PRODUCTION OF SIRUP FROM SWEET POTATOES. 33 
Tahle 12. — Chemical composition of dried sweet-potato pomace. 
Determination. 
Per cent. 
Determination. 
Per cent. 
4.59 
4.46 
4.30 
Protein 
23.06 
Ash 
13.50 
50.09 
This analysis indicates the probable high feed value of this pomace. 
SUMMARY. 
A method for the commercial manufacture of sweet-potato sirup, 
based on laboratory and plant experimental work, has been developed 
by the Bureau of Chemistry. The following important points were 
brought out in the course of this work: 
Conversion of starch is accomplished satisfactorily by using malt 
equivalent to one-fifth of 1 per cent of the weight of the potatoes, 
by maintaining a temperature of 140° F., and by allowing the sirup 
to stand for 45 minutes after the addition of the malt. 
The drying of the pomace proved to be uneconomical, although it 
may have a high value as a feed. 
The use of the atmospheric or open-kettle evaporator was prac- 
ticable in concentrating the crude and filtered sirups. 
To produce a permanently clear sirup it was practicable to let the 
crude sirup cool and stand for 40 hours and then filter it, in order to 
remove certain salts which caused turbidity. 
Satisfactory results were obtained in the filtration of the sirup by 
using ignited kieselguhr as a filtering aid, 2 per cent of the weight of 
the potatoes being employed, and filtering cold at 45° Brix. 
The yield obtained varied. During the spring of 1921 it was 1.55 
gallons of sirup to a 50-pound bushel of potatoes. An average yield 
of 1.37 gallons of sirup to a 50-pound bushel of potatoes was obtained 
during the spring of 1922. 
Adding 10 per cent of other sirups with a sucrose or invert sugar 
content increased the sweetness of the experimental sirup. 
From the standpoint of quality the sweet-potato sirup has possi- 
bilities for use as a table sirup, for cooking purposes, and in the 
manufacture of colored and short-grain candies, such as taffy, kisses, 
and caramels. For baking purposes it might find use in dark 
products, such as ginger snaps. It also has properties suitable for use 
in blending with other sirups to prevent crystallization. 
For the proposed plant of 100 gallons per day capacity the cost of 
manufacture of plain sweet-potato sirup, exclusive of containers, is 
estimated to be 64.3 cents per gallon. 
The commercial possibilities of sweet-potato sirup are limited by 
the high cost of manufacture under the present method. 
