Sensitivity of Staphylococcus aureus and Lactobacillus helveticus in ovine milk subjected to high hydrostatic pressure

R. Gervilla, E. Sendra, V. Ferragut, B. Guamis

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    Abstract

    Ovine milk, standardized to 6% fat, was inoculated with Staphylococcus aureus CECT 534 and Lactobacillus helveticus CECT 414 at a concentration of 107 cfu/ml and treated by high hydrostatic pressure. Treatments consisted of combinations of pressure (200, 300, 400, 450, and 500 MPa), temperature (2, 10, 25, and 50°C), and time (5, 10, and 15 min). Staphylococcus aureus was highly resistant to pressure; only pressurizations at 50°C of 500 MPa for 15 min achieved reductions of ≥7.3 log units. For L. helveticus, the number of surviving cells was reduced considerably at pressures of 400 MPa or more (up to 4.5 log units at 50°C for 15 min), and pressure was more effective at low (2 and 10°C) and moderately high (50°C) temperatures than at room temperature (25°C). Both species showed first-order kinetics of destruction in the range 0 to 60 min. The D values for S. aureus were 20 min (2°C at 450 MPa) and 16.7 min (25°C at 450 MPa), and D values for L. helveticus were 7.1 min (2°C at 450 MPa) and 9.1 min (25°C at 450 MPa). Lactobacillus helveticus showed higher rates of survival of pressure than those reported in previous studies for other Lactobacillus spp.
    Original languageEnglish
    Pages (from-to)1099-1107
    JournalJournal of Dairy Science
    Volume82
    DOIs
    Publication statusPublished - 1 Jan 1999

    Keywords

    • High hydrostatic pressure
    • Lactobacillus helveticus
    • Ovine milk
    • Staphylococcus aureus

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