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item Uhlich, Gaylen
item Luchansky, John
item Tamplin, Mark
item Molina-corral, Francisco
item Anandan, Shivanthi
item Porto-fett, Anna

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/6/2005
Publication Date: 2/20/2006
Citation: Uhlich, G.A., Luchansky, J.B., Tamplin, M.L., Molina-Corral, F., Anandan, S., Porto Fett, A.C. 2006. Effect of storage temperature on viability of listeria monocytogenes in queso blanco. [Abstract] 12th Australian Food Microbiology Conference.

Interpretive Summary:

Technical Abstract: A five-strain cocktail of Listeria monocytogenes was inoculated onto individual vacuum-packaged slices (ca. 50 g each) of a commercial, Hispanic-style cheese, that being Queso Blanco. Growth was determined either hourly, daily, or weekly depending on the temperature during storage at 5, 10, 15, 20, and 25ºC. In general, as the incubation temperature increased, a shorter lag phase duration (LPD) and a faster growth rate (GR) were observed. The LPD at 5, 10, 15, 20, and 25°C were 65.3, 19.9, 2.1, 8.4 and 11.4 hours, respectively. The GR were 0.011, 0.036, 0.061, 0.090, and 0.099 log cfu/h at 5, 10, 15, 20, and 25°C, respectively. There were no statistical differences in LPD at 10, 15, 20, and 25ºC. However, the LPD during growth at 5ºC was statistically (P is less than or equal to 0.05) longer than at all other temperatures. The GR at 20 and 25ºC were not significantly different from each other, whereas the GR at 5, 10, and 15ºC were significantly different from each other as well as from 20 and 25ºC (P is less than or equal to 0.05). The maximum population density showed relatively little variation over the range of storage temperatures tested, with an average of 8.38 log cfu/g (std. dev. = 0.33). The results of this study indicate that L. monocytogenes replicates in commercially-prepared Queso Blanco at a temperature range of 5 to 25ºC and that proper storage and handling procedures are required to prevent the bacterium from contaminating the product and/or for controlling its growth.