Interactions des protéines du lait et des oligoélémentsG. BRULÉ and J. FAUQUANT
Institut National de la Recherche Agronomique, Laboratoire de Recherches de Technologie Laitière, 65, rue de Saint-Brieuc - 35042 Rennes cedex
Abstract - Repartition of trace elements (Cu, Fe, Zn, and Mn) in milk between casein, whey proteins and non protein fraction was investigated. Casein bound about 95 % of manganese and zinc and 50-75 % of copper and iron; 15 to 33 % of copper and iron were present in non protein fraction and 18 to 33 % of iron in whey proteins fraction.
Addition of trace elements in milk modified the repartition especially for copper and manganese. Affinity of cas αs1 and of cas β for copper and iron compared to affinity for calcium and magnesium and competition between calcium and iron for chelation of casein suggested that phosphoserine groups are element binding sites. Effect of orotical and citrate concentration on the repartition of trace element was studied. Citrate increased concentration of iron, manganese and copper in non protein fraction. Orotic acid only increased the copper content. The high degree of affinity of phosphoproteins. for trace element suggested to use phosphopeptides as chelators
Key words: Milk / Trace element / Casein / Orotic acid / Citrate / Zinc / Copper / Manganese / Iron / Calcium