Sorbic Acid and Sorbates

Sorbic acid (2,4-hexadienoic acid) and its salt, sorbate, have been used in the preservation of food products since the 1940s. While it can be isolated naturally from rowanberries (mountain ash tree), that used in foods is chemically synthesized. Sorbates have regulatory approval throughout the globe for application as antimicrobial preservatives for foods, animal feeds, pharmaceuticals, and cosmetics. Sorbate has efficacy against many bacteria, molds, and yeasts but has historically been used primarily as an antifungal agent in foods. Because it is a weak acid (pKa = 4.76) and the most effective antimicrobial form is the undissociated acid, sorbate activity is greatest at lower pH. Thus it is more consistently effective as an antimicrobial in foods with pH < 5.0–5.5. While it is inhibitory to most molds, some, including species of Penicillium, Aspergillus, Fusarium, Mucor, and Geotrichum, have the ability to metabolize sorbates and produce off-odors. Subjects covered in this chapter include the chemical and physical characteristics of sorbates, their antimicrobial activity spectrum (including interactions with food components, degradation, and mechanisms of action), application of the compounds to dairy, vegetable, fruit, bakery, meat, and other miscellaneous products, safety and toxicology of the compounds, detection and analysis methods, and regulatory status.