Susceptibility of food-borne bacteria to binary combinations of antimicrobials at selected a(w) and pH.
OBJECTIVE
To evaluate the antibacterial susceptibilities of food-borne bacteria to individual and binary mixtures of a synthetic antimicrobial agent with a natural phenolic compound.


RESULTS
Antibacterial susceptibilities of Escherichia coli, Listeria innocua, Salmonella Typhimurium and Staphylococcus aureus to individual and binary mixtures of potassium sorbate with a phenolic compound (thymol, carvacrol, or eugenol) were evaluated, at selected water activity (a(w); 0.99 or 0.97) and pH (5.5 or 4.5). The bacteria studied were susceptible to the action of the antimicrobials individually with minimal inhibitory concentrations that varied from 800-ppm potassium sorbate for Staph. aureus at a(w) 0.99, and pH 5.5 to 100-ppm thymol or carvacrol for the four studied bacteria at a(w) 0.97 and pH 4.5. Several binary mixtures of potassium sorbate with thymol, carvacrol or eugenol inhibited bacterial growth. Antimicrobial agent inhibitory concentrations in the mixture varied among bacteria, additionally depending on the a(w) and the pH tested.


CONCLUSIONS
Synergistic binary mixtures with fractional inhibitory concentration index <0.6 include 100- or 200-ppm potassium sorbate with 50- or 100-ppm thymol, carvacrol or eugenol.


CONCLUSIONS
The synergistic combinations could be useful in reducing the amounts of antimicrobials needed to inhibit growth, thus diminishing consumer concerns regarding chemical preservatives.
Santiesteban-López
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A
Departamento de Ingeniería Química y Alimentos, Universidad de las Américas, Puebla, Mexico.
Palou
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E
López-Malo
A
A
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000081007:Cymenes; D004357:Drug Synergism; D004926:Escherichia coli / Q000187:drug effects; D005054:Eugenol / Q000494:pharmacology; D005516:Food Microbiology; D006863:Hydrogen-Ion Concentration; D008087:Listeria / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D039821:Monoterpenes / Q000494:pharmacology; D010636:Phenols / Q000494:pharmacology*; D012486:Salmonella typhimurium / Q000187:drug effects; D013011:Sorbic Acid / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects; D013943:Thymol / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D000081007:Cymenes; D039821:Monoterpenes; D010636:Phenols; D013943:Thymol; D005054:Eugenol; C073316:carvacrol; D013011:Sorbic Acid