Migeemanathan, Suguna
(2013)
The Effects Of Shifting Temperature On The Growth Of
Listeria Monocytogenes And Salmonella Typhimurium In Goat Milk
Samples Collected From Local Dairy Farms.
Masters thesis, Universiti Sains Malaysia.
Abstract
The main objective of this study was to determine the adaptation and survival curves
of Listeria monocytogenes and Salmonella Typhimurium in goat milk samples
collected in local dairy farm in Penang Island. This research was conducted to
understand the effects of shifting L. monocytogenes and S. Typhimurium from 37°C
to various selected stress temperature in goat milk samples as growth media. The
study was divided into 3 main parts. First part of the study was to determine the
prevalence microorganisms and pathogens especially L. monocytogenes, S.
Typhimurium, total plate count, yeast and mould count and coliform count in goat
milk samples from 2 farms. The second part was to establish the growth profile for
these two pathogens at 37°C in Tryone Soy Broth media. From the plotted growth
curve, stationary phase at 10-7 CFU/ml at 18 and 10 hours of growth was used as the
starting inoculum for the stress conditions for L. monocytogenes and S.
Typhimurium, respectively. In the third part of study, these pathogens were grown at
37°C in TSB medium before shifting to goat milk at different temperature ranging
from 0°C to 90°C. Results of shifting L. monocytogenes and S. Typhimurium from
37°C to lower temperatures from 0 up to 15°C showed bacteriostatic effects, while
shifting from 37°C to 25°C showed the ability of L. monocytogenes and S.
Typhimurium to grow gradually in goat milk. In contrast, shifting of L.
monocytogenes and S. Typhimurium to higher temperatures (from 50°C to 70°C)
exhibited growth of both pathogens after few hours of stress and demonstrated
straight-line death kinetics.
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