Prediction of the impact of processing critical conditions for Listeria monocytogenes growth in artisanal dry-fermented sausages (salami) through a growth/no growth model applicable to time-dependent condition

L. monocytogenes data from artificially contaminated salami batter samples and from published data were used to evaluate a newly-developed, time-dependent probability parameter (Pt), which was then incorporated in the existing and already validated simplified modelling approach (SMA), taking into account time in assessing the pathogen growth probability. The SMA was further expanded to quantify the impact of each preservative factor (f) to growth probability. The modified SMA (mSMA) was used to evaluate those environmental conditions that could decrease the safety status of artisanal salami. The dependence of the probability of growth, and of the growth of L. monocytogenes on temperature, pH, aw, lactic acid and indigenous lactic acid bacteria of salami was predicted and the impact of each factor was quantified under dynamically changing conditions. Characteristics were measured in 5 salami batches and for two of them the predicted final population size was higher than the European Commission (EC) tolerated level for L. monocytogenes (100 CFU g1). Applying the mSMA to potential scenarios that included the contribution of starter cultures, the onset of Listeria inhibition was predicted earlier, preventing the pathogen to exceed its critical limit. Given its prediction capability, the mSMA is expected to assist small-sized enterprise users in the effective management of preventive and corrective measures in salami processing.