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



STERILIZATION OF FRUIT JUICES. 



Containers of glass, porcelain, or tinned iron (tin cans) in which 

 fruit juices may be sealed and sterilized are available. The juice may 

 also be poured while very hot into sterilized wooden casks which are 

 then sealed. Vessels of glass possess an obvious advantage in that a 

 view of the contents may be had at any time without being opened. 



Glass Containers. 



The process of sterilizing the juice in glass carboys consists in fill- 

 ing previously warmed 5-gallon carboys with hot juice and sealing 

 them while hot. They are warmed, either by placing them for a 

 time in a closet heated by steam pipes, or by partly submerging and 

 rotating them in a bath of hot water. The juice is conveniently 

 heated in the steam-jacketed kettle already described (page 2) and 

 then poured into the hot vessel, leaving space for the stopper, which 

 is forced tightly into position. 



Experience shows that the contents of partially filled carboys spoil 

 more readily than those of full carboys, doubtless due to the fact that in 

 the former the surface of the cork, which is further removed from the 

 surface of the hot juice, does not receive the necessary heat treatment. 

 When carboys of juice become infected, it is usually possible to 

 trace the infection to the growth of organisms on the surface of the 

 cork. It is, therefore, clear that the corks should be sterilized as 

 completely as possible before use. Successful sterilization of the cork 

 is somewhat difficult to accomplish. A satisfactory method consists 

 in dipping the corks in melted paraffin, removing and then heating 

 them in a steam closet for several days, during which time the paraffin 

 is gradually absorbed. The corks should be steamed for a few 

 moments or dipped in scalding water immediately before use. 



After cooling, the carboys should be transferred to racks in a cool 

 place where they can be inspected at frequent intervals. Such ex- 

 amination is imperative, as, in spite of the precautions described, a 

 small portion of the juice usually shows evidence of infection, in the 

 form of patches of mold floating on the surface. The flavor is often 

 greatly injured and the juice rendered worthless by such infection. 

 Before the colony of mold lias become larger than a small dot floating 

 on the surface, it should be removed and the juice sterilized. The 

 advantage of the transparency possessed by glass containers is hero 

 evident. If development of yeasts, with the consequent bursting of 

 carboys, occurs, serious defects in technique are probable, as yeasts 

 in fruit juices are very easily killed by heating. 



