BUTTER DEFECTS 489 



of lactic acid and acetic acid added to sweet cream, although 

 cream with high acid did not uniformly develop fishiness. He 

 further states that overworking of butter produced fishiness 

 with a reasonable degree of certainty. He offers the opinion 

 that fishy flavor is caused by a slow, spontaneous, chemical 

 change to which acid is essential and which is favored by the 

 presence of small amounts of oxygen, and that it may be pre- 

 vented with certainty by making butter from sweet cream; also 

 that butter made from pasteurized cream with a starter but 

 without ripening seldom, if ever, becomes fishy. 



In a subsequent publication, dealing with results on the 

 Manufacture of Butter for Storage, Rogers, Thompson and 

 Keithley 1 show still more conclusively the freedom from fishiness 

 in butter made from unripened pasteurized cream, and the ten- 

 dency of butter made from ripened, raw or pasteurized cream to 

 become fishy in storage. 



Dyer 2 , as the result of a chemical study of fresh and stored 

 butter, concludes that "the production of off-flavors" so com- 

 monly met with in cold storage butter (and of which the fishy 

 flavor is a very prominent one) is attributable to a chemical 

 change expressed through a slow oxidation progressing in some 

 one or more of the non-fatty substances occurring in buttermilk. 

 The extent of this chemical change is directly proportional to 

 the quantity of acid present in the cream from which the butter 

 was prepared. Dyer further emphasizes that the development 

 of undesirable flavor in butter held in cold storage at a tempera- 

 ture of F. is not dependent upon an oxidation of the fat itself* 



The writer's experience has been fully in accord with the 

 findings of Rogers and Dyer, to the effect that high acid cream 

 and overworking of butter are conditions favorable to the devel- 

 opment of fishy butter. Fishy butter is very closely related to 

 oily and metallic butter. It appears to be the result of a com- 

 bination of certain factors, one of which is high acidity and 

 another a weak body of butter due to overworking, which 

 destroys the grain and excessively exposes the butter to the 

 action of air. Other factors may embrace the presence in the 



1 Rogers, Thompson and Keithley The Manufacture of Butter for Stor- 

 age, U. S. Dept. Agr., B. A. I. Bulletin 148, 1912. 



2 Dyer Progressive Oxidation in Cold Storage Butter. Jour. Agr. Re- 

 search, Vol. VI, No. 24, 1916. 



