WHAT IS IT?
Potassium sorbate is a food grade preservative generally regarded as safe (GRAS) worldwide. It is the inactive salt of sorbic acid. It readily dissolves in water where it converts to sorbic acid, its active form, at a low pH. Sorbic acid is very pH dependent. While it shows some activity up to pH 6 (about 6%), it is most active at pH 4.4 (70%). At pH 5.0 it is 37% active. As sorbic acid, it is considered to be active against mold, fair against yeast and poor against most bacteria. Sorbic acid is an unsaturated fatty acid and as such is subject to oxidation (use of an antioxidant like Mixed Tocopherols T50 is recommended). It is also sensitive to UV light and may turn yellow in solution. Gluconolactone is reported to stabilize potassium sorbate against discoloration and darkening inaqueous solutions and may be useful in stabilizing sorbic acid in the water phase of a product.
While sorbic acid is naturally occurring in some fruits (like the berries of the mountain ash), virtually all of the world's production of sorbic acid, from which potassium sorbate is derived, is manufactured synthetically, and is a nature-identical compound chemically equivalent to the molecule found in nature.