An increase in the use of additives, such as potassium sorbate, as food preservatives has raised concerns about the side effects they might have. This situation has led many countries to place rigid controls on the use of additives. In the United States potassium sorbate is coded as generally recognised as safe (GRAS). Other countries, though, have set tolerance levels on the amount of potassium sorbate permitted in food. For instance, the Korean Food Additives Code sets strict controls on the levels of potassium sorbate in cheese, meat products, and margarine. The need to enforce such controls has led to the creation of accurate, fast, and reliable testing methods.
Potassium sorbate can be identified by testing the effect of a bromine solution. To identify a potassium sorbate solution, add 1 millilitre of acetone, diluted hydrochloric acid, and 2 drops of bromine solution. Shake the solution. If the initial solution contained potassium sorbate, the colour of the solution will disappear immediately.
Testing methods for potassium sorbate in foods with high contents of sugars and other compounds that mask its presence can be difficult when using conventional tests. This is the problem, for example, with dried prunes. In this case laboratories can prepare an extract from the prunes and take readings directly with a UV instrument. The UV levels read by the instrument provide information about the concentration levels of potassium sorbate used on the prunes.
Potassium sorbate is used as a preservative in sweet wines because it inhibits the growth of yeasts. Not all wines need potassium sorbate, though; it all depends on the sugar levels present in the wine. You can test your wine by using a hydrometer, a device that measures the density of fluids. If the hydrometer shows levels below -1.5 degrees, then your wine is safe to bottle without potassium sorbate.