Physico-chemical characterization of dairy calcium phosphate industrial powders

Dairy industry recovers calcium phosphates from dairy liquids by different technologies and proposes this mineralized ingredient (under powder forms) for several applications especially for the enrichment of different food products in calcium. The objective of this study was to characterize chemically and physically 6 calcium phosphate powders coming from different international industries. All powders were rich in minerals with important quantitative variations in calcium phosphate contents depending on the powder origin. Among the powders, two were different from others because they contained less minerals and were richer in proteins (about 10% of dry matter) identified as whey proteins and lactose (about 60% of dry matter). The chemical characterization of calcium phosphate indicated that the mass ratio calcium/phosphate was closed to 0.6-0.7, except for the two powders which have higher or smaller ratios than 0.6-0.7. The profiles of dry particles size determined by laser granulometry and electron microscopy indicated also differences between powders: their sizes varied between less than one μm to several hundred μm. These size differences were attributed to a step of micronisation during the manufacture of some powders. Analyses by infrared spectroscopy (IR) and X-Ray diffraction (XRD) revealed that the precipitated calcium phosphate is a very poorly crystallized calciumdeficient apatite presenting typical PO4 vibrational bands in IR but no sharp diffraction peak. After the reconstitution of powders in water, all suspensions were at neutral pH and their zeta potentials (surface charge) were always negative (between -15 and -20mV). All these variations of physico-chemical properties between powders will be discussed to understand their functionalities with a special attention paid on their solubilities in different solutions.