300 VINEGAR, CIDER, AND FRUIT-WINES. 



remaining insoluble portion consists chiefly of cellulose, starch, 

 a gum-like body, a few inorganic substances, and, further, the 

 characteristic constituent of unripe fruits, to which the term pec- 

 to#e has been applied. It forms the initial point for the phe- 

 nomena observed during the growth and ripening of fruits, and, 

 therefore, requires a somewhat closer examination. 



In regard to its behavior, pectose approaches cellulose and 

 starch ; it is chiefly found in the pulp of unripe fruits, but also 

 in certain roots, especially in carrots, beets, and others. It is 

 insoluble in water, spirits of wine, and ether, but during the 

 ripening of the fruit it undergoes a change, induced by the acids 

 and heat, and is converted into pectine, which is readily soluble 

 in water. To pectose are due the hardness of unripe fruits and 

 also the property of many fruits and roots of boiling hard in 

 water containing lime, the pectose combining with the lime. 



The formation of pectine commences as soon as the fruits are 

 exposed to the action of heat, and then depends on the influence 

 of the vegetable acid present upon he pectose. To be convinced 

 of this it suffices to express the pulp of an unripe apple. The 

 juice thus obtained contains scarcely a trace of pectine, but, by 

 boiling it for a few minutes with the pulp of the fruit, the fluid, 

 in consequence of the formation of pectine, acquires a viscous 

 quality, like the juice obtained from ripe fruits. 



Pectine, nearly pure, is white, soluble in water, non-crystal- 

 lizable, and without effect upon vegetable colors. From its 

 dilute solution it is separated as a jelly by alcohol, and from its 

 more concentrated solution, in long threads. Brought into con- 

 tact with alkalies or alkaline earths, pectine is transformed into 

 pectic acid. Under the influence of a peculiar ferment called 

 pectase, which will be described later on, pectine is transformed 

 into pectosic acid, and by dilute acids into metapectic acid. 



By boiling a solution of pectine in water for a few hours, it 

 partially loses its viscous condition and separates a substance 

 called parapectine, which shows the same behavior as pectine, 

 except that it is not precipitated by neutral lead acetate. When 

 treated with dilute acids the parapectine is transformed into meta- 

 pectine, which might be called metapectous acid, as it shows a 

 decidedly acid reaction and colors litmus paper strongly red. 



