Survival and growth of Yersinia enterocolitica strains inoculated in skimmed milk treated with high hydrostatic pressure.

ABSTRACT

Four human pathogenic strains of Yersinia enterocolitica (serotypes O1, O3, O8, and O9) were inoculated (7-8 log CFU/ml) in UHT skimmed milk and treated at 300, 400, and 500 MPa for 10 min at 20 degrees C, and then kept at 8 degrees C to assess their evolution for 15 days. Treatments at 400 and 500 MPa caused the highest lethality, generally reaching counts below detection level (1 CFU/ml) in the culture media. At 300 MPa, the most baroresistant serotypes were O3 and O8. After 15 days of storage at 8 degrees C, Y. enterocolitica showed growth over 8 log (CFU/ml) in all treatments. Kinetic study of microbial inactivation in skimmed milk was performed with serotype O8 at 300 MPa, showing a tailing after 35 min of pressure treatment.