Antibacterial properties of lactic acid bacteria for meat bio-preservation

Some lactic acid bacteria (LAB) are capable of growing on stored meat and inhibiting pathogenic and spoilage bacteria of concern to the meat industry using a range of mechanisms including general competition and/or the production of specific inhibitory molecules such as bacteriocins. Provided they do not represent a safety or spoilage risk themselves, such LAB offer a potentially useful source of strains for the bio-preservation of stored meat. A study was undertaken to determine if such LAB could be isolated from New Zealand meat-related environments and if so the nature of their inhibitory activities. A collection of 199 strains, including 75 isolates from chilled meat sources, was evaluated using simple screening methods for inhibitory activities against meat-associated pathogens and spoilage bacteria. Three strains of Lactobacillus sakei and one strain each of Leuconostoc carnosum, Carnobacterium maltaromaticum, Lactococcus lactis and Lactococcus garvieae were found to inhibit one or more of the spoilage and pathogenic bacteria Brochothrix thermosphacta, Clostridium estertheticum, Listeria monocytogenes and Campylobacter jejuni. Much of this inhibition was attributed to the activity of bacteriocin-like molecules. Meat inoculation and storage experiments were then performed using selected strains. Three strains of L. sakei were observed to grow on lamb and beef and to be associated with inhibition of eo-inoculated L. monocytogenes and C. jejuni and reduced gas production in packs eo-inoculated with Cl. estertheticum. Sensory and spoilage product analysis of stored lamb inoculated with a three-strain cocktail of L. sakei showed that although higher levels of lactic and acetic acid and lower pH levels were associated with inoculated samples, overall sensory acceptance of inoculated samples was no lower than for normal product. The results of this work characterize a collection of predominantly L. sakei LAB strains that may provide the basis for developing useful products for the bio-preservation of chilled New Zealand export meat