Flame‐made Calcium Phosphate/Carbonate Nanopowders for Nutrition

Background Nanostructured calcium phosphate (CaP) and carbonate (CaCO 3 ) powders may be well absorbed in humans because of their high specific surface area (SSA). The material properties of these powders (size, crystallinity, and phase composition) are likely predictors of their calcium solubility and bioavailability. Objective: To understand how process parameters affect the material properties and size stability of CaP/CaCO 3 nanopowders. Methods: Nanosized CaP/CaCO 3 powders were produced using flame‐assisted spray pyrolysis (FASP) and characterized by X‐ray diffraction (XRD), SSA, Raman spectroscopy, and transmission electron microscopy (TEM). Results: Particle size and carbonate content of CaCO 3 ‐containing powders can be controlled by changing process parameters resulting in SSA values of 40‐100 m 2 /g. Aging such powders under ambient conditions resulted in an increase in crystal size and decrease in SSA. Doping with Mg or P stabilized the small CaCO 3 particle size. In CaP nanopowders, at Ca:P 蠄 1.5 the powders were XRD amorphous, and Raman analysis confirmed the presence of calcium pyrophosphate with increasing contents of stable hydroxyapatite at higher Ca:P ratios. Powders with 1.5 蠄 Ca:P 蠄 2.33 contained mainly hydroxyapatite which is undesired for its high stability and low solubility. Aging of powders with Ca:P = 1.0 and 1.5 resulted in a gradual increase in particle size but this effect was significantly less than for CaCO 3 . Conclusions FASP‐produced nanosized CaCO 3 powders containing Mg or P to stabilize their high SSA, and nanosized CaP powders at Ca:P 蠄 1.5 may be promising new compounds to deliver highly bioavailable calcium for food and nutrition applications.