BUTTER DEFECTS 481 



and fishy flavor. The oily flavor is more prevalent in butter 

 made in summer than in winter. Oily butter is not suitable for 

 storage. It usually scores a " Seconds." 



The specific reactions which produce oily-flavored butter 

 are not well understood, but it is known from practical ex- 

 perience that high temperature pasteurization and the use of 

 a surface cooler for cooling the hot pasteurized cream, are 

 prone to produce an oily flavor in butter. This is especially the 

 case with cream that is excessively sour at the time of pasteuriza- 

 tion. The pasteurization of very rich cream and of cream that 

 has been much diluted with water also tends to make butter 

 oily. Overworking of the butter under certain conditions has 

 a similar effect. 



The oily flavor has also been attributed by some investi- 

 gators to bacterial action. Jensen 1 isolated an organism be- 

 longing to the group of sour milk bacteria, which was capable, 

 aside from curdling the milk into a solid clot in 24 hours, to 

 produce an unpleasant odor and taste resembling that of ma- 

 chine oil. The oily flavor was transmitted from the cream in 

 which it developed to the butter. Others 2 claim that oily but- 

 ter is due to the action of microorganisms that decompose the 

 fat, such as Oidium lactis, yeasts and liquefying bacteria. To 

 what extent specific microorganisms are directly responsible for 

 the oily flavor in butter is uncertain, but it is quite possible 

 that they assist in bringing about such combinations of condi- 

 tions as are conducive to the development of oiliness and there- 

 by may become indirectly responsible for this defect. 



The oily flavor of butter occassionably may be due to 

 causes other than those pertaining to the process of manu- 

 facture. It has at times been found to be caused by the print- 

 er's ink on the butter carton. In this case the oily flavor is 

 usually especially pronounced on the surface of the print while 

 the interior of the butter may be practically free from this 

 defect. 



In the case of cartons with heavy, solid coloring, that are 

 inclined to transmit to the butter an oily flavor, the danger can 

 be greatly minimized, if not entirely prevented, by allowing 



1 Russell Outlines of Dairy Bacteriology, 1902, p. 158. 

 * Marshall Microbiology, 1911, p. 343. 



