Estimating the non-thermal inactivation of Listeria monocytogenes in fermented sausages relative to temperature, pH and water activity.

Data relative to in situ Listeria monocytogenes inactivation in fermented sausages were collected from 13 individual studies found in the literature. Inactivation rates were extrapolated and used to develop a predictive model to evaluate the relative effects of pH, water activity (a(w)) and temperature on L. monocytogenes fate during fermentation and ripening. Temperature explained ca. 60% of the data variability, while pH and a(w) only a small part. Temperature alone may not be sufficient to cause pathogen's inactivation, but inactivation rate is dominated by temperature when pH and a(w) are in the range which prevent L. monocytogenes growth. A predictive model based on two Arrhenius equations (ln[inactivation rate]=-25.71-[-0.6829 / (8.314 × T)] for fermentation; and ln[inactivation rate]=-44.86-[-1.219/(8.314 × T)] for ripening)was developed. The model can be used to quantify the effect of temperature and/or time changes on fermented sausage safety. The advantages and limitations of the model are discussed.