Use of Lactobacillus Plantarum as Starter Culture in Fermentation of Salami
Dry Italian-type salami can be considered as a ready-to-eat product with a low risk of causing listeriosis due to the hurdles created during the manufacturing process such as low pH and aw high salt concentration and presence of LAB. However, several studies have detected survival of Listeria monocytogenes in these products and also shown that process parameters, LAB and Listeria monocytogenes strains directly influence the results. In a study by Degenhardt and Sant‘Anna (2007) survival of Listeria monocytogenes was followed in salami prepared with and without the additional starter culture of Lactobacillus plantarum and 2% of sodium lactate, using the manufacturing process usually employed in Brazil. Naturally contaminated sausages presented a small increase in the counts of Listeria monocytogenes during the first days of the process, however, this was followed by a gradual decrease by the end of the process (Degenhardt and Sant‘Anna 2007). In experimentally contaminated samples containing Lactobacillus plantarum, the reduction in the counts of Listeria monocytogenes during processing was considerable, but there were no significant differences between the treatments. Although no significant differences were detected among the three artificially contaminated batches (p > 0.05), the batch inoculated with Lactobacillus plantarum presented a slightly different reduction in the counts of Listeria monocytogenes when compared to the standard batch, which had received no additional starter culture. In the case of the added sodium lactate, the results displayed very similar behaviour to the standard curve, this was without the added Lactobacillus plantarum. Therefore, the use of bio-protective cultures such as Lactobacillus plantarum is highly recommended in the commercial production of Italian salami. However, the use of sodium lactate must be better evaluated, especially when used with other inhibitory substances (Degenhardt and Sant‘Anna 2007).