Il6 MODIFIED MILK AND MILK PRODUCTS 



English butter usually contains when fresh a very large 

 number of bacteria, often one to ten million, and sometimes as 

 many as 40 million or more per gramme. The majority of these 

 are lactic acid bacilli such as B. acidi lactici, B. lactis aerogenes y 

 etc. The number of bacteria materially decrease with keeping. 



Butter "faults" are not infrequently met with. The majority 

 of these are due to faulty management, resulting in the develop- 

 ment of unwelcome species of bacteria which produce rancidity, 

 abnormal flavours, bitter taste, etc. Of these unfavourable 

 bacteria may be mentioned B. subtilis, B. mesentericus, B. fluo- 

 rescens liquefaciens, etc., and probably some yeasts. Some of 

 these changes, for example rancidity, are due to the inter-action 

 of several kinds of bacteria. These unfavourable bacteria are 

 usually kept in check by the lactic acid bacteria. 



If the cream is pasteurised and pure cultures added there is 

 obviously much less risk of these abnormal bacteria developing 

 and producing butter faults. 



No data of special value are likely to be obtained from an 

 enumeration of the bacteria in ordinary butter samples. From 

 the public health point of view the bacteriological examination 

 of butter is at present limited to its examination for pathogenic 

 bacteria, particularly B. tuberculosis. 



Pathogenic bacteria in butter. 



B. tuberculosis. The investigations of numerous workers have 

 proved that tubercle bacilli are not infrequently present in butter. 

 Different investigators have, however, obtained very varying 

 results, their percentages of positive results varying from about 8 

 to 30. There are few available English records, but it is probably 

 safe to state that at least 10 per cent, of samples contain 'living 

 virulent tubercle bacilli. A recent report of the Local Govern- 

 ment Board 1 states that a number of butter samples were 

 examined in the Board's Laboratory. Of 48 samples of foreign 

 butter four were " inconclusive," the others showed no tubercle 

 bacilli. Of 60 samples of British origin 22 were "inconclusive," 

 while two showed the presence of tubercle bacilli. 



J Local Govt. Board Medical Officer's Report, 1911-12, p. 184. 



