The antimicrobial properties of the lowbush blueberry (Vaccinium angustifolium) fractional components against foodborne pathogens and the conservation of probiotic Lactobacillus rhamnosus

The antimicrobial properties of lowbush blueberry (Vaccinium angustifolium) were studied against Escherichia coli O157:H7, Listeria monocytogenes, Salmonella Typhimurium, and Lactobacillus rhamnosus to determine which fractional components have antimicrobial effects and which microorganisms are most susceptible to these antimicrobial properties. Lowbush blueberry extract (F1) was separated using a C-18 Sep-Pak cartridge into monomeric phenolics (F2) and anthocyanins plus proanthocyanidins (F3). Fraction 3 was further separated into anthocyanins (F4) and proanthocyanidins (F5) using a LH-20 Sephadex column. Each fraction was initially screened for antimicrobial properties using agar diffusion assay. Treatments that demonstrated inhibition were further analyzed for inhibition in liquid culture. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined using a two-fold dilution series and viable cell counts taken at 0 and 24 h to examine growth reduction. Fraction 3 demonstrated the lowest MICs/MBCs followed by F1, F2, F4, and F5. L monocytogenes was the most susceptible to blueberry fraction treatment, followed by E. coli O157:H7, and S. Typhimurium. L rhamnosus was the least susceptible to each fraction treatment. The results can be applied to the field of preventive medicine, food safety, and enrich the understanding of the health benefits of lowbush blueberries. (C) 2011 Elsevier Ltd. All rights reserved.