Tracing of Listeria monocytogenes Contamination Routes in Fermented Sausage Production Chain by Pulsed-Field Gel Electrophoresis Typing.

In this study, the presence of Listeria monocytogenes was assessed along the production process of fermented sausages in a small-scale facility. Following the isolation of the pathogen from the final product (ISO 11290-1), retrospective sampling was performed during the production of a new batch of sausages, including raw materials, casings, additives, sausage mixtures, sausages during fermentation, and environmental samples. L. monocytogenes was recovered from the following sampling points: the defrosting room and the cuttering, mixing, stuffing, and fermentation phases. Ten strains were isolated, molecularly confirmed as L. monocytogenes by means of a molecular detection system, and subjected to pulsed-field gel electrophoresis (PFGE) typing. On the basis of an unweighted pair group method with arithmetic mean (UPGMA) dendrogram from Ascl pulsotypes, the strains were indistinguishable (no band difference). The same pulsotypes of strains present in both batches of sausages, as well as in environmental samples, indicated the persistence of L. monocytogenes in the sausage production unit.

Microbial and physicochemical succession in fermented sausages produced with bacteriocinogenic culture of Lactobacillus sakei and semi-purified bacteriocin mesenterocin Y.

The influence of the bacteriocinogenic culture Lactobacillus sakei (10(5)/g) and semi-purified bacteriocin mesenterocin Y (2560AU/kg) on the safety and quality of traditional Croatian fermented sausages was investigated. The addition of Lb. sakei and/or mesenterocin Y reduced microbial counts (P<0.05) in the final products. After 28 days of ripening, coagulase-negative cocci decreased 1.5-2.0log, yeasts 1.2-1.4log and enterococci 1.7-2.7log. In the case of the addition of Lb. sakei, the lactic acid bacteria count was significantly (P<0.05) higher at day 7 of ripening, and was accompanied by a lower pH and a higher amount of lactic acid (P<0.05). In the final product the amount of acetic acid was significantly lower. More intensive proteolysis and an increase in ammonia content were found at the beginning of fermentation, and in the second phase of ripening in the control samples, respectively. The free fatty acid concentration was significantly lower during the entire ripening process compared to the control (P<0.05). Semi-purified mesenterocin Y did not affect the sensory properties of the sausages, whilst the addition of Lb. sakei enhanced them.