FERMENTATION 341 



there may be seen extremely minute black specks, having somewhat the shape of a 

 four-rayed rhomboidal star : it is difficult to determine what these may be ; their 

 opacity almost precludes the idea of their being of organic origin ; perhaps they may 

 bo a particle of the lime-salts in an insoluble state, originally contained in the water 

 from which the beer was brewed ; many of them are attached to spherules of yeast, 

 after the manner that an air-bubble is sometimes seen to suspend small particles of - 

 solid substances. 



It often happens that, mixed with the yeast proper, there may be other ferments, 

 and these, so far as science has lent us aid, it is desirable to describe. The lactic 

 ferment is of the most common occurrence. M. W. Schultze is very definite in his 

 description of it. He says : ' When completely developed, it presents an appearance of 

 minute, translucent strips, in four divisions, slightly drawn together in the middle ; 

 in its early stages, it only presents a quantity of small specks moving around each 

 other. It refracts light strongly, has a peculiar mild brilliancy, and the contents of 

 the exterior membrane cannot bo seen.' M. Pasteur says the diameter of this parasite 

 is about one fifteen-thousandth of an inch, and that by its physical appearance it is 

 most easily distinguished from yeast ferment. 



The ordinary atmosphere contains an abundance of germs of ferment, and M. Schultze 

 affirms that the motes floating in the air are, by the spores which they contain, capable 

 of aiding the development of lactic, fermentation in worts. M. Hoffinan assures us of 

 their presence upon grain and the stalks of grapes ; and it is suspected that the dust 

 adhering to grain, and even malt, may be a means of developing lactic fermentations ; 

 and, in the same way that yeast multiplies itself in sweet wort, the lactic ferment may 

 also propagate itself, and, independently of the- original lactic fermentation, produce 

 what is commonly designated secondary fermentation. M. Schultze says that lactic 

 fermentation requires a supply of nitrogen, and its presence, duration, and force 

 depend on the quantity present of that element. The heating of wort from 140 to 

 149 appears to oppose the development of the cellules of lactic ferment ; a little 

 below 140 its production is slow and not abundant ; between 120 and 70 it becomes 

 rapid and energetic ; the temperature most favourable to its production being between 

 95 and 113. When lactic acid is present in a wort it appears to check a further 

 production of it, but if the free acid be neutralised with soda a fresh formation com- 

 mences at once. Whenever a wort has become sour, the lactic ferment is always to 

 be found in it, more abundantly in proportion to the amount of spontaneous fermen- 

 tation that has occurred ; therefore spontaneous fermentation is judged to be of lactic 

 origin, and, indeed, is lactic fermentation which has passed its ordinary limits. Ex- 

 perienced chemists also affirm that in the fermentation of beer with yeast, if the 

 temperature is allowed to attain 89 alcohol ceases to be produced, but that the 

 fermentation degenerates into the lactic condition, and lactic acid is the product 

 of it. 



Butyric Ferment. There is another kind of ferment which it is very important to 

 describe, and which, probably, is without exception the most troublesome and deadly 

 of the brewer's enemies ; this is the butyric ferment : it appears to originate princi- 

 pally from organic impurities in the water, but it is asserted also to be produced in 

 the ordinary fermentation of beer, if such fermentation be allowed to attain a tem- 

 perature above 84 ; in all cases diarrhoaa is produced when it is drunk whether in 

 beer or water ; in beer it may be suspected when there is odour of pine-apple, especially 

 if the beer has the character of soon producing headache. Mr. Charles Heisch is of 

 opinion that it is to be found in all water that has become contaminated with sewage, 

 even to the smallest amount ; the brewer will do well to make himself acquainted 

 with Mr. Heisch's researches upon this particular subject. It may be briefly stated 

 that the conclusions he appears to have arrived at are : First, that where this fer- 

 ment is found in water, be the amount of it ever so small, that water must not 

 be used for food purposes till the ferment is thoroughly eradicated from it, for 

 they increase so rapidly under favourable circumstances, that they must ultimately 

 prove injurious to health ; Secondly, in any dilute solution of sugar they quickly 

 betray their presence by a turbidity accompanied eventually by the butyric odour. 

 He describes them as minute spherical cells, with, in most cases, a very bright 

 nucleus. Their vitality is in no way destroyed even by half-an-hour's boiling; 

 ordinary filtration, even through the finest Swedish filter-paper, does not remove 

 them ; filtering through a good bed of animal charcoal, frequently dried, appears 

 to remove them effectually : the softer the water the more quickly they grow ; in hard 

 water they appear at first to form small clots, consisting of cells mixed with crystals 

 of carbonate of lime. The addition of nitrates or ammoniacal salts to the water does 

 not seem to accelerate their growth. By permitting the action of these germs on 

 sugar to go on, at a temperature between 60 and 70, they present uniformly the 

 following appearances : The cells generally group together in bunches like grapes, 



