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Department of Dairy Industry, University of California, Davis
ABSTRACT
Under some conditions, dissolved copper becomes associated with stainless steel in a form that is readily available for contamination of milk. A small amount of copper-nickel alloy, either used or cleaned with stainless steel, can cause disproportionately large copper contamination of milk. Adsorption of dissolved copper on stainless steel was appreciable in the pH range of 6 to 10, especially in the presence of hypochlorite. The amount of copper that adsorbed increased with the concentration of copper in solution, the temperature, and the time of exposure. Copper adsorption was slight or absent at low or very high pH or in the presence of a chelating agent (EDTA). Adsorbed copper was not removed by thorough rinsing with water, but largely was removed by a chelating agent (EDTA) or milk, or exhaustively by hot nitric acid.
1 This study was supported in part by funds from the California Dairy Industry Advisory Board.
2 Present address: Dairy Department, University of Maryland, College Park, Maryland.
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