31<n\ 2, 1908.] AgHcultural Gazette of N.S.W. 285 



Wine Makii^g. 



Notes on ihe Fermentation of Must.* 



M. BLUNNO. 



The agent of fermentation is a microscopic plant of the fungi order, called 

 Saccharomyces ellipsoideus, which is usually spoken of as elliptic fern\ent, on 

 account of its oval-shaped cells ; or it is called alcoholic yeast, because of its 

 faculty to change grape-sugar in alcohol. 



Alcohol, however, is not the only substance derived from the action of the 

 yeast over the grape-sugar ; a l?trge amount of carbonic acid is also formed, 

 which is that pungent, asphyxiating gas that is noticeable in badly-ventilated 

 cellars at wane-making time. Alcohol remains in the wine, carbonic acid is 

 set free, and the bubbling noise is due to that gas, which is released. Some 

 of it still remains in the juice even after fermentation ; and it is enough to 

 shake in a glass a little wine a few weeks old to see small bubbles collecting 

 on the surface : but gradually with age, through the racking and fining, all 

 the carbonic acid is driven away. That is rather a pity, because a small pro- 

 portion of this gas — in such a quantity as not to make the wine over-saturated 

 with it, but leave it quite still — -is a good thing, conferring on the wine more 

 vim, while preventing it from growing too old and becoming flat. That is 

 why wines that are too old and flat are in a way rejuvenated by dissolving 

 in it some carbonic acid. 



The third substance that is formed in wine through fermentation is 

 glycerine, though in much smaller quantity than the previous ones. Glycerine 

 gives the wine sapidity, smoothness, mellowness. Often the natural harshness 

 of some wine is corrected by the addition of glycerine. 



Succinic acid is also formed during fermentation ; its quantity, however, is 

 so small that it is quite unimpoi'tant to dwell on it here. 



The alcoholic yeast is a minute, organised, living body, in the shape of an 

 oval cell. Its germs are scattered in the air, in the soil ; they are found on 

 every part of the vine, viz., bark, canes, leaves, and are specially plentiful on 

 the berries and stalk. When grapes are squeezed they get into the grape- 

 juice, and their life begins. They grow and multiply at a terrific rate, and 

 in a few hours from a relativelv small number countless millions of other cells 

 are produced, which in their turn originate billions uf like cells. A drop of 

 grape-juice in fermentation, looked at under the microscope, shows the field 

 of the instrument literally covered by such cells, free and isolated, or budfling^ 

 without even the smallest interstice to accomimodate one single individual 

 Like all living bodies, the life of alcoholic yeast is favoured or obstructed by 

 certain conditions of environment ; and the environment in this case is the 



* Notes of lecture delivered at Albury, 190S. 



