Effects of Potassium Sorbate on Growth and Ochratoxin Production by Aspergillus ochraceus and Penicillium Species1,2

Effects of potassium sorbate on growth and ochratoxin production by Aspergillus ochraceus NRRL 3174 and Penicillium sp. isolated from cheese were studied. Potassium sorbate at 0.05, 0.10 and 0.15% delayed or prevented spore germination and initiation of growth, and decreased the rate of growth of both organisms in yeast-extract sucrose (YES) broth at 12°C. However, at 25°C germination and growth of A. ochraceus was more rapid. Increasing concentrations of sorbate caused more variation in the amount of total mycelial growth of Penicillium sp. and generally resulted in a decrease in total mycelial mass. Potassium sorbate also greatly reduced or prevented production of ochratoxin by Penicillium sp. for up to 70 d at 12°C. At 0.05 and 0.10% sorbate, ochratoxin production was greatly reduced over the control, and was eliminated at 0.15%. Overall, ochratoxin production by Penicillium sp. in the presence of sorbate was very low or eliminated. On the other hand, A. ochraceus responded somewhat differently to sorbate. At 12°C, A. ochraceus was similarly inhibited by all three levels of sorbate, and did not produce ochratoxin. When incubated at 25°C, A. ochraceus grew quite readily and appeared to produce greater amounts of ochratoxin in the presence of sorbate, especially at the 0.05% level. Considerably higher levels of ochratoxin were produced at 0.05% sorbate than the control, and somewhat higher levels were obtained at 0.10 and 0.15% sorbate.