Improving calcium citrate food functions through spherulitic growth in reactive crystallization and a mechanism study

Calcium citrate, a high-end daily calcium supplement, whose irregular particle morphology leads to poor powder properties, limited food functions, and paste-like suspension problems. This study prepared the spherical calcium citrate by investigating four aspects of this reactive process: side reaction, crystallization, agglomeration, and fragmentation. Consequently, a concentration-dependent spherulitic growth operating space was established, in which reactive crystallization followed the second-category spherulitic growth mechanism depending on supersaturation. Besides, the temperature, stirring rate, and residence time were critical parameters for regulating the spherulite shape and size. These spherulites exhibited improved flowability and tabletability as calcium fortification ingredient, it also had a smoother and more pleasant texture. Furthermore, the micronized spherical powder showed high suspension stability as a calcium supplement during brewing. These spherical particles did not form paste-like suspension. Finally, the success of the scale-up experiments in semi-batch mode raised the possibility of industrialization of spherical calcium citrate.