1250 The Cornell Reading-Courses 



time for concentration), and possibly to some extent also with the pro- 

 portion of acid in the juice. Of course there is an interdependence among 

 these factors that may either lessen or lengthen the necessary time of 

 boiling in the case of any particular juice. In currant juice, for example, 

 these factors are so nicely adjusted that 8 to 10 minutes is sufficient time 

 for making jelly from Extraction I, while the corresponding juice from 

 raspberries, blackberries, apples, and the like, may demand 20 to 30 

 minutes. But in any case, any jelly, when the process is once begun, 

 should be made as quickly as possible; no simmering for hours should be 

 allowed, since long action of the acid in the juice transforms the pectin 

 into substances that have no jelly-making power. An example of this 

 sort did come to the writer's attention through the failure of one home- 

 jelly-maker to make her grape jelly " jell." Hours of simimering on the 

 back of the stove had destroyed the pectin; also, too much sugar had been 

 used; and between the two errors, a dark, gummy, unpalatable mass had 

 resulted. 



TIME NECESSARY FOR BOILING SUGAR WITH JUICE 



Directly connected with the total time necessary for the jelly-making 

 process, is the question of when the sugar shall be added to the juice. 

 Shall it be at the beginning of the process, according to the old method? 

 or (hot) near the end of the process, according to the newer method? or 

 (hot) midway between these extremes? Let us designate these three 

 methods, respectively, as long-boiling,, short-boiling, and mean-boiling. 



Very elaborate and careful experiments (the details of which need not 

 be described here) have been made in this laboratory in order to answer 

 these questions. The results, so far as they yet indicate a choice in the 

 methods, show that the mean-boiling method is probably the best, all 

 things considered. The chemist knows that the longer sugar is boiled 

 with a weak acid (as fruit juice suitable for jelly-making is), the more 

 this sugar is inverted (split) into two simpler sugars each less sweet than 

 the original sugar. Although this loss of sweetening power may be dis- 

 regarded, yet the extent of the inversion that has taken place does affect 

 the texture of the jelly. For example, if little inversion has occurred 

 (short-boiling method) , the original sugar used is likely to crystallize out ; if 

 much inversion has occurred (long-boiling method) , one of the simpler sugars 

 formed may appear in crystalline masses. However, it should be said 

 that neither of these crystalHzations is likely to occur if the sugar has been 

 originally properly proportioned to the juice and if the resulting jelly has 

 been properly scaled up. Illustrative of this statement is the fact that 

 from seven different fruits a series of three jellies each (long-, short-, and 

 mean-boiling) were carefully made and sealed two years ago, but as yet 



