437. Copper and iron in dairy produce. improved methods of analysis

Abstract

1. Improvements are described in the methods for the extraction and colorimetric estimation of metals in dairy produce, using the carbamate reagent for copper and thiocyanate for iron.2. A combined filtration procedure has been developed to enable both metals to be determined on the same sample, and with slight modifications this procedure has been applied to the analysis of samples of butter, cream, buttermilk and whey.3. The wet-ashing technique has also been improved to enable it to be used for the estimation of both metals on the same digest.4. Comparisons show that the combined filtration method is capable of giving results which agree very well with those yielded by wet-ashing.5. The results of many analyses show that the majority of creamery butter samples have a satisfactorily low content of both copper and iron.6. Many whey butter samples have a rather high metallic content.7. Notes are given on the results obtained when the methods described are applied to other dairy produce.

Dosage simultané du fer et du cuivre daims le lait et les produits laitiers

“…La minéralisation par voie humide proposée dabord par WILLIAMS [5], reprise et modifiée par de nombreux auteurs, a fait l'objet de travaux récents par HUSSONGet HAMMER [15] MoDo-WELL [2], PERRIN, LIGHTFOOT et MOIR [6]. Elle donne de bons résul-tats.…”

“…Plus récemment, den HERDER et KROL [12] ont extrait le fer, le cuivre et le manganèse du beurre par chauffage avec un mélange d'acide chlorhydrique et d'alcool. PERRIN et al [6] extraient également les métaux par un traitement acide, séparent la matière grasse après fusion, puis éliminent par filtration les protéines précipitées par l'acide trichlOracétique ou l'acide tungstique. La minéralisation par voie humide et l'extraction acide leur ont donné des résultats très voisins, sauf dans le cas du lait pour lequel ils donnent la préférence à la première méthode.'…”

Section D. Nutritive value of milk and milk products

“…Methods for the determination of iron in milk or cream are given in (250,251,252,253); that described in (251) is for the determination of both iron and copper in the one sample. Feuillen & Plumier (254) quote a value of 45^.g./100 ml.…”

“…Methods for the determination of copper in milk and milk products are given in (251,252,253,264,265); a micro-method for the detection of copper in foods, including milk, will be found in (266). Papers (267,268) confirm that the copper content of milk is not influenced by the feed of the cow.…”

“…Values for the calcium and phosphorus content of whey obtained at different stages in the manufacture of Cheddar and Stilton cheese are included in (441). Values for the iron and copper content of whey cream are given in (251).…”