Antimicrobial Effect of Pressurized Carbon Dioxide onStaphylococcus aureusin Broth and Milk

Abstract

Studies were carried out to assess the use of high pressure CO2treatment to inhibitStaphylococcus aureusin broth and raw cow's milk at 25 °C. Two phases in the survival curves were observed. The early stage was characterized by a slow rate of decrease in number ofS. aureus; this rate increased sharply at the later stage.Staphylococcus aureussuspended in broth was completely inactivated after CO2treatment at 7 MPa for 100 min and 8 MPa for 60 min. The sterilization effects of CO2on bothS. aureusand aerobic bacteria were observed at 14.6 MPa for 5 h and 9 MPa for 2 h in whole and skim milk, respectively.Staphylococcus aureusand aerobic bacteria were more difficult to inactivate when they were suspended in whole milk that may have protected the cell from penetration by CO2. Reduction rates ofS. aureusand aerobic bacteria were sensitive to pressure, exposure time and the suspending medium. © 1997 Academic Press Limited.