50 THE THEORY OF FERMENTATION. 



The Mucilage^ or Fectosine, when abundant, forms another 

 element of distinction between good and bad juice. It renders 

 the fresh juice more thick and viscous, and eventually gives softness 

 and body to the liquor. It helps also to preserve the Alcohol, by 

 opposing the Acetous fermentation, and is thus always present in 

 long keeping Cider and Perry. 



The Malic and Tartaric Acids give the refreshing character to 

 Cider and Perry, which is so desirable in a summer beverage. 

 The Malic Acid abounds most in Apples, and Tartaric Acid in 

 Pears, and their too great abundance is rather to be feared, than 

 their failure. The acidity these acids give, together with the Per- 

 fume and Bitter Principle in the juices, which tend also to render 

 the Cider and Perry more pleasant and agreeable, are difficult to 

 to determine chemically ; but their proper quantity can be esti- 

 mated with sufficient practical accuracy by smell and taste. An 

 excess of acidity — is the chief characteristic in fruits of poor character. 



The Theory of Fermentation. — The natural saccharine 

 juices of all fleshy fruits, if left to themselves at a temperature of 

 50 to 80 degrees, will immediately begin to take on vinous fermen- 

 tation, especially if they are acid, which is usually the case. 

 This fermentation, moreover, takes place without the addition of 

 any substance to bring it on. Thus, if pulp, or pomage, from 

 ripe apples, or pears, as taken from the mill, be left to itself at the 

 ordinary autumnal temperature, minute bubbles are soon observed 

 to rise to the surface and form a white froth ; its bulk will be in- 

 creased, and if the thermometer is plunged into it, its temperature 

 will be found to have risen. These changes are due to the com- 

 mencement of Alcoholic Fermentation. The bubbles contain 

 Carbonic Acid gas, and if the juice is tasted, it will be found to 

 have acquired a spirituous fragrance due to the formation of alcohol. 

 Why should the simple crushing of ripe fruit lead up to a series of 

 changes, so curious, and yet so certain ? The distinguished French- 

 man, M. Pasteur, has occupied some years of his life in attempting 

 to answer this question. He has concluded a long series of ex- 

 periments, requiring the utmost patience, with the closest attention 



