Effect of the Dry-Cured Fermented Sausage "Salchichón" Processing with a Selected Lactobacillus sakei in Listeria monocytogenes and Microbial Population

Abstract

In the present work, the effect of processing of dry-cured fermented sausage "salchichón" spiked with the selected Lactobacillus sakei 205 was challenge-tested with low and high levels of L. monocytogenes. The evolution of the natural microbial population throughout the "salchichón" ripening was also evaluated. For this, a total of 150 "salchichón" were elaborated and divided into six equal cases which were inoculated with different levels of L. monocytogenes, and L. sakei 205. Afterwards, sausages were ripened for 90 days according to a typical industrial process. Moisture content (%) and water activity (a_w) decreased throughout the ripening up to values around 26% and 0.78, respectively. No differences for moisture content, a_w, pH, NaCl and nitrite concentration were observed between the analyzed cases. Lactic acid bacteria counts in the L. sakei 205 inoculated cases were always higher than 6 log CFU g^-1 during ripening. Enterobacteriaceae counts were reduced during ripening until non-detectable levels at the end of processing. Reductions in L. monocytogenes counts ranged from 1.6 to 2.2 log CFU g^-1; therefore, the processing of "salchichón" itself did not allow the growth of this pathogen. Reduction in L. monocytogenes was significantly higher in the cases inoculated with L. sakei 205.

Keywords: L. monocytogenes reduction; L. sakei; challenge test; dry-cured fermented sausages.

Figure 1

Evolution of lactic acid bacteria counts throughout the ripening process of “salchichón”. C (uninoculated control), B (inoculated with L. sakei), LI+LAB (inoculated with L. monocytogenes at ≈4 log CFU g⁻¹ combined with L. sakei), HI+LAB (inoculated with L. monocytogenes at ≈7 log CFU g⁻¹ combined with L. sakei), LI (inoculated with L. monocytogenes at ≈4 log CFU g⁻¹), HI (inoculated with L. monocytogenes at ≈7 log CFU g⁻¹). Bars with different letters (a–d) indicate significant differences (p ≤ 0.05) between cases on the same day. Bars with different numbers (1–4) indicate significant differences (p ≤ 0.05) between days in the same case.

Figure 2

Reduction in the L. monocytogenes levels throughout the processing of dry-cured fermented “salchichón”. LI (inoculated with L. monocytogenes at ≈4 log CFU g⁻¹), LI+LAB (inoculated with L. monocytogenes at ≈4 log CFU g⁻¹ combined with L. sakei), HI (inoculated with L. monocytogenes at ≈7 log CFU g⁻¹), HI+LAB (inoculated with L. monocytogenes at ≈7 log CFU g⁻¹ combined with L. sakei). Bars with different letters (a,b) indicate significant differences (p ≤ 0.05) between cases on the same day.