Sorbic acid and it's mineral salts, Sodium sorbate (201), Potassium sorbate (202) and Calcium sorbate (203) are naturally derived from the berries of the Mountain-ash tree (Sorbus aucuparia). They are commercially produced in varying chemical pathways to produce a white crystalline powder that is used as a preservative to inhibit the growth of moulds, yeasts and fungi. It is not effective against bacteria. It's optimal pH values are below 6.5. The main differences between the salts is their varying solubility in water, and they are preferred over Sorbic acid itself. This is why some salts are used in different products, especially Calcium sorbate used mainly in dairy products and rye bread.http://www.creative-enzymes.com/product/Calcium-Sorbate_715.html