Folate-binding protein in milk: a review of biochemistry, physiology, and analytical methods

Folate-binding protein (FBP) was discovered in cow's milk around 40 years ago. Bovine FBP belongs to a family of several folate-binding proteins. In milk, it is a soluble whey protein with the ability to sequester folate from blood plasma. Bovine FBP is a well-characterized protein in terms of amino acid sequence and binding characteristics. Affinity and binding kinetics towards various folate forms have been intensively studied because they are crucial in using bovine FBP as an analytical tool. Shortly after the identification of bovine FBP, a competitive protein-binding assay for measuring serum and blood folate concentrations was introduced. Another analytical application of bovine FBP is in affinity chromatography, as a clean-up/concentration step for analysis of folates in foods and biological samples by liquid chromatographic methods. Concentrations of FBP in milk and dairy products have been determined by ELISA and Surface Plasmon Resonance-biosensor techniques. Since the initial reports of FBP in cow's milk, its physiological role has been discussed, especially regarding its effects on folate absorption from milk and dairy products. This review summarizes recent biochemical, analytical, food science, and nutritional advances regarding folate-binding protein in milk.