Binding added iron to various milk proteins

Area of Science:

• Dairy Science
• Biochemistry
• Radiochemistry

Background:

• Understanding radionuclide binding in milk is crucial for food safety and nuclear medicine.
• Cow's milk contains various protein fractions, including casein and whey proteins, with different binding capacities.

Purpose of the Study:

• To determine the binding of Iron-59 to specific milk protein components.
• To quantify the association of Iron-59 with different casein fractions (alpha-, beta-, kappa-casein).

Main Methods:

• Cow's milk was fractionated using Sephadex G-150 gel filtration and diethylaminoethyl-cellulose chromatography.
• Iron-59 labeled ferric chloride was added to raw whole milk.
• Chromatographic separation identified casein, whey protein, and nonprotein fractions.
• Further chromatography resolved casein into its alpha-, beta-, and kappa-components.

Main Results:

• Casein proteins bound approximately 85% of the added Iron-59 in skim milk.
• Within the casein fraction, alpha-casein associated with 72% of the bound iron.
• Beta-casein accounted for 21% and kappa-casein for 4% of the bound iron.

Conclusions:

• Casein is the primary milk protein fraction responsible for binding added Iron-59.
• Alpha-casein exhibits the highest affinity for Iron-59 among the identified casein components.