MICROBIAL MODELING AND BIOINFORMATICS FOR FOOD SAFETY AND SECURITY
Location: Residue Chemistry and Predictive Microbiology
Title: Modeling the Survival of Escherichia coli O157:H7 During Fermentation, Drying, and Storage of a Soudjouk-Style Fermented Dry or Semi-Dry Sausage
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 15, 2007
Publication Date: July 8, 2007
Citation: Hwang, C., Porto Fett, A.C., Juneja, V.K., Ingham, S.C., Ingham, B.H., Luchansky, J.B. 2007. Modeling the Survival of Escherichia coli O157:H7 During Fermentation, Drying, and Storage of a Soudjouk-Style Fermented Dry or Semi-Dry Sausage. Abstract. International Association for Food Protection. T-707.
Cases of foodborne illness have been linked to the consumption of fermented dry or semi-dry sausages (FDSS) contaminated with Escherichia coli O157:H7. The purpose of this study was to model the inactivation of E. coli O157:H7 during FDSS manufacturing and storage. Beef batter (20% fat) containing 0.25, 0.5, or 0.6% dextrose, spices and a lactic acid starter culture was inoculated with a three-strain cocktail of E. coli O157:H7 to approximately 7.0 log10 cfu/g. The raw sausage (pH 6.0, aw 0.97) was fermented at 24 degree C with RH 90-95% for 72 h to pH 5.2, 4.9, or 4.6, and then dried at 22 degree C with 80-85% RH to aw 0.92, 0.89, or 0.86. The sausages were vacuum-packed and stored at 4, 21, or 30 degree C for up to 60 days. During fermentation, the inactivation of E. coli O157:H7 could be described by two linear regressions in which the inactivation rates were 0.0224 and 0.1333 log10 cfu/g for every 0.1 unit decrease in pH in the range of pH 5.55-4.82 and pH 4.81-4.50, respectively. During drying, the inactivation could be described by a linear regression in which the inactivation rates were 0.3167, 0.4833, and 0.5833 log10 cfu/g for every 0.01 unit decrease in aw for sausages fermented to pH 5.2, 4.9, and 4.6, respectively. The inactivation rates of E. coli O157:H7 (log10 cfu/day) during storage at 4, 21, or 30 degree C were fitted to a quadratic model as a function of sausage pH and aw and storage temperature. The model (R2=0.87) indicated that inactivation during storage was significantly higher (p<0.01) in sausage with lower pH and lower aw than otherwise similar sausage that were stored at 30 degree C. These models will enable manufacturers of FDSS to estimate the reduction of E. coli O157:H7 and modify their product formulations and processes to meet existing food safety guidelines.