Natural antimicrobials, from plant, animal or microbial sources, have good potential
for use as preservative systems to improve food safety, extend shelf life and enhance the
overall quality of food products, while promoting the image of “healthier” foods. The overall
objective of this research was to evaluate the antimicrobial efficacy of phosvitin alone or
combined with carvacrol or nisin against four human enteric foodborne pathogens. Growth
inhibition of Salmonella enterica, Listeria monocytogenes, Escherichia coli O157:H7 or
Staphylococcus aureus by the antimicrobials used singly or in combination in brain heart
infusion (BHI) broth (35 °C, 24 hours) was evaluated using a Bioscreen C turbidometer (OD
600nm). Subsequently, selected concentrations of the antimicrobials were evaluated for their
effectiveness in controlling growth of the pathogens and background microflora in onion
mushroom soup at 12 ºC and 35 ºC. Additional experiments involving UV spectroscopy and
transmission electron microscopy (TEM) were performed to investigate the antibacterial
mechanism of action of carvacrol in E. coli O157:H7 and L. monocytogenes Scott A. In BHI
broth the minimum inhibitory concentration (MIC) of phosvitin and carvacrol was 80 mg/ml
and 0.14 mg/ml, respectively, for both S. enterica and L. monocytogenes. The MIC of
phosvitin and carvacrol was greater than 100 mg/ml and 0.12 mg/ml, respectively (for S.
aureus) and 80 mg/ml and 0.12 mg/ml, respectively, for E. coli. In onion mushroom soup,
the combination of phosvitin (60 mg/ml) and carvacrol (0.40 mg/ml) exerted the greatest
cidal effect throughout storage against all foodborne pathogens tested. Irrespective of
storage temperature (12 °C or 35 °C), phosvitin combined with nisin did not offer enhanced
antibacterial effect above that provided by phosvitin used alone. For all organisms, leakage