THE CHEMISTRY OF FRUIT RIPENING. 



155 



;uiy mode of cookui<,% produces upon these substances the chief results of 

 ripening, and, if continued long enough, tlic results of over-ripening. Vnripe 

 fruits a^i'e made more edible and wholesome by cooking, owing to its artificial 

 (imperfect) ripening of pcctose. Fruit jellies owe their substance to pcctic acid, 

 pectine, and sliglitly to parupectine, the products of early maturity, with the 

 cooperation of sugar. For jellies, it is well-known, tlie use of over-ripe fruits 

 must be avoided, and too long boiling in the preparation must be avoided. If 

 the fruit be undcr-rii)e, the juice should be boiled much longer tlian if the 

 fruit be fully ripe, and if the fruit be over-ripe, boiling should be maintained 

 no longer tlian necessary to clarify, and standing in hot solution should be 

 avoided. Grapes bear full ripening, for jellies. 



The following statements of tlio quantities of pectous suhstances and of pedose 

 are compiled from the reports of Fresenius. It should be mentioned tliat Fres- 

 enius found widely different (juantities in the different varieties of the same 

 fruit, and the average here drawn from the varieties of each fruit would greatly 

 vary from an average obtained from other varieties of the same. Tiie percent- 

 age in the fresh fruit is first given, and then percentage of solids, or strictly 

 dry fruit, as obtained by calculation from the percentage of water. 



Peaches — mean of 2 varieties. 



Apples — mean of 4 varieties. .- 



Pears — mean of 2 varieties 



Raspberries — mean of 3 varie 

 ties - 



Gooseberries — mean of G vaiie 

 ties 



Cherries — mean of 3 varieties. 



Grapes — mean of 2 varieties.. 



Currents— mean of G varieties. 



Strawberries — mean of 3 varie- 

 ties 



Pj-XTUUS Sl'BSTANCES (SOLUBLE). 



Of Fresh Fruit, 



1.1. 



8.45 percent 



5.85 



3.84 



1.42 



1.17 

 1.59 

 0.3G 

 0.17 



0.10 



Of Solids. 



42.25 percent 

 34.41 '• *' 



22.58 " " 



10.14 " " 



8.36 

 7.23 

 2.00 

 1.13 



0.79 



u u 



rECTOSE (I.VSOLCBLE). 



Fresh Fruit. 



0.85 per cent 



1.23 " " 



0.97 " " 



0.24 " •' 



0.65 " " 



0.78 '• •' 



0.84 •' " 



0.84 " " 



0.50 '• " 



Solids. 



4.25 per cent 

 6.59 '' '• 



5.70 " " 



1.71 '' " 



4.64 

 3.54 

 4.66 

 5.66 



3.85 





Kb food materials, the pectous substances seem to be well-nigh indispensable 

 to the health of man. They are not very nutritious; it is not known that they 

 are fully digested into material which can be appropriated ; and, being non- 

 nitrogenous, they could scarcely yield ti>'sue-building matter. What service 

 they perform is not clearly undeistood. Tliey may supply lirpiids impor- 

 tant in digestion or assimilation. We obtain them in acidulous fruits, and in 

 starchy tubers, and it is not clear how much of the value of each of these sorts 

 of food is due to their pectous constituents ; but, when all food containing pec- 

 tine is cut oii, the scurvy is liable to ensue, and tlien any food supplying pectine 

 will serve as a remedy. At the same time, it is found tiiat pectous food is- 

 needed only in small quantities ; large proportions proving not only innutritions 

 but injurious, causing derangements of digestion and excretion. 



3. Acids. T'he principal fruit-acids, not astringent, are the following, givea 

 in the order of their importance : 



Malic Acid: Very widely distributed; predominating in apples, pears, cherries, 

 gooseberries, strawberries, raspberries, and niouutaia-ash berries. Not extracted. 

 for use. 



