606 MILK 



butter is worked too much, some of the water-soluble aromatic 

 substances are lost and the taste of the butter becomes flat. 



Finished butter has a relatively small bacterial content owing 

 to the unfavorable conditions for bacterial life and multiplication. 

 Oleomargarine and butterine usually contain fewer bacteria than 

 natural butter. The droplets of buttermilk or water remaining 

 enmeshed after churning and washing dissolve the salt which is 

 worked into the butter, and this salt solution is unfavorable for 

 bacterial growth. The fat itself offers food for a few types only. 

 The latter, however, are undesirable, since they decompose fat 

 and produce fatty acids and glycerin. They are the cause of 

 rancidity in butter. 



After churning there is an increase in bacterial content, fol- 

 lowed by a decrease. Lohnis gives the following numeric rela- 

 tion of bacteria in butter according to age. The numbers are to 

 be multiplied by 1,000,000: 



Sweet cream butter. Sour cream butter. 



Outside. Inside. Outside. Inside. 



Fresh butter 1.1 10 10 



One week old 30 10 8 



Two months old 2 0.6 2 0.1 



According to this table sweet cream butter contains fewer 

 bacteria right after churning than sour cream butter, but after 

 one week, the relation is reversed. After two months both kinds 

 of butter contain less bacteria than after one week. 



The number of micro-organisms in butter depends to some 

 extent upon the thoroughness with which it is washed. If washed 

 insufficiently buttermilk remains and offers food for bacteria. 

 After repeated washing the buttermilk is replaced by water and 

 bacteria find little food. The fat is of food value only to a few 

 types of micro-organisms which, as stated before, decompose 

 the fat, with production of a rancid taste and odor. The com- 

 monest ones of these are Oidium lactis, Chladosporium butyrii, 

 Bacillus fluorescens, and more rarely B. prodigiosus. Decomposi- 

 tion by these organisms commences from the outside, since they 

 are aerobic. 



Abnormal conditions of- butter may be due to one or more of 

 the following causes : 



1. Poor control of conditions in butter making. 



2. Abnormal ripening of the cream. 



3. Poor milk. 



Poor control frequently shows itself in the texture of the 

 butter. If cows are permitted to feed on marshy vegetables, or 

 if a wet spring has caused watery plants, the fat in milk is soft. 

 The fat is hard when straw, potatoes, or beet tops are fed in 



