Tallowiness in butterfat

Butterfat exposed to light and air rapidly takes on an odor and off flavor which has been termed “tallowy.” Among the early workers who attributed the tallowness in fats to the direct action of oxygen are Winckel, 1 Scala, 2 Ryan and Marshall, 3 Vintilesco and Popesco, 4 and others. Winckel attributes such a state to the action of oxygen upon oleic acid, but he was not able to show the reactions in butter and cocoanut oil that he showed in other fats. Vintilesco and Popesco were apparently the first to postulate the direct union of oxygen with the unsaturated linkages of fats to form peroxides which readily release their oxygen in the presence of peroxidases, giving reactions with guaiacol.

Smith 5 favors the view that rancidity is induced by enzymes, while Hunziker and Hosman 6 attribute tallowness in butter to oxidation with subsequent splitting and the formation of fatty acids and glycollic acid. Palmer and Combs, 7 more recently, favor the view that tallowness in butter is dependent 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 disappearance 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 work show that the reactions of tallowy butterfat 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 Na₂S₂O₃ titre, forms a comparative test of how much oxygen has ken absorbed by various fats.