8 BULLETIN 241, U. S. DEPARTMENT OF AGRICULTURE, 
CoLtp 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 OF 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. 3 
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 are 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 
