Antibacterial activities of a polyphenolic-rich extract prepared from American cranberry (Vaccinium macrocarpon) fruit pomace against Listeria spp.

Cranberry (Vaccinium macrocarpon) fruits are known for their high polyphenolics content making them a rich source of antioxidants. These polyphenolics have been reported to promote human health and are gaining attention for their antimicrobial activities against foodborne pathogens. We investigated the antimicrobial activity of an ethanolic extract (#FC111-1) prepared from cranberry pomace against Listeria spp. Many polyphenolics were identified in this extract which could be responsible for growth-inhibitory effects against 12 Listeria strains including L. monocytogenes. The minimum inhibitory concentration (MIC) of #FC111-1 determined in cation adjusted Muller Hinton broth (CAMHB) was approximately 2 mg/mL for 11 (91.7%) of these strains. The inclusion of 2-8 mg/mL (1-4 x MIC) of #FC111-1 decreased (> 3 log(10)) viable bacterial cells of all Listeria strains in CAMHB over a 24 h period, while dose-dependently reducing bacterial salt tolerance, bacterial bile-salt hydrolase activity, bacterial biofilm formation capacity, and increasing cell-membrane permeability. The #FC111-1 extract (0.4 and 0.8% concentrations) had no effect on L. monocytogenes survival in a cooked chicken-breast meat model, highlighting the influence of protein-rich matrices on antibacterial activity and the need to consider the role of food composition when using extracts or polyphenolics from cranberry fruits to improve food-safety.