Precipitation of Calcium Phosphate from Simulated Milk Ultrafiltrate Solutions

Abstract

The present work deals with the influence of pH and temperature on the spontaneous precipitation of calcium phosphate from simulated milk ultrafiltrate (SMUF) solutions. The pH range investigated is 5.7-7.0, and the temperature varied from 55 to 75 °C. It was found that the precipitates were prisms of hydroxyapatite (HAP) with low crystallinity preceded by amorphous calcium phosphate (ACP). Crystallinity improved with solution aging. Microscopic particles in the range of 200 nm were obtained at relatively high supersaturation (pH ) 6.8), whereas at relatively low supersaturation (pH ) 6.0), aggregates in the range of 1 µm were formed. Moreover, it was found that although the SMUF solution is also supersaturated with respect to magnesium phosphate, no magnesium salt was identified in the precipitates, thus precluding the coprecipitation of magnesium phosphate. At the same temperature, the supersaturation was regulated by adjusting the solution pH. Kinetics study of precipitation showed a parabolic dependence of the (initial) rates on the solution supersaturation, suggesting a surface diffusion-controlled mechanism with activation energy equal to 96 kJ mol -1 . The rates of precipitation were significantly reduced in the presence of citrate ions due to the decrease of the solution supersaturation caused by complexation of citrates with Ca 2+ ions. Additionally, a decreasing effect of citrates on the precipitation rate resulted from the adsorption of these species on the formed crystals, blocking some active sites of crystal growth and diminishing the constant of precipitation rate.

Stability of milk-derived calcium phosphate suspensions

“…At the natural pH of milk, this calcium and phosphate is distributed between the colloidal (casein micelles) and soluble phases of the milk. It is possible to isolate the calcium phosphate from milk as an insoluble calcium phosphate material from acidic whey solutions, cheese whey or milk/whey permeate [7,16]. The pH reduction of milk to 4.6 will completely solubilize the calcium phosphate [4] and will precipitate the casein [17] leaving a whey solution containing all the milk minerals as well as the lactose and the whey proteins.…”

“…ACP can transform by a process of redissolving and reprecipitation to semicrystalline solids such as DCPD and octacalcium phosphate (OCP), depending on the pH. The DCPD and OCP gradually take on the characteristics of HAP [14,16]. Further characterization of the various phosphates could be made by obtaining 31 P NMR spectra.…”

“…Most calcium additives are from non-food-derived sources such as calcium carbonates or calcium phosphates. A few reports have indicated that it is possible to isolate calcium phosphate from dairy streams, such as cheese whey or milk permeate, and that these could be considered a natural food-derived source for calcium phosphate [7,16]. A richer source of milk-derived calcium phosphate (MDCP) would be whey derived from acid casein or cottage cheese manufacture, as the calcium phosphate in milk is completely solubilized at the pH used in the manufacture of these products [4].…”

Calcium orthophosphates (CaPO 4 ): Occurrence and properties

“…Other popular physiological solutions comprise Hanks' balanced salt solution (HBSS), which contains almost similar inorganic salts and glucose (Hanks and Wallace 1949;Shibata et al 2004;Marques et al 2003a;Mareci et al 2010), Eagle's minimum essential medium (MEM) and its variation Dulbecco's modified Eagle's medium (DMEM), which contain numerous bioorganic (alanine, aspartic acid, glycine, biotin, vitamin C, folic acid, riboflavin) and inorganic (CaCl 2 , KCl, NaCl, NaH 2 PO 4 ) components (Meuleman et al 2006;Touny et al 2011;Coelho et al 2000;Mandel and Tas 2010;Rohanová et al 2014), phosphate-buffered saline (PBS) that contains only inorganic (CaCl 2 , MgCl 2 , KCl, KH 2 PO 4 , NaCl, NaH 2 PO 4 ) components (Gao et al 2006;Lichtenauer et al 2011). Furthermore, artificial saliva Ionta et al 2014;Okulus et al 2014), synthetic urine (Assimos 2013Dbira et al 2015) and simulated milk ultrafiltrate (SMUF) (Jenness and Koops 1962;Spanos et al 2007;Gao et al 2010a, b) solutions are available. They contain both bioorganic (e.g., xanthan gum or sodium carboxymethylcellulose, sorbitol, etc.)…”

Biomimetic hydroxyapatite particulate nanofiber modified silicon: In vitro bioactivity

“…Also, this phenomenon is favored by complexation between Ca 2þ and acetate ions in solid-state reactions, because in wet chemistry, the rate of precipitation reduces efficiently due to the complexation and hence decreases the solution supersaturation and the adsorption of ions on the surface of the initially formed crystal nuclei, thereby blocking the growth-active centers. 24 Because Figure 1. X-ray diffraction patterns of Si-HA matrix.…”