The fate of Listeria monocytogenes in brine and on Gouda cheese following artificial contamination during brining

Abstract

The fate of 3 different Listeria monocytogenes strains (Scott A, 2F and 6E) was studied independently in brine and on factory-scale Gouda cheeses that had been submerged in brine that was artificially contaminated with these individual strains. Viable numbers of L. monocytogenes in the brine decreased during brining (0, 1, 2.9 and 8.9 d). L. monocytogenes was enumerated on the surface of Gouda cheese directly after brining and over 26 weeks of ripening at 12.5 °C. Transfer of L. monocytogenes from brine to cheese during brining was limited. L. monocytogenes was detected in the outer layer of Gouda cheese but not in the centre directly after brining or during ripening. Throughout the ripening period, the viable numbers of L. monocytogenes declined significantly. This study adds to the understanding of the fate of L. monocytogenes in brine and on Gouda cheese, and demonstrates that growth of L. monocytogenes on Gouda cheese is not supported following contamination during brining.