12 BULLETIN 1041, U. S. DEPARTMENT OF AGRICULTURE. 
their yields, canning qualities, and other characters. These descrip- 
tions may be found of value in choosing the variety or varieties best 
suited for any particular purpose. 
COMPARATIVE CANNING TESTS IN 1920. 
There remained to be determined the comparative qualities of the 
different varieties when canned as whole potatoes, and certain of the 
problems connected with the canning of sweet potatoes required 
further investigation. Moreover, several additional varieties were 
made available for use. It was decided, therefore, to continue the 
studies for another season in order to make the work as complete as 
possible. 
Forty-three varieties and strains were grown especially for this 
purpose. They were dug on October 14. and 15 and the main portion 
of each cured and stored, as in 1919. From the Porto Rico. Xaney 
Hall. Big- Stem Jersey, and Southern Queen varieties a sample was 
canned immediately : another at the end of 10 days' curing, when it 
was transferred to storage : a third sample after 10 days in storage ; 
and a final sample after 20 days in storage. This was done to deter- 
mine just what effect curing and storage have upon the canning 
qualities of different types of sweet potatoes. These results will be 
considered under the heading of "Consistency*' (see page 16). 
The main variety canning tests were made from Xovember 26 to 
December 6. The handling of the potatoes differed from that ot 
the 1919 season in that they were packed in two forms, as pie stock 
and as whole potatoes. For packing whole the potatoes were washed, 
the largest roots cut into smaller sizes to facilitate cooking, when 
necessary ; placed on trays in a steam chamber ; and cooked in steam 
at 100 c C. for 30 to 10 minutes, or until done. They were peeled 
rapidly by hand while still very hot. a towel being used to protect 
the hands, the hot potatoes packed into Xo. 3 sanitary cans, and 
sealed immediately. The potatoes being very hot and the cans well 
filled, no exhaust was found necessary. The cans thus prepared 
were then processed at 116' C. for one hour, at the end of which 
time they were removed from the retort and cooled in air. The va- 
rieties canned as pie stock were handled as during the 1919 season, 
the material after passing through the food grinder going directly 
into No. 2 sanitary cans, then sealed at once, and processed imme- 
diately at 116° C. for 15 minutes. 
On December 10 these samples of canned sweet potatoes, both in 
the form of pie stock and as whole potatoes, were submitted to a 
committee of judges, as in 1919. This committee was made up of 
representatives from the Research Laboratory of the National Can- 
ners" Association and of the States Relations Service, the Office of 
