Degradation of Potassium Sorbate by Penicillium Species

Abstract

Molds were isolated from natural and processed Cheddar cheese previously treated with potassium sorbate. When grown on potato dextrose agar fortified with up to 8,400 ppm potassium sorbate and adjusted to pH 5.3 to 5.5, Penicillium roqueforti, a mutant of P. roqueforti, Penicillium notatum, Penicillium frequentans, and Penicillium cyaneofulvum (all recovered from cheese), were able to grow in the presence of up to 5,400, 7,100, 2,300, 2,800, and 1,800 ppm potassium sorbate, respectively. All of the penicillia studied depleted sorbate from liquid culture media; highest concentrations were degraded by P. roqueforti and its mutant. Depletion of sorbate from the medium was enhanced by a highly nutritious substrate and retarded by a minimal growth medium. Degradation of sorbate was accompanied by formation of a volatile compound with a hydrocarbon-like odor. This substance was identified as 1,3-pentadiene by means of gas chromatographic and infrared analyses. It is believed that the molds degrade sorbate into an inactive material through decarboxylation.