P.ACTERIA AND BUTTER-MAKING IQ7 



paratively few in numbers, forming sometimes not more than 

 i to 2 per cent. ; but their percentage rises rapidly until they 

 come to form an appreciable portion of the whole. After sev- 

 eral hours, the time varying with different specimens, the acid 

 bacteria constitute a large percentage of the whole. From this 

 time, after they form perhaps 50 per cent, of all of the bacteria 

 present, the other species begin to be injuriously affected by the 

 growth of the lactic bacteria, probably by the acid produced. 

 The acid forming germs still continue to increase in numbers, 

 while the others cease to grow so rapidly. After a time they 

 begin to diminish and may finally largely or wholly disappear. 

 The result of this is that during the last stages of the ripening 

 there may be present in the cream nothing but acid bacteria, 

 which sour the cream and produce the final changes in the 

 ripening. 



It will thus be seen that the ripening of the cream may be 

 divided into two stages: In the first the growth of the miscel- 

 laneous species of bacteria continues, and all types may become 

 more or less abundant. In the second the acid-forming germs 

 take possession of the cream and gradually force the others 

 into the background and, finally, may crowd them out entirely. 

 Both of these stages doubtless contribute to the final product. 

 Without the proper lactic organisms it is impossible to get 

 the proper flavored butter. But butter made from pasteurized 

 cream and ripened by pure cultures of lactic acid bacteria does 

 not develop so much flavor as that in which the original bac- 

 teria are allowed to grow with the acid germs. Hence, it is 

 probable that the development of the miscellaneous bacteria in 

 the first phase of the ripening has not a little to do with the final 

 butter flavors. Concerning the matter, however, nothing is 

 positively known, the problems being too complex to have ad- 

 mitted of any solution at the present time. 



