High pressure homogenization inactivation of Escherichia coli and Staphylococcus aureus in phosphate buffered saline, milk and apple juice.

Abstract

High pressure homogenization (HPH) offers new opportunities for food pasteurization/sterilization. Escherichia coli and Staphylococcus aureus suspended in phosphate buffered saline (PBS) buffer, milk and apple juice at initial concentration of ~106 log10 CFU per ml were subjected to HPH treatments up to 200MPa with inlet temperatures at 4-40°C. After HPH at 200MPa with the inlet temperature at 40°C, the count of E. coli suspended in PBS, milk and apple juice reduced by 3·42, 3·67 and 3·19 log10 CFU per ml respectively while the count of S. aureus decreased by 2·21, 1·02 and 2·33 log10 CFU per ml respectively suggesting that S. aureus was more resistant. The inactivation data were well fitted by the polynomial equation. Milk could provide a protective effect for S. aureus against HPH. After HPH at 200MPa with the inlet temperature at 20°C, the cell structure of E. coli was destroyed, while no obvious damages were found for S. aureus.