Removal of Listeria spp. in a cheese factory

A total of 311 samples of 10 mt for liquids and 400-cm(2) for surfaces were analyzed in a cheese plant in Galicia (Spain) within a period of 10 months (Feb. Nov. 1996). Forty-six samples were positive for Listeria spp., 36 of which corresponded to L. innocua, 8 to L, monocytogenes and 2 to L, welshimeri. Twenty percent of raw milk samples were Listeria-positive. Listeria was initially detected on some surfaces of production and ripening rooms, but was never detected after replacing old iron machinery with stainless steel machinery, avoiding the movement of the plant equipment outside the factory building, eliminating wooden boards in the ripening chambers and modifying the disinfection system.