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The Combined Effect of pH and Temperature on the Survival of Salmonella enterica Serovar Typhimurium and Implications for the Preparation of Raw Egg Mayonnaise

Environmental Health Group, College of Science and Engineering, Flinders University, GPO BOX 2100, Adelaide 5001, Australia
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Pathogens 2019, 8(4), 218; https://doi.org/10.3390/pathogens8040218
Received: 10 October 2019 / Revised: 29 October 2019 / Accepted: 2 November 2019 / Published: 4 November 2019
Raw egg products are often associated with salmonellosis. The Australian guidelines recommend raw egg mayonnaise to be prepared and stored under 5 °C and adjusted to a pH less than 4.6 or 4.2. Despite these guidelines, a significant amount of salmonellosis outbreaks are recorded annually in Australia. The aim of this study was to investigate the effect of pH and temperature on the survival of Salmonella Typhimurium (ST) in peptone water (PW) and mayonnaise. The pH of PW and mayonnaise was adjusted to 4.2, 4.4 and 4.6 using acetic acid and vinegar, respectively. The PW and mayonnaise were inoculated with ST and incubated at 37 °C, 23 °C, and 4 °C. The survival of Salmonella was determined using the drop plate method. Survival was significantly (p < 0.05) improved at 4 °C. In both mayonnaise and PW, following 24 h, there was no ST growth at pH 4.2. Resuscitation of ST was rapidly observed at 4 °C while complete inactivation was observed at 37 °C at pH 4.2, 4.4, and 4.6 in both PW and mayonnaise. Lower temperatures protected ST from the bactericidal effect of low pH. “The preparation of mayonnaise at pH 4.2 or less and incubating it at room temperature for at least 24 h could reduce the incidence of salmonellosis”. View Full-Text
Keywords: resuscitation; mayonnaise; salmonellosis; gastroenteritis; public health; chicken eggs resuscitation; mayonnaise; salmonellosis; gastroenteritis; public health; chicken eggs
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Keerthirathne, T.P.; Ross, K.; Fallowfield, H.; Whiley, H. The Combined Effect of pH and Temperature on the Survival of Salmonella enterica Serovar Typhimurium and Implications for the Preparation of Raw Egg Mayonnaise. Pathogens 2019, 8, 218.

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