High sucrose concentration protects E. coli against high pressure inactivation but not against high pressure sensitization to the lactoperoxidase system

• Published in: International journal of food microbiology 2003-11, Vol.88 (1), p.1-9
• Main Authors: Van Opstal, Isabelle, Vanmuysen, Suzy C.M., Michiels, Chris W.
• Format: Article
• Language: English
• Subjects: bacterial contamination; Biological and medical sciences; buffers; cell suspension culture; Colony Count, Microbial; Dose-Response Relationship, Drug; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - growth & development; food contamination; Food industries; Food Microbiology; food pathogens; food preservation; Food Preservation - methods; food safety; Fundamental and applied biological sciences. Psychology; High hydrostatic pressure; high pressure treatment; Hydrostatic Pressure; lactoperoxidase; Lactoperoxidase - pharmacology; Lactoperoxidase system; lethal dose; potassium phosphates; stress tolerance; sucrose; Sucrose - pharmacology; sunlethal injury; Temperature; Time Factors; viability; Water - metabolism; Water activity
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/S0168-1605(03)00070-9

The inactivation of Escherichia coli by high hydrostatic pressure treatment at up to 550 MPa and 20 °C was studied in potassium phosphate buffer containing high concentrations of sucrose. E. coli strain MG1655 was pressure-sensitive in the absence of sucrose, but became highly pressure resistant in the presence of 10% to 50% (w/v) sucrose. The pressure resistance of E. coli strain LMM1010, a previously described derivative of MG1655 that is pressure resistant in the absence of sucrose, was further increased in the presence of sucrose, to a similar level as for strain MG1655 in the presence of sucrose. When cell suspensions of either strain were stored after pressure treatment for 24 h at 20 °C, a further reduction of the plate counts indicative of pressure induced sublethal injury was observed, that was positively correlated with pressure intensity and negatively with sucrose concentration. Addition of the lactoperoxidase system to the cell suspensions strongly enhanced high pressure inactivation of E. coli at high sucrose concentrations. Using a pressure intensity of only 250 MPa, both E. coli strains were sensitized for the lactoperoxidase system in up to 30% (w/v) sucrose, resulting in at least 10 6-fold inactivation within 24 h or less after pressure treatment. For comparison, a pressure treatment at 250 MPa in the absence of the lactoperoxidase system did not cause any inactivation of either strain even in the absence of sucrose. At sucrose concentrations above 30% (w/v), no or very little inactivation occurred even in the presence of the lactoperoxidase system.