Predicting the concentration of verotoxin-producing Escherichia coli bacteria during processing and storage of fermented raw-meat sausages.

A model to predict the population density of verotoxigenic Escherichia coli (VTEC) throughout the elaboration and storage of fermented raw-meat sausages (FRMS) was developed. Probabilistic and kinetic measurement data sets collected from publicly available resources were completed with new measurements when required and used to quantify the dependence of VTEC growth and inactivation on the temperature, pH, water activity (aw), and concentration of lactic acid. Predictions were compared with observations in VTEC-contaminated FRMS manufactured in a pilot plant. Slight differences in the reduction of VTEC were predicted according to the fermentation temperature, 24 or 34°C, with greater inactivation at the highest temperature. The greatest reduction was observed during storage at high temperatures. A population decrease greater than 6 decimal logarithmic units was observed after 66 days of storage at 25°C, while a reduction of only ca. 1 logarithmic unit was detected at 12°C. The performance of our model and other modeling approaches was evaluated throughout the processing of dry and semidry FRMS. The greatest inactivation of VTEC was predicted in dry FRMS with long drying periods, while the smallest reduction was predicted in semidry FMRS with short drying periods. The model is implemented in a computing tool, E. coli SafeFerment (EcSF), freely available from http://www.ifr.ac.uk/safety/EcoliSafeFerment. EcSF integrates growth, probability of growth, and thermal and nonthermal inactivation models to predict the VTEC concentration throughout FRMS manufacturing and storage under constant or fluctuating environmental conditions.

Bacteriological safety issues in red meat and ready-to-eat meat products, as well as control measures.

The importance of Eschericha coli O157, Listeria monocytogenes and Salmonella typhimurium DT104 as meat-borne pathogens is well established. Pathogenic bacteria such as Aeromonas spp., Arcobacter spp., psychrotrophic Bacillus cereus, Campylobacter spp., Clostridium botulinum and non-invasive Listeria monocytogenes can be regarded as rookies, but not yet firmly associated with today's production of red meat and meat products. The development of PCR and other DNA-based techniques will shed new light on so called emerging pathogens. Important safety issues in meat production, such as insufficient cleaning and disinfection (including the stable/lairage, processing environment), carcass decontamination and chilling, and cross contamination are discussed. Furthermore, probability modelling of survival and growth is identified as an important way to achieve a better understanding of how to deal with the complexity of further processing, including heat treatment and storage.