Evaluation of meat born lactic acid bacteria as protective cultures for the biopreservation of cooked meat products

In this study, 91 strains, originating from meat products, were subjected to a step-by-step screening and characterisation to search for potential protective cultures to be used in the cooked cured meat industry. Strains were first tested on their homofermentative and psychrotrophic character and salt tolerance. Secondly, the antibacterial capacities towards Listeria monocytogenes, Leuconostoc mesenteroides, Leuconostoc carnosum and Brochotrix thermosphacta were determined in an agar spot test. In total, 38% of the tested strains were inhibitory towards all indicator strains. However, 91%, 88% and 74% of the strains could inhibit, respectively, L. monocytogenes, B. thermosphacta and Leuc. mesenteroides. Finally, 12 strains, with the highest antibacterial capacities, were evaluated on their competitive nature by comparing their growth rate, acidifying character and lactic acid production at 7 °C under anaerobic conditions in a liquid broth. All 12 strains, except for a bacteriocin producing Lactobacillus plantarum strain and the lactocin S producing Lactobacillus sakei 148, combined a fast growth rate with a deep and rapid acidification caused by the production of high levels of lactic acid. The 12 selected strains were then further investigated for their growth capacity on a model cooked ham product to establish whether the presence of these cultures on the ham did not negatively influence the sensory properties of the ham. All strains grew in 6 days at 7 °C from a level of 10 5–10 6 to 10 7–10 8 cfu/g and again the bacteriocin producing L. plantarum strain was the slowest growing strain. As the glucose level of the model cooked ham product was low (0.09±0.03%), growth of the putative protective cultures resulted in glucose depletion and a limited lactic acid production and accompanying pH decrease. Cooked ham inoculated with isolates 13E, 10A, 14A (all three identified as L. sakei subsp. carnosus by SDS-PAGE) and with strains L. sakei 148 (LS5) and L. sakei subsp. carnosus SAGA 777 (LS8) were not rejected by the sensory panel at the 34th day of the vacuum packaged storage at 7 °C. Therefore, these strains could have potential for the use as protective culture in cooked meat products.