Fate of Escherichia coli O157:H7 during the manufacture of Mozzarella cheese

Aims: The fate of Escherichia coli O157:H7 was investigated during the manufacture of Mozzarella cheese. Methods and Results: The Mozzarella cheese was made from unpasteurized milk which was inoculated to contain ca 10(5) cfu ml(-1) E. coli O157:H7. Two different heating temperatures (70 and 80degreesC), commonly used during curd stretching, were investigated to determine their effects on the viability of E. coli O157:H7 in Mozzarella cheese. Stretching at 80degreesC for 5 min resulted in the loss of culturability of E. coli O157:H7 strains, whereas stretching at 70degreesC reduced the number of culturable E. coli O157:H7 by a factor of 10. Conclusions: The results show that stretching curd at 80degreesC for 5 min is effective in controlling E. coli O157:H7 during the production of Mozzarella cheese. Brining and storage at 4degreesC for 12 h was less effective than the stretching. Significance and Impact of the Study: Mozzarella cheese should be free of E. coli O157:H7 only if temperatures higher than or equal to 80degreesC are used during milk processing.