Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 7, 1998
Publication Date: N/A
Interpretive Summary: Salmonella continues to be a major cause of food borne illness in humans. Historically, some food preservatives such as salt have been used to inhibit the growth of bacteria. Many of these preservatives are on a GRAS list (Generally Recognized as Safe). In this study, the ability of propionic acid and chloride salts to inhibit Salmonella typhimurium growth was examined. Bacteriological media was supplemented with various concentrations of one chloride salt (potassium chloride or sodium chloride) or with both salts. Propionic acid was added to media that contained salts and to media that did not contain salts. Salmonella typhimurium, was then added to the media and the ability of the bacteria to grow was measured. In some cases, high concentrations of propionic acid, potassium chloride, and sodium chloride reduced S. typhimurium growth. However, mixtures of propionic acid and one or both of the salts were more effective in inhibiting S. typhimurium growth than either substance alone. Findings indicate that mixtures containing propionic acid, potassium chloride, and sodium chloride may be useful in inhibiting S. typhimurium growth in foods and on food contact surfaces.
Technical Abstract: The ability of propionic acid and chloride salts to inhibit Salmonella typhimurium growth was determined. Brain Heart Infusion (BHI) was supplemented with 0-750 mM of either potassium chloride (KCl) or sodium chloride (NaCl) or with 0-375 mM of both KCl and NaCl. Propionic acid was added to the BHI and BHI-salts to produce a final concentration of 0-75 mM of propionic acid. The final pH of the media was 6.5. Supplemented BHI was inoculated with 1000 S. typhimurium/ml and incubated at 37 C for 48 hr. After incubation, the absorbance of the cultures was measured spectrophotometrically, and the colony-forming- units (cfu)/ml were enumerated on Plate Count Agar (PCA), BG Sulfa Agar (BGS),and Bismuth Sulfite Agar (BS). Although propionic acid, KCl, and NaCl reduced S. typhimurium growth, mixtures of propionic acid and one or both of the salts were more effective in inhibiting S. typhimurium growth than either substance alone. Propionic acid and the chloride salts produced no injury that reduced bacterial growth on BGS or BS. Both absorbance and cfu/ml measurements detected inhibition of S. typhimurium growth by propionic acid and the salts. Findings indicate that the synergistic reaction between propionic acid and KCl or NaCl may be a useful principle to apply in the formulation of products designed to inhibit S. typhimurium growth in foods and on food contact surfaces.