FERMENTATION 345 



As to temperature, avoid extremes, and especially dangerously high ones ; rather 

 employing an extra quantity of yeast than a high temperature ; and the less heating 

 that is attempted, in the progress of the fermentation, by the means of attemperaters, 

 the better. The fermentation should be expedited by all safe means available, for 

 either heat or protracted working diminish the alcoholic excellence and tend to impair 

 the flavour, in proportion as they have been permitted to affect the process. 



When the desired amount of attenuation is obtained, no time should bo lost in 

 freeing the alcoholised product from degeneracy by contact with the yeast, and pre- 

 serving by refrigeration as much as possible of the alcohol and carbonic acid gas that 

 have been generated. To this end it is best to draw off the alcoholised product as 

 quietly as possible into a clean settling back provided with a means of refrigeration, 

 and when it has become sufficiently bright, rack and store at once ; great experience 

 and judgment are a necessity in determining this last point, and no amount of theory 

 can supply the lack of them. Peculiarities of water, modes of mashing and fermenta- 

 tion, character of the barley season and malting, state of the weather, gravity of the 

 wort, and peculiarities of the market for which the beer is brewed, are all points which 

 have to be carefully attended to, or the previous management and care will result only 

 in bitter disappointment. On the care with which the settling and racking have been 

 conducted depend the flavour, brilliancy, and briskness of the product. Finings of any 

 sort are of very little avail, and if their effects were more generally known, they would 

 bo but very seldom used ; for, chemically, they must be injurious both to the beer and 

 the consumer, and practically they prove so both to the cask and its contents. If they 

 meet with either acids or alkalis, acetic and lactic tendencies are generated in the 

 alcoholic solution with which they are mixed, and by their decay butyric decomposition 

 is generated. If they are rendered insoluble, they become indigestible, and this latter 

 result is found to be the effect of bisulphate of lime. All finings, be they soluble or 

 insoluble, flatten the beers when mixed by the amount of agitation they require 

 to make them take effect ; thereby much of the carbonic acid gas (which is the 

 product that gives to beers that brilliancy, sparkle, and pungency so grateful to the con- 

 sumer's palate) is liberated and lost, and this also diminishes the keeping ability of the 

 beer. 



Liebig calls putrefactive fermentation every process of decomposition which, 

 caused by external influences in any part of an organic compound, proceeds through 

 the entire mass without the further co-operation of the original cause. Fermen- 

 tation, according to Liebig's definition, is the decomposition exhibited in the pre- 

 sence of putrefying substances or ferments, by compounds nitrogenous or non- 

 nitrogenous, which alone are not capable of putrefaction. He distinguishes, in both 

 putrefaction and fermentation, processes in which the oxygen of the atmosphere 

 continually co-operates, from such as are accomplished without further access of 

 atmospheric air. 



Liebig opposes the view which considers putrefaction and fermentation as the result 

 of vital processes, the development of vegetable formations or of microscopic animals. 

 He adduces that no trace of vegetable formations are perceptible in milk which is left 

 for some time in vessels carefully tied over with blotting-paper, not even after fermen- 

 tation has regularly set in, a large quantity of lactic acid having been formed. He 

 further remarks of fermentativ'e processes, that alcoholic fermentation having been 

 observed too exclusively, the phenomena have been generalised, while the explana- 

 tion of this process ought to be derived rather from the study of fermentative pheno- 

 mena of a more general character. 



Blondeau propounds the view that every kind of fermentation is caused by the 

 development of fungi. Blondeau states that alcoholic fermentation is due to a fungus 

 which he designates Torula cerevisies ; whilst another, Penicillium glaucum, gives rise 

 to lactic fermentation. The latter fermentation follows the former in a mixture of 

 30 grm. of sugar, 10 grm. of yeast, and 200 c. c. of water, which has undergone 

 alcoholic fermentation at a temperature of about 20, being terminated in about two 

 days. Beer yeast, when left in contact with water in a dark and moist place, contains, 

 according to Blondeau, germs both of Torula cerevisics, and of Penicillium glaucum ; 

 the former can be separated by a filter, and will induce alcoholic fermentations in 

 sugar-water, whilst the latter are extremely minute, and pass through the filter ; the 

 filtrate, mixed with sugar-water, gives rise to lactic fermentation. Acetic fermen- 

 tation is dtie to the development of Torula aceti ; sugar is converted into acetic acid 

 without evolution of gas, if 500 grm. dissolved in a litre of water be mixed with 

 200 grm. of casein, and confined in contact for a month at a temperature of about 20. 

 The conversion of nitrogenous substances into fat for instance, of casein, in the 

 manufacture of Eoquefort cheese ; of fibrin under similar circumstances, which Blon- 

 deau designated by the term fatty fermentation (fermentation adipeuse) is caused by 

 Penicillium glaucum or Torula viridis; and the former fungus is stated to act like- 



