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THEORY OF FERMENTATION. 
It is believed also to possess the great virtue, by its astringent qualities, of moderating the action of 
the Alcohol on the system in the wine and other liquors containing it, and thus rendering them at 
once less exciting and more strengthening. The French chemists state that it requires from 2 to 3 
parts in 1000 to produce its full effect in the manufacture of Cider and Perry, and that from 2 to 3 
more thousandths should be present for its wholesome qualities. 
The Mucilage , or Pectosine , 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 to be feared rather than their failure. The Acidity these 
acids give, together with the Perfume and Bitter Principle in the juices, which also tend to render 
the Cider and Perry more pleasant and agreeable, are difficult to determine chemically ; but their 
proper quantity can be estimated, with sufficient practical accuracy, by smell and taste. An excess 
of acidity is the chief characteristic in fruits of poor character. 
Theory of Fermentation. —The natural saccharine juices of all fleshy fruits, if left to 
themselves at a temperature from 50 to 80 degrees, will immediately begin to take on vinous 
fermentation, and especially if they are acid, as is usually the case. This fermentation, moreover, 
takes place without the addition of any substance to bring it on. Thus, if the pulp, or pommage, from 
ripe Apples, or Pears, as taken from the mill, be left to itself, at the ordinary autumnal tempera¬ 
ture, minute bubbles are soon observed to rise to the surface and form a white froth ; its 
bulk will be increased ; and, if the thermometer is plunged into it, its temperature will be found to 
have risen. These changes are due to the commencement 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 Frenchman, M. Pasteur, has 
occupied much of his life in attempting to answer this question. He has conducted a long series of 
experiments, requiring the utmost patience, with the closest attention to minute details throughout, 
and he happily possesses the genius which has enabled him to arrive at many very interesting and 
important results. 
M. Pasteur has succeeded in proving that on the external surfaces of all fleshy fruits, when 
they become ripe, there exist certain minute particles or germs, which when brought into contact 
with the ripe juices of the fruits develop into minute plants, which grow with great rapidity. These 
plants are the yeast plants, which belong to a great family of microscopic funguses. They are 
called Saccharomyces, or “ Sugar-eating Funguses,” from the peculiar power they possess of decom¬ 
posing, and living upon the saccharine principle of plants, the grape sugar, or glucose, as it is 
termed by the chemists, and thus causing their elements to be re-arranged into Alcohol, Carbonic 
Acid Gas, Glycerine, Succinic Acid, Volatile Acids, and other products. 
