Antibacterial activities of blueberry and muscadine phenolic extracts

Phenolics are one category of phyto-antimicrobials that refer to the antimicrobial substances extracted from plant sources. This study was undertaken to determine the influence of blueberry and muscadine phenolic extracts on the growths of 2 important foodborne bacterial pathogens, Salmonella Enteritidis and Listeria monocytogenes. Cells of S. Enteritidis (n = 4) or L. monocytogenes (n = 4) strains were inoculated (3 log CFU/mL) into tryptic soy broth (TSB) supplemented with 46.25 ppm of muscadine phenolics and 24 ppm of blueberry phenolics, respectively. The inoculated and un-inoculated broth with or without the supplemented phenolics were incubated at 37 °C for 24 h. Samples were drawn periodically, and cell populations of Salmonella and Listeria were determined on tryptic soy agar (TSA). It was observed that Salmonella was relatively more susceptible than Listeria to the phenolic extracts used in the study. The growth of Salmonella was significantly inhibited in all samples at all sampling points except for the sample that was supplemented with muscadine water extract and drawn at the 24-h sampling point. Blueberry phenolics were relatively more effective than muscadine phenolic extracts in inhibiting the growth of Salmonella. One tested strain of Listeria was more susceptible to ethanol than water phenolic extracts. The study revealed the potentials and limitations of using blueberry and muscadine phenolics to control the growths of selected Salmonella and Listeria strains.