520 BUTTER DEFECTS 



bright yellow color and gives the butter a dull and lifeless 

 appearance. 



It is obvious that this defect can readily be avoided by in- 

 corporating a normal amount of moisture and not overworking 

 the butter. The difficulty of incorporating the desired amount 

 of moisture in butter that is naturally very firm and dry, and 

 does not readily take up and hold moisture, in order to secure a 

 reasonable overrun, may best be overcome by raising the churn- 

 ing temperature sufficiently to give the butter a somewhat less 

 firm body. 



Mottled and Wavy Butter. General Description. Uneven- 

 ness in the color of butter is shown in the butter in the form of 

 streaks, waves and mottles. Streakiness or waviness refers to 

 butter in which the unevenness in color shows in the form of 

 layers or waves of different shades of yellow, the color in the 

 layer or wave itself, however, may be perfectly uniform. In the 

 case of mottles the butter is dappled with spots of lighter and 

 deeper shades of yellow throughout its body. 



Unevenness in color, and especially 'mottles, in butter, are a 

 serious defect from the standpoint of its market value. This 

 defect has nothing to do with the quality of the butter, mottled 

 butter is just as good and just as wholesome as butter that is not 

 mottled. But while the criticism of the trade is a superficial one, 

 the objection is no less real. Butter that is otherwise perfect 

 and might score a good "Extras," if it is mottled, clears as a 

 "Seconds" and is sold on that basis by the dealer. 



Causes and Prevention of Mottles. Extensive experiments 

 by Hunziker and Homan 1 have shown that the causes of mottles 

 are due to the following factors : 



1. Mottles are caused by an uneven distribution of the 

 water droplets in butter. 



2. The white, opaque dapples in mottled butter are caused by 

 the presence, or localization of innumerable very small water drop- 

 lets. The small size, high curvature and large number of these drop- 

 lets bend, refract and deflect the rays of light to such an extent 

 that they render the butter opaque and give it a whitish appear- 

 ance. 2 



1 Hunziker & Hosman. A Study of the Causes of Mottles in Butter. Blue 

 Valley Research Lab., Chicago 1918 and 1919. Journal Dairy Science, Vol. Ill, 

 No. 2, 1920. 



2 The opacity is further intensified by the difference in the refractive in- 

 dex between butterfat and water. 



