89D-13 |
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A. ABUSHELAIBI, M. E. Janes, and A. Khachatryan. Dept. of Food Science, Louisiana State Univ. Agricultural Center, 111 Food Science Bldg., Baton Rouge, LA 70803-4200 Listeria monocytogenes (Lm) found in the environment of ready-to-eat (RTE) processing plants has been linked to the contamination of these products. We evaluated the effect of pH (3, 4, 5, 6, 7, 8, or 9) on the antimicrobial activity of copper ions against Lm when grown on the surface of copper or brass surfaces. Copper and brass sheets were cut into disks and autoclaved. A decimally diluted overnight culture of Lm (10 µl) was inoculated into Modified Welshimers soft agar that was adjusted to a desired pH, poured over the surface of copper, brass or Petri dishes (control) and incubated at 4°C. Bacterial counts were determined after 0, 2, 4, 6, 8, and 24h. The agar was collected, stomached for 2 min, decimally diluted and plated onto Oxford agar. The plates were incubated at 37°C for 24 h and CFU/g determined. An initial Lm inoculum of 3 Log CFU/g had grown to 5.5 Log CFU/g in the control at a pH of 6, 7, or 8 by 24 h. The control Lm counts reached non-detectable levels at a pH of 3 by 2h and pH of 4 by 24 h. At a pH of 9 the control Lm counts were 2.2 Log CFU/g by 24h. Lm counts at pH 3, 4, 5, 6, 7, 8, or 9 on copper were reduced to non-detectable levels by 2 h. Lm counts were reduced to non-detectable levels on the surface of brass at a pH of 3, 4, 5, or 6 by 2h. At a pH of 7, 8, or 9 Lm counts reached non-detectable levels by 4 h on the surface of brass. Our results indicated that pH has no effect on the antimicrobial activity of copper ions against Lm. Copper or brass metals could possibly be used to control Lm in the RTE processing environment.
Session 89D, Food Microbiology: Antimicrobial effects on foodborne microorganisms
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |