Minerals: protein interactions

Protein – mineral interactions in dairy drinks

PhD-fellow: Ir. E.J.P. de Kort, MSc (Esther)

Prof. Dr. Ir. A.C.M. van Hooijdonk
Prof. E. van der Linden

Project term: January 2007 - January 2011

Sponsor: Danone


Clinical nutrition contains milk components such as protein, fat, carbohydrates, minerals and vitamins. However, clinical nutrition is more concentrated in these components than normal milk. The minerals and caseins in the system are in dynamic equilibrium with the micellar and serum phase and the partitioning of these constituents in both phases is mainly influenced by temperature, pH, mineral concentrations and calcium chelating agents. In this way the ions play an important role on the structure, stability, hydrodynamic volume and sensory properties of casein micelles. In order to produce even more concentrated clinical nutrition, which retains its heat stability, further investigation in the protein-mineral interaction mechanisms is needed. The behaviour of colloidal calcium phosphate and the effect of mono- and divalent ions on casein micelles in skimmed milk systems has been studied extensively. These mono- and divalent ions are all anorganic minerals, while in baby and clinical nutrition also organic phosphates are used. Therefore, in this research project interaction of organic phosphates with calcium and caseins will be studied.


The general aim of this project is to obtain a better understanding of the interaction of minerals with calcium and casein proteins for the development of (concentrated) dairy products with respect to heat stability and shelf life.

The main aim can be divided into four sub aims:

1. Study and unravel the physical/chemical interactions of organic and anorganic phosphates with calcium and casein proteins.
2. Study the effect of varying ionic environments on the hydrodynamic volume of casein proteins.
3. Develop, with the obtained protein-mineral interaction knowledge, compact protein particles for concentrated dairy products.
4. Relate the physico-chemical properties of the casein micelles to the sensory perception of dairy products.


The first part of the research will focus on the interaction of calcium and casein (caseinate and micellar casein isolate) with organic and anorganic phosphates. We have selected two organic phosphates, namely disodium uridine monophosphate (Na2UMP) and inositol hexaphosphate (= phytate, Na12C6H6O2P6), and two anorganic phosphates, namely disodium phosphate (Na2HPO4) and sodium hexametaphosphate ((NaPO3)6). In this way we can compare the behaviour of orthophosphates and polyphosphates originated from organic and anorganic origin. The interactions of these phosphates with calcium and caseins will be analysed in model systems with or without proteins and/or simulated milk ultrafiltrate. Micellar casein isolate and calcium caseinate will be used as protein sources for this research.
The second part of the research will focus on the effect of these minerals (phosphates, citrate, SMUF) on the hydrodynamic volume of caseinate and micellar caseinate by varying the ionic environment in the model systems. With the obtained knowledge on the protein-mineral interactions we can produce compact or loose protein particles. Consequently, we can obtain dairy products with low and high viscosities and also with short or long textures, respectively. In the final part of this research we would like to link the physico-chemical properties of the casein micelles to the sensory perception of dairy products.