32 BULLETIj^ 1041, U. S. DEPARTMENT' OF AGRICULTURE. 



become soft have a low percentage of starch l)ut a comparatively 

 high percentage of dextrin. During camiing, storage, and cooking 

 the starch is transformed into sugar, dextrin, and probably all the 

 intermediate products, the proportions in which they are formed 

 varying with the method of handling and with different varieties. 

 Changes in plasticity are due to these transformations, which affect 

 the ratio of starch to moisture. 



(8) The essential points in the canning of sweet potatoes are: 



(a) Steaming for a sufficient lengtli of time to make peeling rapid and easy 

 and to coolv tlie potato. 



{b) Handling so as to expose the cooked material to tlie air for the minimum 

 time possible. 



(c) Packing the cans as full as convenient in order to eliminate oxygen and 

 prevent darkening. 



(d) Filling the can with material as hot as possible, not below 70° C, in 

 order .to exclude oxygen and shorten the processing period required. 



(e) Avoiding bringing the material into contact with iron or iron com- 

 pounds. 



(f ) Processing the material the mini-mum length of time necessary to insure 

 its safe preservation. 



