INTERACTIONS BETWEEN MILK PROTEINS AND CALCIUM PHOSPHATE PARTICLES IN A MILK SYSTEM

Calcium fortification is a growing trend in the food industry, especially for dairy products. Calcium phosphate particles are often used in calcium-fortified milks, as they do not cause any heat instability, unlike soluble calcium salts [1] and they are generally believed not to interact with other milk components. However, it is well-known that proteins bind strongly to calcium phosphate materials, and this has been exploited in techniques such as hydroxyapatite chromatography [2]. It is therefore logical to expect some binding of milk proteins to calcium phosphate particles in a calcium-fortified milk system.

Binding studies, confocal microscopy and zeta-potential measurements showed that both caseins and whey proteins from commercial milk ingredients bound to food-grade hydroxyapatite (HA) micro-particles, resulting in an increase in the zeta-potential of the particles and a decrease in their sedimentation rate in water [3]. The adsorbed protein layer is believed to provide combined steric and electrostatic stabilisation, which is necessary to prevent aggregation and sedimentation of the particles.

The effects of ionic strength, pH and milk serum composition on the adsorption of the milk proteins onto the HA particles have also been investigated and the interactions between milk proteins and HA under different physico-chemical conditions will be discussed in relation to the structure and the surface properties of both.

This work could be of interest for optimizing the stability of the particles when suspended in a calcium-fortified milk product. The results of this study also demonstrate the potential to modify the surface of nano or micro-sized calcium phosphate particles, which may be useful in the design of food products with improved stability and functional properties.

 

 

[1] M.J. Lewis, Int. J. Dairy Technol. 64 (2011) 1.

[2] Q. Luo, J.D. Andrade, J. Colloid Interface Sci. 200 (1998) 104.

[3] L. Tercinier, A. Ye, S.G. Anema, A. Singh. H. Singh, J. Colloid Interface Sci. 394 (2013) 458.