52 



FRUITS AND FRUIT PRODUCTS. 



TABLE 17. Composition of jelly. 



The analyses of the fruits and juices in these tables are not compara- 

 ble, owing to the fact that the amount of water added in their prepara- 

 tion was varied in order to obtain the desired product. Regarding 

 the content of cane sugar, the analyses are in accord with those already 

 given. 



The inversion of cane sugar during the process of preparation, as 

 shown in the analyses of jams and jellies, is of particular interest. 

 The amount of inversion that takes place varies in general with the 

 length of time of heating and with the content of acid, although 

 other factors have a material influence. It is well known that the 

 different fruit acids vary widely in their power of inverting cane 

 sugar, and many of the variations are undoubtedly due to this cause. 

 Apple jam, with an acidity of 0.282 per cent, shows a much larger 

 amount of cane sugar inverted than blackberry, orange, and pineap- 

 ple jams, which have an acidity of 0.851 percent, 0.433 per cent, and 

 0.315 per cent, respectively, while grape jam, with an acidity of 

 0.698 per cent, shows almost complete inversion of the cane sugar. 

 Wild fox plum jam, with an acidit}^ of 1.355 per cent, shows but a 

 slightly larger amount of sugar inverted than the apple jam. The 

 amount of sugar inverted in the jellies is much less than in the corre- 

 sponding jams, owing to the fact that they were heated for a much 

 shorter time. The amount of inversion was very small in case of the 

 orange, pineapple husk, and peach. In all of these cases the acid- 

 ity is low. The Ives grape, wild fox plum, and mixed fruit jellies all 



