28 BULLETIN 1265, U. S, DEPARTMENT OF AGRICULTURE 
SWEET POTATOES. 
The work with sweet potatoes was designed to determine the effects 
of the precooking which is usually given sweet potatoes to facilitate 
their peeling and packing during canning operations. Several vari- 
eties were used,' including representatives of both the dry firm 
varieties and the soft moist types. These were grown at the Arling- 
ton Experiment Farm, near Rosslyn. Va.. and the experiments were 
performed immediately after digging, and again after 30 days of 
curing and storage. 8 
The sweet potatoes were graded for size, washed, and weighed. 
Some were precooked for different periods in a steam chamber, and 
some were given similar treatment in boiling water. They were then 
peeled, the losses in peeling noted, and then, while still hot, packed 
in tin cans, sealed, and processed immediately. Samples before and 
after precooking were taken for chemical analysis. 
Sweet potatoes were also canned without any precooking. One 
lot. after washing, was placed in cans without peeling, and the cans 
sealed and processed immediately. Another was peeled by hand 
before cooking, the potatoes cut into pieces 1 to 1^ inches in diameter, 
and put in the cans, water added to fill the interspaces, sealed, and 
processed immediately. A third lot, after peeling b} T hand, was 
passed through a food grinder, packed into the cans raw, and then 
sealed and processed as above. 
The canned material prepared in the various ways was opened for 
careful examination for quality of the product, and chemical analy- 
ses were made to determine the effect of the preliminary treatment. 
The water in which the potatoes were precooked was also analyzed. 
The findings follow. 
RELATION OF PRECOOKING TO THE PEELING OF SWEET POTATOES. 
TVhen sweet potatoes are peeled raw, whether by hand or by 
abrading machines, the losses are very high, amounting sometimes 
to as much as 30 per cent of the original weight. The loss varies 
with the size, shape, and variety of the potatoes. The greatest loss 
is with small and irregular-shaped roots, and the smallest with 
large smooth ones. In some of these tests, using potatoes 2 to 2 -J inches 
in diameter, there was an average loss of 22.8 per cent when the 
potatoes were peeled by hand. With machine peeling, the losses 
average about the same. 9 Although some of this loss is of inedible 
material, considerable valuable food is lost in this way. for it is 
not possible to remove the peel economically without removing con- 
siderable of the edible part with it. 
\Ylien sweet potatoes are peeled after preliminary cooking, either 
in steam or in boiling water, the losses are much less. In these ex- 
periments, the loss in peeling after steaming for 30 minutes amounted 
to only 13.2 per cent, and the figures were about the same (13.8 
per cent) when the precooking was in boiling water for the same 
Length of time. 
8 The po: cured for 10 days, at a temperature of 85° F. and then stored ar 
55° to 65° F. for 20 days longer. 
8 Dr. J. S. Caldwell, Office of Horticultural Investigations. Bureau of Plant Industry. 
U. S. Department of Agriculture, in a personal communication, reports for 12 varieties of 
sweet potatoes of all Blzes losses ranging between 22 and 25 per cent. With lye peeling, 
the losses were from 2 to 2% per cent less. 
