Characterization and behavior of salmonella Javiana during manufacture of mozzarella-type cheese

A patient isolate of Salmonella javiana implicated in an outbreak of salmonellosis in Minnesota was characterized and used to examine its response to Mozzarella manufacturing conditions. The strain possessed biochemical-metabolic activities typical of Salmonella species. Growth was observed in 6.5% NaCl Trypticase Soy Broth (TSB) but not in 12% NaCl TSB. This S. javiana strain was resistant to two antibiotics, penicillin G and erythromycin. Pasteurization trials indicated the strain did not survive pasteurization and that pasteurization affected a log reduction of greater than 9 cycles. Mozzarella-type cheese was manufactured from milk inoculated with S. javiana at levels of 1 × 10⁴ and 1 × 10⁶ per ml milk. Manufacturing process was monitored by following pH, titratable acidity, and temperature. Survival of S. javiana was monitored using traditional enrichment procedures and direct plating procedures. S. javiana survived and grew through the acid-ripening phase, but temperatures attained in cheese mass during stretching and molding (60°C, 140°F) killed all Salmonella present. No subsequent process steps were found positive for Salmonella.