Bioprotective Effect of Lactic Acid Bacteria Against Listeria Monocytogenes In Heat-Treated Reconstituted Milk
Citation (APA 7)
Loforte, Y., Cadavez, V., & Gonzales-Barron, U. (2024). Bioprotective Effect of Lactic Acid Bacteria Against Listeria Monocytogenes In Heat-Treated Reconstituted Milk. 16th AgroStat Conference (AgroStat 2024) (AGROSTAT2024), Bragança, Portugal. Zenodo. https://doi.org/10.5281/zenodo.14787878
Abstract
Lactic acid bacteria (LAB) play an important role in fermented products, by promoting desirable organoleptic properties, and by their antimicrobial properties limiting the growth of pathogenic bacteria. The objective of this study was to determine the growth kinetics of Listeria monocytogenes (LM) in heat-treated reconstituted milk, as affected by selected LAB strains Leuconostoc mesenteroides, Lacticaseibacillus paracasei and Loigolactobacillus coryniformis isolated from goats’ milk cheeses.Challenge tests of each LAB strain in monoculture and in coculture with LM in milk adjusted to three initial pH levels (5.5, 6.0 and 6.5) were performed. Inoculated milk samples were left to ferment at 12ºC for 8 days. A pH-driven dynamic growth model was fitted in separate to the LM and LAB experimental curves from both monoculture and coculture experiments; and a Jameson-effect growth model was fitted only to the coculture growth curves. In monoculture, L. mesenteroides, when compared to the other LAB strains, showed the highest growth rates at the three initial pH levels; whereas in coculture, this strain was able to better control the growth of LM, by decreasing their growth rates [day-1] to 1.469 ± 0.205 at pH 5.5; 2.293 ± 0.284 at pH 6.0 and 1.552 ± 0.132 at pH 6.5. L. paracasei and L. coryniformis strains were only able to inhibit and reduce the growth of LM at pH 5.5. In relation to the maximum concentration of LM (LMmax), L. mesenteroides was again the most effective at all initial pH tested. The LMmax [log CFU/ml] values were reduced to 15.05 ± 0.367; 16.32 ± 0.204 and 16.91 ± 0.132 at pH 5.5; 6.0 and 6.5, in comparison to the values 20.85 ± 0.060; 21.10 ± 0.212 and 21.31 ± 0.085, obtained in monoculture, respectively. This indicates that this particular strain of L.mesenteroides has a broader and more inhibitory effect on LM growth across different pH levels, whereas L. paracasei and L. coryniformis are only effective in more acidic conditions (pH 5.5). These research results provide valuable insights into the use of LAB as a natural biopreservative for controlling LM in dairy products, thereby enhancing food safety.