COUNTERACTING PUFFINESS IN CHEESE. 327 



183. Counteracting Puffiness in Cheese. 



The reader will now probably inquire whether any method 

 exists whereby milk that will produce puffy cheese may be recog- 

 nised as dangerous before it is worked up and rejected by the 

 cheese-maker. This course will be advisable when the gas-forming 

 bacteria greatly preponderate, a condition ascertainable by the 

 so-called fermentation test. A sample of the milk to be exa- 

 mined is kept in a fermentation flask ( 126) for twelve hours at 

 40 C., a conclusion based on experience being then formed as to 

 its suitability or the reverse, according to the changes occurring 

 during this period. Fuller particulars on this point will be found 

 in Adametz's monograph, as also in the highly commendable text- 

 book of W. FLEISCHMANN (I.). 



As a means of preventing the malady, FREUDENREICH (IX.) 

 recommends the addition of 3 per cent, of common salt to the 

 freshly precipitated curd, freed from the main bulk of the whey. 

 For restricting incipient puffiness, Adametz counsels setting the 

 cheese to cool, since the ferment is found, by experience, to be 

 violent and injurious solely at higher temperatures. 



From the results of an investigation made by H. L. BOLLEY 

 and C. M. HALL (I.) it must be concluded that gas-forming bac- 

 teria are not present in milk at the moment it leaves the udder. 

 If this observation is confirmed by renewed (highly desirable) 

 researches in other places and under different conditions, and thus 

 become a general law, it will indicate the means of preventing 

 puffiness, viz., by taking care to keep the fresh-drawn milk free 

 from dirt and dung, which are the vehicles by which the gas- 

 forming bacteria are introduced. 



184. Bitter Milk and Bitter Cheese. 



According to a rule based on experience, and observed by all 

 housewives skilled in cookery, boiled milk must be stored in un- 

 covered vessels, otherwise it is liable to turn bitter. The attention 

 of Pasteur was also directed to this matter in the course of his 

 studies on spontaneous generation. We have already seen, in a 

 previous section, that the French investigator here made the im- 

 portant discovery that, though the lactic acid bacteria are thus de- 

 stroyed, the more highly resistant spores of butyric acid bacteria can 

 withstand such a brief exposure to boiling heat. Now, since the 

 majority of these latter are anaerobic, they can then only manifest 

 their activity provided the admission of oxygen is either entirely 

 prevented, or at least restricted, a condition ensured by covering 

 the milk-pan with a lid. There then gradually accumulates 

 within the pan an atmosphere of carbon dioxide, &c., produced 

 by the vital activity of bacteria and preventing the access of 



