The Chemistry of Wine. 



85 



tides containing carbonic acid and 

 the flavor are subjected to a change 

 by means of fermentation, in conse- 

 quence of which they are partially se- 

 creted. By the same process, potassa 

 and cream of tartar as well as tar- 

 taric lime is separated, when the 

 alcohol in the wine increases, and in 

 consequence, the solubility of the dif- 

 ferent kinds of salt is diminished. 



The skin of the grape contains tan- 

 nin, the color of w^hich, if exposed to 

 the air, as for instance in drying the 

 grape for raisins, turns light brown. 

 The skin contains besides astringen- 

 cy tannin and in some kinds of 

 grapes coloring matter, which through 

 the influence of the acids turns red, 

 and also on the outer skin "wax" or 

 rather a coating resembling wax. 



The stems contain the same ingre- 

 dients, much less of coloring matter 

 and wax, but yet, however, to a small 

 degree, the acrid tasting substance. 

 In many completely ripened grapes 

 from 6 to 7 per cent tannin is found. 

 The seeds contain tannin and oils, 

 both in the greatest quantity when 

 the grape is ripe. In the average the}" 

 contain 10 per cent oil and 7 per cent 

 tannin.. 



The proportion of the different com- 

 ponent parts of the grape juice difi'ers 

 according to the state of ripeness, the 

 vai'iety of grape, the quality of the 

 soil and the temperature during the 

 year. 



So far, the following component 

 parts of the grape have been discovered 

 viz : 



Grape, sugar, gum, gluten or alburaen_, 

 tartaric acid, pyroracemic acid, malic 

 acid, tannin, phosphoric acid, sulphu- 

 ric acid, muriatic acid, sebacic acid. 



potassa, natron, lime, magnesia, ar- 

 gillious earth, sesquioxyd of iron, 

 sesquioxyd of mangae, chlorine, com- 

 mon salt, gravel, coloring matter and 

 water. 



One part . of these acids is connec- 

 ted with the alcali of the soil ; for in- 

 stance : Tartaric acid in potash as 

 cream of tartar ; sulphuric acid in 

 the potash as sulphate of potash; 

 phosphoric acid in clay as aluminate 

 of potassa &c. — In this connection, 

 the acids communicate hardly any 

 taste, as acids, to the wine, with the 

 exception of cream of tartar, which as 

 bitartrate of potassa still tastes sour, 

 only the vaporous acids are of any 

 acfount, when the more or less sour 

 taste of the wine is to be considered. 

 On the contrary, the combinations of 

 acids aud alcali, earth or metals 

 (which combination is called "salts") 

 have no distinct influence on the flavor 

 of the wine, which in Germany is 

 called the "aroma." By this name 

 the particular taste of the juice of the 

 grapo is distinguished, according to 

 the soil on which the grape was grown. 

 So for instance is slate bottom dis- 

 tinguished by the peculiar taste. The 

 "Riesling," grown on the borders of 

 the Khine, is in taste very diff'erent 

 from that grown on the banks of the 

 Mosel or at the Cape of Good Hope. 

 This diflTerence is produced merely by 

 the difference in the component parts 

 of the soil. According to the pre- 

 dominance of either component part 

 the taste, and often even the smell of 

 the wine changes. 



The total amount of these fungi is 

 very small. Only from 1| to c,\ parts 

 were discovered in 1000 parts of 

 grape-juice. 



