440 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



cases was increased about 2.5 times for each rise in temperature of 

 10° C. In cooperation with the Oflice of Nutrition Investigations, 

 Oflice of Expermicnt Stations, the bureau is now studying tlie heat 

 evolved by tlie banana during ripening in the respiration calorimeter. 



THE MANUFACTURE OF CITRUS BY-PRODUCTS. 



Owing to the difl'erence in economic conditions the methods em- 

 ployed for the manufacture of citrus by-products in southern Europe 

 are not applicable in the United States. A laboratory study has 

 been made ■with a view to increasing the use of mechanical devices 

 and otherwise lessening the cost of production, and has reached the 

 stage where it seems advisable to conduct the work on a commercial 

 scale. It is proposed, therefore, at the beginning of the next packing 

 season, to equip a small experimental plant for the study of the eco- 

 nomic manufacture from waste citrus fruits of citric acid, citrus oils, 

 juices, and several preserved products, 



ESSENTIAL OILS USED FOR FLAVORING FOOD PRODUCTS. 



An investigation of citrus-fruit oils extending over several years 

 has been completed during the past year, and a report upon the 

 subject is in preparation. A study was also made of the manufacture, 

 composition, and methods of analysis of the oils of wintergreen and 

 birch and of methyl salicylate. It is important to know the dis- 

 tinguishing characteristics of these products, as the last two are fre- 

 quently substituted for the wintergreen. Other essential oils, such 

 as oil of sassafras and spearmint oil, were also studied. 



FIELD EXPERIMENTS IN THE MANUFACTURE OP CIDER VINEGAR. 



In order to determine the changes taking place during the conver- 

 sion of cider into vinegar under commercial conditions, a field labora- 

 tory was established at a factory in Benton Harbor, Mich., and also 

 one in Albion, N. Y. The plan of the work was to make analyses of 

 the cider used as a vinegar stock and then collect samples of this 

 after it had passed through generators and been converted into 

 vinegar, in order to determine the exact changes which took place 

 during this acetification. 



This experiment was carried on during a period of several months, 

 as it was found to take some time for the effect of a change in com- 

 position of the cider to show itself in the finished vinegar. Some very 

 valuable information was obtained, showing that in the acetification 

 of the cider by the generator process practically the only change is 

 the conversion of the alcohol into acetic acid. It was also shown 

 that the generator vinegar is very much more uniform in composition 

 than vinegars made by the old-fashioned barrel process, during which 

 they are subjected to varying conditions, and that certain relations 

 exist between the ingredients of the generator vinegar which are 

 valuable in detecting adulteration of the commercial product. The 

 glycerin present in the fermented cider was not affected by the con- 

 version into vinegar, and a very valuable factor was thus obtained 

 for the detection of adulteration, which has been used in a number of 

 cases to great advantage, proving conclusively the dilution of cider 

 vinegar with the distilled product. 



