THR PREDICTION OF ESCHERICHIA COLI O157:H7 DECLINE IN TRYPTIC SOY BROTH WITH YEAST EXTRACT TREATMENTED WITH DIFFERENT TEMPERATURES AND ACIDITY VALUES USING A PATHOGEN MODELING PROGRAM

Abstract

The aim of this study was to assess the sensitivity of Escherichia Coli O157:H7 towards temperature
and acidity. E. Coli O157:H7 is regarded to be a pathogenic microorganism producing verotoxins called Shiga
toxins which provoke hemorrhagic diarrhea in people. There is a strong need to design and develop highly
successful methods of enabling the elimination of E. Coli O157:H7 from food. The present research evaluates the
tools of predictive microbiology based on the USDA Agricultural Research Service Pathogen Modeling Program
which is a very useful software package available at http://pmp.errc.ars.usda.gov. Strains were inoculated to
reach a number of approximately 9 log10 bacteria/gram, acidified with lactic acid to achieve pH 7.0, 5.5 or 4.0,
and then they were exposed to a specific temperature: 55C, 58C or 62.5C. The decline in the number of
E. Coli O157:H7 cells can be achieved due to the application of different acidity values in combination with
different temperatures which are inserted into the predictive microbiological software package. The decline
in a number of E. Coli O157:H7 cells depends on the temperature and pH value. The acidity has a huge
influence on the survival of E. Coli O157:H7 cells. At pH 7.0, the decline in a value of 1.00 log10 cfu/ml is
achieved after 10.38 minutes of holding in 55C, while at pH 5.5 the decline in a value of 1.00 log10 cfu/ml is
achieved after 7.24 minutes, and at pH 4.0 the decline in a value of 1.00 log10 cfu/ml is achieved after 3.52
minutes. The program estimates the microbiological risk of presence of food borne pathogens in food products. It
brings many benefits for the food industry and makes it possible to control each production process through the
application of successful combination of temperature and acidity values to completely destroy the pathogen in food.