32 BULLETIN 1041, TJ. S. DEPARTMENT OF AGRICULTURE. 
become soft have a low percentage of starch but a comparatively 
high percentage of dextrin. During canning, 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: 
i a i Steaming for a sufficient length of time to make peeling rapid and easy 
and to cook the potato. 
I Handling so as to expose the cooked material to the 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, net below 70" C. in 
order to exclude oxygen and shorten the processing period required. 
i t i Avoiding bringing the material into contact with iron or iron com- 
pounds. 
(r) Processing the material the minimum length of time necessary to insure 
its safe preservation. 
