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 cooliing. 



(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. 



