C, Richardson and 

 Mayfield (38) consider stored potatoes which have been boiled as a good source. 

 One average serving contained 10 milligrams of ascorbic acid. 



According to Stiebeling and Clark (46), the percentage of total specified nu- 

 trients contributed to the diet by potatoes when 5 percent of the food money was 

 spent for them, based on families of city workers. East North Central region, 

 spring 1936, is: 



