FLAVORS OF BUTTER 171 



stated that he commonly used the term rancid when 

 butter had an over-sour strong flavor. He pronounced 

 the odor of the distillate of the Reichert-Meissl determi- 

 nation to be much like the rancid flavor. By others 

 rancidity is considered to be a butyric acid flavor. It is 

 easily recognized by an expert butter-judge. 



Rancidity in butter is not common. In a recent pub- 

 lication l a review has been given of the subject of ran- 

 cidity, and in subsequent experimental work, such as 

 pumping air through the cream, subjecting the butter 

 for various periods of time to the air, high temperature, 

 and various conditions of light, rancidity was not 

 found. The examination of two samples of old butter 

 did not reveal the rancid flavor. One of these samples 

 was twelve years and the other 680 days old. In each 

 case the iodine number which is a measure of oxidation, 

 and the Reichert-Meissl number which shows the extent 

 of development of volatile fatty acids, remained within 

 the range of these constants in fresh butter. There was 

 an increase in the acid number but no rancidity. 



The final conclusion of the study of this flavor is that 

 the cause of rancidity is probably butyric acid ; also 

 that rancidity of butter as defined by butter-dealers and 

 expert butter judges is rarely found. It is not the flavor 

 usually known as such by the average person. 



128. Effect of pasteurization. If the temperature 

 during pasteurization is too high, a cooked flavor is likely 

 to be imparted to the butter. In a few days this scorched 

 taste will disappear ; nevertheless, it is wise not to permit 

 the temperature of the cream to rise too high. For further 

 discussion see par. 69. 



1 Guthrie, E. S., Concerning Rancidity of Butter, Jour. Dairy 

 Sci., vol. 1, No. 3, p. 218, 1917. 



