2 BULLETIN 241, U. S. DEPARTMENT OF AGRICULTURE. 



densing and keeping them by refrigeration or by the use of steriliza- 

 tion in carbon dioxid. 



In this bulletin it is deemed best, therefore, to discuss first the 

 general methods of extracting the juice and the ordinary forms of 

 sterilization applicable to certain of these fruits, as a preliminary to 

 the discussion of the special methods and their application to the 

 juices of individual fruits. 



GENERAL METHODS OF PREPARATION. 



EXTRACTION OF JUICES. 



Grinding. 



If to be cold pressed, it is usually necessary to crush the fruit to 



facilitate the outflow of juice. Exceptions are the citrus fruits, 



which should be pressed after cutting in two, and pineapples, which 



may be pressed whole. Crushing is probably best effected by passing 



the f raits through an apple grater. The moving part of this machine, 



which is operated by power, consists of a rapidly rotating iron cylinder 



carrying short knives. 



Heating. 



To increase the juice yield, intensify the color, or impart the desired 

 flavor to the juice, the fruit may be heated before pressing, in 

 which case crushing may be omitted. Juices of the small fruits are 

 successfully prepared with or without previous heating. Pine- 

 apples, peaches, and the citrus fruits should be cold pressed. 



Heating is conveniently conducted in a steam-jacketed kettle 

 made of copper with tin lining or in one of aluminum which should be 

 fitted with a gate valve at the bottom for discharging the juice. To 

 avoid scorching while heating, it is necessary to stir the fruit con- 

 tinuously. 



Pressing. 



The system of racks and cloths extensively employed in this 

 country in the manufacture of grape juice and cider is probably 

 also best for preparing the juices of other fruits. The fruit or fruit 

 pulp is built up in the following manner, in the form of square masses 

 called "cheeses," in heavy press cloths separated by racks. A square 

 rack is placed on the press floor. On this is laid a square form, over 

 which is spread the press cloth arranged diagonally, the corners 

 lying on the sides of the form. The cloth is large enough to permit 

 a depression to be made in the center and still inclose the pulp com- 

 pletely when the corners are folded over. In the depression is placed 

 the ground fruit, which takes the shape of the interior of the form, 

 thus making a square cake or ''cheese." The corners of the cloth 

 are folded over and, if necessary, pinned together. The form is 

 then lifted off and another rack placed upon the cloth inclosing the 

 "cheese." If desired another press cake may now be formed upon 

 this rack, in which way a series of press cakes is built up until the 



