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



receiving a heat treatment much longer than necessary, which may 

 injure the flavor. Another objection to casks is that the color and 

 flavor of the juices are injured by the gradual solution of extract 

 from the walls of the container. Wooden casks can not, therefore, 

 be generally recommended as containers for fruit juices. 



Tin Cans. 



Juices may be far more easily sterilized in cans than in wooden 

 casks. Cans, however, can not at the present time be generally recom- 

 mended, as experiment shows that the tin is constantly dissolv- 

 ing in the juice, even when the type of can designated as "enamel 

 lined" is used. There is consequent injury to color, in case of deli- 

 cately tinted juices, and the flavor also is often injuriously affected. 

 The ease with which juices are sealed and sterilized in tin cans, 

 however, makes it seem probable that they may be successfull} T used 

 in special instances for storage of sterilized juices, during limited 

 periods at least. 



Temperatures and Times op Heating. 



In cooking the fruit pulp in the kettle the temperature does not 

 exceed 95° C. (203° F.) during the time ordinarily required to reduce 

 the fruit to a pulp, usually less than 5 minutes. In heating juice 

 to be transferred to hot carboys the temperature should be carried 

 up to from 85° to 90° C. (185° to 194° F.). The sterilizing temper- 

 atures here recommended for general use in preparing fruit juices are 

 higher than those used in the earlier part of the experimental studies 

 to be described later. In this work it was found that while at 

 times complete sterilization was effected at a temperature of 70° C. 

 (158° F.), or even lower, upon other occasions mold developed. Em- 

 ployment of higher temperatures resulted in almost wholly eliminat- 

 ing the difficulties of mold growth in juices heated in bottles. 



A temperature of at least 80° C. (176° F.) is recommended for all 

 fruit juices sterilized in bottles, allowing, when starting with cold 

 juice, half an hour for the juices to attain bath temperature, and 

 keeping the bottles at this point for at least half an hour. Where it 

 is found that no injury to flavor results, this temperature may be 

 increased with advantage. Usually merely filling the bottles or fruit 

 jars with the boiling-hot juice and sealing them immediately is sat- 

 isfactory. An exception, however, to this treatment is found in the 

 case of lemon juice, the flavor of which is much injured by heating 

 to 80° C. This juice is easily sterilized, without serious injury to the 

 flavor, by being heated to 70° C. for half an hour, allowing half an 

 hour for the juice to attain bath temperature. 



With juices sterilized in carboys the situation is less satisfactory, 

 as infection with molds often occurs when all of the precautions 

 already described have been taken. The method of sterilizing 



