ADDENDUM 191 



7. Condensed and Dried Milk. 



Two investigations upon these varieties of milk have been 

 recently carried out in this country and some of the findings are 

 of considerable interest. Andrewes 1 found that condensed milk 

 like fresh milk samples contained large numbers of cells, including 

 numerous polymorphs, but when quantitative estimations were 

 made the actual numbers per c.mm. in machine-skimmed con- 

 densed milks were hardly greater than in fresh uncondensed 

 milk, although in the latter the milk is reduced to a quarter or 

 less of its bulk. Andrewes considers that the reduction is due 

 to the mode of preparation, the centrifugalisation removing 

 many cells with the cream, debris and dirt. 



Andrewes examined bacteriologically 43 samples of machine- 

 skimmed condensed milk and all contained bacteria but the 

 quantitative method used was only a rough one. The results 

 obtained fell into three main groups : 



(a) Seven which yielded a moderate number of colonies, 

 amongst which staphylococci were relatively few. B. mesen- 

 tericus was commonly present. 



(b) Five yielded a more abundant growth in which white 

 staphylococci and coliform bacilli were the prevailing organisms 

 in almost equal numbers. Staphylococcus aureus was only 

 present in one sample and in that in scanty numbers. 



(c) Thirty-one samples yielded almost pure cultures of 

 staphylococci, amongst which Staphylococcus pyogenes aureus was 

 conspicuous and often predominant. 



Andrewes discussed the significance of Staphylococcus aureus 

 and albus in the samples and showed that staphylococci can 

 multiply abundantly in condensed milk, the numbers found 

 depending upon the age of the milk. " It would appear that if 

 only a few Staphylococcus aureus were present and escaped 

 destruction in the process of condensation, there is no limit 

 to the number which later may be found on opening the tin." 



1 Journ. of Pathology and Bacteriology, 1913, xvm, p. 169. 



