STUDIES ON FERMEISTATION. 3 



when under 70° C. (158° F.), and particularly when at a tem- 

 perature of from 25° C. to 35° C. (77° F. to '95° F), it wiU be 

 quickly invaded by lactic and butyric ferments. Rapidity in 

 cooling is so essential that to secure it recourse is had to special 

 apparatus.* Even in the preparation of wort, especially when 

 it is effected by successive mashings, in summer, deterioration 

 is imminent : in fact, it is not rare to see the wort becoming 

 acid during the mashes, if these are not accomplished with all 

 possible celerity. 



After the wort has been cooled, it is mixed with yeast. 

 This is obtained from a previous fermentation, and, after being 

 thoroughly pressed, is added at the rate of from one to two 

 thousandth parts of the weight of the wort, that is, from 100 to 

 200 grammes per hectolitre (about 4 oz. to 8 oz. average for 

 every 25 gallons). At first sight, this yeast seems free from 

 the possible diseases of the wort and beer ; but this is by no 

 means the case. 



Now, why do we add yeast to our wort ? This practice is 

 unknown in the art of vinification. The must is alwaj's left 

 to spontaneous fermentation. Why should we not leave the 

 wort to operate in the same manner ? 



It would be a mistake to suppose that in the brewing of 

 beer yeast is added with the sole object of accelerating fer- 

 mentation, and making it more rapid. Rapidity in fermen- 

 tation is a very questionable advantage, and one which is not 

 desired by brewers, who rather agree in pronouncing it injurious 

 to the quality of beer. It is in the easy deterioration of the 

 wort, or what is tantamount to it, in the facility it afibrds to 

 various spontaneous fermentations, that we find an answer to 

 these questions. The must, through its acidity, due to the 

 presence of bitartrate of potash — which seems to promote 

 alcoholic fermentation — through its proportion of sugar, and 

 perhaps in consequence of some other peculiarity of its compo- 

 sition, always undergoes regular alcoholic fermentation. The 



* We shall hereafter revert to this rapidity in cooling, to show that it 

 is also of use in the subsequent clarification of beer. 



B 2 



