Olive mill wastewater extracts exert in vitro antimicrobial activity against common meat spoling and pathogenic bacteria

Polyphenol mixtures obtained from olive mill wastewater were tested for their activity against spoiling and pathogenic bacteria commonly isolated from meat products, such as Brochothrix thermosphacta, Listeria monocytogenes, Salmonella enterica subsp. Derby and Staphylococcus aureus. Minimal Inhibitory Concentrations were determined, and time kill kinetics revealed a strong action at very low concentrations. In particular, 0.25% extract was able to immediately inhibit the growth of L. monocytogenes ATCC 7644 and S. aureus ATCC 32760, while at the same concentration Salmonella enterica subsp. Derby S1 and B. thermosphacta ATCC 11059 were inhibited after 60 and 120 minutes, respectively. Moreover, growth dynamics were evaluated by means of automated turbidimetry. The analysis of growth parameters revealed a bacteriostatic action of olive wastewater extracts at concentrations lower than or equal to 0.5%, depending on the strain, and a bactericidal action at higher concentrations. Results obtained showed that olive mill wastewater extracts exerted a strong and fast in vitro antimicrobial activity against some spoiling and pathogenic microorganisms. Our data provide insight into a possible application of these extracts as antimicrobial compounds, although their application on foods still has to be optimized. Moreover, olive mill wastewaters have a strong polluting impact, and therefore their application as biopreserving agents could increase their value, converting a waste material into a powerful resource.