ISO 5738|IDF 76:2004 specifies a reference method for the determination of the copper content of milk and milk products.
The method is applicable to: a) milk, skimmed milk and buttermilk; b) evaporated milk and sweetened condensed milk; c) whole and skimmed milk powder; d) cream and butter; e) butterfat; f) ice-cream; g) hard, semi-hard and soft cheeses of various ages, and processed cheese; and h) caseins, caseinates and coprecipitates.
The method is suitable for determining copper contents as low as 0,05 mg/kg in test samples of butter and butterfat.