142 Dairy Bacteriology. 



upon the general appearance of the starter as determined 

 by taste and smell. Where it is possible to propagate 

 the starter as has been described, it is hardly worth run- 

 ning any risk in using an old starter when a fresh one 

 -can be so easily kept in condition. 



142. Bacteria in butter. As ripened cream is neces- 

 sarily 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 

 120-300 bacteria per cc., while in butter from sour cream 

 2,000-55,000 germs per cc. were found. Pammel 2 found 

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

 butter sold in Munich from 10-20,000,000 organisms per 

 gram. 



The germ content of butter on the outside of a pack- 

 age is much greater than it is in the middle of a mass ; 

 this doubtless being due to the freer access of air favor- 

 ing the growth of aerobic forms. 



143. Changes in germ content. The bacteria that 

 are incorporated with the butter as it first ' ' comes ' 7 un- 

 dergo a slight increase for the first few days. The dura- 

 tion of this period of increase is dependent largely upon 

 the condition of the butter. If the buttermilk is well 

 worked out of the butter, the increase is slight and lasts 

 for a few days only, while the presence of so nutritious a 

 medium as buttermilk affords conditions much more 

 favorable for the continued growth of the organisms. 



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



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



3 Lafar, Arch. f. Hyg., 13: 1, 1891. 



