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Inoculation density is affecting growth conditions of Listeria monocytogenes on fresh cut lettuce

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posted on 2018-02-21, 15:01 authored by Oisin McManamon, Johann Scollard, Achim SchmalenbergerAchim Schmalenberger
Listeria monocytogenes is a particular risk for the ready-to-eat food sector because of its ability to grow in various environmental conditions. In the literature, growth and survival of L. monocytogenes on food is tested using inoculation densities ranging from less than 10(2) to over 10(5) CFU g(-1). Inoculation densities on food have been rarely tested as a factor for growth. In this study, inoculation densities from 10(2) to 10(5) of L. monocytogenes were tested on iceberg lettuce (Lactuca sativa) in modified atmospheres and air in model packages at 4 and 8 degrees C to identify any potential inoculation density effects. On days 0, 2, 5 and 7, L. monocytogenes was extracted from the lettuce surface and enumerated via selective media. The resulting growth curves identified a significant inoculation density effect at 4 and 8 degrees C with significantly higher amounts of growth (1-2 logs) when lettuce was inoculated at 10(2) CFU g(-1) as opposed to 10(4) and 10(5) CFU g(-1). In contrast, the use of different atmospheres had limited influence on growth of L. monocytogenes. In conclusion, greater emphasis on inoculation density of L. monocytogenes should be taken in inoculation experiments when confirmation of growth or the efficacies of growth inhibiting treatments are tested on ready-to-eat food such as lettuce.

History

Publication

World Journal Of Microbiology & Biotechnology;33, 217

Publisher

Springer

Note

peer-reviewed

Other Funding information

Irish Department of Agriculture, Food and the Marine

Rights

The original publication is available at www.springerlink.com

Language

English

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