SAI/TING THE BUTTER 339 



While the results above quoted all point toward improved 

 keeping quality of salted butter, both experimental results and 

 the experience of the butter manufacturer have demonstrated 

 that the beneficial influence of salt on the keeping quality of 

 butter, depends to a very considerable extent on a variety of 

 factors incident to the making and storing of butter and the 

 amount of salt, butter contains. 



Again, all micro-organisms present in butter do -not take 

 part in the decomposition of the ingredients of the buttermilk 

 and therefore do not affect its keeping quality and some spe- 

 cies are considered capable to actually prolong the life of but- 

 ter. On the other hand, the inhibiting action of salt varies 

 greatly with different micro-organisms and with the concen- 

 tration of the brine present. In slightly . salted butter, i. e., 

 butter containing not to exceed about two per cent salt, the 

 liquid parts of the butter contain only about thirteen per cent 

 salt, which is insufficient to retard the growth of most micro- 

 organisms. Weigmann found that 2.5 per cent salt in butter, 

 or about sixteen per cent in the brine of butter, inhibits the 

 growth of some species of germs and that the molds are, affected 

 by this salt more than the bacteria and yeast. When, however, 

 the salt is increased to 4 and 5 per cent, or approximately 21 

 to 25 per cent in the brine, the keeping quality is not only not 

 improved, but it suffers. In this case the lactic acid bacteria 

 which improve the keeping quality are affected unfavorably, 

 their growth is inhibited, while other bacteria which give the 

 butter undesirable flavors, such as those of the coli and aero- 

 genes groups, Bacillus subtilis, Bacillus putrificus and several 

 molds, are more resistant to salt. These results are corroborated 

 by experiments by Gray and McKay 1 who show that in the case 

 of butter stored at temperatures varying from 10 F. to 

 -j-32 F., lightly salted butter averaged 2.16 points higher in 

 score than heavily salted butter. These investigators therefore 

 concluded that butter containing low percentages of salt, keeps 

 better than butter containing a high per cent of salt. Fettig 

 also found that if the salt concentration is so high as to stop 

 the activity of lactic acid bacteria, some of the more resistant 



1 Gray and McKay, Investigations in the Manufacture and Storage of But- 

 ter. U. S. B. A. I. Bulletin 84, 1906, p. 17. 



