Food and Drink 9 1 



140. Nature of Fermentation. The ceaseless action of 

 minute forms of plant life in bringing about the decom- 

 position of the elaborated products of organized animal or 

 vegetable structures is described in Chapter XIII. 



All such work of vegetable organisms, whether going 

 on in moulding cheese, in souring milk, in putrefying meat, 

 in rotting fruit, or in decomposing fruit juice, is essentially 

 one of fermentation. There are many kinds of fermentation, 

 each produced by some special form of minute plant or 

 micro-organism. 



141. Alcoholic Fermentation. Let us now briefly turn 

 our attention to that fermentation which results from 

 the decomposition of sweet fruit, or other vegetable juices, 

 which are composed largely of water, containing sugar and 

 flavoring matters. 



This special form of fermentation is known as alcoholic 

 or vinous fermentation, and the minute germs, or micro- 

 organisms, that cause it are familiarly termed "alcoholic 

 ferments." There are several varieties of these germs, 

 classed by scientists as saccharomycetes, which are found 

 on the surfaces and stems of fruit as it is ripening. 



While the juice is in the fruit the conditions are less 

 favorable for the work of the alcoholic ferments than for 

 that of moulds. 1 Hence fruit rots as a result of the work 

 of moulds, which, growing within and upon it, cause its 

 decomposition. 



1 The work of some kinds of moulds may be apparent to the eye, as in 

 the growths that form on old leather and stale bread and cheese. That of 

 others goes on unseen, as when acids are formed in stewed fruits. Con- 

 cerning the work of the different kinds of moulds, Troussart says : " Mucor 

 mucedo devours our preserves ; Ascophora mucedo turns our bread mouldy ; 

 Molinia is nourished at the expense of our fruits ; and Chatomium chartatum 

 develops itself in books and on their bindings, when they come in contact 

 with a damp wall." TROUSSART'S Microbes, Ferments, and Moulds. 



