558 ANNUAL REPORTS OF THE DEPARTMENT OF AGRICULTURE. 



During the year some of the orange districts suffered from frost 

 and many of the oranges were frozen on the trees. This resulted in 

 the placing on the market of a large number of shipments of oranges 

 containing a varying percentage of frozen fruit. A preliminary 

 study of possible methods for the detection of frozen fruit was made 

 in the Division of Foods, and the matter was then transferred to the 

 San Francisco laboratory for field investigation. 



Characteristic acids. — INfuch attention has been given to the iden- 

 tification of the acids occurring naturally in various fruits and to the 

 determination of the amounts of those acids. This information is of 

 value in the examination of samj^les taken under the food and drugs 

 act and also in connection with the constructive work of the bureau. 

 The character of the acid present in a prepared fruit product may be 

 used for the identification in a general way of the variety of fruit em- 

 ployed in its preparation, or at least it ma}^ often afford evidence of 

 the absence of a fruit claimed to have been employed. It also affords 

 means of determining the changes of composition during the manu- 

 facture of some foods, as, for instance, wine, and of determining to a 

 certain extent the method of manufacture that has been employed. 

 The fruits examined included many varieties of apples, pears, straw- 

 berries, raspberries, blackberries, cherries, curi'ants, gooseberries, 

 quinces, huckleberries, apricots, and peaches. 



SuGAR-Acm RATIO. — It is the practice in the preparation of the high- 

 est grade of canned fruits to vary the strength of the sirup added ac- 

 cording to the flavor desired. This seems to depend mainly on the 

 acidity of the fruit ; for instance, a 60 per cent sirup is employed with 

 some strongly acid fruits, whereas with certain fruits of medium or 

 low acidity the maximum sugar content is 40 per cent. It is believed 

 that more satisfactoiy results can be obtained by determining the 

 acidity of the fruit in the cannerj^ and giving closer attention to the 

 sugar-acid ratio in the finished product. This matter is being studied 

 in the canning laborator}^ of the bureau located at San Francisco, Cal., 

 and m collaboration with this work the Division of Foods has deter- 

 mined the sugar and acids and the ratio of the two in about 200 

 samples of fresh apples and peaches and a somewhat larger number 

 of samples of canned fruits of various varieties. 



CiTBUS BY-PBODUCTS. 



The field work of this laboratory has made splendid progress 

 during the year. The experimental plant has been installed at Los 

 Angeles, Cal., for making practical commercial tests upon the pro- 

 duction of citrus by-products early in the coming winter. Experi- 

 ments have been tried both in the field and at the laboratory in 

 Washington, and man}^ practical experiments now await only the 

 practical field test as a final proof of their efficiency. The chief of 

 the laboratory has visited several commercial plants and made 

 practical tests as to the availability of the manufacturers' machines 

 for use in this work, and no little benefit has been derived from the 

 experience gained. 



