Tan, Jie Yi
(2021)
Survival And Penetration Of Salmonella Spp.
Inoculated On Washed And Unwashed
Eggshell Stored At Different Temperatures.
Project Report.
Universiti Sains Malaysia.
(Submitted)
Abstract
Egg washing and storage temperature are the key factors at influencing Salmonella
contamination on egg surface and content over a period of storage. In the present study,
experiment explored the effect of washing and storage temperatures on the survival and
penetration ability of Salmonella on the eggshell and into the egg content stored at 1, 5, 7,
15, 22, and 28 days. Tap water and dish sponge were used to mimic the household washing
practice. Salmonella concentration at approximately 8 log CFU/mL was inoculated on egg
surface with whole egg penetration method. Salmonella enumeration was carried out on
the surface of eggshell, crushed eggshell and egg content. The study indicated that overall
survival of Salmonella declined after 28 days of incubation at 4°C and 25°C for washed
and unwashed eggs. A significant higher Salmonella survival was observed on the washed
(P < 0.05) and unwashed (P < 0.05) eggshell surface at 4°C than 25°C on 28 days of
incubation. After 1 day of incubation, the highest reduction of Salmonella (1.31 log
CFU/mL) was observed on washed eggs incubated at 25oC. Egg content were tested for
the presence and absence of Salmonella. There were 22.22% (8/36 washed eggs) and
8.33% (3/36 unwashed eggs) of egg contents were detected with Salmonella throughout
28 days of incubation. However, all the washed and unwashed eggs stored at 4°C was
tested Salmonella negative in content at any time point. This study emphasize egg washing
do not give a significant impact to the survival of Salmonella in eggshell and content.
Storage temperature at 4°C showed potential inhibition toward the penetration of
Salmonella in to the egg content. This finding had reflected on the food safety issue
whereby the penetration risk of Salmonella into the egg content can be reduced.
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