Inhibitory action of potassium sorbate degradation products against Staphylococcus aureus growth in laboratory media

The inhibitory action of potassium sorbate (KS) degradation products against Staphylococcus aureus growth was examined in model aqueous systems. KS degradation products formation was induced by the storage at 70 degrees C for 7 days or at 37 degrees C for 90 days of aqueous systems containing basically brain heart infusion, yeast extract and different amounts of KS at pH 5.5. After storage, residual amounts of KS were measured and each system was inoculated with a pool of three S. aureus strains at 10(4) colony forming units/ml. Degradation products from KS generally inhibited S. aureus growth by two to three log cycles. However, the population of S. aureus reached a higher level when the degradation products were formed at 37 degrees C suggesting that the nature of the degradation products seemed to depend on the temperature at which they were produced. The inhibitory activity produced by KS degradation products along with residual amounts of KS was smaller than the one produced by the initial amounts of the preservative.