BUREAU OF CHEMISTRY. 271 



Jaboratory experiments and in the factory -work that will be of value 

 to anyone midertakin^ the production of sweet-potato sirup. In 

 general, the results of the factory work substantiated those previ- 

 ously obtained in the laboratory. It was practicable to produce 

 a clear sweet-potato sirup of excellent flavor on a small factory 

 scale. It is believed that the process developed will pi'ovid • an out- 

 let for many of the cull and surplus sweet potatoes. 



Work in the laboratory was done on the changes which occur in 

 the sweet potato on heating, and these results were submitted for 

 publication. Before this work was done it was well known that the 

 sweet potato contains large quantities of an active diastase. The 

 laboratory results show that the diastase is so Avell distributed 

 throughout the sweet potato and is so closely associated with sweet- 

 potato starch that more or less complete hydrolysis of starch results 

 whenever sweet potatoes are cooked. The action is very rapid, and, 

 indeed, it was found difficult to heat sweet potatoes in any way with- 

 out causing some digestion of the starch through the action of the 

 diastase. The principal carbohydrate formed was found to be 

 maltose. 



This study is believed to have value in guiding future efforts which 

 may be made in converting surplus and cull sweet potatoes into 

 economic pi'oducts. I'or example, if it should be desired to convert 

 potatoes into the dehydrated form, for use in alcohol or vinegar 

 production, the recognition of the presence of the diastase and its 

 action in digesting the starch upon cooking would be of great assist- 

 ance in the determination of the process to be used. 



Investigations to improve further methods for the utilization 

 of cull and surplus oranges and lemons were continued at Los An- 

 geles. Calif. The development of commercial industries utilizing 

 much of the cull and surplus citrus fruit of California has been re- 

 ported previously. Several concerns are now profitably manu- 

 facturing valuable commodities from fruit by methods resulting 

 from these investigations. Growers of fruit can now dispose of 

 culls at a greatly increased price. A paper on the work on orange 

 vinegar was puljlished during the year. Work on the cr^^stalliza- 

 tion of citric acid without previous precipitation as calcium citrate 

 was completed. An investigation was made of the use of dialysis 

 in the preparation of commercial pectin from the waste products 

 of both oranges and lemons. The laboratory work has reached a 

 stage where manufacture on a semicommercial scale will soon be 

 started. 



Progress Avas made in the investigations aimed to improve 

 processes for the dehydration of fruits and vegetables. Dehydrated 

 fruits and vegetables greatly superior in appearance and flavor to 

 the old-fashioned dried products have been put on the market. It 

 is expected that still further improvements will result from this 

 work. The dehydration work was transferred on July 1, 1922, from 

 Washington to Los Angeles, Calif., and combined with the labora- 

 tory which has done such excellent work on the utilization of 

 oranges and lemons. This change enables the bureau to effect certain 

 economies and to increase the efficiency of the work. 



Work similar to that in utilizing by-products from oranges and 

 lemons, however, should be extended to include other fruits and 



