1,2,3-Propanetricarboxylic acid, 2-hydroxy-, calcium salt → Tricalcium Citrate

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Reaction Steps

The amorphous water-soluble calcium citrate salts of this invention are prepared by reacting a calcium compound with citric acid in an aqueous medium to produce calcium citrate having a calcium to citrate mole ratio of less than 2.5:2. The resulting reaction mixture is then quickly dried (or quickly frozen for drying at a later time) in order to separate and isolate amorphous calcium citrate as a dry powder. It is important that the amorphous water-soluble calcium citrate reaction salt is recovered from the aqueous reaction mixture as a dry amorphous material before it can be transformed into insoluble crystalline tricalcium citrate (TCC) or other water-insoluble calcium citrate salts. As shown in the examples below, both the condition of providing a calcium:citrate mole ratio of less than 2.5:2, and the condition of drying the reaction mixture soon enough after the salt-producing reaction, as detailed herein, to avoid reaction product transformation into water-insoluble calcium citrate salts, are important to ensure that the solid calcium citrate reaction product is recovered in an amorphous state. Preferably rapid drying techniques are also used to minimize the opportunity for crystallization of the reaction product during the drying operation. Suitable rapid drying techniques include, for example, freeze drying and spray drying.

Provenance & Evidence