Codissolution of calcium hydrogenphosphate and sodium hydrogencitrate in water. Spontaneous supersaturation of calcium citrate increasing calcium bioavailability

Abstract

The sparingly soluble calcium hydrogenphosphate dihydrate, co-dissolving in water during dissolution of freely soluble sodium hydrogencitrate sesquihydrate as caused by proton transfer from hydrogencitrate to hydrogenphosphate, was found to form homogenous solutions supersaturated by a factor up to 8 in calcium citrate tetrahydrate. A critical hydrogencitrate concentration for formation of homogeneous solutions was found to depend linearly on dissolved calcium hydrogenphosphate: [HCitr] = 14[CaHPO] - 0.05 at 25 °C. The lag phase for precipitation of calcium citrate tetrahydrate, as identified from FT-IR spectra, from these spontaneously formed supersaturated solutions was several hours, and the time to reach solubility equilibrium was several days. Initial calcium ion activity was found to be almost independent of the degree of supersaturation as determined electrochemically. The supersaturated solutions had a pH around 4.7, and calcium binding to hydrogencitrate as the dominant citrate species during precipitation was found to be exothermic with a determined association constant of 357 L mol at 25 °C for unit ionic strength, and ΔH° = -22 ± 2 kJ mol, ΔS° = -26 ± 8 J K mol. Calcium binding to hydrogencitrate and, more importantly, to citrate is suggested to decrease the rate of precipitation by lowering the driving force of precipitation, and becoming important for the robust spontaneous supersaturation with perspectives for design of functional foods with increased calcium bioavailability.

Preparation of Al2O3@CaCO3 aggregates and its effects on the thermal shock resistance of Al2O3‐MgO castables

“…The results show that the degree of agglomeration of CaCO 3 increases as the concentration of Ca 2+ in the solution increasing owing to the increasement of the amount of carboxyl functional groups (‐COOH) adsorbed on the surface of Ca 2+ increases. Furthermore, the viscosity of the solution increases, the adsorption of Ca 2+ and carboxyl functional groups are enhanced, thus, it is prone to agglomerate 31,32 …”

“…Furthermore, the viscosity of the solution increases, the adsorption of Ca 2+ and carboxyl functional groups are enhanced, thus, it is prone to agglomerate. 31,32 According to Table 3, the water absorption rates primordially decreased and finally increased. Meanwhile, the mass change rates (∆m) of the Al 2 O 3 @CaCO 3 aggregates increased with the concentration of Ca 2+ increases gradually.…”

Influence of Pulsed Electric Field on Accumulation of Calcium in Lactobacillus rhamnosus B 442

“…in the contraction of skeletal, smooth and heart muscles, and the conduction of nerve impulses and blood clotting [ 1 ]. Osteoporosis, caused by the lack of calcium absorption irrespective of age, afflicts 75 million people worldwide [ 2 ].…”

Novos ingredientes alimentícios a base de proteína e peptídeos aplicados a cor de carnes e biodisponibilidade de íons de cálcio

“…O decaimento na concentração dos íons de Ca 2+ livres é acompanhado pelo decaimento na concentração do Ca 2+ total em solução. Este decaimento indica a precipitação do cálcio, possivelmente na forma de citrato de cálcio, conforme reportado na literatura (VAVRUSOVA et al, 2018).…”