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



Cold Storage of Sterilized Juices at 32° to 35° F. 



Experiments which consisted simply of keeping bottled sterilized 

 juices at from 32° to 35° F. indicate that certain fruit juices, notably 

 orange, pineapple, and currant, retain their color and flavor far better 

 at low temperatures than at the temperatures of ordinary storage. 



Freezing Storage op Raw Juices. 



Juices may be kept in freezing storage at temperatures approxi- 

 mating — 10° C. (14° F.) for many months without marked change in 

 composition or flavor or development of microorganisms. 



CONCENTRATION BY FREEZING. 



Upon freezing a fruit juice, ice separates, the juice becoming corre- 

 spondingly concentrated. As the temperature falls lower and lower, 

 more and more ice forms, and the nonfrozen liquid becomes more 

 and more concentrated, until finally a solid block of frozen fruit juice, 

 consisting of ice and concentrated, sirupy liquid, results. If the 

 block of frozen fruit juice is now coarsely broken up and centrifugal- 

 ized, the sirup can be removed from the ice, and the latter discarded. 

 A concentrated fruit juice possessing the color and flavor of the 

 original fruit is thus obtained. 



In freezing the juices are placed in containers having slightly 

 flaring sides, so that by warming the sides and bottom the block of 

 frozen juice may be easily removed. Slow freezing is more satis- 

 factory than rapid freezing in an ice-cream freezer, as in the former 

 instance the crystals of ice formed are large, consisting toward the 

 end of the freezing of long, thin plates reaching in toward the center 

 of the container, while in the ice-cream freezer the ice forms a finely 

 felted mass from which the concentrated juice is separated with 

 difficulty. On the laboratory scale the crushing and centrifugal- 

 izing is best carried on in a cool room, thus avoiding undue melting. 

 On a commercial scale this precaution is not so necessary. Tem- 

 peratures approximating —10° C. (14° F.) are sufficiently low to 

 give to concentrated juices a solids content of about 50 per cent. 

 Such juices ferment very slowly at room temperatures, the presence 

 of sugar and acid retarding greatly the growth of microorganisms. 



The method may be easily extended to commercial proportions, 

 as ice crushers and centrifugals, readily obtainable in the market, 

 can be used without modification. 



STERILIZATION in carbon dioxid. 



In Carboys. 



The carboys arc filled nearly full with the cold juice to be sterilized 

 and placed in a bath of cool water. The bath temperature is rapidly 

 brought up to the point at which it is desired to sterilize the product, 

 while a stream of carbon dioxid is slowly passed into each carboy 



