Fruits and Seeds 



255 



to malic (Latin : malum, an apple) 

 acid. During the process of ripening, 

 great chemical changes occur. The 

 starch is changed to sugar, — sucrose, 

 glucose, and fructose. The water 

 content increases, and the acid gradu- 

 ally becomes less and less. The middle 

 lamella of the cell walls is partly dis- 

 solved and the cells separate more 

 or less, thus producing intercellular 

 spaces, and making the fruit softer 

 and more '' mealy." The ripening 

 process begins at the core and gradu- 

 ally extends outward, until all the 

 tissues are affected. 



The middle lamella, composed of 

 calcium pectate and pectose, makes 



up part of the cell walls. The chang- u.s.Depi. of Agriculture 



ing of these substances to pectin and ^ig. 163. Fruit of mango, now 



. , . 11 ,., 1 , being successfully grown in south- 



pectic acid, jelly-like substances, con- ^^^ Florida. 

 tributes to the softening of the 



fruit. The pectic compounds are important in jelly mak- 

 ing, and those fruits that contain large amounts of them 

 form jellies readily when they are mixed with sugar, boiled, and 

 allowed to cool. Fruits like the quince, apple, and currant are 

 plentifully supplied with pectic compounds. In elderberries and 

 grapes the pectic compounds are less abundant, and juices of 

 apple or quince are commonly added to them in jelly making to 

 make them jell more readily. When fruit juices and sugar are 

 boiled too long, they may not jell. This is because the pectins 

 have been chemically changed to mother substances which do not 

 have this property. 



Recently it has been found possible to remove pectin from 

 carrot roots, which contain large amounts, and the pectin may be 

 added to fruit juices to insure jelHng. 



