Combined action of nisin and carvacrol on Bacillus cereus and Listeria monocytogenes

Nisin, a small antimicrobial protein, was tested for its bactericidal actio n against Listeria monocytogenes and Bacillus cereals and a typical biphasi c reduction of the viable count was observed. The reduction was most fast d uring the first 10 min of exposure, while the viable count remained stable in the last part of the exposure period. Bacillus cereus was more sensitive towards nisin than L. monocytogenes and the inhibitory effect of nisin was stronger towards cells cultivated and exposed at 8 degrees C than towards cells cultivated and exposed at 20 degrees C. Combining nisin with subletha l doses of carvacrol resulted in an increased reduction in the viable count of both organisms, indicating synergy between nisin and carvacrol. Additio n of lysozyme as a third preservative factor increased the synergistic effe ct between nisin and carvone, especially in the last part of the exposure p eriod.