DAIRY FARMING DAIRYING. 1125 



Tho proteids of butter in relation to mottled butter, L. L. Van Slyke ami 

 E. B. Hart i [New York State Sta. Bui. 263, pp. 69-93, pi. 1). — The authors' summary 



of this bulletin is as follows: 



"The questions studied in this bulletin are: (1) The relation of casein compounds 

 to cream-ripening; (2) casein compounds present in butter and buttermilk; (3) the 



relation of casein compounds to mottled butter. 



"In ordinary methods of cream ripening, neither calcium casein nor free casein is 

 present, but only casein lactate, when the lactic acid is allowed to exceed 0.5 per 

 cent. Casein lactate is the substance most familiar as curdled sour milk. 



" When the amount of lactic aid in cream exceeds 0.5 per cent the casein in the 

 butter and buttermilk is present as casein lactate. In butter and buttermilk made 

 from so-called sweet cream, we usually find calcium casein and some free casein, and 

 on standing for some weeks these may be changed in the butter into a mixture of 

 free casein and casein lactate or wholly into casein lactate. 



"It has been quite universally believed that the light spots or streaks in butter 

 known as mottles, are caused by the uneA'en distribution of salt, the more concen- 

 trated brine deepening the yellow color of the fat, and the lighter portions being the 

 unsalted or lightly salted areas. 



"The investigation covered the following conditions in relation to the mottling 

 of butter: (1) Richness of cream; (2) degree of ripeness of cream; (3) temperature of 

 churning; (4) size of butter granules; (5) temperature of wasli water; (6) working of 

 butter. 



"When the churning was managed so as to make the butter granules of the size 

 of rice grains and these were carefully washed twice with water below 45° F., 

 removing most of the buttermilk adhering to the outer surface of the granules, no 

 mottles were obtained, however conditions were varied in other respects. Mottles 

 were always found when the buttermilk was not sufficiently removed. 



"The amount of proteid (casein lactate) in mottled butter is greater in the light 

 portions than in the darker portions, and is the cause of the lighter color of the 

 mottles. 



"Salt brine does not change in any way the color of butter fat; salt brine, as it 

 commonly occurs in butter, has the power of hardening and localizing the proteid 

 particles, the action requiring several hours for completion; butter, free from butter- 

 milk adhering to the outer surface of the granules, does not produce mottles when 

 salted, whether the salt is evenly or unevenly distributed; mottles do not occur in 

 unsalted butter; in mottled butter the light portions usually contain less salt than 

 the darker portions. 



"Mottles in butter are due, primarily, to the presence and uneven distribution of 

 buttermilk adhering to the outer surface of the small granules; and, secondarily, to 

 the hardening and localizing effect of salt brine upon the proteid of the buttermilk 

 thus retained in butter. The light portions of mottled butter owe their lighter color 

 to the presence of localized proteid (usually casein lactate). The yellow or clear 

 portions occur where the spaces between the butter granules are filled with clear 

 brine and are comparatively free from casein compounds. Several hours are required 

 to complete the action of the brine upon the proteid of the butter. 



"Mottles in butter can be prevented by avoiding those conditions that retain 

 buttermilk in the butter and observing those conditions that favor the removal of 

 buttermilk from butter granules before salting. The butter granules should be about 

 the size of rice grains and should be washed twice with water at a temperature of 

 35 to 45° F." 



The causes and prevention of mottles in butter, F. H. Hall, L. L. Van 

 Slyke, and E. B. Hart (New Yuri; State Sta. Bui. 263, popular ed., pp. 10, fig. 1). — 

 A popular edition of Bulletin 263 of this station noted above. 



