Bacterial inactivation by high-pressure homogenisation and high hydrostatic pressure

• Published in: International journal of food microbiology 2002-08, Vol.77 (3), p.205-212
• Main Authors: Wuytack, Elke Y, Diels, Ann M.J, Michiels, Chris W
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Colony Count, Microbial; Food engineering; Food industries; Food microbiology; Fundamental and applied biological sciences. Psychology; General aspects; Gram-Negative Bacteria - growth & development; Gram-Negative Bacteria - physiology; Gram-Positive Bacteria - growth & development; Gram-Positive Bacteria - physiology; High hydrostatic pressure; High-pressure homogenisation; Hydrogen-Ion Concentration; Hydrostatic Pressure; Inactivation; Pressure; Sodium Chloride - pharmacology; Sodium Dodecyl Sulfate - pharmacology; Sublethal injury
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/S0168-1605(02)00054-5

The resistance of five gram-positive bacteria, Enterococcus faecalis, Staphylococcus aureus, Lactobacillus plantarum, Listeria innocua and Leuconostoc dextranicum, and six gram-negative bacteria, Salmonella enterica serovar typhimurium, Shigella flexneri, Yersinia enterocolitica, Pseudomonas fluorescens and two strains of Escherichia coli, to high-pressure homogenisation (100–300 MPa) and to high hydrostatic pressure (200–400 MPa) was compared in this study. Within the group of gram-positive bacteria and within the group of gram-negative bacteria, large differences were observed in resistance to high hydrostatic pressure, but not to high-pressure homogenisation. All gram-positive bacteria were more resistant than any of the gram-negative bacteria to high-pressure homogenisation, while in relative to high hydrostatic pressure resistance both groups overlapped. Within the group of gram-negative bacteria, there also existed another order in resistance to high-pressure homogenisation than to high hydrostatic pressure. Further it appears that the mutant E. coli LMM1010, which is resistant to high hydrostatic pressure is not more resistant to high-pressure homogenisation than its parental strain MG1655. The preceding observations indicate a different response of the test bacteria to high-pressure homogenisation compared to high hydrostatic pressure treatment, which suggests that the underlying inactivation mechanisms for both techniques are different. Further, no sublethal injury could be observed upon high-pressure homogenisation of Y. enterocolitica and S. aureus cell population by using low pH (5.5–7), NaCl (0–6%) or SDS (0–100 mg/l) as selective components in the plating medium. Finally, it was observed that successive rounds of high-pressure homogenisation have an additive effect on viability reduction of Y. enterocolitica and S. aureus.