Sweetened Condensed Milk: VI. Tallowiness

Abstract

Summary 1.Tallowy condensed milk is produced through the action of the oxygen of the air in the container on the butter fat of the milk, the reaction being catalyzed ordinarily by small amounts of copper. 2.Tallowiness develops below 32°F. apparently just as rapidly as at room temperature; heat sterilization of the product does not prevent it; the bacterial counts of tallowy samples are low; addition of strong preservatives do not prevent the development of the flavor. All these points are taken as proof that the reaction involved is chemical and that biological agencies have nothing to do with it. 3.Pure oxygen was found to be more active in producing tallowiness than air. The development of the flavor could be prevented by displacing the air with carbon dioxide, or, by filling containers so full that no air space remained. Tallowiness increases, therefore, with the extent of exposure to oxygen. 4.Tallowiness was found to increase with the amount of copper present. When the percentage of copper is small, much more oxygen or air space must be in contact with the sample to produce the flavor. And when there is but little air space more copper must be present. 5.Condensed skimmilk may become slightly tallowy if it contains any fat at all, which it usually does in commercial practice. 6.Copper condensing pans and hot wells that have not been used for some time previously yield an excessive amount of copper to the first few batches manufactured; accordingly, these batches are most likely to become tallowy. 7.Tin was found not to catalyze the tallowiness reaction. Iron was found to do so but to a very much less degree than copper; it cannot be important in practice.