Tallowiness in Butterfat 



177 



upon the natural oxidases present, while Rogers 8 concludes 

 from his studies that the changes in butter "is brot about by 

 spontaneous chemical action/' 



The latter workers mentioned have dealt mainly with factors 

 influencing the rate of formation of tallowness in butter. 



The problem of the oxidation of butter was studied from 

 another standpoint by Dyer, 9 who measured the rate of dis- 

 appearance of oxygen in stored butter. 



Numerous products of oxidation of butter have been isolated 

 and identified, but the nature of the oxidation which occurs has 

 never been satisfactorily explained. 



Results of our w r ork show that the reactions of tallowy butter- 

 fat substantiate the view that peroxides are formed. Such fats 

 have the power of liberating iodine slowly from potassium iodide, 

 and the amount liberated in a certain length of time, as shown 

 by the Na 2 S 2 0 3 titre, forms a comparative test of how much 

 oxygen has been absorbed by various fats. 



These fats also give the Kreis test, seemingly in direct propor- 

 tion to the amount of oxygen which they have absorbed. Ex- 

 treme cases of oxidation have been found, however, in which 

 little or no iodine is liberated from potassium iodide, but the 

 Kreis test is very pronounced. Oxidized butterfats also give a 

 peroxide test with chromic acid when acidified and allowed to 

 stand for a comparatively long time. 



It has been found that oleic acid exposed to oxygen for some 

 time will give the characteristic tallowy odor and proportionate 

 peroxide and Kreis tests. Triolein under similar conditions will 

 give an even more characteristic odor and both the named re- 

 actions. Its tendency toward oxidation seems less than that of 

 oleic acid. 



Unsaturated linkages other than those found in the oleic 

 radical may be involved in the oxidation, but the oleic acid 

 radical is undoutedly one of the constituents of butterfat largely 

 involved in the production of tallowiness. 



5 Smith, H. L., Phann. Jour., 1915, xcv, 4. 



6 Hunziker, O. F., and Hosman, D. F., Jour. Dairy Sci., 1917, i, 321. 



7 Palmer, L. S., and Combs, W. B., Jour. Dairy Sci., 1919, ii, 444. 



8 Rogers, L. A., Third Internat. Congress of Refrigeration, Washington- 

 Chicago, 1913. 



9 Dyer, D. C, J. Agr. Research, 191C, iv, 927. 



