A STUDY OF SWEET POTATO VARIETIES. 7 
storage tests were made available, and work was undertaken with 
the view to determining what varieties were best suited for canning 
purposes. From preliminary investigations it soon became evident 
that a satisfactory comparison of the different varieties could be 
made only after inquiry into a number of problems which presented 
themselves. What should be the methods used in the preliminary 
handling of the potatoes before placing them in the cans? What 
was the nature of the discoloration which occurred, and how could 
it be avoided? And, from the standpoint of appearance and flavor 
of the product, what temperatures and time periods should be 
adopted in the processing of the material in the cans? These were 
matters which received first attention. As the work progressed new 
facts and conditions were brought to light, so that it was found 
necessary to continue the studies over a period of three successive 
seasons. The problems involved in the canning of sweet potatoes 
have by no means been exhausted, but it is felt that enough has been 
done to warrant the presentation of the results so far obtained. 
These will be considered in the order of their sequence. 
WORK IN 1918. 
The sweet potatoes were received at the time of or shortly after 
digging and were not cured. On the other hand, they were held in 
open crates in the floor space of a large well- ventilated building, with 
no attempt made to control the temperature other than to prevent 
freezing during the latter part of the season. Experiments were 
begun at once and continued up to about the middle of December. 
The tendency of the material to darken on exposure to the air was 
encountered at the outset of the work. Examination of the potatoes 
showed that the cortex contained the larger part of the substance 
causing the darkening, and it was thought that a complete removal of 
the cortex would greatly diminish the trouble from this cause. Since 
the entire cortex could not be removed satisfactorily after cooking, it 
was decided to peel the potatoes before cooking. Consequently, the 
potatoes were peeled raw and then placed immediately in water until 
ready for cooking. This excluded the air from them more or less and 
they turned brown only after long standing in the water. Brine was 
tried in the place of water, but it proved only slightly more effective 
than the water alone. Dilute citric acid was very effective, but it 
gave an undesirable acid taste to the product. The following pro- 
cedure seemed to offer promise of avoiding most of the difficulties, 
and it was temporarily adopted : 
(1) Peeling the potatoes raw, after washing to remove dirt, and cutting the 
larger potatoes into pieces to facilitate cooking. 
(2) Rinsing the potatoes in cold water, placing them at once in a steam re- 
tort, and cooking for 10 minutes at a steam pressure of 10 pounds. 
