Calcium citrate is an intermediate in the isolation of citric acid from the fermentation process by which citric acid is produced industrially.The citric acid in the broth solution is neutralized by calcium hydroxide, precipitating insoluble calcium citrate. This is then filtered off from the rest of the broth and washed to give clean calcium citrate.
3Ca(OH)2(s) + 2C6H8O7(l) → Ca3(C6H5O7)2(s) + 3H2O(l)
The calcium citrate thus produced may be sold as-is, or it may be converted to citric acid using dilute sulfuric acid.