I9O BACTERIA IN BUTTER. 



result of this is a complex struggle, in which some species 

 are rapidly crowded into the background and have little or 

 no effect on the character of the ripened cream. Laboratory 

 experiments carefully exclude all of the miscellaneous 

 species of bacteria, and especially the lactic forms which 

 develop in normal cream. The results of such experiments, 

 are, therefore, quite unlike those of normal cream ripening. 

 These experiments do show, however, the different effect of 

 different species of bacteria upon butter, and prove beyond 

 question that different species of milk bacteria have the 

 power of producing different flavors in the butter. 



The Growth of Bacteria in Ripening Cream. In order to 

 understand properly the phenomena of cream ripening it is 

 necessary to study the actual growth of bacteria in cream 

 under normal conditions, rather than under these rather un- 

 usual conditions of laboratory experiments. This has been 

 done in recent years with considerable satisfaction, and we 

 now know tolerably well the essential facts. The develop- 

 ment of bacteria in cream is very similar to that which we 

 have described in an earlier chapter as the growth of bacteria 

 in milk (101). It is essentially as follows: 



Fresh cream contains commonly a very large variety of 

 bacteria. This is especially true in the case of creameries, for 

 here the cream is collected from a somewhat wide territory, 

 and consequently receives a varied stock of bacteria. The 

 number of species that may be found in such ripened cream 

 is sometimes comparatively few and sometimes very great. 

 Moreover, the number found under these circumstances is 

 dependent, in a measure, upon the age of the cream, for the 

 older the cream the smaller is the number of kinds of bacteria 

 which are found by bacteriological analysis. In cream that is 

 brought into the ordinary creamery the character of the bac- 

 teria will, therefore, be different in accordance w.ith the age 

 of the cream. 



