Microbiological Sources and Impact of Variability on QMRA (Exposure Assessment and Hazard Characterisation)

Quantitative microbiology is used in risk assessment studies, microbial shelf life studies, product development, and experimental design. Realistic risk estimation is, however, complicated by different sources of variability. The variability in hazard characterization is fairly unexplored, though highly relevant. The final concentration of microorganisms at the moment of consumption (exposure assessment) depends, amongst others, on the variability in the storage times and temperatures, variability in product characteristics, variability in process characteristics, variability in the initial contamination of the raw materials, and last but not least, microbiological variability. This presentation compares different sources of microbiological variability in growth and inactivation kinetics of a pathogen, namely experimental variability, reproduction variability (within strain variability), strain variability (between strain variability) and variability between individual cells within a population (population heterogeneity), and prioritizes their importance. Also, the microbiological variability is compared to other variability factors encountered in a model food chain to evaluate the impact of different variability factors on the variability in microbial levels encountered in the final product.