Bactericidal Activities of Health‐Promoting, Food‐Derived Powders Against the Foodborne Pathogens Escherichia coli , Listeria monocytogenes , Salmonella enterica , and Staphylococcus aureus

We evaluated the relative bactericidal activities (BA 50 ) of 10 presumed health‐promoting food‐based powders (nutraceuticals) and, for comparison, selected known components against the following foodborne pathogens: Escherichia coli O157:H7, Salmonella enterica , Listeria monocytogenes , and Staphylococcus aureus . The relative activities were evaluated using quantitative bactericidal activity [(BA 50 value, defined as the percentage of the sample in the assay mixture that resulted in a 50% decrease in colony forming units]. The BA 50 values were determined by fitting the data to a sigmoidal curve by regression analysis using concentration–antimicrobial response data. Antimicrobial activity is indicated by a low BA 50 value; meaning less material is needed to kill 50% of the bacteria. Olive pomace, olive juice powder, and oregano leaves were active against all 4 pathogens, suggesting that they behave as broad‐spectrum antimicrobials. All powders exhibited strong antimicrobial activity against S. aureus . The following powders showed exceptionally high activity against S. aureus (as indicated by the low BA 50 values shown in parentheses): apple skin extract (0.002%); olive pomace (0.008%); and grape seed extract (0.016%). Listeria bacteria were also highly susceptible to apple skin extract (0.007%). The most active substances provide candidates for the evaluation of antimicrobial effectiveness in human food and animal feed. Practical Application : Plant‐derived health‐promoting food supplements, high in bioactive compounds, are candidates for use as antimicrobials in food.