BACTERIA AND BUTTER-MAKING 217 



associated with rancidity. It would be natural to assume, there- 

 fore, that they have some important relation thereto. But the 

 change goes on after the bacteria cease to grow and may occur 

 independently of bacteria. Rancidity may be certainly looked 

 upon as a fermentation change, and the only method the dairy- 

 man has of controlling it is by cool temperatures, by packing 

 the butter in large masses, and by keeping it from the light. It 

 may be delayed by pasteurizing the cream and using pasteurized 

 water for washing, a fact that shows its close relation to bac- 

 teria. Fortunately, it is a matter of no very great importance, 

 because butter can be kept without difficulty for some months, 

 and before it has spoiled it is almost always possible to 

 market it. 1 



BUTTER DEFECTS 



Quite a variety of defects occur in butter, some of which are 

 associated with bacteria, while others apparently have no con- 

 nection with micro-organisms. The former are in most cases 

 due to the growth of undesirable bacteria in the cream, producing 

 there certain by-products, which affect the cream and butter. 

 In some cases, apparently, the troubles are due to bacteria grow- 

 ing in the butter itself. The following list includes the most 

 important of these troubles, which have been demonstrated to 

 be associated with bacterial action. 



Red Spots. The development of red spots in butter has been 

 studied in a few cases, and has been found to be due to a growth 

 of micro-organisms. 2 In one case, a yeast, known as a pink 

 yeast, has been found to develop somewhat abundantly in butter, 

 producing a red color, and in other cases investigated, the cause 

 was due to bacteria. 3 The trouble is a rare one. 



1 Reinmann. Cent. f. Bact., II., vi., p. 131, 1900. 



Shattenfroh and Grassberger. Arch. f. Hyg., xxvii., p. 54; xlii., p. 219; 

 lx., p. 40. 



Eichholz. Hyg. Rund., xiii., p. 130, 1903. 



Jensen. Tahr. d. Land. d. Schweiz, 1901. 

 2 Weigmann. Milch. Zent., I., p. 4, 1905. 

 3 Poda. Milch. Zent., II., p. 97, 1906. 



