Microbiological safety of Portuguese dry fermented chouriço sausages as affected by processing and physicochemical factors

Introduction: In Portugal, chouriço is mainly produced by small-scale artisanal manufacturers, employing their own traditional techniques. Accidental variations of the production process, even within the same processing unit, can occur, since process variables may not be fully controlled, thus resulting in final products of variable microbiological quality, stability and safety. Purpose: This study aims to: (i) elucidate the critical process variables responsible for the varying levels of Enterobacteriaceae, Staphylococcus aureus and Listeria monocytogenes in chouriço; and (ii) assess relationships between physicochemical properties of the product and microbial counts along processing. Methods: Microbiological and physicochemical surveys at five stages of production were conducted in 12 batches sampled from two factories of chouriço (one using curing salts in their formulation). Longitudinal or stepwise multiple regression models (α=0.20) were fitted to the counts of each microbial group, according to the objective of the analysis. Results: Maceration was found to be a critical point of the process since Enterobacteriaceae (P=0.017) and S. aureus (P=0.087) could significantly increase until the end of this stage. Furthermore, the contamination of chouriço correlated positively with the maceration room temperature (S. aureus: P=0.034; L. monocytogenes: P=0.010) and the final pH of the macerated meat (L. monocytogenes P=0.048). Batches with lower salt concentration in smoked meat (P=0.021), higher maceration temperature (P=0.034) and shorter ripening time (P=0.171) presented higher S. aureus counts in the end product, whereas higher levels of contamination in the mixture (P<0.0001) and casings (P=0.044) and shorter production time (P=0.090) led to higher L. monocytogenes counts in the end product. Although nitrite showed a strong effect on reducing Enterobacteriaceae during smoking (P<0.0001) and controlling L. monocytogenes during ripening (P=0.036), it did not hinder (P=0.007) S. aureus growth. Significance: These results reveal the urgent need to standardise and optimise the production process of chouriço in order to assure consumers’ safety.