PRODUCTION OF SIRUP FROM SWEET POTATOES. 3 
were worked up into the crnmblike product, flour, or flakes. Produc- 
tion, however, was unprofitable and eventually ceased. 
The manufacture of sweet-potato flour by the flake process was 
taken up by Mangels and Prescott of the Bureau of Chemistry dur- 
ing the spring of 1919. 3 Their method was as follows : The potatoes 
were washed, steamed under 15 pounds pressure for 15 minutes, and 
then dried in a drum drier of the type extensively used abroad in 
treating Irish potatoes. The drier consisted of two revolving drums 
supplied with steam at from 35 to 53 pounds pressure. The cooked 
potato was spread out on the cylindrical surface of the drum by 
means -of smaller auxiliary rollers, dried rapidly, and then removed 
by scraper knives. The flakes thus obtained were ground into flour. 
This process could not be applied to sweet potatoes on account of the 
difficulties encountered in securing a product of attractive color and 
flavor and because the flour obtained was so hygroscopic that it 
hardened upon storage, forming gummy cakes. 
The study of McDonnell 4 on the manufacture of sweet-potato 
starch has great general technical value. Despite his satisfactory 
results, the simplicity of the process, and the favorable reports on the 
market value of starch, commercial development of sweet-potato 
starch manufacture has never been undertaken. 
COMMERCIAL POSSIBILITIES FOR SWEET-POTATO SIRUP. 
From 5 to 6 gallons of sweet-potato sirup produced by the Bureau 
of Chemistry was sent to each of many manufacturers of sirup and 
various products made with sirup to obtain their opinions as to the 
quality and commercial application of the sirup. Most of these 
manufacturers submitted a report. 
The consensus of opinion was that the sirup produced during 1922 
was superior to that which had been produced during the preceding 
year. There was, however, a wide variation of opinion as to the 
quality of the sirup. Some claimed that the sirup was not sweet 
enough; others that it was too sweet. Some thought the color was 
too dark; others that it was good. Some reported that the sirup 
had a sweet-potato taste, which was objectionable ; others stated that 
the sweet-potato taste in the sirup was hardly noticeable, and even 
if present would not be objectionable. Some said the sirup was 
either too thin or too thick; others that its consistency was about 
right. This difference of opinion was to have been expected. Each 
manufacturer measured the quality of the sirup by the requirements 
of his product or of his particular method of manufacture. 
In several cases the sirup fermented readily. This may not be 
a serious objection, as it probably may be avoided by concentrating 
the sirup to a certain degree Brix. This, however, would have to 
be determined by a series of tests. The claim has also been made 
that the sirup will scorch when cooking on a fire before it reaches a 
temperature of 250° F. 
The replies of the manufacturers show that the qualities of the 
sirup limit its field of use. Because of its color the sirup could not 
be used generally in the manufacture of candies other than colored 
3 " Manufacture of sweet-potato flour by the ' flake ' process," Chemical Age, 29 (1921 > : 
132-135. 
4 " The manufacture of starch from sweet potatoes," S. C. Agr. Expt. Sta M Clemson 
College, S. C, Bull. 136, April, 1908. 
