230 STUDIES ON FERMENTATION. 



"VVe cultivated this yeast (Fig. 58), to some considerable 

 extent, in beer-wort. It produced a peculiar beer, of vinous 

 character, in fact a true barley wine. This proves, we may 

 here remark, that ordinary wine, in its flavour and quality, 

 depends to a great extent on the specific nature of the ferments 

 which develop during the fermentation of the vintage ; and 

 we may fairly assume that if we were to subject the same 

 must to the action of different ferments we should obtain wines 

 of different characters. With a view to the practical appli- 

 cation of this idea, it would be well to undertake new studies 

 in this direction ; and the methods of cultivating and managing 

 ferments, explained in this work, would be of great value in 

 such researches. 



The purification of ferments may be accomplished by various 

 methods, according as we have to deal with an intermixture 

 of ferments, or to regard as our principal object the expulsion 

 of ferments of disease, such as vibrio germs, lactic ferment, 

 the filamentous ferment of turned beer, mycoderma aceti or 

 myeoderma vini. 



One method of easy application consists in sowing the yeast 

 in water sweetened with 10 per cent, of sugar. This liquid 

 should be first boiled, and preserved in the two-necked flasks 

 which we have so often described. Sweetened water is a very 

 exhaustive medium for ferments, and the organisms mixed 

 with them. A great many cells perish in it, and the chances 

 are that the foreign germs, which are always scarce in com- 

 parison with the great number of cells of ferment, may be 

 amongst those which die, or those which become so exhausted 

 that when the yeast, after this treatment, is sown in wort, they 

 disappear, and allow those cells which have remained vigorous 

 enough to develop alone. The addition of a little tartaric 

 acid to the saccharine solution — say, from , - ^,\ , ^ to -nrVu P^^t 

 by weight — often facilitates the destruction of certain germs 

 of impurity. Mycoderma aceti and mycoderma rini do not find 

 suitable life-conditions in the sweetened water ; the}' soon 

 disappear if cultivated alternately in sweetened water and wort. 



