Seasonal variations of copper and iron in Irish milk and butter

Levels of Cu and Fe in fresh milk and in bulk pasteurized milk were measured. The endogenous levels varied during the lactation period. The level of Cu in bulk pasteurized milk was greater than the endogenous level, suggesting some contamination. This apparent Cu contamination was greater in winter than in summer. No similar contamination was observed with Fe. The levels of Cu and Fe in butter manufactured each month and in retail butter were measured. Higher levels of Cu were detected in ripened cream butter produced in winter compared to that produced in summer. No similar trend was evident for Fe in ripened cream butter. Very low levels of Cu, Fe and lipid oxidation were detected in Irish sweet cream butter and consequently Cu and Fe contamination and resultant oxidation are not a problem in this product.