Sorbic Acid - Properties and Uses

Properties and Uses

With a pKa of 4.76, it is about as acidic as acetic acid.

Sorbic acid and its salts, such as sodium sorbate, potassium sorbate, and calcium sorbate, are antimicrobial agents often used as preservatives in food and drinks to prevent the growth of mold, yeast, and fungi. In general the salts are preferred over the acid form because they are more soluble in water, but it is the acid form that is active. The optimal pH for the antimicrobial activity is below pH 6.5. Sorbates are generally used at concentrations of 0.025% to 0.10%. Adding sorbate salts to food will, however, raise the pH of the food slightly so the pH may need to be adjusted to assure safety. It is found in many other foods, such as cheeses and breads.

The E numbers are:

• E200 Sorbic acid
• E201 Sodium sorbate
• E202 Potassium sorbate
• E203 Calcium sorbate

Some molds (notably some Trichoderma and Penicillium strains) and yeasts are able to detoxify sorbates by decarboxylation, producing trans-1,3-pentadiene. The pentadiene manifests as a typical odor of kerosene or petroleum. Other detoxification reactions include reduction to 4-hexenol and 4-hexenoic acid.