Disclosed is a hydroxycitric acid salt composition comprising a mixture of calcium and potassium salts of hydroxycitric acid, preferably in a defined proportion. The HCA salts are prepared by a process that includes treating an aqueous extract of Garcinia cambogia or Garcinia indica fruit with a liquid quaternizing agent such as a trialkylamine in which the alkyl groups are octyl, caprylyl, isooctyl, lauryl or decyl. The process yields a very pure, stabilized mixed salt composition that is free of potentially toxic chemical residues, and is substantially tasteless for optimal use in a variety of foods, beverages and dietary supplements.