LE3 .A278 1997

1997

Bell, Colin
Jackson, Eric

Acadia University

Master of Science

Masters

Biology

Biology

The growth of L. monocytogenes in modified atmosphere packages and ambient air packages was studied at refrigeration temperature, 3$\sp\circ$C, and at the slightly higher temperature of 8$\sp\circ$C, since it is possible that at some point during distribution or consumer handling temperature abuse will occur. Three levels of L. monocytogenes inoculum were used: non-inoculated, 10$\sp4$/g and 10$\sp6$/g. Modified atmosphere did not affect the growth of L. monocytogenes. The higher temperature resulted in a higher level of growth of Listeria in the coleslaw but obvious indication of spoilage (odour, discoloration and/or package swelling) was not present before populations of L. monocytogenes had reached 10$\sp6$ cfu/g. The length of storage has a significant effect (p $\le$ 0.001) on counts of both total bacteria and L. monocytogenes. Inoculum levels did not have a significant effect on total bacterial counts overall. In the second phase of this study, the ability of L. monocytogenes to utilize 95 different carbon sources at 2 different temperatures was examined by monitoring O.D. readings over time using a Biolog$\sp{\rm TM}$ MicroPlate. L. monocytogenes metabolised 33 carbon sources at 30$\sp\circ$C and only 21 at 8$\sp\circ$C.

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