314 VINOUS FERMENTATION. 



Although it cannot be doubted that these volatile liquids are 

 formed by a mutual interchange of the elements of gluten and of 

 sugar, in consequence, therefore, of a true process of putrefac- 

 tion, still it is certain, that other causes exercise an influence 

 upon their production and peculiarities. 



The substances in wine to which its taste and smell are owing, 

 are generated during the fermentation of the juice of such grapes 

 as contain a certain quantity of tartaric acid ; they are not found 

 in wines free from all acid, or which contain a different organic 

 acid, such as acetic acid. 



The wines of warm climates possess no odor ; wines grown in 

 France have it in a marked degree, but in the wines from the 

 Rhine the perfume is most intense. The kinds of grapes on th-3 

 Rhine, which ripen very late, and scarcely ever completely, such 

 as the Riessltng and Orleans, have the strongest perfume or 

 bouquet, and contain, proportionally, a larger quantity of tartaric 

 acid. The wines from the earlier grapes, such as the Ru- 

 lander, and others, contain a large proportion of alcohol, and 

 are similar to Spanish wines in their flavor, but they possess no 

 bouquet. 



The grapes grown at the Cape from Riesslings, transplanted 

 from the Rhine, produce an excellent wine, which does not, how- 

 ever, possess the aroma peculiar to the Rhenish wine. 



It is evident, from these facts, that the acid of wines, and their 

 characteristic perfumes, have some connexion, for they are al- 

 ways found together ; and it can scarcely be doubted that the 

 presence of the former exercises a certain influence on the for- 

 mation of the latter. This influence is very plainly observed in 

 the fermentation of liquids destitute of tartaric acid, and particu- 

 larly of those which are nearly neutral or alkaline, such as the 

 mash* of potatoes or corn. 



The brandy obtained from corn and potatoes contains an 

 ethereal oil of a similar composition in both, to which these li- 

 quors owe their peculiar smell. This oil is generated during the 

 fermentation of the mash ; it exists ready formed in the fer- 



* Mash is the mixture of malt, potatoes, and water, in the mash tun, a 

 large vessel in which it is infused. 



