154 STATE POMOLOGICAL SOCIETY. 



fumed and Ihivored, contain alct)hol radicals in union, as compound ethers. 

 It is probable from every point of view, tiiatthe slight occurrence of the vinous 

 fermentation in fruits belongs to an important class of chemical formations, 

 by means of ■which a multitude of odor-giving substances are scattered through- 

 out vegetation. We shall inquire more carefully into the fruit-flavor compounds 

 and tiieir formation, farther on. 



y. The Pectous Substances. These are, in general terms, the constitu- 

 ents of plant-jelly. As vegetable products, they correspond to the varieties of 

 gelatine obtained from animal tissues. Unlike gelatine, however, they are 

 iion-nitrogenous. They arc found in the soft parts of plants generally, as in 

 the tuber of the potato and the root of the carrot, but it is in fruits that they 

 have most importance for edible value. The immediate origin of the pectous 

 substances is pretty well known, being due to a specific fermentation, a prom- 

 inent feature in fruit ri])ening. The material from which all the pectous sub- 

 stances proceed is the fermentable body called pectose, an insoluble, tasteless 

 substance, found abundantly in unripe fruits, also to some extent in iinmature 

 roots and tubers, and having no more value for food than cellulose. Now there 

 is formed along with this substance, a "ferment," as it is called, a body which 

 by contact induces a specific fermentation — a definite chemical cliange. Pec- 

 tase is the name of the ferment. Just as, in the germinating seed, starch by 

 contact with diastase suffers fermentation witli production of sugar, and as, in 

 bruised and wetted mustard seeds, sinigrin by contact with myrosin splits up 

 into pungent oil of mustard and sugar, etc., so the crude pectose of green 

 fruits by contact of their pectasc at the time of ripening changes to the edible 

 plant-jellies or pectous substances. Long boiling with water alone effects the 

 same clumge. Why tliis fermentation occurs just at the ripening time and not 

 earlier or later we do not precisely know ; it may be that the pectose is just then 

 become capable of fermentation, or the pectase then acquires potency for its 

 office, or then and not before are other conditions of the change established. 

 AVe know only that the fermentation gives us the before-mentioned {)ectous 

 substances, which, moreover, succeed each other, during ripening, by repeated 

 changes. It must be confessed that these products have been but imperfectly 

 defined, but as a class their chief properties arc known. They are given by 

 chemists as follows (distinctions having value only in analysis, being omitted) : 



Pectine : readily soluble in hot or cold water, gelatinizing when concentrated and 

 more perfectly by addition of sugar, changed by very long boiling to parapectine. 



Peclic Acid: gelatinous, insoluble in cold water and but slightly soluble in hot water, 

 hardened in jelly hy solution of sugar, slowly changed by boiling to i)arapectic acid 

 and afterward to metapectic acid. Pectine and Pectic Acid result from long boil- 

 ing of the crude pectose. 



Parapectine : soluble in water, capable of gelatinizing slighth', changed by boiling 

 to inetapectine. 



Parapectic Acid: soluble in water, the solution changing into one of metapectic 

 acid. Not gelatinous. 



Metapectine : soluble in water, not gelatinous. (Found in over-ripe fruits), 



Metapectic Acid: soluble in water, incapable of gelatinizing. (Found in over-ripe 

 fruits. Produced by fernienation in over-iiponing from all the other pectous sub- 

 stances. Also produced, from most of the other i)ectous substances, by long boiling, 

 much more readilj' if acids are present). 



Alkalies change pectine, and parapectine, and metapectine, to salts of pectic 

 acid. 



The properties of the separated pectous conijiounds represent certain well- 

 known characteristics of fruits, as these are found in cooking. Moist heat, as in 



