Influence of cinnamon and clove essential oils on the D- and z-values of Escherichia coli O157:H7 in apple cider.
Escherichia coli O157:H7 has become a concern within the apple cider industry. The purpose of this study was to screen several essential oils and isolated components for antimicrobial activity against E. coli O157:H7 in tryptic soy broth at neutral and acidic pH and to assess the effect of these additives on the D-value of E. coli O157:H7 in apple cider in combination with mild heat treatments. Cinnamon oil and clove oil strongly inhibited the growth of E. coli O157:H7 at neutral and acidic pH, (R)-(-)-carvone and (S)-(-)-perillaldehyde were moderately inhibitory at both pH 7.2 and pH 4.5, and citral and geraniol displayed moderate activity at pH 4.5 only. Lemon oil, methyl jasmonate, and p-anisaldehyde displayed little or no antibacterial activity. A synergistic effect between the essential oils and the lower pH of the growth medium was evident by consistently lower MICs at pH 4.5. Cinnamon and clove oils (0.01%, vol/vol) were further tested in apple cider in combination with mild heat treatments for the practical control of E. coli O157:H7 in apple cider. The addition of either essential oil resulted in lower D-values than those for cider alone, suggesting a synergistic effect and the potential efficacy of a mild heat treatment for apple cider.
Knight
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KP
Food Research Program, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada N1G 5C9. knightk@agr.gc.ca
McKellar
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RC
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001628:Beverages / Q000382:microbiology*; D045783:Clove Oil / Q000494:pharmacology*; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000254:growth & development; D005511:Food Handling / Q000379:methods; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D027845:Malus / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D009822:Oils, Volatile / Q000494:pharmacology*; D013696:Temperature
D000900:Anti-Bacterial Agents; D045783:Clove Oil; D009822:Oils, Volatile; C510049:cinnamon oil, leaf