The Copper Content of Cows’ Milk

Abstract

Copper was found to be a normal constituent of freshly drawn cows’ milk. The amounts found in the milk of individual animals varied from 0.2 to 0.8 mgm. per liter. The average amount found in 23 such samples was 0.52 mgm. per liter. On the basis of results from several samples representing mixed milk taken during periods of pasture feeding and stall feeding, there appears to be no difference in the copper content of milk as affected by the two different types of ration. The maximum amount found in these samples was 0.6 mgm. per liter and the minimum was 0.4 mgm. per liter. The potassium ethyl xanthate method proved to be the most satisfactory method for the quantitative measurement of the small amounts of copper found in normal milk. Tests to determine the reliability and delicacy of this method show that as low as 0.005 mgm. could be measured with a fair degree of accuracy. Other methods however, were used to advantage for the qualitative detection of copper in large quantities of milk. The amount of copper in milk may be measureably increased by storing or heating in the presence of metallic copper. Slight increases in the copper content of milk may also result from the passage of milk through the sanitary type copper pipes from which the tin has been worn off. Copper taken up from this source however, is not as great as would result from the formation of copper compounds around brass or bronze fittings as a consequence of poor sanitary practices. The significance of minute amounts of copper in plant and animal tissues is as yet unknown. Its presence in milk, particularly when taken up as extraneous contamination may prove to be significant in connection with the high susceptibility of the antiscorbutic vitamine to oxidation. In fact, Hess (14) has already reported the destruction of this vitamine by accelerated oxidation as a result of pasteurizing milk in a copper vessel. © 1922, American Dairy Science Association. All rights reserved.