154: Dairy Bacteriology. 



retention of its purity will depend more upon the ability 

 of the contained organism to choke out foreign growths 

 than upon any other factor. Experience seems to indicate 

 that pure-culture starters " run out " sooner than domestic 

 starters. While it is possible, by bacteriological methods, 

 to determine with accuracy the actual condition of a starter 

 as to its germ content, still such methods are inapplicable 

 in creamery practice. Here the maker must rely largely 

 upon the general appearance of the starter as determined 

 by taste and smell. The supply houses that deal in cult- 

 ures of this class generally expect to supply a new culture 

 at least every month. 



Bacteria in butter. As ripened cream is necessarily rich 

 in bacteria, it follows that butter will also contain germ 

 life in varying amounts, but as butter- fat is not well adapted 

 for bacterial food, the number of germs in butter is usually 

 less than in ripened cream. 



Sweet-cream butter is naturally poorer in germ life than 

 that made from ripened cream. Grotenfelt 1 reports in 

 sweet-cream butter, the so-called " Paris butter," only 

 120 to 300 bacteria per cc., while in butter from sour crearn 

 2,000 to 55,000 germs per cc. were found. Pammel 8 found 

 from 125,000 to 730,000 per gram, while Lafar 3 found in 

 butter sold in Munich from 10,000,000 to 20,000,000 organ- 

 isms per gram. 



The germ content of butter on the outside of a package 

 is much greater than it is in the middle of a mass, this 

 doubtless being due to the freer access of air favoring the 

 growth of aerobic forms. 



Grotenfelt-Woll, Prin. Mod. Dairy Practice, p. 244. 

 Pammel, Bull. 21, Iowa Expt. Stat., p. 801. 

 Lafar, Arch. f. Hyg., 1891, 18:1. 



