THE CLARIFICATION OF FRUIT JUICES. 23 



the soluble pectin into a colloidal suspension may occur. Whatever 

 the nature of the reaction, it is clear that it becomes complete within 

 24 hours at temperatures approximating 40° F., and in a shorter 

 period at higher temperatures, becoming complete in a few minutes 

 when juices are heated to the temperature of pasteurization. Conse- 

 quently, if juices are held in the settling tank overnight, or for 24 

 hours if the temperature is low enough to prevent fermentation, and 

 are then decanted, clarified, and bottled, no difficulty due to subse- 

 quent clouding of the liquid in the bottles will be encountered. 



EXPEDIENTS TO SHORTEN THE PROCESS. 



Various expedients have been resorted to in the course of the work 

 in attempts to increase the ease of nitration or to shorten the process 

 by permitting clarification and bottling immediately after pressing. 

 Some of these gave negative results and are mentioned only in order 

 that they may be avoided by others ; some are advantageous if prop- 

 erly employed. 



HEATING THE JUICE BEFORE FILTERING. 



Heating the juice prior to filtration has many obvious advantages, 

 chief among which are the precipitation of heat-coagulable constitu- 

 ents and the lowering of the viscosity of the liquid thereby produced. 

 Hot filtration, however, is of very definitely limited applicability 

 to fruit juices. It can be advantageously employed only for such 

 juices as do not readily lose their characteristic flavors on heating and 

 subsequent exposure to the air while hot. Such grape juices as those of 

 Concord, Norton, Clinton, Clevener, Early Victor, Worclen, Ives, Di- 

 ogenes, Moore {Moore's Early), Cynthiana, Montefiore, and Niagara 

 are not injured in quality or flavor by such treatment, which makes 

 possible the usual commercial practice of crushing the grapes and 

 heating to 175° F. in kettles prior to pressing. With all of these 

 varieties excellent results are obtained by hot filtration. If the grapes 

 are heated before pressing, the hot juice is taken directly from the 

 press, thoroughly mixed with the earth, and immediately passed 

 through the filter. If the grapes are pressed cold, the juice is at once 

 heated to 165° to 175° F., mixed with the earth, and filtered. The 

 juice obtained from any given variety by pressing cold is, of course, 

 quite different from that obtained from heated grapes, but such juices 

 are not injuriously affected by subsequent heating and hot filtration. 



This method of treatment can not be employed with apple juice 

 or with the more delicately flavored grape juices without considerable 

 loss in quality. Juices of such varieties of grapes as Agawam, 

 Brighton, Barry, Catawba, Delaware, Diana, Goethe, Elvira, 

 Eumelan, Isabella, Lady, Massasoit, Missouri Riesling, Noah, Salem, 



