182 EXPERIMENT STATION RECORD. 



22 were above 16 and only 3 were below 13. The lowest samples of 

 Swedish and German butter showed 13.7 and 13.5, respectively. 



A study of the cause of mottled butter, C. F. Doane {Maryland 

 Sta. Bui. GJi^jyp. ^i-J^)- — Experiments were conducted to test various 

 theories as to the cause of mottled butter. 



The butter from each of 5 churnings was divided into 2 lots, one of 

 which was washed with water at 50- and the other with water at 35 to 

 40°. The washing occupied about 1 minute. A portion of each lot 

 was worked 3 minutes and the remaining portion 4 minutes. Of the 

 5 lots washed with water at 50° and worked 3 minutes one was slightly 

 mottled. Of the 5 lots washed with cold water and worked the same 

 time 1 were mottled. The more frequent occurrence of mottled butter 

 in the latter case is attributed to the less thorough working of the 

 harder butter resulting from washing in ice water. None of the butter 

 worked -1 minutes was mottled. In 4 additional experiments to deter- 

 mine the effect of using cold water the butter was allowed to remain 

 in water at 40° for 15 minutes, after which one-half of each churning 

 was worked 3 minutes and the other half 4 minutes. The butter worked 



4 minutes was free from mottles in every case; that worked 3 minutes 

 was slightly mottled in 2 of the tests. No material difference was 

 observed between washing 1 minute and 15 minutes. 



To determine the effect of the uneven distribution of salt the butter 

 from each of 20 churnings was divided into 2 lots immediately after 

 washing. One lot in each case was salted and the other left unsalted. 

 Both lots were worked one minute and then set in the refrigerator. 

 "Not one of the unsalted lots was at all mottled, while in every case 

 the salted lots were very distinctl}' mottled." It was found by tasting 

 that the light portions of the mottled butter contained very much less 

 salt than the more deeply colored portions. The same difference was 

 observed in a large number of samples of unevenly colored butter from 

 commercial sources. The author therefore concludes that the uneven 

 distribution of salt is the cause of mottles. 



The effect of salt on the appearance of butter was further tested in 



5 experiments, in each of which 2 lots of butter from the same churn- 

 ing were thoroughly worked and otherwise treated alike except that 

 only 1 lot in each case was salted. The salted butter had a darker 

 color than the unsalted butter, the difference being distinguishable 

 immediately after working and very marked after 21 hours. 



To determine if the more pronounced color of the salted butter was 

 brought about by the action of salt in driving out more of the butter- 

 miik, the content of casein in the samples of butter made in the experi- 

 ments last noted was determined. In 3 churnings the salted butter 

 had less casein than the unsalted butter, and in the other 2 compari- 

 sons the results were reversed. In each of 10 experiments 1 lot of 

 butter was salted and worked without being washed and another lot 



